Biochemistry, Genetics and Molecular Biology › Molecular Biology

Geomagnetism and Paleomagnetism Studies

Works Count: 76778

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This cluster of papers focuses on the formation of magnetosomes in prokaryotes, the study of geomagnetic field variations over centuries, the application of dynamo simulations, and the analysis of magnetic properties and biomineralization processes. It also includes research on paleomagnetic data, environmental magnetism, and the development of geomagnetic models.

Keywords

Magnetosome Formation; Geomagnetic Field; Magnetotactic Bacteria; Paleomagnetic Data; Dynamo Simulations; Magnetic Properties; Biomineralization; Secular Variation; Geomagnetic Model; Environmental Magnetism

Magnetic anisotropy of rocks and its application in geology and geophysics

1982-04-01

Frantis̆ek Hrouda

Paleomagnetism: magnetic domains to geologic terranes

1992-06-01

Robert F. Butler

Introduction to geomagnetism Ferromagnetic minerals Origins of natural remanent magnetism Sampling, measurement, and display of NRM Paleomagnetic stability Statistics of paleomagnetic data Paleomagnetic poles Special topics in rock magnetism Geochronologic … Introduction to geomagnetism Ferromagnetic minerals Origins of natural remanent magnetism Sampling, measurement, and display of NRM Paleomagnetic stability Statistics of paleomagnetic data Paleomagnetic poles Special topics in rock magnetism Geochronologic applications Applications to paleogeography Applications to regional tectonics Appendix: Derivations

Scientific and Clinical Applications of Magnetic Carriers

1997-01-01

Urs O. Häfeli , Wolfgang Schütt , Joachim Teller +1 more

The fit of the continents around the Atlantic

1965-10-28

E. C. Bullard , James E. Everett , Alan G. Smith

The geometrical fit of the continents now separated by oceans has long been discussed in relation to continental drift. This paper describes fits made by numerical methods, with a ‘least … The geometrical fit of the continents now separated by oceans has long been discussed in relation to continental drift. This paper describes fits made by numerical methods, with a ‘least squares’ criterion of fit, for the continents around the Atlantic ocean. The best fit is found to be at the 500 fm. contour which lies on the steep part of the continental edge. The root-mean-square errors for fitting Africa to South America, Greenland to Europe and North America to Greenland and Europe are 30 to 90 km. These fits are thought not to be due to chance, though no reliable statistical criteria are available. The fit of the block assembled from South America and Africa to that formed from Europe, North America and Greenland is much poorer. The root-mean-square misfit is about 130 km. These geometrical fits are regarded as a preliminary to a comparison of the stratigraphy, structures, ages and palaeomagnetic results across the joins.

A UNIFYING THEORY OF HIGH-LATITUDE GEOPHYSICAL PHENOMENA AND GEOMAGNETIC STORMS

1961-10-01

W. I. Axford , C. O. Hines

This paper is concerned with the occurrence at high latitudes of a large number of geophysical phenomena, including geomagnetic agitation and bay disturbances, aurorae, and various irregular distributions of ionospheric … This paper is concerned with the occurrence at high latitudes of a large number of geophysical phenomena, including geomagnetic agitation and bay disturbances, aurorae, and various irregular distributions of ionospheric electrons. It shows that these may all be related in a simple way to a single causal agency, namely, a certain convection system in the outer portion of the earth's magnetosphere. The source of this convection is taken to be a viscous-like interaction between the magnetosphere and an assumed solar wind, though other sources of an equivalent nature may also be available. The model is capable of accounting for many aspects of the phenomena concerned, including the morphology of auroral forms and the occurrence of 'spiral' patterns in the loci of maximum intensities of several features. It also bears directly on the steady state of the magnetosphere, and in particular on the production of trapped particles in the outer Van Allen belt. In short, it provides a new basis on which a full understanding of these several phenomena may in time be built.

Magnetic Anomalies Over Oceanic Ridges

1963-09-01

F. J. Vine , D. H. Matthews

Phanerozoic polar wander, palaeogeography and dynamics

2012-07-09

Trond H. Torsvik , Rob Van der Voo , Ulla Preeden +7 more

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Cosmic ray contributions to dose rates for luminescence and ESR dating: Large depths and long-term time variations

1994-04-01

J.R. Prescott , J.T. Hutton

Some theoretical aspects of rock-magnetism

1955-04-01

Louis Néel

Summary The memoir is devoted to a brief theoretical study of the most typical magnetic properties of rocks. In particular §§ 3–16 are on ferrimagnetism, §§ 17–35 on single domain … Summary The memoir is devoted to a brief theoretical study of the most typical magnetic properties of rocks. In particular §§ 3–16 are on ferrimagnetism, §§ 17–35 on single domain particles and §§ 36–57 on large multi-domain particles. Theoretical studies are made of the following aspects of the subject and compared with the experimental results: remanent magnetization (§ 38), initial susceptibility (§ 39), variation with applied field of thermoremanent magnetization (abbreviated to T.R.M.) (§§ 40, 41, 57), the ratio Qk of T.R.M. acquired in a given field to the induced magnetization in the same field (§ 42), the additivity of partial T.R.M.'s in the case both of small grains (§ 28) and large grains (§ 57). Considerable space is devoted to the magnetic 'viscosity' due to thermal agitation in small grains (§§ 24–27) and in larger ones (§§ 49–56). Expressions are given for magnetic 'viscosity' in the range of Rayleigh's relations (§ 51) particularly with a demagnetizing field present (§ 54). The theoretical and experimental results on the irreversible decrease in isothermal remanent magnetization are briefly quoted both for small (§ 30) and large (§ 55) grains. Different reversing mechanisms are reviewed which could cause a negative T.R.M., that is one directed in the opposite sense to the field applied during cooling. Some are related to negative Weiss-Heisenberg exchange forces: reversal by diffusion involving ionic exchange between the two sub-lattices in a ferrimagnetic (§ 7), reversal by anomalous thermal variation is spontaneous magnetization (§§ 11, 12), reversal by diffusion with complete change of composition (§ 16). The others are effects of the demagnetizing field: reversal in mixtures of two constituents with different Curie Points (§§ 31–34), reversal by segregation, allotropy and chemical alteration (§ 35). The actual examples so far known are recalled.

