Physics and Astronomy › Astronomy and Astrophysics

Ionosphere and magnetosphere dynamics

Works Count: 149420

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Description

This cluster of papers focuses on the study of space weather, magnetospheric physics, and the interactions between the solar wind and Earth's magnetosphere. It covers topics such as magnetospheric dynamics, ionospheric variability, radiation belt dynamics, magnetic reconnection, plasma waves, and the impact of geomagnetic storms on the near-Earth space environment.

Keywords

Magnetosphere; Ionosphere; Solar Wind; Geomagnetic Storms; Radiation Belts; Magnetic Reconnection; Plasma Waves; Space Environment Modeling; Electron Acceleration; Gravity Waves

The Earth's Ionosphere - Plasma Physics and Electrodynamics

1989-01-01

M. C. Kelley , R. Heelis

Introduction to Ionospheric Physics

1969-01-01

H. Rishbeth , O. K. Garriott

Extension of the MSIS Thermosphere Model into the middle and lower atmosphere

1991-02-01

A. E. Hedin

The MSIS‐86 empirical model has been revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating temperature and density … The MSIS‐86 empirical model has been revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating temperature and density profiles representative of the climatological average for various geophysical conditions. Tabulations from the Handbook for MAP 16 are the primary guide for the lower atmosphere and are supplemented by historical rocket and incoherent scatter data in the upper mesosphere and lower thermosphere. Low‐order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, and simplified local time and longitude variations. While month to month details cannot be completely represented, lower atmosphere temperature data are fit to an overall standard deviation of 3 K and pressure to 2%. Comparison with rocket and other data indicates that the model represents current knowledge of the climatological average reasonably well, although there is some conflict as to details near the mesopause.

Radio Waves in the Ionosphere

1962-02-01

K. G. Budden , Howard Chang

Modeling the dynamics of the inner magnetosphere during strong geomagnetic storms

2005-03-01

N. A. Tsyganenko , M. I. Sitnov

This work builds on and extends our previous effort (Tsyganenko et al., 2003) to develop a dynamical model of the storm‐time geomagnetic field in the inner magnetosphere, using space magnetometer … This work builds on and extends our previous effort (Tsyganenko et al., 2003) to develop a dynamical model of the storm‐time geomagnetic field in the inner magnetosphere, using space magnetometer data taken during 37 major events in 1996–2000 and concurrent observations of the solar wind and interplanetary magnetic field (IMF). The essence of the approach is to derive from the data the temporal variation of all major current systems contributing to the distant geomagnetic field during the entire storm cycle, using a simple model of their growth and decay. Each principal source of the external magnetic field (magnetopause, cross‐tail current sheet, axisymmetric and partial ring currents, and Birkeland current systems) is driven by a separate variable, calculated as a time integral of a combination of geoeffective parameters N λ V β B s γ , where N , V , and B s are the solar wind density, speed, and the magnitude of the southward component of the IMF, respectively. In this approach we assume that each source has its individual relaxation timescale and residual quiet‐time strength, and its partial contribution to the total field depends on the entire history of the external driving of the magnetosphere during a storm. In addition, the magnitudes of the principal field sources were assumed to saturate during extremely large storms with abnormally strong external driving. All the parameters of the model field sources, including their magnitudes, geometrical characteristics, solar wind/IMF driving functions, decay timescales, and saturation thresholds, were treated as free variables, and their values were derived from the data. As an independent consistency test, we calculated the expected Dst variation on the basis of the model output at Earth's surface and compared it with the actual observed Dst . A good agreement (cumulative correlation coefficient R = 0.92) was found, in spite of the fact that ∼90% of the spacecraft data used in the fitting were taken at synchronous orbit and beyond, while only 3.7% of those data came from distances 2.5 ≤ R ≤ 4 R E . The obtained results demonstrate the possibility to develop a truly dynamical model of the magnetic field, based on magnetospheric and interplanetary data and allowing one to reproduce and forecast the entire process of a geomagnetic storm, as it unfolds in time and space.

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A magnetospheric magnetic field model with a warped tail current sheet

1989-01-01

N. A. Tsyganenko

An empirical relationship between interplanetary conditions andDst

1975-11-01

Rande K. Burton , R. L. McPherron , C. T. Russell

An algorithm is presented for predicting the ground-based Dst index solely from a knowledge of the velocity and density of the solar wind and the north-south solar magnetospheric component of … An algorithm is presented for predicting the ground-based Dst index solely from a knowledge of the velocity and density of the solar wind and the north-south solar magnetospheric component of the interplanetary magnetic field. The three key elements of this model are an adjustment for solar wind dynamic pressure, an injection rate linearly proportional to the dawn-to-dusk component of the interplanetary electric field which is zero for electric fields below 0.5 mV m−1, and an exponential decay rate of the ring current with an e folding time of 7.7 hours. The algorithm is used to predict the Dst signature of seven geomagnetic storm intervals in 1967 and 1968. In addition to being quite successful, considering the simplicity of the model, the algorithm pinpoints the causes of various types of storm behavior. A main phase is initiated whenever the dawn-to-dusk solar magnetospheric component of the interplanetary electric field becomes large and positive. It is preceded by an initial phase of increased Dst if the solar wind dynamic pressure increases suddenly prior to the main phase. The recovery phase is initiated when the injection rate governed by the interplanetary electric field drops below the ring current decay rate associated with the ring current strength built up during the main phase. Variable recovery rates are generally due to additional injection during the recovery phase. This one algorithm accounts for magnetospheric behavior at quiet and at disturbed times and seems capable of predicting the behavior of Dst during even the largest of storms.

Velocity Space Diffusion from Weak Plasma Turbulence in a Magnetic Field

1966-12-01

C. F. Kennel , F. Engelmann

The quasi-linear velocity space diffusion is considered for waves of any oscillation branch propagating at an arbitrary angle to a uniform magnetic field in a spatially uniform plasma. The space-averaged … The quasi-linear velocity space diffusion is considered for waves of any oscillation branch propagating at an arbitrary angle to a uniform magnetic field in a spatially uniform plasma. The space-averaged distribution function is assumed to change slowly compared to a gyroperiod and characteristic times of the wave motion. Nonlinear mode coupling is neglected. An H-like theorem shows that both resonant and nonresonant quasi-linear diffusion force the particle distributions towards marginal stablity. Creation of the marginally stable state in the presence of a sufficiently broad wave spectrum in general involves diffusing particles to infinite energies, and so the marginally stable plateau is not accessible physically, except in special cases. Resonant particles with velocities much larger than typical phase velocities in the excited spectrum are scattered primarily in pitch angle about the magnetic field. Only particles with velocities the order of the wave phase velocities or less are scattered in energy at a rate comparable with their pitch angle scattering rate.

The ionospheric disturbance dynamo

1980-04-01

Michel Blanc , A. D. Richmond

A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbance dynamo. … A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbance dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid‐latitudes. The transport of angular momentum by these winds produces a subrotation of the mid‐latitude thermosphere or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E × B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid‐latitude current is found to close partly via lower latitudes, resulting in an ‘anti‐Sq’ type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet‐day behavior. This total pattern of disturbance winds, electric fields, and currents is superimposed upon the background quiet‐day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E × B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm‐time ionospheric electric fields at middle and low latitudes.

International Reference Ionosphere 2007: Improvements and new parameters

2008-03-03

D. Bilitza , B. W. Reinisch

A global mapping technique for GPS‐derived ionospheric total electron content measurements

1998-05-01

A. J. Mannucci , Brian Wilson , Dah‐Ning Yuan +3 more

A worldwide network of receivers tracking the transmissions of Global Positioning System (GPS) satellites represents a new source of ionospheric data that is globally distributed and continuously available. We describe … A worldwide network of receivers tracking the transmissions of Global Positioning System (GPS) satellites represents a new source of ionospheric data that is globally distributed and continuously available. We describe a technique for retrieving the global distribution of vertical total electron content (TEC) from GPS‐based measurements. The approach is based on interpolating TEC within triangular tiles that tessellate the ionosphere modeled as a thin spherical shell. The high spatial resolution of pixel‐based methods, where widely separated regions can be retrieved independently of each other, is combined with the efficient retrieval of gradients characteristic of polynomial fitting. TEC predictions from climatological models are incorporated as simulated data to bridge significant gaps between measurements. Time sequences of global TEC maps are formed by incrementally updating the most recent retrieval with the newest data as it becomes available. This Kalman filtering approach smooths the maps in time, and provides time‐resolved covariance information, useful for mapping the formal error of each global TEC retrieval. Preliminary comparisons with independent vertical TEC data, available from the TOPEX dual‐frequency altimeter, suggest that the maps can accurately reproduce spatial and temporal ionospheric variations over latitudes ranging from equatorial to about ±65°.

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Basic Data of Plasma Physics

1961-02-01

Sanborn C. Brown , Steve Singer

The COSMIC/FORMOSAT-3 Mission: Early Results

2008-03-01

Richard A. Anthes , P. A. Bernhardt , Y. Chen +7 more

The radio occultation (RO) technique, which makes use of radio signals transmitted by the global positioning system (GPS) satellites, has emerged as a powerful and relatively inexpensive approach for sounding … The radio occultation (RO) technique, which makes use of radio signals transmitted by the global positioning system (GPS) satellites, has emerged as a powerful and relatively inexpensive approach for sounding the global atmosphere with high precision, accuracy, and vertical resolution in all weather and over both land and ocean. On 15 April 2006, the joint Taiwan-U.S. Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3, hereafter COSMIC) mission, a constellation of six microsatellites, was launched into a 512-km orbit. After launch the satellites were gradually deployed to their final orbits at 800 km, a process that took about 17 months. During the early weeks of the deployment, the satellites were spaced closely, offering a unique opportunity to verify the high precision of RO measurements. As of September 2007, COSMIC is providing about 2000 RO soundings per day to support the research and operational communities. COSMIC RO data are of better quality than those from the previous missions and penetrate much farther down into the troposphere; 70%–90% of the soundings reach to within 1 km of the surface on a global basis. The data are having a positive impact on operational global weather forecast models. With the ability to penetrate deep into the lower troposphere using an advanced open-loop tracking technique, the COSMIC RO instruments can observe the structure of the tropical atmospheric boundary layer. The value of RO for climate monitoring and research is demonstrated by the precise and consistent observations between different instruments, platforms, and missions. COSMIC observations are capable of intercalibrating microwave measurements from the Advanced Microwave Sounding Unit (AMSU) on different satellites. Finally, unique and useful observations of the ionosphere are being obtained using the RO receiver and two other instruments on the COSMIC satellites, the tiny ionosphere photometer (TIP) and the tri-band beacon.

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The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on RBSP

2013-05-31

C. Kletzing , W. S. Kŭrth , M. H. Acuña +7 more

The Electric and Magnetic Field Instrument and Integrated Science (EMFISIS) investigation on the NASA Radiation Belt Storm Probes (now named the Van Allen Probes) mission provides key wave and very … The Electric and Magnetic Field Instrument and Integrated Science (EMFISIS) investigation on the NASA Radiation Belt Storm Probes (now named the Van Allen Probes) mission provides key wave and very low frequency magnetic field measurements to understand radiation belt acceleration, loss, and transport. The key science objectives and the contribution that EMFISIS makes to providing measurements as well as theory and modeling are described. The key components of the instruments suite, both electronics and sensors, including key functional parameters, calibration, and performance, demonstrate that EMFISIS provides the needed measurements for the science of the RBSP mission. The EMFISIS operational modes and data products, along with online availability and data tools provide the radiation belt science community with one the most complete sets of data ever collected.

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What is a geomagnetic storm?