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Rock Magnetism: Fundamentals and Frontiers

1998-09-01

David J. Dunlop , Özden Özdemir , Michael D. Fuller

Share Icon Share Twitter Facebook Reddit LinkedIn Reprints and Permissions Cite Icon Cite Search Site Citation David Dunlop, Özden Özdemir, Michael D. Fuller; Rock Magnetism: Fundamentals and Frontiers. Physics Today … Share Icon Share Twitter Facebook Reddit LinkedIn Reprints and Permissions Cite Icon Cite Search Site Citation David Dunlop, Özden Özdemir, Michael D. Fuller; Rock Magnetism: Fundamentals and Frontiers. Physics Today 1 September 1998; 51 (9): 64–66. https://doi.org/10.1063/1.882466 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentPhysics Today Search Advanced Search

Characterization of the magnetic fabric of rocks

1981-11-01

Vit Jelínek

Statistical Analysis of Circular Data.

1995-06-01

Nicholas Lange , N. I. Fisher

Preface 1. The purpose of the book 2. Survey of contents 3. How to use the book 4. Notation, terminology and conventions 5. Acknowledgements Part I. Introduction: Part II. Descriptive … Preface 1. The purpose of the book 2. Survey of contents 3. How to use the book 4. Notation, terminology and conventions 5. Acknowledgements Part I. Introduction: Part II. Descriptive Methods: 2.1. Introduction 2.2. Data display 2.3. Simple summary quantities 2.4. Modifications for axial data Part III. Models: 3.1. Introduction 3.2. Notation trigonometric moments 3.3. Probability distributions on the circle Part IV. Analysis of a Single Sample of Data: 4.1. Introduction 4.2. Exploratory analysis 4.3. Testing a sample of unit vectors for uniformity 4.4. Nonparametric methods for unimodal data 4.5. Statistical analysis of a random sample of unit vectors from a von Mises distribution 4.6. Statistical analysis of a random sample of unit vectors from a multimodal distribution 4.7. Other topics Part V. Analysis of Two or More Samples, and of Other Experimental Layouts: 5.1. Introduction 5.2. Exploratory analysis 5.3. Nonparametric methods for analysing two or more samples of unimodal data 5.4. Analysis of two or more samples from von Mises distributions 5.5. Analysis of data from more complicated experimental designs Part VI. Correlation and Regression: 6.1. Introduction 6.2. Linear-circular association and circular-linear association 6.3. Circular-circular association 6.4. Regression models for a circular response variable Part VII. Analysis of Data with Temporal or Spatial Structure: 7.1. Introduction 7.2. Analysis of temporal data 7.3. Spatial analysis Part VIII. Some Modern Statistical Techniques for Testing and Estimation: 8.1. Introduction 8.2. Bootstrap methods for confidence intervals and hypothesis tests: general description 8.3. Bootstrap methods for circular data: confidence regions for the mean direction 8.4. Bootstrap methods for circular data: hypothesis tests for mean directions 8.5. Randomisation, or permutation, tests Appendix A. Tables Appendix B. Data sets References Index.

Hydromagnetic Dynamo Models.

1955-09-01

E. N. Parker

view Abstract Citations (1638) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hydromagnetic Dynamo Models. Parker, Eugene N. Abstract The purpose of this paper is to … view Abstract Citations (1638) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hydromagnetic Dynamo Models. Parker, Eugene N. Abstract The purpose of this paper is to investigate the steady-state amplification of magnetic fields in a fluid It is shown that a rotating sphere of conducting fluid can regenerate a dipole magnetic field. It is sufficient for the angular velocity of rotation to vary with distance from the axis of rotation and for cyclonic fluid motions to be present The nonuniform rotation generates a toroidal field from the dipole field; the cyclones generate, from the toroidal field, loops of flux in the meridional plane which coalesce to amplify the dipole field The rotating sphere is discussed in relation to the liquid core of the earth and the geomagnetic dipole field. If, instead of a rotating sphere, one has a prismatic volume of fluid, it is possible to construct migratory dynamo waves The dynamo waves are discussed in relation to the solar convective zone; it is shown that such waves can account for many of the principal features of the observed solar magnetic activity Publication: The Astrophysical Journal Pub Date: September 1955 DOI: 10.1086/146087 Bibcode: 1955ApJ...122..293P full text sources ADS |

Cosmical magnetic fields

1978-05-01

R. Hide

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The degree of knottedness of tangled vortex lines

1969-01-16

H. K. Moffatt

Let u(x) be the velocity field in a fluid of infinite extent due to a vorticity distribution w(x) which is zero except in two closed vortex filaments of strengths K … Let u(x) be the velocity field in a fluid of infinite extent due to a vorticity distribution w(x) which is zero except in two closed vortex filaments of strengths K 1 , K 2 . It is first shown that the integral \[ I=\int{\bf u}.{\boldmath \omega}\,dV \] is equal to α K 1 K 2 where α is an integer representing the degree of linkage of the two filaments; α = 0 if they are unlinked, ± 1 if they are singly linked. The invariance of I for a continuous localized vorticity distribution is then established for barotropic inviscid flow under conservative body forces. The result is interpreted in terms of the conservation of linkages of vortex lines which move with the fluid. Some examples of steady flows for which I ± 0 are briefly described; in particular, attention is drawn to a family of spherical vortices with swirl (which is closely analogous to a known family of solutions of the equations of magnetostatics); the vortex lines of these flows are both knotted and linked. Two related magnetohydrodynamic invariants discovered by Woltjer (1958 a, b ) are discussed in ±5.

Apparent and true polar wander and the geometry of the geomagnetic field over the last 200 Myr

2002-11-01

Jean Besse , Vincent Courtillot

We have constructed new apparent polar wander paths (APWPs) for major plates over the last 200 Myr. Updated kinematic models and selected paleomagnetic data allowed us to construct a master … We have constructed new apparent polar wander paths (APWPs) for major plates over the last 200 Myr. Updated kinematic models and selected paleomagnetic data allowed us to construct a master APWP. A persistent quadrupole moment on the order of 3% of the dipole over the last 200 Myr is suggested. Paleomagnetic and hot spot APW are compared, and a new determination of “true polar wander” (TPW) is derived. Under the hypothesis of fixed Atlantic and Indian hot spots, we confirm that TPW is episodic, with periods of (quasi) standstill alternating with periods of faster TPW (in the Cretaceous). The typical duration of these periods is on the order of a few tens of millions of years with wander rates during fast tracks on the order of 30 to 50 km/Myr. A total TPW of some 30° is suggested for the last 200 Myr. We find no convincing evidence for episodes of superfast TPW such as proposed recently by a number of authors. Comparison over the last 130 Myr of TPW deduced from hot spot tracks and paleomagnetic data in the Indo‐Atlantic hemisphere with an independent determination for the Pacific plate supports the idea that, to first order, TPW is a truly global feature of Earth dynamics. Comparison with numerical modeling estimates of TPW shows that all current models still fail to some extent to account for the observed values of TPW velocity and for the succession of standstills and tracks which is observed.

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Geochronology and thermochronology by the [40]Ar/[39]Ar method

1988-01-01

Ian McDougall , T. Mark Harrison

1. Historical introduction 2. Basis of the 40AR/39AR dating method 3. Technical aspects 4. 40AR/39AR data presentation and interpretation App.4.1 Isochron analysis 5. Diffusion theory and measurements: App.5.1 Derivation ofthe … 1. Historical introduction 2. Basis of the 40AR/39AR dating method 3. Technical aspects 4. 40AR/39AR data presentation and interpretation App.4.1 Isochron analysis 5. Diffusion theory and measurements: App.5.1 Derivation ofthe diffusion equation App.5.2 Separation of the variables solution for a plane sheet App.5.3 Translation to spherical coordinates App.5.4 Sample diffusion calculation 6. 40Ar/39Ar thermochronology App.6.1 Closure temperature of first-order loss 7. Application and case histories References

Marine magnetic anomalies, geomagnetic field reversals, and motions of the ocean floor and continents

1968-03-15

J. R. Heirtzler , G. O. Dickson , E. M. Herron +2 more

Anaerobic production of magnetite by a dissimilatory iron-reducing microorganism

1987-11-01

Derek R. Lovley , John F. Stolz , G. L. Nord +1 more

Minerals Formed by Organisms

1981-03-13

Heinz A. Lowenstam

Organisms are capable of forming a diverse array of minerals, some of which cannot be formed inorganically in the biosphere. The initial precipitates may differ from the form in which … Organisms are capable of forming a diverse array of minerals, some of which cannot be formed inorganically in the biosphere. The initial precipitates may differ from the form in which they are finally stabilized, or during development of the organism one mineral may substitute for another. Biogenic minerals commonly have attributes which distinguish them from their inorganic counterparts. They fulfill important biological functions. They have been formed in ever-increasing amounts during the last 600 million years and have radically altered the character of the biosphere.

First‐order reversal curve diagrams: A new tool for characterizing the magnetic properties of natural samples

2000-12-10

Andrew P. Roberts , Christopher R. Pike , Kenneth L. Verosub

Paleomagnetic and environmental magnetic studies are commonly conducted on samples containing mixtures of magnetic minerals and/or grain sizes. Major hysteresis loops are routinely used to provide information about variations in … Paleomagnetic and environmental magnetic studies are commonly conducted on samples containing mixtures of magnetic minerals and/or grain sizes. Major hysteresis loops are routinely used to provide information about variations in magnetic mineralogy and grain size. Standard hysteresis parameters, however, provide a measure of the bulk magnetic properties, rather than enabling discrimination between the magnetic components that contribute to the magnetization of a sample. By contrast, first‐order reversal curve (FORC) diagrams, which we describe here, can be used to identify and discriminate between the different components in a mixed magnetic mineral assemblage. We use magnetization data from a class of partial hysteresis curves known as first‐order reversal curves (FORCs) and transform the data into contour plots (FORC diagrams) of a two‐dimensional distribution function. The FORC distribution provides information about particle switching fields and local interaction fields for the assemblage of magnetic particles within a sample. Superparamagnetic, single‐domain, and multidomain grains, as well as magnetostatic interactions, all produce characteristic and distinct manifestations on a FORC diagram. Our results indicate that FORC diagrams can be used to characterize a wide range of natural samples and that they provide more detailed information about the magnetic particles in a sample than standard interpretational schemes which employ hysteresis data. It will be necessary to further develop the technique to enable a more quantitative interpretation of magnetic assemblages; however, even qualitative interpretation of FORC diagrams removes many of the ambiguities that are inherent to hysteresis data.

Non-linear properties of thermal convection

1978-12-01

F. H. Busse

Thermal convection in a layer heated form below is an exemplary case for the study of non-linear fluid dynamics and the transition to turbulence. An outline is given of the … Thermal convection in a layer heated form below is an exemplary case for the study of non-linear fluid dynamics and the transition to turbulence. An outline is given of the present knowledge of the simplest realisation of convection in a layer of fluid satisfying the Oberbeck-Boussinesq approximation. Non-linear properties such as the dependence of the heat transport on Rayleigh and Prandtl numbers and the stability properties of convection rolls are emphasised in the discussion. Whenever possible, theoretical results are compared with experimental observations. A section on convection in rotating systems has been included, but the influence of other additional physical effects such as magnetic fields, side wall geometry, etc., has not been considered.

Hysteresis properties of titanomagnetites: Grain-size and compositional dependence

1977-01-01

Richard O. Day , M. Fuller , Victor A. Schmidt

Coordinates for mapping the distribution of magnetically trapped particles

1961-11-01

C. E. McIlwain

Dipole representations of the earth's magnetic field have been found to have insufficient accuracy for the study of magnetically trapped particles. A coordinate system consisting of the magnitude of the … Dipole representations of the earth's magnetic field have been found to have insufficient accuracy for the study of magnetically trapped particles. A coordinate system consisting of the magnitude of the magnetic field B and the integral invariant I has been found to organize adequately measurements made at different geographic locations. The present paper shows that a parameter L = ƒ(B,I) can be defined that retains most of the desirable properties of I and that has the additional property of organizing measurements along lines of force. Since the parameter L is the analog of a physical distance in a dipole field (the equatorial radius of a magnetic shell), it is usually found to present fewer conceptual difficulties than the integral invariant I.