1994-04-01

W. D. González , Jo Ann Joselyn , Y. Kamide +4 more

After a brief review of magnetospheric and interplanetary phenomena for intervals with enhanced solar wind‐magnetosphere interaction, an attempt is made to define a geomagnetic storm as an interval of time … After a brief review of magnetospheric and interplanetary phenomena for intervals with enhanced solar wind‐magnetosphere interaction, an attempt is made to define a geomagnetic storm as an interval of time when a sufficiently intense and long‐lasting interplanetary convection electric field leads, through a substantial energization in the magnetosphere‐ionosphere system, to an intensified ring current sufficiently strong to exceed some key threshold of the quantifying storm time Dst index. The associated storm/substorm relationship problem is also reviewed. Although the physics of this relationship does not seem to be fully understood at this time, basic and fairly well established mechanisms of this relationship are presented and discussed. Finally, toward the advancement of geomagnetic storm research, some recommendations are given concerning future improvements in monitoring existing geomagnetic indices as well as the solar wind near Earth.

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First multispacecraft ion measurements in and near the Earth’s magnetosphere with the identical Cluster ion spectrometry (CIS) experiment

2001-09-30

H. Rème , C. Aoustin , J. M. Bosqued +7 more

Abstract. On board the four Cluster spacecraft, the Cluster Ion Spectrometry (CIS) experiment measures the full, three-dimensional ion distribution of the major magnetospheric ions (H+, He+, He++, and O+) from … Abstract. On board the four Cluster spacecraft, the Cluster Ion Spectrometry (CIS) experiment measures the full, three-dimensional ion distribution of the major magnetospheric ions (H+, He+, He++, and O+) from the thermal energies to about 40 keV/e. The experiment consists of two different instruments: a COmposition and DIstribution Function analyser (CIS1/CODIF), giving the mass per charge composition with medium (22.5°) angular resolution, and a Hot Ion Analyser (CIS2/HIA), which does not offer mass resolution but has a better angular resolution (5.6°) that is adequate for ion beam and solar wind measurements. Each analyser has two different sensitivities in order to increase the dynamic range. First tests of the instruments (commissioning activities) were achieved from early September 2000 to mid January 2001, and the operation phase began on 1 February 2001. In this paper, first results of the CIS instruments are presented showing the high level performances and capabilities of the instruments. Good examples of data were obtained in the central plasma sheet, magnetopause crossings, magnetosheath, solar wind and cusp measurements. Observations in the auroral regions could also be obtained with the Cluster spacecraft at radial distances of 4–6 Earth radii. These results show the tremendous interest of multispacecraft measurements with identical instruments and open a new area in magnetospheric and solar wind-magnetosphere interaction physics.Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; magnetopheric configuration and dynamics; solar wind - magnetosphere interactions)

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The amplitude distribution of field-aligned currents at northern high latitudes observed by Triad

1976-05-01

Takesi Iijima , T. A. Potemra

The spatial distribution and magnitudes of field-aligned currents at 800-km altitude over northern high latitudes were determined from Triad magnetometer data recorded at College, Alaska, during the period from July … The spatial distribution and magnitudes of field-aligned currents at 800-km altitude over northern high latitudes were determined from Triad magnetometer data recorded at College, Alaska, during the period from July 1973 to October 1974. The characteristics that were determined include the following: (1) Large-scale field-aligned currents are concentrated in two principal areas encircling the geomagnetic pole: region 1, located near the poleward part of the field-aligned current region; and region 2, located near the equatorward part. (2) In region 1 during moderately disturbed conditions (2− ≤ Kp ≤ 4+) the largest current densities occur on the forenoon sector, with currents flowing into the ionosphere (with a peak value of ∼2 µA/m² between 0700 and 0800 MLT), and in the afternoon sector, with currents flowing away from the ionosphere (with a peak value of ∼1.8 µA/m² between 1500 and 1600 MLT). These areas of maximum current density in region 1 are approximately coincident with the location of the foci of the Sqp current system. (3) In region 2 for 2− ≤ Kp ≤ 4+ the largest current densities occur on the night side where auroral electrojets are usually most active, namely, in the evening to premidnight sector, with currents flowing into the ionosphere (with a peak value of ∼ 1 µA/m² between 2100 and 2300 MLT), and in the midnight to morning sector, with currents flowing away from the ionosphere (with a peak value of ∼ 1.3 µA/m² between 0200 and 0300 MLT). (4) The currents in region 1 are statistically larger than the currents in region 2 at all local times except for the sector near midnight (∼2100–0300 MLT), where the region 2 currents are comparable to or slightly larger than the region 1 currents. (5) The region 2 currents in the midnight to morning sector are correlated with the intensity of the westward electrojet, and the region 2 currents in the evening to premidnight sector are correlated with the intensity of the eastward electrojet. (6) The region 1 currents appear to persist, especially on the day side, even during very low geomagnetic activity with a value of current density ≳0.6 µA/m² for Kp = 0. We suggest that the magnetosphere-ionosphere current system which contains field-aligned currents consists of two distinct parts: a permanent part with field-aligned currents in region 1 and the other part having field-aligned currents in region 2, which is an important element of the auroral electrojets.

Empirical high‐latitude electric field models

1987-05-01

J. P. Heppner , N. C. Maynard

Electric field measurements from the Dynamics Explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn‐dusk OGO 6 measurements (J. P. Heppner, 1977). The analysis … Electric field measurements from the Dynamics Explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn‐dusk OGO 6 measurements (J. P. Heppner, 1977). The analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones. Paralleling the previous analysis, the modeling is based on the distinctly different polar cap and dayside convective patterns that occur as a function of the sign of the Y component of the interplanetary magnetic field. The objective, which is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns, is met by deriving one pattern (model BC) for the northern hemisphere with a + Y interplanetary magnetic field (IMF) and southern hemisphere with a − Y IMF and two patterns (models A and DE) for the northern hemisphere with a − Y IMF and southern hemisphere with a + Y IMF. The most significant large‐scale revisions of the OGO 6 models are (1) on the dayside where the latitudinal overlap of morning and evening convection cells reverses with the sign of the IMF Y component, (2) on the nightside where a westward flow region poleward from the Harang discontinuity appears under model BC conditions, and (3) magnetic local time shifts in the positions of the convection cell foci. The modeling above was followed by a detailed examination of cases where the IMF Z component was clearly positive (northward). Neglecting the seasonally dependent cases where irregularities obscure pattern recognition, the observations range from reasonable agreement with the new BC and DE models, to cases where different characteristics appeared primarily at dayside high latitudes. The analysis of these differences for strong + B z conditions, using passes through different MLT zones, led to finding that the deviations from both the BC and DE models could be modeled by extending the evening cell foci toward, and beyond, noon with a deformation that roughly resembles a rotational twist of the extended evening cell. The morning cell accommodation to the model BC deformation produces a narrow tongue of eastward convection near 75° invariant latitude on the dayside. The model DE deformation compresses the morning cell toward the night hours such that the sunward convection in the morning cell is diverted to polar latitudes in the 0400 to 0700 MLT sector. In both cases, the deformations of the two‐cell patterns lead to sunward convection in dayside polar regions while maintaining the integrity of the nightside convection pattern. Thus the nightside dilemmas that plague three‐ and four‐cell models designed to explain sunward convection in polar regions under + B z conditions do not appear.

Some features of field line resonances in the magnetosphere

1974-03-01

D. J. Southwood

A theory of long-period magnetic pulsations: 1. Steady state excitation of field line resonance

1974-03-01

Liu Chen , Akira Hasegawa

A theory of long-period (Pc 3 to Pc 5) magnetic pulsations is presented based on the idea of a steady state oscillation of a resonant local field line that is … A theory of long-period (Pc 3 to Pc 5) magnetic pulsations is presented based on the idea of a steady state oscillation of a resonant local field line that is excited by a monochromatic surface wave at the magnetosphere. A coupled wave equation between the shear Alfvén wave representing the field line oscillation and the surface wave is derived and solved for the dipole coordinates. The theory gives the frequency, the sense of polarizations, orientation angle of the major axis, and the ellipticity as a function of magnetospheric parameters. It also clarifies some of the contradicting ideas and observations in relation to the sense of polarization and excitation mechanism. At lower latitude it is shown that the orientation angle rather than the sense of rotation is a more critical parameter in finding the direction of wave propagation in the azimuthal coordinate and hence in finding the evidence of wave excitation at the magnetospheric surface by the solar wind.

Waves in a Plasma in a Magnetic Field

1958-01-01

Ira B. Bernstein

The small oscillations of a fully ionized plasma, in which collisions are negligible, in a constant external magnetic field, is treated by the Laplace transform method. The full set of … The small oscillations of a fully ionized plasma, in which collisions are negligible, in a constant external magnetic field, is treated by the Laplace transform method. The full set of Maxwell equations is employed and the ion dynamics are included. Various limiting cases are considered. It is shown that self-excitation of waves around thermal equilibrium is impossible. It is also demonstrated that for longitudinal electron oscillations propagating perpendicular to the constant magnetic field, there are gaps in the spectrum of allowed frequencies at multiples of the electron gyration frequency, but zero Landau damping. These particular waves are also associated with a nonuniformity of convergence in the limit of vanishing magnetic field which phenomenon, however, is of no physical consequence. When the ion dynamics are included, two classes of low frequency oscillations are found, the existence of both of which has been predicted by the simple hydrodynamic theory, namely longitudinal ion waves, and transverse hydromagnetic waves. The well known results for the propagation of electromagnetic waves in an ionized atmosphere are also recovered, as well as the effects on such waves in various limiting cases of the magnetic field and particle motion. These calculations indicate that in many cases the transport equations are capable of yielding correct results, apart from such things as Landau damping, for a wide class of waves in a collision-free plasma.

Geospace Environmental Modeling (GEM) Magnetic Reconnection Challenge

2001-03-01

J. Birn , J. F. Drake , M. A. Shay +7 more

The Geospace Environmental Modeling (GEM) Reconnection Challenge project is presented and the important results, which are presented in a series of companion papers, are summarized. Magnetic reconnection is studied in … The Geospace Environmental Modeling (GEM) Reconnection Challenge project is presented and the important results, which are presented in a series of companion papers, are summarized. Magnetic reconnection is studied in a simple Harris sheet configuration with a specified set of initial conditions, including a finite amplitude, magnetic island perturbation to trigger the dynamics. The evolution of the system is explored with a broad variety of codes, ranging from fully electromagnetic particle in cell (PIC) codes to conventional resistive magnetohydrodynamic (MHD) codes, and the results are compared. The goal is to identify the essential physics which is required to model collisionless magnetic reconnection. All models that include the Hall effect in the generalized Ohm's law produce essentially indistinguishable rates of reconnection, corresponding to nearly Alfvénic inflow velocities. Thus the rate of reconnection is insensitive to the specific mechanism which breaks the frozen‐in condition, whether resistivity, electron inertia, or electron thermal motion. The reconnection rate in the conventional resistive MHD model, in contrast, is dramatically smaller unless a large localized or current dependent resistivity is used. The Hall term brings the dynamics of whistler waves into the system. The quadratic dispersion property of whistlers (higher phase speed at smaller spatial scales) is the key to understanding these results. The implications of these results for trying to model the global dynamics of the magnetosphere are discussed.

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DARN/SuperDARN

1995-02-01

R. A. Greenwald , K. B. Baker , J. R. Dudeney +7 more

Dusty plasmas in the solar system

1989-05-01

C. K. Goertz

The processes that lead to charging of dust grains in a plasma are briefly reviewed. Whereas for single grains the results have been long known, the reduction of the average … The processes that lead to charging of dust grains in a plasma are briefly reviewed. Whereas for single grains the results have been long known, the reduction of the average charge on a grain by “Debye screening” has only recently been discovered. This reduction can be important in the Jovian ring and in the rings of Uranus. The emerging field of gravitoelectrodynamics which deals with the motion of charged grains in a planetary magnetosphere is then reviewed. Important mechanisms for distributing grains in radial distance are due to stochastic fluctuations of the grain charge and a systematic variation due to motion through plasma gradients. The electrostatic levitation model for the formation of spokes is discussed, and it is shown that the radial transport of dust contained in the spokes may be responsible for the rich radial structure in Saturn's rings. Finally, collective effects in dusty plasmas are discussed which affect various waves, such as density waves in planetary rings and low‐frequency plasma waves. The possibility of charged grains forming a Coulomb lattice is briefly described.