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Magnetosome formation in prokaryotes

2004-02-20

Dennis A. Bazylinski , Richard B. Frankel

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Deep Mantle Convection Plumes and Plate Motions

1972-01-01

W. Jason Morgan

Evidence shows that volcanic island chains and aseismic ridges are formed by plate motion over fixed-mantle (Iceland, Hawaii, Galapagos, etc.) and new arguments link these hot-spots with the driving mechanism … Evidence shows that volcanic island chains and aseismic ridges are formed by plate motion over fixed-mantle (Iceland, Hawaii, Galapagos, etc.) and new arguments link these hot-spots with the driving mechanism of continental drift. It is assumed that the hot-spots are surface expressions of deep mantle plumes roughly 150 km in diameter, rising 2 m/year, and extending to the lowest part of the mantle. The rising material spreads out in the asthenosphere, producing stresses on the plate bottoms. Order-of-magnitude estimates show these stresses are sufficiently large to influence plate motion significantly. the total upward flow in the plumes is estimated at 500 cu km/year, which would require the entire mantle to overturn once each 2 billion years.

Identification of ferromagnetic minerals in a rock by coercivity and unblocking temperature properties

1990-02-01

William Lowrie

The common ferromagnetic minerals have distinctive, characteristic coercivities and thermomagnetic properties. The analysis of the acquisition curve of isothermal remanent magnetization (IRM) is a useful but often ambiguous diagnostic technique. … The common ferromagnetic minerals have distinctive, characteristic coercivities and thermomagnetic properties. The analysis of the acquisition curve of isothermal remanent magnetization (IRM) is a useful but often ambiguous diagnostic technique. For a more conclusive interpretation, IRM acquisition must be combined with subsequent thermal demagnetization of the IRM. A modification of this method is proposed as a more powerful analytical technique. Different coercivity fractions of IRM are remagnetized in successively smaller fields along three orthogonal directions. The thermal demagnetization of each orthogonal component of the composite IRM is then plotted separately. This method often gives a clearer interpretation of the ferromagnetic mineral content of a rock. Examples are described for limestone and sandstone samples.

A new geomagnetic polarity time scale for the Late Cretaceous and Cenozoic

1992-09-10

S. C. Cande , Dennis V. Kent

We have constructed a magnetic polarity time scale for the Late Cretaceous and Cenozoic based on an analysis of marine magnetic profiles from the world's ocean basins. This is the … We have constructed a magnetic polarity time scale for the Late Cretaceous and Cenozoic based on an analysis of marine magnetic profiles from the world's ocean basins. This is the first time, since Heirtzler et al. (1968) published their time scale, that the relative widths of the magnetic polarity intervals for the entire Late Cretaceous and Cenozoic have been systematically determined from magnetic profiles. A composite geomagnetic polarity sequence was derived based primarily on data from the South Atlantic. Anomaly spacings in the South Atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles. Fine‐scale information was derived from magnetic profiles on faster spreading ridges in the Pacific and Indian Oceans and inserted into the South Atlantic sequence. Based on the assumption that spreading rates in the South Atlantic were smoothly varying but not necessarily constant, a time scale was generated by using a spline function to fit a set of nine age calibration points plus the zero‐age ridge axis to the composite polarity sequence. The derived spreading history of the South Atlantic shows a regular variation in spreading rate, decreasing in the Late Cretaceous from a high of almost 70 mm/yr (full rate) at around anomaly 33–34 time to a low of about 30 mm/yr by anomaly 27 time in the early Paleocene, increasing to about 55 mm/yr by about anomaly 15 time in the late Eocene, and then gradually decreasing over the Oligocene and the Neogene to the recent rate of about 32 mm/yr. The new time scale has several significant differences from previous time scales. For example, chron C5n is ∼0.5 m.y. older and chrons C9 through C24 are 2–3 m.y. younger than in the chronologies of Berggren et al. (1985b) and Harland et al. (1990). Additional small‐scale anomalies (tiny wiggles) that represent either very short polarity intervals or intensity fluctuations of the dipole field have been identified from several intervals in the Cenozoic including a large number of tiny wiggles between anomalies 24 and 27. Spreading rates on several other ridges, including the Southeast Indian Ridge, the East Pacific Rise, the Pacific‐Antarctic Ridge, the Chile Ridge, the North Pacific, and the Central Atlantic, were analyzed in order to evaluate the accuracy of the new time scale. Globally synchronous variations in spreading rate that were previously observed around anomalies 20, 6C, and in the late Neogene have been eliminated. The new time scale helps to resolve events at the times of major plate reorganizations. For example, anomaly 3A (5.6 Ma) is now seen to be a time of sudden spreading rate changes in the Southeast Indian, Pacific‐Antarctic, and Chile ridges and may correspond to the time of the change in Pacific absolute plate motion proposed by others. Spreading rates in the North Pacific became increasingly irregular in the Oligocene, culminating in a precipitous drop at anomaly 6C time.

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Viscous and resistive eddies near a sharp corner

1964-01-01

H. K. Moffatt

Some simple similarity solutions are presented for the flow of a viscous fluid near a sharp corner between two planes on which a variety of boundary conditions may be imposed. … Some simple similarity solutions are presented for the flow of a viscous fluid near a sharp corner between two planes on which a variety of boundary conditions may be imposed. The general flow near a corner between plane boundaries at rest is then considered, and it is shown that when either or both of the boundaries is a rigid wall and when the angle between the planes is less than a certain critical angle, any flow sufficiently near the corner must consist of a sequence of eddies of decreasing size and rapidly decreasing intensity. The ratios of dimensions and intensities of successive eddies are determined for the full range of angles for which the eddies exist. The limiting case of zero angle corresponds to the flow at some distance from a two-dimensional disturbance in a fluid between parallel boundaries. The general flow near a corner between two plane free surfaces is also determined; eddies do not appear in this case. The asymptotic flow at a large distance from a corner due to an arbitrary disturbance near the corner is mathematically similar to the above, and has comparable properties. When the fluid is electrically conducting, similarity solutions may be obtained when the only applied magnetic field is that due to a line current along the intersection of the two planes; it is shown that the effect of such a current is to widen the range of corner angles for which eddies must appear.