The THEMIS ESA Plasma Instrument and In-flight Calibration

2008-10-20

J. P. McFadden , C. W. Carlson , D. E. Larson +6 more

Whistlers and Related Ionospheric Phenomena

1966-01-01

R. A. Helliwell , Agnar Pytte

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Radar observations ofFregion equatorial irregularities

1976-11-01

R. F. Woodman , C. La Hoz

The paper presents some results of backscatter observations of the F region irregularities made with the large 50-MHz radar at Jicamarca, Peru, during a few days of observations. The results … The paper presents some results of backscatter observations of the F region irregularities made with the large 50-MHz radar at Jicamarca, Peru, during a few days of observations. The results were obtained by using three observational techniques: the modified range-time-intensity technique, the digital power mapping technique, and the digital raw data recording technique. Backscatter intensity maps as a function of altitude and time are presented, which can be interpreted as radar pictures of F region irregularities. A classification of spread F spectral signatures resulting from approximately 30,000 spectra obtained in sets of 64 simultaneous heights under a variety of conditions is also given.

Magnetopause structure and attitude from Explorer 12 observations

1967-01-01

B. U. Ö. Sonnerup , L. J. Cahill

It is shown how satellite magnetometer data at a magnetopause penetration can be used to determine the vector normal to the magnetopause current layer and the magnetic-field component along this … It is shown how satellite magnetometer data at a magnetopause penetration can be used to determine the vector normal to the magnetopause current layer and the magnetic-field component along this normal. According to theory such a component is a measure of the amount of field reconnection at magnetopause. Results from 22 Explorer 12 boundary penetrations are presented indicating normal-field components of less than 5 γ in two-thirds of the cases. Measured field variations within the current layer are presented to demonstrate the existence of two fundamentally different types of boundary structure, the rotational and the tangential discontinuity. The former of these permits a nonzero normal field component, whereas the latter does not. The rotational discontinuity seems to occur predominantly during magnetic storms and two of these cases, involving substantial normal-field components, provide compelling evidence that field reconnection takes place during the storm main phase. Finally, the calculated normal vector is compared with the normal to the surface of the Mead-Beard magnetosphere model.

A survey of low-energy electrons in the evening sector of the magnetosphere with OGO 1 and OGO 3

1968-05-01

V. M. Vasyliūnas

Observations of electrons of energy 125 ev to ∼2 kev with the OGO 1 satellite and of electrons of energy 40 ev to ∼2 kev with OGO 3 (by means … Observations of electrons of energy 125 ev to ∼2 kev with the OGO 1 satellite and of electrons of energy 40 ev to ∼2 kev with OGO 3 (by means of modulated Faraday cup detectors) are used to investigate the low-energy electron population in the magnetosphere within the local-time range ∼17 to ∼22 hours. Intense fluxes of these electrons are confined to a spatial region, termed the plasma sheet, which is an extension of the magnetotail plasma sheet discovered by the Vela satellites and is identified with the soft electron band first detected by Gringauz. The plasma sheet extends over the entire local-time range studied in this investigation, from the magnetospheric tail past the dusk meridian toward the dayside magnetosphere. In latitude it is confined to within 4–6 RE of the geomagnetic and/or solar magnetospheric equatorial plane, in agreement with observations already reported from the Vela satellites; no electron fluxes are detected high above the equator, not even very near the magnetopause. In radial distance the plasma sheet is terminated by the magnetopause on the outside and by a well-defined sharp inner boundary on the inside. The inner boundary has been traced from the equatorial region to the highest latitudes investigated, ∼40°; during geomagnetically quiet periods, it is observed at an equatorial distance of 11 ± 1 RE and appears to extend to higher latitudes along magnetic field lines. Weak or no electron fluxes are found between the inner boundary of the plasma sheet and the outer boundary of the plasmasphere. Detection (by an indirect process) of the very high ion densities within the plasmasphere gives positions for its boundary in good agreement with other determinations. During periods of magnetic bay activity, the plasma sheet extends closer to the earth; the inner boundary of the plasma sheet is then found at equatorial distances of 6–8 RE. This is most simply interpreted as the result of an actual inward motion of the plasma during a bay. In one case, it was possible to associate the beginning of this motion with the onset of the bay and to estimate an average radial speed of ∼12 km/sec, from which an electric field corresponding to ∼48 kilovolts across the magnetospheric tail was inferred. Within the plasma sheet, the electron population is characterized by number densities from 0.3 to 30 cm−3 and mean energies from 50 to 1600 ev and higher, with a strong anticorrelation between density and mean energy, so that the electron energy density (∼1 kev cm−3) and energy flux (∼3 ergs cm−2 sec−1) show relatively little variation. The lower energies and higher densities tend to occur during periods of geomagnetic disturbance. The nonobservation of electrons in regions above the plasma sheet implies an upper limit on the electron number density of 5 × 10−2 cm−3 if their mean energy is assumed to be ∼50 ev (typical of the magnetosheath) and 10−2 cm−3 if the energy is ∼1 kev (typical of the plasma sheet). At the inner boundary of the plasma sheet there is a sharp softening of the electron spectrum with decreasing radial distance but apparently little change in the electron number density. The electron energy density decreases across the inner boundary roughly as ∼exp (distance/0.4 RE) during quiet periods; during times of magnetic bay activity the energy density decreases as ∼exp (distance/0.6 RE), and there is a more complicated spatial structure of density and mean energy.

The THEMIS Fluxgate Magnetometer

2008-05-15

Hans‐Ulrich Auster , Karl‐Heinz Glaßmeier , W. Magnes +7 more

Magnetopause location under extreme solar wind conditions

1998-08-01

Jih‐Hong Shue , Pu Song , C. T. Russell +7 more

During the solar wind dynamic pressure enhancement, around 0200 UT on January 11, 1997, at the end of the January 6–11 magnetic cloud event, the magnetopause was pushed inside geosynchronous … During the solar wind dynamic pressure enhancement, around 0200 UT on January 11, 1997, at the end of the January 6–11 magnetic cloud event, the magnetopause was pushed inside geosynchronous orbit. The LANL 1994–084 and GMS 4 geosynchronous satellites crossed the magnetopause and moved into the magnetosheath. Also, the Geotail satellite was in the magnetosheath while the Interball 1 satellite observed magnetopause crossings. This event provides an excellent opportunity to test and validate the prediction capabilities and accuracy of existing models of the magnetopause location for producing space weather forecasts. In this paper, we compare predictions of two models: the Petrinec and Russell [1996] model and the Shue et al. [1997] model. These two models correctly predict the magnetopause crossings on the dayside; however, there are some differences in the predictions along the flank. The Shue et al. [1997] model correctly predicts the Geotail magnetopause crossings and partially predicts the Interball 1 crossings. The Petrinec and Russell [1996] model correctly predicts the Interball 1 crossings and is partially consistent with the Geotail observations. We further found that some of the inaccuracy in Shue et al.'s predictions is due to the inappropriate linear extrapolation from the parameter range for average solar wind conditions to that for extreme conditions. To improve predictions under extreme solar wind conditions, we introduce a nonlinear dependence of the parameters on the solar wind conditions to represent the saturation effects of the solar wind dynamic pressure on the flaring of the magnetopause and saturation effects of the interplanetary magnetic field B z on the subsolar standoff distance. These changes lead to a better agreement with the Interball 1 observations for this event.

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International Reference Ionosphere 2000

2001-03-01

D. Bilitza

The International Reference Ionosphere (IRI) is the international standard for the specification of ionospheric densities and temperatures. It was developed and is being improved‐updated by a joint working group of … The International Reference Ionosphere (IRI) is the international standard for the specification of ionospheric densities and temperatures. It was developed and is being improved‐updated by a joint working group of the International Union of Radio Science (URSI) and the Committee on Space Research (COSPAR). A new version of IRI is scheduled for release in the year 2000. This paper describes the most important changes compared to the current version of IRI: (1) an improved representation of the electron density in the region from the F peak down to the E peak including a better description of the F 1 layer occurrence statistics and a more realistic description of the low‐latitude bottomside thickness, (2) inclusion of a model for storm‐time conditions, (3) inclusion of an ion drift model, (4) two new options for the electron density in the D region, and (5) an improved model for the topside electron temperatures. The outcome of the most recent IRI Workshops (Kühlungsborn, 1997, and Nagoya, 1998) will be reviewed, and the status of several ongoing task force activities (e.g., efforts to improve the representation of electron and ion densities in the topside ionosphere and the inclusion of a plasmaspheric extension) will be discussed. A few typical IRI applications will be highlighted in section 6.

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A thermosphere/ionosphere general circulation model with coupled electrodynamics

1992-03-20

A. D. Richmond , E. C. Ridley , R. G. Roble

A new simulation model of upper atmospheric dynamics is presented that includes self‐consistent electrodynamic interactions between the thermosphere and ionosphere. This model, which we call the National Center for Atmospheric … A new simulation model of upper atmospheric dynamics is presented that includes self‐consistent electrodynamic interactions between the thermosphere and ionosphere. This model, which we call the National Center for Atmospheric Research thermosphere‐ionosphere‐electrodynamic general circulation model (NCAR/TIE‐GCM), calculates the dynamo effects of thermospheric winds, and uses the resultant electric fields and currents in calculating the neutral and plasma dynamics. A realistic geomagnetic field geometry is used. Sample simulations for solar maximum equinox conditions illustrate two previously predicted effects of the feedback. Near the magnetic equator, the afternoon uplift of the ionosphere by an eastward electric field reduces ion drag on the neutral wind, so that relatively strong eastward winds can occur in the evening. In addition, a vertical electric field is generated by the low‐latitude wind, which produces east‐west plasma drifts in the same direction as the wind, further reducing the ion drag and resulting in stronger zonal winds.

Limit on stably trapped particle fluxes

1966-01-01

C. F. Kennel , H. E. Petschek

Whistler mode noise leads to electron pitch angle diffusion. Similarly, ion cyclotron noise couples to ions. This diffusion results in particle precipitation into the ionosphere and creates a pitch angle … Whistler mode noise leads to electron pitch angle diffusion. Similarly, ion cyclotron noise couples to ions. This diffusion results in particle precipitation into the ionosphere and creates a pitch angle distributon of trapped particles that is unstable to further wave growth. Since excessive wave growth leads to rapid diffusion and particle loss, the requirement that the growth rate be limited to the rate at which wave energy is depleted by wave propagation permits an estimate of an upper limit to the trapped equatorial particle flux. Electron fluxes >40 kev and proton fluxes >120 kev observed on Explorers 14 and 12, respectively, obey this limit with occasional exceptions. Beyond L = 4, the fluxes are just below their limit, indicating that an unspecified acceleration source, sufficient to keep the trapped particles near their precipitation limit, exists. Limiting proton and electron fluxes are roughly equal, suggesting a partial explanation for the existence of larger densities of high-energy protons than of electrons. Observed electron pitch angle profiles correspond to a diffusion coefficient in agreement with observed lifetimes. The required equatorial whistler mode wide band noise intensity, 10−2γ, is not obviously inconsistent with observations and is consistent with the lifetime and with limiting trapped particle intensity.

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Bursty bulk flows in the inner central plasma sheet

1992-04-01

V. Angelopoulos , W. Baumjohann , C. F. Kennel +6 more

High‐speed flows in the inner central plasma sheet (first reported by Baumjohann et al. (1990)) are studied, together with the concurrent behavior of the plasma and magnetic field, by using … High‐speed flows in the inner central plasma sheet (first reported by Baumjohann et al. (1990)) are studied, together with the concurrent behavior of the plasma and magnetic field, by using AMPTE/IRM data from ≈ 9 to 19 R E in the Earth's magnetotail. The conclusions drawn from the detailed analysis of a representative event are reinforced by a superposed epoch analysis applied on 2 years of data. The high‐speed flows organize themselves in 10‐min time scale flow enhancements which we call bursty bulk flow (BBF) events. Both temporal and spatial effects are responsible for their bursty nature. The flow velocity exhibits peaks of very large amplitude with a characteristic time scale of the order of a minute, which are usually associated with magnetic field dipolarizations and ion temperature increases. The BBFs represent intervals of enhanced earthward convection and energy transport per unit area in the y‐z GSM direction of the order of 5×10 19 ergs/ R E ².

Neutral line model of substorms: Past results and present view

1996-06-01

D. N. Baker , T. I. Pulkkinen , V. Angelopoulos +2 more

The near‐Earth neutral line (NENL) model of magnetospheric substorms is reviewed. The observed phenomenology of substorms is discussed including the role of coupling with the solar wind and interplanetary magnetic … The near‐Earth neutral line (NENL) model of magnetospheric substorms is reviewed. The observed phenomenology of substorms is discussed including the role of coupling with the solar wind and interplanetary magnetic field, the growth phase sequence, the expansion phase (and onset), and the recovery phase. New observations and modeling results are put into the context of the prior model framework. Significant issues and concerns about the shortcomings of the NENL model are addressed. Such issues as ionosphere‐tail coupling, large‐scale mapping, onset triggering, and observational timing are discussed. It is concluded that the NENL model is evolving and being improved so as to include new observations and theoretical insights. More work is clearly required in order to incorporate fully the complete set of ionospheric, near‐tail, midtail, and deep tail features of substorms. Nonetheless, the NENL model still seems to provide the best available framework for ordering the complex, global manifestations of substorms.

The THEMIS Mission

2008-04-21

V. Angelopoulos

NRLMSISE‐00 empirical model of the atmosphere: Statistical comparisons and scientific issues

2002-12-01

J. M. Picone , A. E. Hedin , D. P. Drob +1 more

The new NRLMSISE‐00 empirical atmospheric model extends from the ground to the exobase and is a major upgrade of the MSISE‐90 model in the thermosphere. The new model and the … The new NRLMSISE‐00 empirical atmospheric model extends from the ground to the exobase and is a major upgrade of the MSISE‐90 model in the thermosphere. The new model and the associated NRLMSIS database now include the following data: (1) total mass density from satellite accelerometers and from orbit determination (including the Jacchia and Barlier data sets), (2) temperature from incoherent scatter radar covering 1981–1997, and (3) molecular oxygen number density, [O 2 ], from solar ultraviolet occultation aboard the Solar Maximum Mission. A new component, “anomalous oxygen,” allows for appreciable O + and hot atomic oxygen contributions to the total mass density at high altitudes and applies primarily to drag estimation above 500 km. Extensive tables compare our entire database to the NRLMSISE‐00, MSISE‐90, and Jacchia‐70 models for different altitude bands and levels of geomagnetic activity. We also explore scientific issues related to the new data sets in the NRLMSIS database. Especially noteworthy is the solar activity dependence of the Jacchia data, with which we study a large O + contribution to the total mass density under the combination of summer, low solar activity, high latitude, and high altitude. Under these conditions, except at very low solar activity, the Jacchia data and the Jacchia‐70 model indeed show a significantly higher total mass density than does MSISE‐90. However, under the corresponding winter conditions, the MSIS‐class models represent a noticeable improvement relative to Jacchia‐70 over a wide range of F 10.7 . Considering the two regimes together, NRLMSISE‐00 achieves an improvement over both MSISE‐90 and Jacchia‐70 by incorporating advantages of each.

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The Cluster Magnetic Field Investigation: overview of in-flight performance and initial results

2001-09-30

A. Balogh , C. Carr , M. H. Acuña +7 more

Abstract. The accurate measurement of the magnetic field along the orbits of the four Cluster spacecraft is a primary objective of the mission. The magnetic field is a key constituent … Abstract. The accurate measurement of the magnetic field along the orbits of the four Cluster spacecraft is a primary objective of the mission. The magnetic field is a key constituent of the plasma in and around the magnetosphere, and it plays an active role in all physical processes that define the structure and dynamics of magnetospheric phenomena on all scales. With the four-point measurements on Cluster, it has become possible to study the three-dimensional aspects of space plasma phenomena on scales commeasurable with the size of the spacecraft constellation, and to distinguish temporal and spatial dependences of small-scale processes. We present an overview of the instrumentation used to measure the magnetic field on the four Cluster spacecraft and an overview the performance of the operational modes used in flight. We also report on the results of the preliminary in-orbit calibration of the magnetometers; these results show that all components of the magnetic field are measured with an accuracy approaching 0.1 nT. Further data analysis is expected to bring an even more accurate determination of the calibration parameters. Several examples of the capabilities of the investigation are presented from the commissioning phase of the mission, and from the different regions visited by the spacecraft to date: the tail current sheet, the dusk side magnetopause and magnetosheath, the bow shock and the cusp. We also describe the data processing flow and the implementation of data distribution to other Cluster investigations and to the scientific community in general.Key words. Interplanetary physics (instruments and techniques) – magnetospheric physics (magnetospheric configuration and dynamics) – space plasma physics (shock waves)

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Turbulence and stress owing to gravity wave and tidal breakdown

1981-10-20

Richard S. Lindzen

It has been suggested (Lindzen, 1967, 1968a, b ; Lindzen and Blake, 1971; Hodges, 1969) that turbulence in the upper mesosphere arises from the unstable breakdown of tides and gravity … It has been suggested (Lindzen, 1967, 1968a, b ; Lindzen and Blake, 1971; Hodges, 1969) that turbulence in the upper mesosphere arises from the unstable breakdown of tides and gravity waves. Crudely speaking, it was expected that sufficient turbulence would be generated to prevent the growth of wave amplitude with height (roughly as (basic pressure) −1/2 ). This work has been extended to allow for the generation of turbulence by smaller amplitude waves, the effects of mean winds on the waves, and the effects of the waves on the mean momentum budget. The effects of mean winds, while of relatively small importance for tides, are crucial for internal gravity waves originating in the troposphere. Winds in the troposphere and stratosphere sharply limit the phase speeds of waves capable of reaching the upper mesosphere. In addition, the existence of critical levels in the mesosphere significantly limits the ability of gravity waves to generate turbulence, while the breakdown of gravity waves contributes to the development of critical levels. The results of the present study suggest that at middle latitudes in winter, eddy coefficients may peak at relatively low altitudes (50 km) and at higher altitudes in summer and during sudden warmings (70–80 km), and decrease with height rather sharply above these levels. Rocket observations are used to estimate momentum deposition by gravity waves. Accelerations of about 100 m/s/day are suggested. Such accelerations are entirely capable of producing the warm winter and cold summer mesopauses.

Science Objectives and Rationale for the Radiation Belt Storm Probes Mission

2012-09-06

B. H. Mauk , N. J. Fox , S. G. Kanekal +3 more

The NASA Radiation Belt Storm Probes (RBSP) mission addresses how populations of high energy charged particles are created, vary, and evolve in space environments, and specifically within Earth’s magnetically trapped … The NASA Radiation Belt Storm Probes (RBSP) mission addresses how populations of high energy charged particles are created, vary, and evolve in space environments, and specifically within Earth’s magnetically trapped radiation belts. RBSP, with a nominal launch date of August 2012, comprises two spacecraft making in situ measurements for at least 2 years in nearly the same highly elliptical, low inclination orbits (1.1×5.8 RE, 10∘). The orbits are slightly different so that 1 spacecraft laps the other spacecraft about every 2.5 months, allowing separation of spatial from temporal effects over spatial scales ranging from ∼0.1 to 5 RE. The uniquely comprehensive suite of instruments, identical on the two spacecraft, measures all of the particle (electrons, ions, ion composition), fields (E and B), and wave distributions (d E and d B) that are needed to resolve the most critical science questions. Here we summarize the high level science objectives for the RBSP mission, provide historical background on studies of Earth and planetary radiation belts, present examples of the most compelling scientific mysteries of the radiation belts, present the mission design of the RBSP mission that targets these mysteries and objectives, present the observation and measurement requirements for the mission, and introduce the instrumentation that will deliver these measurements. This paper references and is followed by a number of companion papers that describe the details of the RBSP mission, spacecraft, and instruments.

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The Magnetospheric Multiscale Magnetometers

2014-08-19

C. T. Russell , B. J. Anderson , W. Baumjohann +7 more

The success of the Magnetospheric Multiscale mission depends on the accurate measurement of the magnetic field on all four spacecraft. To ensure this success, two independently designed and built fluxgate … The success of the Magnetospheric Multiscale mission depends on the accurate measurement of the magnetic field on all four spacecraft. To ensure this success, two independently designed and built fluxgate magnetometers were developed, avoiding single-point failures. The magnetometers were dubbed the digital fluxgate (DFG), which uses an ASIC implementation and was supplied by the Space Research Institute of the Austrian Academy of Sciences and the analogue magnetometer (AFG) with a more traditional circuit board design supplied by the University of California, Los Angeles. A stringent magnetic cleanliness program was executed under the supervision of the Johns Hopkins University’s Applied Physics Laboratory. To achieve mission objectives, the calibration determined on the ground will be refined in space to ensure all eight magnetometers are precisely inter-calibrated. Near real-time data plays a key role in the transmission of high-resolution observations stored on board so rapid processing of the low-resolution data is required. This article describes these instruments, the magnetic cleanliness program, and the instrument pre-launch calibrations, the planned in-flight calibration program, and the information flow that provides the data on the rapid time scale needed for mission success.

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The IGS VTEC maps: a reliable source of ionospheric information since 1998

2009-02-18

Manuel Hernández Pajares , José Miguel Juan Zornoza , Jaume Sanz Subirana +6 more

Satellite studies of magnetospheric substorms on August 15, 1968: 9. Phenomenological model for substorms

1973-06-01

R. L. McPherron , C. T. Russell , M. P. Aubry

In the eight preceding papers, two magnetospheric substorms on August 15, 1968, were studied with data derived from many sources. In this, the concluding paper, we attempt a synthesis of … In the eight preceding papers, two magnetospheric substorms on August 15, 1968, were studied with data derived from many sources. In this, the concluding paper, we attempt a synthesis of these observations, presenting a phenomenological model of the magnetospheric substorm. On the basis of our results for August 15, together with previous reports, we believe that the substorm sequence can be divided into three main phases: the growth phase, the expansion phase, and the recovery phase. Observations for each of the first three substorms on this day are organized according to this scheme. We present these observations as three distinct chronologies, which we then summarize as a phenomenological model. This model is consistent with most of our observations on August 15, as well as with most previous reports. In our interpretation we expand our phenomenological model, briefly described in several preceding papers. This model follows closely the theoretical ideas presented more quantitatively in recent papers by Coroniti and Kennel (1972a, b; 1973). A southward turning of the interplanetary magnetic field is accompanied by erosion of the dayside magnetosphere, flux transport to the geomagnetic tail, and thinning and inward motion of the plasma sheet. Our observations indicate, furthermore, that the expansion phase of substorms can originate near the inner edge of the plasma sheet as a consequence of rapid plasma sheet thinning. At this time a portion of the inner edge of the tail current is ‘short circuited’ through the ionosphere. This process is consistent with the formation of a neutral point in the near-tail region and its subsequent propagation tailward. However, the onset of the expansion phase of substorms is found to be far from a simple process. Expansion phases can be centered at local times far from midnight, can apparently be localized to one meridian, and can have multiple onsets centered at different local times. Such behavior indicates that, in comparing observations occurring in different substorms, careful note should be made of the localization and central meridian of each substorm.