Four centuries of geomagnetic secular variation from historical records

2000-03-15

Andrew Jackson , Art R. T. Jonkers , Matthew R. Walker

We present a new model of the magnetic field at the core–mantle boundary for the interval 1590–1990. The model, called gufm1, is based on a massive new compilation of historical … We present a new model of the magnetic field at the core–mantle boundary for the interval 1590–1990. The model, called gufm1, is based on a massive new compilation of historical observations of the magnetic field. The greater part of the new dataset originates from unpublished observations taken by mariners engaged in merchant and naval shipping. Considerable attention is given to both correction of data for possible mislocation (originating from poor knowledge of longitude) and to proper allocation of error in the data. We adopt a stochastic model for uncorrected positional errors that properly accounts for the nature of the noise process based on a Brownian motion model. The variability of navigational errors as a function of the duration of the voyages that we have analysed is consistent with this model. For the period before 1800, more than 83 000 individual observations of magnetic declination were recorded at more than 64 000 locations; more than 8000 new observations are for the 17th century alone. The time–dependent field model that we construct from the dataset is parametrized spatially in terms of spherical harmonics and temporally in B–splines, using a total of 36 512 parameters. The model has improved the resolution of the core field, and represents the longest continuous model of the field available. However, full exploitation of the database may demand a new modelling methodology.

Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic

1995-04-10

S. C. Cande , Dennis V. Kent

Recently reported radioisotopic dates and magnetic anomaly spacings have made it evident that modification is required for the age calibrations for the geomagnetic polarity timescale of Cande and Kent (1992) … Recently reported radioisotopic dates and magnetic anomaly spacings have made it evident that modification is required for the age calibrations for the geomagnetic polarity timescale of Cande and Kent (1992) at the Cretaceous/Paleogene boundary and in the Pliocene. An adjusted geomagnetic reversal chronology for the Late Cretaceous and Cenozoic is presented that is consistent with astrochronology in the Pleistocene and Pliocene and with a new timescale for the Mesozoic.

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International Geomagnetic Reference Field: the eleventh generation

2010-10-12

Christopher C. Finlay , S. Maus , Ciarán Beggan +7 more

The eleventh generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2009 by the International Association of Geomagnetism and Aeronomy (IAGA) Working Group V-MOD.It updates the previous … The eleventh generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2009 by the International Association of Geomagnetism and Aeronomy (IAGA) Working Group V-MOD.It updates the previous IGRF generation with a definitive main field model DGRF 2005.0, for 2005.0, a main field model IGRF 2010.0, for 2010.0, and a linear predictive secular variation model for 2010.0-2015.0.In this note the equations defining the IGRF model are provided together with the spherical harmonic coefficients for the eleventh generation.Maps of the magnetic Declination, Inclination and Total Intensity for epoch 2010.0 and their predicted rate of change for 2010.0 -2015.0 are presented and the recent evolution of the South Atlantic Anomaly and magnetic pole positions are examined.

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Extraterrestrial Cause for the Cretaceous-Tertiary Extinction

1980-06-06

Luis W. Alvarez , Walter Álvarez , Frank Asaro +1 more

Platinum metals are depleted in the earth's crust relative to their cosmic abundance; concentrations of these elements in deep-sea sediments may thus indicate influxes of extraterrestrial material. Deep-sea limestones exposed … Platinum metals are depleted in the earth's crust relative to their cosmic abundance; concentrations of these elements in deep-sea sediments may thus indicate influxes of extraterrestrial material. Deep-sea limestones exposed in Italy, Denmark, and New Zealand show iridium increases of about 30, 160, and 20 times, respectively, above the background level at precisely the time of the Cretaceous-Tertiary extinctions, 65 million years ago. Reasons are given to indicate that this iridium is of extraterrestrial origin, but did not come from a nearby supernova. A hypothesis is suggested which accounts for the extinctions and the iridium observations. Impact of a large earth-crossing asteroid would inject about 60 times the object's mass into the atmosphere as pulverized rock; a fraction of this dust would stay in the stratosphere for several years and be distributed worldwide. The resulting darkness would suppress photosynthesis, and the expected biological consequences match quite closely the extinctions observed in the paleontological record. One prediction of this hypothesis has been verified: the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other. Four different independent estimates of the diameter of the asteroid give values that lie in the range 10 ± 4 kilometers.

The least-squares line and plane and the analysis of palaeomagnetic data

1980-09-01

Joseph L. Kirschvink

The classic, multivariate technique of principal component analysis can be used to find and estimate the directions of lines and planes of best least-squares fit along the demagnetization path of … The classic, multivariate technique of principal component analysis can be used to find and estimate the directions of lines and planes of best least-squares fit along the demagnetization path of a palaeomagnetic specimen, thereby replacing vector subtraction, remagnetization circles and difference vector paths with one procedure. Eigenvalues from the analysis are the variance of the data along each principal axis, and provide a relative measure of collinearity or coplanarity which may be used to define a general palaeomagnetic precision index. Demagnetization planes found with principal component analysis may be used in place of difference vector paths for locating Hoffman—Day directions, avoiding unnecessary vector subtraction and intensity truncation steps. Two methods are discussed for jointly estimating an average remanence direction from demagnetization lines and planes.

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A Revised Cenozoic Geochronology and Chronostratigraphy