Gravity wave dynamics and effects in the middle atmosphere

2003-03-01

David C. Fritts , M. Joan Alexander

Atmospheric gravity waves have been a subject of intense research activity in recent years because of their myriad effects and their major contributions to atmospheric circulation, structure, and variability. Apart … Atmospheric gravity waves have been a subject of intense research activity in recent years because of their myriad effects and their major contributions to atmospheric circulation, structure, and variability. Apart from occasionally strong lower‐atmospheric effects, the major wave influences occur in the middle atmosphere, between ∼ 10 and 110 km altitudes because of decreasing density and increasing wave amplitudes with altitude. Theoretical, numerical, and observational studies have advanced our understanding of gravity waves on many fronts since the review by Fritts [1984a] ; the present review will focus on these more recent contributions. Progress includes a better appreciation of gravity wave sources and characteristics, the evolution of the gravity wave spectrum with altitude and with variations of wind and stability, the character and implications of observed climatologies, and the wave interaction and instability processes that constrain wave amplitudes and spectral shape. Recent studies have also expanded dramatically our understanding of gravity wave influences on the large‐scale circulation and the thermal and constituent structures of the middle atmosphere. These advances have led to a number of parameterizations of gravity wave effects which are enabling ever more realistic descriptions of gravity wave forcing in large‐scale models. There remain, nevertheless, a number of areas in which further progress is needed in refining our understanding of and our ability to describe and predict gravity wave influences in the middle atmosphere. Our view of these unknowns and needs is also offered.

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INTERNAL ATMOSPHERIC GRAVITY WAVES AT IONOSPHERIC HEIGHTS

1960-11-01

C. O. Hines

Irregularities and irregular motions in the upper atmosphere have been detected and studied by a variety of techniques during recent years, but their proper interpretation has yet to be established. … Irregularities and irregular motions in the upper atmosphere have been detected and studied by a variety of techniques during recent years, but their proper interpretation has yet to be established. It is shown here that many or most of the observational data may be interpreted on the basis of a single physical mechanism, namely, internal atmospheric gravity waves.A comprehensive picture is envisaged for the motions normally encountered, in which a spectrum of waves is generated at low levels of the atmosphere and propagated upwards. The propagational effects of amplification, reflection, inter-modulation, and dissipation act to change the spectrum continuously with increasing height, and so produce different types of dominant modes at different heights. These changes, coupled with an observational selection in some cases, lead to the various characteristics revealed by the different observing techniques. The generation of abnormal waves locally in the ionosphere appears to be possible, and it seems able to account for unusual motions sometimes observed.

Magnetospheric Multiscale Overview and Science Objectives

2015-05-29

J. L. Burch , T. E. Moore , R. B. Torbert +1 more

Magnetospheric Multiscale (MMS), a NASA four-spacecraft constellation mission launched on March 12, 2015, will investigate magnetic reconnection in the boundary regions of the Earth’s magnetosphere, particularly along its dayside boundary … Magnetospheric Multiscale (MMS), a NASA four-spacecraft constellation mission launched on March 12, 2015, will investigate magnetic reconnection in the boundary regions of the Earth’s magnetosphere, particularly along its dayside boundary with the solar wind and the neutral sheet in the magnetic tail. The most important goal of MMS is to conduct a definitive experiment to determine what causes magnetic field lines to reconnect in a collisionless plasma. The significance of the MMS results will extend far beyond the Earth’s magnetosphere because reconnection is known to occur in interplanetary space and in the solar corona where it is responsible for solar flares and the disconnection events known as coronal mass ejections. Active research is also being conducted on reconnection in the laboratory and specifically in magnetic-confinement fusion devices in which it is a limiting factor in achieving and maintaining electron temperatures high enough to initiate fusion. Finally, reconnection is proposed as the cause of numerous phenomena throughout the universe such as comet-tail disconnection events, magnetar flares, supernova ejections, and dynamics of neutron-star accretion disks. The MMS mission design is focused on answering specific questions about reconnection at the Earth’s magnetosphere. The prime focus of the mission is on determining the kinetic processes occurring in the electron diffusion region that are responsible for reconnection and that determine how it is initiated; but the mission will also place that physics into the context of the broad spectrum of physical processes associated with reconnection. Connections to other disciplines such as solar physics, astrophysics, and laboratory plasma physics are expected to be made through theory and modeling as informed by the MMS results.

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Fast Plasma Investigation for Magnetospheric Multiscale

2016-03-01

C. J. Pollock , T. E. Moore , A. D. Jacques +7 more

The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution … The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution to resolve kinetic-scale plasma dynamics. This increased resolution has been accomplished by placing four dual 180-degree top hat spectrometers for electrons and four dual 180-degree top hat spectrometers for ions around the periphery of each of four MMS spacecraft. Using electrostatic field-of-view deflection, the eight spectrometers for each species together provide 4pi-sr field-of-view with, at worst, 11.25-degree sample spacing. Energy/charge sampling is provided by swept electrostatic energy/charge selection over the range from 10 eV/q to 30000 eV/q. The eight dual spectrometers on each spacecraft are controlled and interrogated by a single block redundant Instrument Data Processing Unit, which in turn interfaces to the observatory's Instrument Suite Central Instrument Data Processor. This paper describes the design of FPI, its ground and in-flight calibration, its operational concept, and its data products.

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Initial ISEE magnetometer results: magnetopause observations

1978-12-01

C. T. Russell , R. C. Elphic

Detection of wave activity in measurements of thermospheric vertical winds and temperatures at subauroral latitudes

2025-06-25

A. Schmidt , J. W. Meriwether , Matthew Cooper +4 more | Frontiers in Astronomy and Space Sciences

The need for high precision measurements of vertical winds with uncertainties on the scale of 3–5 m <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"><mml:mrow><mml:msup><mml:mrow><mml:mtext>s</mml:mtext></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math> and a temporal cadence of 1–2 min to achieve detection … The need for high precision measurements of vertical winds with uncertainties on the scale of 3–5 m <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"><mml:mrow><mml:msup><mml:mrow><mml:mtext>s</mml:mtext></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math> and a temporal cadence of 1–2 min to achieve detection of gravity wave (GW) structure has made it exceedingly difficult to study the response of the thermosphere to the propagation of GW activity. Herein we present subauroral, midlatitude thermospheric wind and temperature observations using redline 630 nm measurements obtained with a 15 cm narrow field Fabry-Pérot Interferometer (FPI), named the Hot Oxygen Doppler Imager (HODI). These measurements were obtained in a first light campaign at Jeffer Observatory ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"><mml:mrow><mml:mn>41.03</mml:mn><mml:mo>°</mml:mo></mml:mrow></mml:math> N, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m3"><mml:mrow><mml:mn>74.83</mml:mn><mml:mo>°</mml:mo></mml:mrow></mml:math> W) located in Jenny Jump State Forest in northwestern New Jersey. The heightened sensitivity of HODI enables analysis of observations with uncertainties of approximately 3–5 m <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m4"><mml:mrow><mml:msup><mml:mrow><mml:mtext>s</mml:mtext></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math> for vertical wind speeds and 10–15 K for temperatures for 2-min exposures. Data was collected during periods of both geomagnetically quiet and active conditions, and GW structures were seen in both data sets. One detailed observation, taken the night of 25 July 2022, enabled the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m5"><mml:mrow><mml:mo>≈</mml:mo><mml:mn>90</mml:mn><mml:mo>°</mml:mo></mml:mrow></mml:math> phase shift between vertical winds and temperatures to be inferred, as per standard GW polarization relations with weak viscous dissipation. However, most other observations are found to have little correlation between the two series of temperature and vertical wind. We interpret this to be a result of the propagation and interaction of multiple GW events superimposed upon one another. Wave-like structures in the ionosphere observed in differential total electron count maps, or traveling ionospheric disturbances (TIDs), are often related to GW induced processes, and we provide comparisons of selected wave events observed by HODI to TIDs. These results suggest in a general sense that a relationship may exist between wave fluctuations seen in both the neutral atmosphere and the ionosphere. However, we suggest that the 35–70 km vertical extent of the 630 nm nightglow layer combined with an environment of multiple GW events with differing propagation speeds and vertical wavelengths may have the effect of diminishing or eliminating possible existing temperature and vertical wind correlation.

The atmospheric oxygen, hydrogen and helium responses for the extreme geomagnetic storm of 11 May 2024 over different regions

2025-06-24

Lake Endeshaw , Alene Seyoum , Amsalu Hundesa +1 more | Discover Atmosphere

Inductively Coupled Radio-frequency Plasmas as Solar Vacuum Ultraviolet Simulators

2025-06-23

J.L. Richmond , J. R. Machacek , Christine Charles +1 more | The Astrophysical Journal Supplement Series

Abstract The solar vacuum ultraviolet (VUV) is relevant to a variety of astrophysical phenomena. Radio-frequency (RF) plasmas of H 2 and H 2 /inert gas mixtures are convenient sources of … Abstract The solar vacuum ultraviolet (VUV) is relevant to a variety of astrophysical phenomena. Radio-frequency (RF) plasmas of H 2 and H 2 /inert gas mixtures are convenient sources of VUV for laboratory simulations. In previous work, we made extensive measurements of the emission spectra for the full range of H 2 plasmas mixed with He, Ne, and Ar. In this work, we examine these data in the context of simulating the solar VUV. It was found that a gas mixture of 35% H 2 : 65% Ar at 20 mTorr best mimics the solar spectrum in the range 110–160 nm. Spatially resolved optical measurements were used to estimate the spatial distribution of the plasma emissivity, and compared with photodiode measurements to estimate the total power emitted from the plasma in the VUV. At 400 W RF input power, approximately 32% (126 W) was emitted in the VUV spectral range, attenuated to 84.8 W by the MgF 2 window. Fluxes in the range 10–40 mW cm −2 were detected, varying with distance from the source aperture, enabling accelerated testing in a simulated space environment with up to 4000× equivalent solar VUV fluxes.

Enhancing the BDGIM model for ionospheric delay correction using GNSS LEO occultation data during high solar activity

2025-06-23

Haojie Liu , Xingliang Huo , Ting Zhang +2 more | GPS Solutions

A flexible ionospheric function model constructed with the aid of NeQuick model

2025-06-23

Lei Xu , Jingxiang Gao , Yibin Yao +1 more | GPS Solutions

Geometry-driven transport and heating of trapped particles in magnetospheric plasmas

2025-06-23

Mehmet Baran Ökten | EPL (Europhysics Letters)

Abstract This paper develops a geometry‐based framework for trapped‐particle dynamics in planetary magnetospheres by casting the guiding‐center Hamiltonian in Frenet–Serret coordinates, so that field‐line curvature and torsion drive particle drifts … Abstract This paper develops a geometry‐based framework for trapped‐particle dynamics in planetary magnetospheres by casting the guiding‐center Hamiltonian in Frenet–Serret coordinates, so that field‐line curvature and torsion drive particle drifts and adiabatic invariants. Envelope equations then capture ensemble phase‐space widths, oscillations and equilibrium scaling under geometric focusing. A minimal Lorentzian diffusion term reproduces resonant, wave‐driven drift‐shell broadening. Numerical tests on ideal dipole fields confirm the predicted scalings for curvature effects, drift‐shell width, envelope oscillation frequencies and broadening rates. This approach bridges microscopic Hamiltonian dynamics and macroscopic transport, and can be extended to realistic field geometries and in situ wave measurements for radiation‐belt modeling.