1995-01-01

William A. Berggren , Dennis V. Kent , Carl C. Swisher +1 more

Since the publication of our previous time scale (Berggren and others, 1985c = BKFV85) a large amount of new magneto- and biostratigraphic data and radioisotopic ages have become available. An … Since the publication of our previous time scale (Berggren and others, 1985c = BKFV85) a large amount of new magneto- and biostratigraphic data and radioisotopic ages have become available. An evaluation of some of the key magnetobiostratigraphic calibration points used in BKFV85, as suggested by high precision 40 Ar/ 39 Ar dating (e.g., Montanari and others, 1988; Swisher and Prothero, 1990; Prothero and Swisher, 1992; Prothero, 1994), has served as a catalyst for us in developing a revised Cenozoic time scale. For the Neogene Period, astrochron- ologic data (Shackleton and others, 1990; Hilgen, 1991) required re-evaluation of the calibration of the Pliocene and Pleistocene Epochs. The significantly older ages for the Pliocene-Pleistocene Epochs predicted by astronomical calibrations were soon corroborated by high precision 40 Ar/ 39 Ar dating (e.g., Baksi and others, 1992; McDougall and others, 1992; Tauxe and others, 1992; Walter and others, 1991; Renne and others, 1993). At the same time, a new and improved definition of the Late Cretaceous and Cenozoic polarity sequence was achieved based on a comprehensive evaluation of global sea-floor magnetic anomaly profiles (Cande and Kent, 1992). This, in turn, led to a revised Cenozoic geomagnetic polarity time scale (GPTS) based on standardization to a model of South Atlantic spreading history (Cande and Kent, 1992/1995 = CK92/95). This paper presents a revised (integrated magnetobiochronologic) Cenozoic time scale (IMBTS) based on an assessment and integration of data from several sources. Biostratigraphic events are correlated to the recently revised global polarity time scale (CK95). The construction of the new GPTS is outlined with emphasis on methodology and newly developed polarity history nomenclature. The radioisotopic calibration points (as well as other relevant data) used to constrain the GPTS are reviewed in their (bio)stratigraphic context. An updated magnetobiostratigraphic (re)assessment of about 150 pre-Pliocene planktonic foraminiferal datum events (including recently avail- able high southern (austral) latitude data) and a new/modified zonal biostratigraphy provides an essentially global biostratigraphic correlation framework. This is complemented by a (re)assessment of nearly 100 calcareous nannofossil datum events. Unrecognized unconformities in the stratigraphic record (and to a lesser extent differences in taxonomic concepts), rather than latitudinal diachrony, is shown to account for discrep- ancies in magnetobiostratigraphic correlations in many instances, particularly in the Paleogene Period. Claims of diachrony of low amplitude (<2 my) are poorly substantiated, at least in the Paleocene and Eocene Epochs. Finally, we (re)assess the current status of Cenozoic chronostratigraphy and present estimates of the chronology of lower (stage) and higher (system) level units. Although the numerical values of chronostratigraphic units (and their boundaries) have changed in the decade since the previous version of the Cenozoic time scale, the relative duration of these units has remained essentially the same. This is particularly true of the Paleogene Period, where the Paleocene/Eocene and Eocene/Oligocene boundaries have been shifted ~2 my younger and the Cretaceous/Paleogene boundary ~1 my younger. Changes in the Neogene time scale are relatively minor and reflect primarily improved magnetobiostratigraphic calibrations, better understanding of chronostratigraphic and magnetobiostratigraphic relationships, and the introduction of a congruent astronom- ical/paleomagnetic chronology for the past 6 my (and concomitant adjustments to magnetochron age estimates).

International Geomagnetic Reference Field: the 12th generation

2015-05-26

Erwan Thébault , Christopher C. Finlay , Ciarán Beggan +7 more

The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). … The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth's magnetic field.

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Theory and application of the Day plot (Mrs/Ms versus Hcr/Hc) 1. Theoretical curves and tests using titanomagnetite data

2002-03-01

David J. Dunlop

Although most paleomagnetic and environmental magnetic papers incorporate a Day plot of the hysteresis parameters M rs / M s versus H cr / H c , a comprehensive theory … Although most paleomagnetic and environmental magnetic papers incorporate a Day plot of the hysteresis parameters M rs / M s versus H cr / H c , a comprehensive theory covering superparamagnetic (SP), single‐domain (SD), pseudo‐single‐domain (PSD), and multidomain (MD) (titano)magnetites is lacking. There is no consensus on how to quantify grain‐size trends within the Day plot, how to distinguish MD from SP trends/mixtures, or whether magnetite, titanomagnetites, and other minerals have distinctive trends by which they might be identified. This paper develops the theory of the Day plot parameters for MD, MD + SD, PSD, and SP + SD grains of titanomagnetite (Fe 3 – x Ti x O 4 ) with compositions x = 0 (TM0 or magnetite) and x = 0.6 (TM60). MD grains have a separate trend that intersects the curve for SD + MD mixtures. SP + SD mixtures generate a variety of trends, depending on the SP grain size. All SP + SD curves lie much above those for MD or SD + MD trends, as has been proposed, but not demonstrated, previously. Data for PSD‐size magnetites of many different origins fall along a single trend, but different levels of internal stress shift points for similar grain sizes along the “master curve.” In order to use the Day plot to determine grain size, one must have independent information about the state of internal stress. Theoretical model curves for SD + MD mixtures match the PSD magnetite and TM60 data quite well, although the SD→MD transition region in grain size is much narrower for TM60 than for magnetite. The agreement between PSD data and SD + MD mixing curves implies that PSD behavior is due to superimposed independent SD and MD moments, either in individual or separate grains, and not to exotic micromagnetic structures such as vortices. The theory also matches M rs and H c values in mechanical mixtures of very fine and very coarse grains, although nonlinear mixing theory is required to explain some H cr and H cr / H c data.

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Classification of the reversal test in palaeomagnetism

1990-12-01

P. L. McFadden , M. W. McElhinny

It is standard practice that a positive reversal test is claimed on the basis of inability to reject the hypothesis that two distributions share a common mean direction, and thus … It is standard practice that a positive reversal test is claimed on the basis of inability to reject the hypothesis that two distributions share a common mean direction, and thus the claim of a positive reversal test is in fact often based on a lack of information. This is unsatisfactory. Therefore it is suggested that positive reversal tests should be classified according to the amount of information that was available for the test. This amount of information is readily indicated by the critical angle (e.g., at the 95 per cent confidence level) between the two sample mean directions at which the hypothesis of common mean direction for the distributions would be rejected. It is recommended that 5°, 10° and 20° be used as the breakpoints in the classification.

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Convection Plumes in the Lower Mantle

1971-03-01

W. Jason Morgan

The Evolution of the Indian Ocean since the Late Cretaceous

1971-12-01

Dan McKenzie , John G. Sclater

Summary All available ship and aeroplane tracks across the Indian Ocean were searched for identifiable magnetic anomalies and transform faults, and hence the age and direction of motion at the … Summary All available ship and aeroplane tracks across the Indian Ocean were searched for identifiable magnetic anomalies and transform faults, and hence the age and direction of motion at the time of formation of about two-thirds of the floor of the ocean established. The magnetic lineations show that India moved away from Antarctica at about 18 cm/y for 20 My in the Early Tertiary. This rapid motion ceased in the Eocene and was followed by a period in which little or no spreading took place west of the Ninety East Ridge. Australia separated from Antarctica during this period. The present spreading episode began about 36 My ago. This detailed study has permitted instantaneous poles of rotation to be obtained, and has established that Africa is now moving northward at 2cm/y relative to Antarctica in the South West Indian Ocean. The evolution of the triple junction between the South East, South West and Central Indian Ridges is clearly reflected in the topography and magnetic lineations. The depth of parts of the ocean formed since the Late Cretaceous increases with age in the manner expected from the temperature structure of a cooling plate, and supports the evolution determined from the magnetic lineations in a most remarkable way. Heat flow observations are more scattered but also consistent with the same thermal model. The proposed evolution agrees with the distribution of known continental fragments and with the Late Cretaceous palaeomagnetic poles from surrounding continents and one obtained from the shape of the magnetic lineations south of India. It is, however, not yet clear how to reconstruct Gondwanaland from the Late Cretaceous reconstructions.

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Sur l'intensite du champ magnetique terrestre dans le passe historique et geologique

1959-01-01

E. Thellier

Magneto-aerotactic bacteria deliver drug-containing nanoliposomes to tumour hypoxic regions

2016-08-12

Ouajdi Felfoul , Mahmood Mohammadi , Samira Taherkhani +7 more

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Statistics of Directional Data

1972-01-01

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Supermagnetism

2008-12-05

Subhankar Bedanta , W. Kleemann

An ensemble of nanoparticles in which the inter-particle magnetic interactions are sufficiently weak shows superparamagnetic behaviour as described by the Néel–Brown model. On the contrary, when inter-particle interactions are non-negligible, … An ensemble of nanoparticles in which the inter-particle magnetic interactions are sufficiently weak shows superparamagnetic behaviour as described by the Néel–Brown model. On the contrary, when inter-particle interactions are non-negligible, the system eventually shows collective behaviour, which overcomes the individual anisotropy properties of the particles. At sufficiently strong interactions a magnetic nanoparticle ensemble can show superspin glass (SSG) properties similar to those of atomic spin glass systems in bulk. With a further increase in concentration, but still below physical percolation, sufficiently strong interactions can be experienced to form a superferromagnetic (SFM) state. SFM domains in a non-percolated nanoparticle assembly are expected to be similar to conventional ferromagnetic domains in a continuous film, with the decisive difference that the atomic spins are replaced by the superspins of the single-domain nanoparticles. In this review we highlight the most important developments in the field of supermagnetism, which comprises three fascinating subjects: superparamagnetism, SSG and superferromagnetism.

New Magnetic Anisotropy

1956-06-01

W. H. Meiklejohn , C. P. Bean

Journal of Geophysical Research

1949-03-01

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Magnetotactic Bacteria

1975-10-24

Richard P. Blakemore

Bacteria with motility directed by the local geomagnetic field have been observed in marine sediments. These magnetotactic microorganisms possess flagella and contain novel structured particles, rich in iron, within intracytoplasmic … Bacteria with motility directed by the local geomagnetic field have been observed in marine sediments. These magnetotactic microorganisms possess flagella and contain novel structured particles, rich in iron, within intracytoplasmic membrane vesicles. Conceivably these particles impart to cells a magnetic moment. This could explain the observed migration of these organisms in fields as weak as 0.5 gauss.

Metal-Insulator Transitions

2004-01-14

Nevill Mott

This is a second edition of a classic book. Written by the late, great Sir Nevill Mott (Britain's last Nobel Prize winner for Physics), Metal Insulator Transitions has been greatly … This is a second edition of a classic book. Written by the late, great Sir Nevill Mott (Britain's last Nobel Prize winner for Physics), Metal Insulator Transitions has been greatly updated and expanded to further enhance its already enviable reputation.

Parametric instability in a magnomechanical system

2025-06-25

NULL AUTHOR_ID | Physical review. B./Physical review. B

A Two‐Protein Chemoreceptor Complex Regulates Oxygen Thresholds in Bacterial Magneto‐Aerotaxis

2025-06-25

Julian Herz , C Weigel , Leonie Scheder +7 more | Advanced Science

Abstract Bacteria in changing environments rely on motility and sensory mechanisms to locate optimal conditions. This process depends on specialized chemoreceptors to sense environmental stimuli. Exceptionally high numbers of chemoreceptor … Abstract Bacteria in changing environments rely on motility and sensory mechanisms to locate optimal conditions. This process depends on specialized chemoreceptors to sense environmental stimuli. Exceptionally high numbers of chemoreceptor genes are present in magnetotactic bacteria (MTB), which combine magnetic alignment via intracellular magnetic nanoparticles (magnetosomes) and oxygen sensing for a unique navigation strategy toward low‐oxygen zones, called magneto‐aerotaxis. However, chemoreceptors for aerotaxis in MTB have not been experimentally identified. This study examines chemoreceptors in the model MTB Magnetospirillum gryphiswaldense . Gene deletion analysis shows that M. gryphiswaldens e relies on a complex and partly redundant set of chemoreceptors to sense oxygen. Within this diverse repertoire of chemoreceptors, a receptor formed by two interacting proteins is identified that plays a key role in aerotaxis. Interaction assays and microscopy confirm that both proteins interact within polar‐lateral regions in the cell. Moreover, genetic, biochemical, and motility experiments demonstrate that the chemoreceptor complex promotes a cellular response away from oxygen via the redox cofactor flavin adenine dinucleotide (FAD), independent of magnetic fields. These findings provide first insights into how MTB control oxygen sensing at the molecular level, shedding light on the mechanisms underlying bacterial navigation and highly complex chemosensory systems.

A new spin on rotating convection

2025-06-25

Stephan Stellmach | Journal of Fluid Mechanics

Studying rotating convection under geo- and astrophysically relevant conditions has proven to be extremely difficult. For the rotating Rayleigh–Bénard system, van Kan et al. ( J. Fluid Mech., vol. 1010, … Studying rotating convection under geo- and astrophysically relevant conditions has proven to be extremely difficult. For the rotating Rayleigh–Bénard system, van Kan et al. ( J. Fluid Mech., vol. 1010, 2025, A42) have now been able to massively extend the parameter space accessible by direct numerical simulations. Their progress relies on a rescaling of the governing Boussinesq equations, which vastly improves numerical conditioning (Julien et al. , arXiv:2410.02702). This opens the door for investigating previously inaccessible dynamical regimes and bridges the gap to the asymptotic branch of rapidly rotating convection.