Estimation of Reconnection Rate From Soft X‐Ray Emission at the Earth's Dayside Magnetopause

2025-06-23

Ryota Momose , Yosuke Matsumoto , Yoshizumi Miyoshi | Geophysical Research Letters

Abstract We propose an approach to estimating the reconnection rate by utilizing soft X‐rays emitted during the solar wind charge exchange (SWCX) process at the Earth's magnetopause. Employing a high‐resolution … Abstract We propose an approach to estimating the reconnection rate by utilizing soft X‐rays emitted during the solar wind charge exchange (SWCX) process at the Earth's magnetopause. Employing a high‐resolution global magnetohydrodynamic (MHD) simulation model of the magnetosphere, we investigated the SWCX emission around the magnetopause during a coronal mass ejection event. Under these intense solar wind conditions, we observed that the current sheet in the dayside reconnection region is remarkably luminous, with the emission structure aligning closely with the reconnected magnetic field topology in the meridional plane. By calculating the opening angle of this bright region, we determined the reconnection rate to be 0.13. We compared this global rate with the one derived from the local reconnection electric field obtained in the MHD simulation. We suggest that coordinated remote and in situ observations of the reconnection region present an opportunity to bridge the gap between local and global reconnection rates.

Uncertainties in Theoretical Chorus Chirping Rates: A Comparative Analysis

2025-06-21

Zeyin Wu , Shangchun Teng , Yifan Wu +1 more | Geophysical Research Letters

Abstract Whistler‐mode chorus waves play a critical role in the dynamics of energetic electrons in the inner magnetosphere. Extensive theoretical research has been conducted to explain the frequency chirping of … Abstract Whistler‐mode chorus waves play a critical role in the dynamics of energetic electrons in the inner magnetosphere. Extensive theoretical research has been conducted to explain the frequency chirping of chorus waves, with two primary theoretical chirping rates proposed: one associated with magnetic field inhomogeneity and the other linked to wave amplitude. The validity of these chirping rates has been a subject of debate. In this study, we compare these two theoretical chirping rates using a data set of 3,166 lower‐band rising‐tone chorus wave elements from Van Allen Probes observations, evaluating their statistical performance. Our analysis shows that the chirping rate associated with magnetic field inhomogeneity exhibits better agreement with observations, demonstrating higher correlation and smaller standard deviation compared to the nonlinear chirping rate. These findings suggest that both chirping rates should be considered valid expressions for chorus waves, supporting a key prediction of a recently proposed theoretical model of chorus.

Construction of a High-Resolution Temperature Dataset at 40–110 KM over China Utilizing TIMED/SABER and FY-4A Satellite Data

2025-06-20

Qian Ye , Mohan Liu , Dan Du +1 more | Atmosphere

This study aims to develop a high-resolution temperature dataset from 40 km to 110 km over China by machine learning techniques, with a horizontal resolution of 0.5° × 0.5° and … This study aims to develop a high-resolution temperature dataset from 40 km to 110 km over China by machine learning techniques, with a horizontal resolution of 0.5° × 0.5° and vertical resolution of 1 km, utilizing measurements from SABER onboard the Thermosphere, Ionosphere, Mesosphere Energetics, and Dynamics (TIMED) and Fengyun 4A (FY-4A) satellites. Accurate temperature profiles play a critical role in understanding the atmospheric dynamics and climate change. However, because of the limitation of traditional detecting methods, the measurements of the upper stratosphere and mesosphere are rare. In this study, a new method is developed to construct a high-resolution temperature dataset over China in the middle atmosphere based on the XGBoost technique. The model’s performance is also validated based on rocket observations and ERA5 reanalysis data. The results indicate that the model effectively captures the characteristics of the vertical and seasonal variations in temperature, which provide a valuable opportunity for further research and improvement of climate models. The model demonstrates the highest accuracy below 80 km with RMSE < 12 K, while its performance decreases above 100 km, where RMSE can exceed 20 K, indicating optimal performance in the upper stratosphere and lower mesosphere regions.

An Analytical Model of Reconnection Rate in Electron-only Reconnection

2025-06-20

Zhan Hu , S. Y. Huang , Q. Y. Xiong +4 more | The Astrophysical Journal

Abstract Modeling the reconnection rate of collisionless electron-only reconnection presents a theoretical challenge. Unlike traditional magnetic reconnection with ion coupling, electron-only reconnection has a higher reconnection rate due to the … Abstract Modeling the reconnection rate of collisionless electron-only reconnection presents a theoretical challenge. Unlike traditional magnetic reconnection with ion coupling, electron-only reconnection has a higher reconnection rate due to the magnetic flux being frozen in the electron flow, which is constrained by the electron-Alfvénic velocity rather than the ion-Alfvénic velocity. Recent observations have revealed that the electron-only reconnection rate is about 0.23, which is at the high end of the theoretical range, and the electron flow velocity in the outflow region falls significantly below the electron-Alfvénic velocity. Based on MHD and gyrokinetic theory, we propose a steady-state analytical model to calculate the reconnection rate in electron-only reconnection. Our model demonstrates that the electric field generated in the outflow direction by the decoupling between ions and electrons in the outflow region plays a crucial role in suppressing electron-only reconnection. The plasma beta value negatively affects the reconnection rate in electron-only reconnection, i.e., the larger the plasma beta, the smaller the reconnection rate. The analytical results of our model align well with the reconnection rates reported in previous studies.

Electron-scale Magnetic Holes Generation Driven by Whistler-to-Bernstein Mode Conversion in Fully Kinetic Plasma Turbulence

2025-06-20

Joaquín Espinoza-Troni , Giuseppe Arrò , Felipe A. Asenjo +1 more | The Astrophysical Journal

Abstract Magnetic holes (MHs) are coherent structures characterized by a strong and localized magnetic field amplitude dip, commonly observed in the heliosphere. These structures come in different sizes, from magnetohydrodynamic … Abstract Magnetic holes (MHs) are coherent structures characterized by a strong and localized magnetic field amplitude dip, commonly observed in the heliosphere. These structures come in different sizes, from magnetohydrodynamic to kinetic scales. Subion-scale MHs are usually sustained by an electron current vortex and exhibit a strong electron temperature anisotropy, with higher temperatures perpendicular to the background magnetic field. Magnetospheric multiscale observations (MMSs) have revealed electron-scale MHs to be ubiquitous in the turbulent Earth’s magnetosheath and the solar wind, potentially playing an important role in the energy cascade and dissipation. Despite abundant observations, the origin of electron-scale MHs is still unclear and debated. In this work, we use fully kinetic simulations to investigate the role of plasma turbulence in generating electron-scale MHs. We find that the turbulence spontaneously produces electron-scale MHs via the following mechanism: first, large-scale turbulent velocity shears produce regions with high electron temperature anisotropy; these localized regions become unstable, generating oblique electron-scale whistler waves; as they propagate over the inhomogeneous turbulent background, whistler fluctuations develop an electrostatic component, turning into Bernstein-like modes; the strong electrostatic fluctuations produce current filaments that merge into an electron-scale current vortex; the resulting electron vortex locally reduces the magnetic field amplitude, finally evolving into an electron-scale MH. We show that MHs generated by this mechanism have properties consistent with MMSs and nontrivial kinetic features with a “mushroom”-shaped electron velocity distribution function. Our results have potential implications for understanding the formation and occurrence of electron-scale MHs in astrophysical turbulent and space environments, such as the Earth’s magnetosheath and the solar wind.

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Global Evolution, Energetics, and Origins of Auroral Streamers

2025-06-19

Ziyi Yang , Binzheng Zhang , W. Lotko +1 more | Geophysical Research Letters

Abstract An auroral streamer—a usually meridionally aligned, arc‐like feature that extend across the auroral oval. We performed a high‐resolution global magnetohydrodynamic simulation to characterize the evolution of streamers and their … Abstract An auroral streamer—a usually meridionally aligned, arc‐like feature that extend across the auroral oval. We performed a high‐resolution global magnetohydrodynamic simulation to characterize the evolution of streamers and their coupling to magnetotail drivers. The results show that streamers, which are a consequence of magnetotail flow bursts, strengthen as the simulation progresses. We calculated the contributions of different precipitating electron energy fluxes to streamer dynamics based on simple empirical proxies and found that monoenergetic precipitation dominates, followed by broadband, with little from diffuse precipitation. Poleward motion (∼1° magnetic latitude) of one streamer preceded its equatorward motion in the high‐resolution simulation. The simulation indicates that the poleward motion is caused by a sequential energy injection into the ionosphere from multiple bursty bulk flows propagating in succession. Our results provide an explanation for the poleward propagation of streamers and illustrate their global evolution and energetics in magnetotail dynamics.

Upper Atmosphere Responses to IPCC's Worst Scenario of CO2 Increase in the 21st Century

2025-06-19

Han Ma , Huixin Liu , Hanli Liu +1 more | Geophysical Research Letters

Abstract Over centuries, the increasing CO 2 emission has intensified the upper atmospheric cooling and contraction effects. To predict the impacts of CO 2 long‐term increase on the upper atmosphere … Abstract Over centuries, the increasing CO 2 emission has intensified the upper atmospheric cooling and contraction effects. To predict the impacts of CO 2 long‐term increase on the upper atmosphere in the future, a 90‐year simulation with CESM2/WACCM‐X is performed. It reveals prominent dynamical responses in addition to density responses reported before. (a) Main thermospheric parameters such as thermosphere temperature, neutral mass density, and electron density almost keep the decreasing trends; (b) The meridional circulation is strengthened especially in June; (c) The diurnal tides have a reduction/enhancement response above/below the 200 km in the thermosphere, while the semi‐diurnal tides decrease throughout the thermosphere. These results are in line with those previously obtained from the GAIA model, thus confirming the acceleration of the upper atmosphere circulation accompanying the cooling effect. The agreement also implies consistency between the two models in predicting the CO 2 impacts on the dynamics of the background thermosphere and ionosphere.

Formation of the Bubble‐Like Ionospheric Super‐Depletion Structure (BLISS): MAGE Simulation of the September, 2017 Storm

2025-06-19

Shanshan Bao , Wenbin Wang , V. G. Merkin +6 more | Geophysical Research Letters

Abstract This study investigates the formation of a newly identified storm‐time ionospheric phenomenon, the bubble‐like ionospheric super‐depletion structure (BLISS) in F‐region plasma densities. The observed BLISS initiates from the magnetic … Abstract This study investigates the formation of a newly identified storm‐time ionospheric phenomenon, the bubble‐like ionospheric super‐depletion structure (BLISS) in F‐region plasma densities. The observed BLISS initiates from the magnetic dip equator in the post‐sunset region and expands westward and poleward, reaching midlatitudes of ∼40°, which is distinct from equatorial plasma bubbles. The mechanism of BLISS formation remains unclear. To systematically study the driving processes for this phenomenon, we employ the Multiscale Atmosphere Geospace Environment (MAGE) model that fully couples the magnetosphere, ionosphere and thermosphere models. Our MAGE simulation successfully reproduced the observed BLISS event during the 8 September 2017 storm. It shows that the depletion is caused by the vertical E × B transport as it expands westward and poleward toward midlatitudes. Numerical experiments demonstrate that sudden enhancements in southward solar wind Bz induce strong prompt eastward penetration electric fields, which are the primary cause of the BLISS and its expansion.

The response of exospheric neutral hydrogen to weak geomagnetic disturbances between June 12 and 29, 2008

2025-06-19

Jochen Zoennchen , Gonzalo Cucho‐Padin | Frontiers in Astronomy and Space Sciences

Stereoscopic remote sensing observations of terrestrial far ultraviolet (Lyman-α at 121.6 nm) emissions at solar minimum have been used to retrieve the time-dependent response of the exospheric 3-D neutral hydrogen … Stereoscopic remote sensing observations of terrestrial far ultraviolet (Lyman-α at 121.6 nm) emissions at solar minimum have been used to retrieve the time-dependent response of the exospheric 3-D neutral hydrogen (H) density at radial distances of 3–6 Earth radii (R e ) to weak geomagnetic disturbances. This study includes continuous observations from the Lyman-α detectors (LADs) onboard NASA’s Two-Wide angle Imaging Neutral-atom Spectrometers (TWINS) 1 and 2 satellites between June 12 and 29, 2008, which covers two minor geomagnetic storms (June 15 and 25). For both storms, we derived the 3-D H-density distributions from prior and during-storm data with 12 h time intervals. The inversion is based on our new H-density EXPGRID model and incorporates the effects of Lyman-α absorption within the exosphere and Lyman-α re-emission from Earth’s albedo. We found that the H-density distributions at 3–6 R e are highly variable. They are correlated and vary in phase with exobase temperatures (from Naval Research Laboratory mass spectrometer and incoherent scatter (NRLMSIS)) during the geomagnetic events. Furthermore, the time dependency and amplitude of the H-density enhancement and the kp index were found to be similar. Because the kp index is assumed to be correlated with the varying size of the plasmasphere, this finding supports theories of physical interaction between the neutral exosphere and the plasmasphere. The disturbances with a significant effect on the neutral H atoms are initiated by a prior increase of the solar wind flow pressure and exobase temperatures (in particular, over the poles). Our time-dependent 3-D results indicate that the H-atom enhancement is not uniformly distributed over the shells. Instead, we found asymmetries (i.e., dawn/dusk near the ecliptic) and temporal evolving zones of regionally strong enhanced H densities. Among the first affected regions after onset are the vicinities of the geotail (at lower distances) and the North Pole (at upper distances). A ∼40% exobase temperature increase (NRLMSIS) at the South Pole on June 15 correlates with a strong H-atom enhancement in the southern hemisphere later this day. Finally, both storms show, at the upper distance, a remarkably delayed enhancement (peak values as late as ∼2 days after onset) of the H atoms density near the sub-solar point (dayside “nose” region).

Evaluation of GNSS ionosphere prediction models Klobuchar-GPS, NTCM-G, and BDGIM: methodology and results for 2021–2024

2025-06-18

Lambert Wanninger , Kim Thiemann | GPS Solutions

Abstract As part of their satellite navigation messages, GPS, Galileo, and BDS broadcast coefficients of ionosphere prediction models. These models are intended to be used for the improvement of single-frequency … Abstract As part of their satellite navigation messages, GPS, Galileo, and BDS broadcast coefficients of ionosphere prediction models. These models are intended to be used for the improvement of single-frequency code-based positioning. We compared vertical electron content derived from these models with those of the more accurate post-processing ionosphere model produced by the International GNSS Service (IGS). On a global scale and for the time period 2021–2024, the Klobuchar-GPS model corrects on average about 59% of the vertical ionospheric delays, the NTCM-G model and a slightly modified BDGIM model give a correction rate of about 74%, while the combination of the latter two models gives a correction rate of 77%. In the case of strong geomagnetic storms with large effects on the ionospheric total electron content, the performance of the prediction models degrades and the global daily correction rates may even drop to below 50%. Single-frequency GNSS receivers with access to all GNSS are recommended to apply ionospheric corrections based on the ionosphere model coefficients and algorithms of Galileo/NTCM-G or BDS/modified BDGIM, or a combination of both. The Klobuchar-GPS model should serve as a backup in case that Galileo and BDS navigation messages are not available.

The Kappa distribution function's impact on EMIC waves in multi-ions magneto-plasma

2025-06-18

Rahul Bhaisaniya , G. Ahirwar | Indian Journal of Physics

SpatioTECformer: Global ionospheric VTEC Forecasting via spatio-temporal modeling and adaptive driver fusion

2025-06-18

Jiawen Chen , Han Zhao , J.W.H. Chi +2 more | Research Square (Research Square)

<title>Abstract</title> The ionosphere plays a vital role in energy exchange between Earth and outer space, and its dynamic variations significantly impact satellite navigation and radio communication. Vertical Total Electron Content … <title>Abstract</title> The ionosphere plays a vital role in energy exchange between Earth and outer space, and its dynamic variations significantly impact satellite navigation and radio communication. Vertical Total Electron Content (VTEC), a key parameter that quantifies ionospheric electron density, is critical for space weather monitoring and Global Navigation Satellite System (GNSS) error correction. However, current forecasting models struggle to accurately represent spatial heterogeneity, capture long-range temporal dependencies, and remain robust under external disturbances such as geomagnetic storms. We propose SpatioTECformer, a novel model that integrates local and global spatiotemporal features to accurately forecast VTEC dynamics. It employs a Transformer encoder for long-sequence temporal modeling, an enhanced convolutional neural network (CNN) module for spatial feature extraction, and an adaptive feature fusion module to integrate solar wind and geomagnetic indices. Validation on Global Ionospheric Map (GIM) data from the Center for Orbit Determination in Europe (CODE) shows that SpatioTECformer achieves state-of-the-art performance, with RMSE and MAE of 1.80 and 1.23 TECU in 2014 (high solar activity), and improved values of 0.78 and 0.58 TECU in 2017 (low solar activity). The model exhibits superior robustness and predictive accuracy across global regions, particularly within the Equatorial Ionization Anomaly (EIA) zone and under geomagnetic disturbance conditions. The source code is publicly available at: https://github.com/jiawenchen1011/SpatioTECformer.

Deep Learning for Ionogram Parameter Extraction: A Time-Series Approach to Ionospheric Monitoring

2025-06-18

Armando Castro Chaupis , Danny Scipión , Percy Condor +1 more | EarthArXiv (California Digital Library)

Ionograms provide a direct measurement of the ionosphere’s electron density profile and its irregularities. By examining critical frequencies researchers can identify key parameters—such as the F region critical frequency (foF2), … Ionograms provide a direct measurement of the ionosphere’s electron density profile and its irregularities. By examining critical frequencies researchers can identify key parameters—such as the F region critical frequency (foF2), the height of maximum electron density (hmF2), and the presence of Spread F irregularities—that are vital for understanding signal propagation, space weather effects, and radio communication reliability. Over the past decades, tools have been developed for the extraction of ionospheric parameters of ionograms: ARTIST-5 and among others. There are approximations in previous works using deep learning for automatic scaling with parameters extraction of great importance as the identification of the E and F2 layer. These tools generally work for relatively quiet days (QD), but not for days with Spread-F, where a lot of variability is observed in the parameters obtained in those days and manual correction is necessary. In this work, we trained a model combining Convolutional Neuronal Network (CNN), Long Short-Term Memory (LSTM) and Dense layers that can capture the short-term variability of the ionosphere and our model returns the frequency profile. Ionograms were recollected from VIPIR ionosondes, part of the Low-Latitude Ionospheric Sensor Network (LISN). We tested and compared the frequency profiles from our model with manual correction and parameters obtained with ARTIST 5.0 showing significant differences.

Characteristics of temporal and spatial variation of the electron density in the plasmasphere and ionosphere during the May 2024 super geomagnetic storm

2025-06-18

Atsuki Shinbori , Naritoshi Kitamura , Kazuhiro Yamamoto +7 more | Research Square (Research Square)

<title>Abstract</title> The spatial distribution of electron density in the ionosphere exhibits notable variability and undergoes considerable changes during storms and substorms driven by solar wind disturbances. Electron density variations and … <title>Abstract</title> The spatial distribution of electron density in the ionosphere exhibits notable variability and undergoes considerable changes during storms and substorms driven by solar wind disturbances. Electron density variations and irregularities can cause total signal blackouts during strong scintillation periods and enhance satellite positioning errors. We analyzed Global Navigation Satellite System (GNSS) - total electron content (TEC) and Arase satellite observation data to elucidate the characteristics of the electron density variation in the plasmasphere and ionosphere during the May 2024 super storm. To identify the electron density variation in the ionosphere, we calculated the ratio of the TEC difference (rTEC), which is defined as the difference from the 10-quiet-day average TEC normalized by the average value. Additionally, we estimated the electron density in the plasmasphere and inner magnetosphere from the upper frequency limit of the upper hybrid resonance (UHR) waves observed by the Arase satellite. Consequently, an L-t plot of the electron density showed that the plasmasphere contracted from L = 7.0 to L = 1.5 within 9 h after a sudden commencement. During the storm recovery phase, the plasmapause gradually shifted to a higher L-shell. The electron density in the plasmasphere recovered the geomagnetically quiet-time level on a 4-day scale. The timescale of the plasmaspheric refilling was much longer than that of other coronal mass ejection (CME)-driven storms during the Arase era. The rTEC in the Northern Hemisphere showed that an enhancement in the rTEC value occurred at high latitudes (60°–70° in magnetic latitude (MLAT)) in the daytime (10–14 in magnetic local time (MLT)), approximately 1 h after the storm onset. Subsequently, a tongue of ionization (TOI) formed in the polar cap owing to the enhancement of two-cell convection in the high-latitude ionosphere. The rTEC was globally depleted during the storm recovery phase. The depletion indicates the occurrence of a negative storm owing to a neutral composition (O/N2) change driven by the energy input from the magnetosphere in the high-latitude thermosphere. The coincidence of the long refilling timescale of the plasmasphere and the depletion of the rTEC suggests that a strong negative storm impedes plasmaspheric refilling.

The Auroral Vortex and Rolling Magnetic Carpet

2025-06-17

X. Zhou , D. L. Hampton | Geophysical Research Letters

Abstract We report a nightside array of cylindrical auroral vortices observed at four wavelengths on 1 January 2024 from Poker Flat, Alaska. A pre‐existing east–west arc just south of the … Abstract We report a nightside array of cylindrical auroral vortices observed at four wavelengths on 1 January 2024 from Poker Flat, Alaska. A pre‐existing east–west arc just south of the site began beading from the west, evolving into curls and then spirals while extending eastward, initiating a substorm expansion within ∼2 min. The vortices were seen in all four wavelengths at 427.8, 557.7, 630.0, and 1100.0 nm, indicating a ∼200 km‐tall cylinder spanning 100–300 km altitude. Vortex dimensions were ∼30 × 40 km (east–west × north–south). Estimated average energy and energy flux were 4–6 keV and 30–40 mW/m 2 . The auroral morphology suggests that a remote shear force triggered the Kelvin–Helmholtz instability, generating local vortices that rolled up the magnetic flux like coiling a carpet. Upward field‐aligned currents (downward electrons) warped with the rolling magnetic carpet, producing a spiraling auroral footprint in the ionosphere.

Deterministic chaos in modulated multi-cell drifts of localized lower-hybrid oscillations excited by high-frequency waves in the ionosphere

2025-06-17

T. B. Leyser | Annales Geophysicae

Abstract. The prominent broad upshifted maximum (BUM) feature in electromagnetic emissions stimulated by powerful high-frequency radio waves in the ionosphere exhibits an exponential spectrum for pump frequencies near a harmonic … Abstract. The prominent broad upshifted maximum (BUM) feature in electromagnetic emissions stimulated by powerful high-frequency radio waves in the ionosphere exhibits an exponential spectrum for pump frequencies near a harmonic of the ionospheric electron gyro frequency. Exponential power spectra are a characteristic of deterministic chaos. In the present treatment, a two-fluid model is derived for lower-hybrid (LH) oscillations driven by parametric interaction of the electromagnetic pump field, the electron Bernstein mode, and the upper-hybrid mode, as previously proposed to interpret the BUM. In two-dimensional geometry across the geomagnetic field, LH oscillations localized in cylindrical density depletions are associated with multi-cell plasma drift patterns. The numerical simulations show that topological modulations of the drift can give rise to approximately Lorentzian-shaped pulses in the LH time signal. For parameter values typical of the ionospheric experiments, the exponential power spectrum of the Lorentzian pulses has a slope that is consistent with the slope of the BUM spectrum. The BUM spectral structure is therefore attributed to deterministic chaos in LH dynamics.

Spacetime profile of electromagnetic fields in intermediate-energy heavy-ion collisions

2025-06-17

NULL AUTHOR_ID | Physical review. C

Ionospheric Time Series Prediction Method Based on Spatio-Temporal Graph Neural Network

2025-06-16

Yifei Chen , Yang Liu , Kun‐Lin Yang +3 more | Atmosphere

Predicting global ionospheric total electron content (TEC) is critical for high-precision GNSS applications, but some existing models fail to jointly capture spatial heterogeneity and multiscale temporal trends. To address the … Predicting global ionospheric total electron content (TEC) is critical for high-precision GNSS applications, but some existing models fail to jointly capture spatial heterogeneity and multiscale temporal trends. To address the problem, this work proposes a spatio-temporal graph neural network (STGNN) that addresses these limitations through (1) a trainable positional attention mechanism to dynamically infer node dependencies without fixed geographical constraints and (2) a GRU–Transformer sequential module to hierarchically model local and global temporal patterns. The proposed network is validated by different solar and geomagnetic activities. With a training dataset with a time span between 2008 and 2018, the proposed model is tested in a high solar phase for the year 2015 and a low solar phase for the year 2018. For 2015, the experimental results show a 21.9% RMSE reduction at low latitudes compared to the results of the iTransformer model. For the geomagnetic storm event, the proposed STGNN achieves 16.0% higher stability. For the one-week (84 step) prediction test, the STGNN shows a 27.0% lower error compared to the MLPMultivariate model. The model’s self-adaptive spatial learning and multiscale temporal modeling uniquely enable TEC forecasting under diverse geophysical conditions.

Impact of Increasing Greenhouse Gases on the Ionosphere and Thermosphere Response to a May 2024‐Like Geomagnetic Superstorm

2025-06-14

N. M. Pedatella , Huixin Liu , Hanli Liu +2 more | Geophysical Research Letters

Abstract The Community Earth System Model (CESM) Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM‐X) is used to investigate how the ionosphere‐thermosphere response to a May 2024‐like geomagnetic storm … Abstract The Community Earth System Model (CESM) Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM‐X) is used to investigate how the ionosphere‐thermosphere response to a May 2024‐like geomagnetic storm changes with increasing greenhouse gases. Coupled CESM(WACCM‐X) simulations are first performed following the Coupled Model Intercomparison Project Phase 6 Shared Socioeconomic Pathway 5–8.5 from 2000 to 2090. The May 2024 geomagnetic superstorm is then simulated in 2016, 2040, 2061, and 2084, corresponding to surface levels of 403, 500, 652, and 918 ppmv, respectively. The CESM(WACCM‐X) simulations indicate that increasing levels of weakens the absolute neutral density response at 350 km. However, the relative response is increased with increasing levels of , which is partly due to the decrease in the background neutral density. Due to a weaker response in thermosphere composition and meridional neutral winds, the ionospheric response in absolute terms also weakens with increasing levels of .

Quantifying Spatial and Temporal Extents of Plasmaspheric Hiss Through Modeling of POES/MetOp Electron Observations

2025-06-14

Zhi‐Gu Li , Weichao Tu , R. S. Selesnick +2 more | Geophysical Research Letters

Abstract We present a novel method to quantify the event‐specific spatial evolution of plasmaspheric hiss wave power using a Drift‐Diffusion model. Constrained by Polar Operational Environmental Satellites/Meteorological Operational Satellites data, … Abstract We present a novel method to quantify the event‐specific spatial evolution of plasmaspheric hiss wave power using a Drift‐Diffusion model. Constrained by Polar Operational Environmental Satellites/Meteorological Operational Satellites data, the model simulates low‐altitude electron distributions, accounting for azimuthal drift, pitch‐angle diffusion, and atmospheric backscatter. Applying to an event on 15 October 2016, the model quantifies the spatial evolution of hiss waves at L = 3.9, which contributes to the steady decay of electron flux observed by Van Allen Probes (VAPs). The model reproduces local‐time dependent features and shows excellent agreement with hiss wave power observed by VAPs. The model shows increased wave power and spatial spread following increased activities in the AL‐index, consistent with previous statistical results. The model also suggests the presence of “low”‐frequency hiss, which was undetected by VAPs, likely masked by instrument noise. This is the first time low‐altitude measurements are used to quantify event‐specific wave distributions which include both diffusion and drift effects.

A numerical approach for modelling the polarisation signals of strong resonance lines with partial frequency redistribution. Applications to two-term atoms and plane-parallel atmospheres

2025-06-13

Fabio Riva , Gioele Janett , Luca Belluzzi +6 more | Astronomy and Astrophysics

The main goal of this paper is to present an accurate and efficient numerical strategy for solving the radiative transfer problem for polarised radiation in strong resonance lines forming out … The main goal of this paper is to present an accurate and efficient numerical strategy for solving the radiative transfer problem for polarised radiation in strong resonance lines forming out of local thermodynamic equilibrium while taking angle-dependent partial frequency redistribution (PRD) effects and J-state interference into account. We considered the polarisation produced both by the Zeeman effect and by the scattering of anisotropic radiation along with its sensitivity to the Hanle and magneto-optical effects. We introduce a formalism that allows for treating both a two-level and a two-term atom in the presence of arbitrary magnetic and bulk velocity fields. The problem is formulated by treating the population of the lower level or term as a fixed input parameter. This approach makes the problem linear with respect to the radiation field, enabling the application of efficient matrix-free preconditioned iterative methods for its solution. Additionally, the computation of the scattering emissivity in the co-moving frame, together with a careful choice of the angular and spectral quadrature nodes, allowed us to speed up the calculations by reducing the number of evaluations of the redistribution functions. We applied the proposed solution strategy in order to synthesise the Stokes profiles of the Mg ii h&k doublet and the H i Ly-α line in 1D semi-empirical models. The results demonstrate that the method is both fast and accurate. A comparison with calculations from HanleRT-TIC displayed an overall good agreement, thereby validating our solution strategy. Moreover, for the wavelength-integrated polarisation profiles of the H i Ly-α line, we found an excellent agreement between the results obtained including PRD effects in their general angle-dependent description and those obtained considering the angle-averaged simplifying approximation.

Enhanced gas-surface scattering modeling for VLEO satellites in DSMC simulations

2025-06-13

M.H.M. Schutte , Stefanos Fasoulas , Marcel Pfeiffer | CEAS Space Journal

Global equatorial F- and E-region ionospheric irregularities from COSMIC-RO and SCINDA-GNSS observations

2025-06-13

Aramesh Seif , Sampad Kumar Panda , S. M. Bailey | Journal of Applied Geodesy

Abstract This study utilizes data from the FORMOSAT-3/Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation (COSMIC-RO) observations and ground-based Scintillation Network Decision Aid (SCINDA) GNSS recordings at four … Abstract This study utilizes data from the FORMOSAT-3/Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation (COSMIC-RO) observations and ground-based Scintillation Network Decision Aid (SCINDA) GNSS recordings at four longitudinal stations situated in the vicinity of the magnetic equator for probing the characteristics of the ionospheric F and E region irregularities in the equatorial region. We utilize the amplitude scintillation index (S4) derived from these datasets to understand the morphology of nighttime and daytime plasma irregularities in the equatorial ionosphere. By combining ground-based data with a limb-viewing geometry from space, valuable complementary information has been obtained on the nighttime/daytime scintillation occurrences and their morphological associations with the equatorial irregularities in the F (equatorial plasma bubbles, EPB) and E (sporadic E layer; Es) region ionosphere. The occurrence of amplitude scintillation retrieved from COSMIC RO data was calculated to analyze its diurnal and seasonal variations. By conducting a statistical analysis on a dataset in 2013, we observed that the occurrence of ionospheric scintillation, as measured by both techniques, displayed similar variations. In this study, it is observed that scintillation in daytime is associated with Es and is predominantly seen over the Asian sector whilst nighttime scintillation associated with plasma bubbles is most frequently observed in the African sector. These results emphasize the need for RO profiles from active missions to serve as effective tools for monitoring scintillation events both regionally and globally.

Temporal and Spatial Analysis of the Impact of the 2015 St. Patrick’s Day Geomagnetic Storm on Ionospheric TEC Gradients and GNSS Positioning in China Using GIX and ROTI Indices

2025-06-12

Zhihao Fu , Ningbo Wang , Xuhui Shen +1 more | Remote Sensing

Geomagnetic storms induce ionospheric disturbances, significantly affecting Global Navigation Satellite System (GNSS) positioning accuracy. This study investigates how geomagnetic storm-induced ionospheric irregularities influence GNSS Precise Point Positioning (PPP), using data … Geomagnetic storms induce ionospheric disturbances, significantly affecting Global Navigation Satellite System (GNSS) positioning accuracy. This study investigates how geomagnetic storm-induced ionospheric irregularities influence GNSS Precise Point Positioning (PPP), using data from approximately 260 GNSS stations across China during 15 storm events between 1 January and 30 June 2015. We applied two indices—the Gradient Ionosphere Index (GIX), representing spatial gradients of vertical total electron content (VTEC), and the Rate of TEC Index (ROTI), describing temporal TEC variations. The analysis identified the St. Patrick’s Day geomagnetic storm (17 March 2015) as causing the most pronounced ionospheric disruptions, with significant east–west TEC gradients (|GIXx,P95| > 50 mTECU/km) consistently associated with substantial PPP errors (>0.5 m). Spatial analyses further indicated that significant 3D PPP errors (PPP, P95 > 0.4 m) closely overlapped with regions experiencing intense east–west TEC gradients, predominantly in the 20–35°N latitude band. Further analysis indicated notable pre-storm ionospheric enhancements driven by zonal electric fields, distinct ionospheric suppression associated with westward disturbance dynamo electric fields (DDEFs) on 18 March, and re-intensification due to eastward penetration electric fields (PEFs) on 19 March.

Editorial: Magnetosheaths

2025-06-12

Zerefşan Kaymaz , X. Blanco‐Cano , Y. Lin +4 more | Frontiers in Astronomy and Space Sciences

Streamer‐Like Red Line Diffuse Auroras Driven by Time Domain Structures Associated With Electron Injection and Braking Ion Flows

2025-06-12

Yangyang Shen , Xu Zhang , Jun Liang +5 more | Geophysical Research Letters

Abstract Auroral streamers are important meso‐scale processes that transport plasma and magnetic energy and drive dynamic magnetosphere‐ionosphere (MI) coupling and space weather. Although streamers are typically studied using imagers sensitive … Abstract Auroral streamers are important meso‐scale processes that transport plasma and magnetic energy and drive dynamic magnetosphere‐ionosphere (MI) coupling and space weather. Although streamers are typically studied using imagers sensitive to energetic (1 keV) electron precipitation, such as all‐sky imagers, some are associated with low‐energy (1 keV) precipitation better captured by red‐line auroral emissions. This paper reports such streamer‐like red‐line auroras observed poleward of a black aurora and an auroral torch, associated with a magnetospheric electron injection and braking ion flows. Using conjugate space‐ground observations, quasilinear theory, and auroral forward modeling, we establish the first direct linkage between streamer‐like red‐line auroras and plasma sheet electron pitch‐angle scattering by time‐domain structures. These results underscore the importance of wave‐driven diffuse auroral processes in generating low‐energy auroral streamers, distinct from the conventional quasi‐electrostatic coupling paradigm.