Reassessing the geocentric-axial-dipole (GAD) model for Proterozoic time with paleomagnetic directions from dike swarms

2025-06-24

Zheng Gong , David A.D. Evans , R. R. Fu +1 more | Earth and Planetary Science Letters

The Biomedical Limitations of Magnetic Nanoparticles and a Biocompatible Alternative in the Form of Magnetotactic Bacteria

2025-06-23

Natalia L. Paul , Rahela Carpa , Rodica Elena Ionescu +1 more | Journal of Functional Biomaterials

Nanotechnology has an increasing impact and a great potential in various biological and medical applications. Magnetic nanoparticles (MNPs) stand out for their unique properties, a reason why they have a … Nanotechnology has an increasing impact and a great potential in various biological and medical applications. Magnetic nanoparticles (MNPs) stand out for their unique properties, a reason why they have a varied spectrum of applicability in different sectors of activity; in this paper we focus on the medical field. Magnetotactic bacteria (MTB) are a group of Gram-negative prokaryotes that migrate in one direction or another under the influence of an external magnetic field and are a category of microorganisms that constitutively perform the biomineralization of magnetic nanoparticles in the cytoplasm. This review focuses on the general and particular characteristics of magnetotactic bacteria in close correlation with their utility in the medical field, starting with the medical applications of magnetic nanoparticles and arriving at the potential role in nanomedicine of MNPs extracted from MTB.

Primordial Magnetogenesis from Killing Vector Fields

2025-06-23

Nagabhushana Prabhu | Universe

Papapetrou showed that the covariant derivative of a Killing vector field satisfies Maxwell’s equations in vacuum. Papapetrou’s result is extended, in this article, and it is shown that the covariant … Papapetrou showed that the covariant derivative of a Killing vector field satisfies Maxwell’s equations in vacuum. Papapetrou’s result is extended, in this article, and it is shown that the covariant derivative of a Killing vector field satisfies Maxwell’s equations in non-vacuum backgrounds as well if one allows electromagnetic currents of purely geometric origin. It is then postulated that every Killing vector field gives rise to a physical electromagnetic field and, in a non-vacuum background, a physical electromagnetic current—hereafter called Killing electromagnetic field and Killing electromagnetic current, respectively. It is shown that the Killing electromagnetic field of the flat FLRW (Friedmann–Lemai^tre–Robertson–Walker) universe comprises a Killing magnetic field and a rotational Killing electric field; an upper bound on the Killing magnetic field is derived, and it is found that the upper bound is consistent with the current observational bounds on the cosmic magnetic field. Next, the time-like Killing vector of the Schwarzschild spacetime is shown to give rise to a radial Killing electric field. It is also shown that in the weak field regime—and far from the matter distribution—the back reaction of the radial Killing electric field changes the Schwarzschild metric to the Reissner–Nordström metric, establishing a partial converse of Wald’s result. Drawing upon Rainich’s work on Rainich–Riemann manifolds, the etiological question of how a physical electromagnetic field can arise out of geometry is discussed; it is also argued that detection of the Killing electric field of flat FLRW spacetime may be within the current experimental reach. Finally, this article discusses the relevance of Killing electromagnetic currents and the aforementioned transmutation of Schwarzschild spacetime to Reissner–Nordstrom spacetime, to Misner and Wheeler’s program of realizing “charge without charge”.

Parabolic Saddles and Newhouse Domains in Celestial Mechanics

2025-06-23

M. Isabel Garrido , Pau Martı́n , Jaime Paradela | Communications in Mathematical Physics

Mechanisms of left–right symmetry breaking across scales

2025-06-21

Nikoloz Tsikolia , Dinh Thach Lam Nguyen , Yee Han Tee | Current Opinion in Cell Biology

Establishment of left-right (LR) asymmetry relies on a multistep interplay of molecular signaling and physical processes. Initial LR symmetry breaking in several model vertebrates was shown to take place at … Establishment of left-right (LR) asymmetry relies on a multistep interplay of molecular signaling and physical processes. Initial LR symmetry breaking in several model vertebrates was shown to take place at the LR organizer (LRO) where chiral rotation of monocilia produces a leftward fluid flow. Subsequent bending of sensory cilia triggers Pkd2-channel-mediated calcium transients which in turn are required for induction of asymmetrical signaling upstream of morphological asymmetries, emphasizing the role of mechanosensation in flow detection. Crucially, unidirectional flow and its detection were suggested to require cellular-scale asymmetries including planar cell polarity-mediated posterior position and ultrastructural chirality of motile cilia as well as asymmetric Pkd2 localization within sensory cilia. Alternative mechanisms of LR symmetry breaking operate in models like the chick embryo, where asymmetry of gene expression is preceded by leftward primitive node rotation suggesting mechanisms based on cytoskeletal chirality known from invertebrate models including Caenorhabditis elegans and fruit fly. Investigation of chirality at the cellular level suggests that chirality of components of cytoskeleton, particularly actin filaments, is amplified by distinct modules based i.e. on formin-actin and myosin-actin interactions which drive intracellular swirling and cortical flow, providing a basis for LR asymmetry. Cellular chirality can organize LR asymmetry of multicellular behavior as observed in the chiral alignment of fibroblasts. The integration of molecular, cellular, and tissue-scale chirality highlights conserved and divergent mechanisms underpinning LR symmetry breaking across species. Unraveling these processes may illuminate pathways connecting cytoskeletal dynamics to organismal asymmetry, offering insights into development and evolution.

Using archaeomagnetism to unravel the occupational history of a medieval site: Cañada Real (Burgos, Northern Spain)

2025-06-20

Eva Vernet , Ãngel Carrancho , Manuel Calvo‐Rathert +4 more | Journal of Archaeological Science Reports

Turbulent dynamo in the shell model and the Kazantsev-Kraichnan approach

2025-06-20

NULL AUTHOR_ID | Physical review. E

Turbulence in Earth’s core generates large topographic torques on the mantle

2025-06-20

Tobias G. Oliver , Eric G. Blackman , J. A. Tarduno +1 more | Communications Earth & Environment

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Mechanism of magnetic enhancement and depletion of the loess from northern piedmont of Dabie Mountains, east-central China

2025-06-20

Yan Han , Guoyong Zhao , Bin Lyu +1 more | CATENA

Magnetic susceptibility artifacts (braces)

2025-06-20

Giorgio Maria Agazzi | Radiopaedia.org

Variations in the magnetic properties of quaternary sediments from various physiographic regions along the bank of Matla River, Sundarban, West Bengal, India

2025-06-19

Swagata Das , M. Venkateshwarlu , Supriya Mondal +3 more | Research Square (Research Square)

<title>Abstract</title> Magnetic susceptibility measurements at low and high frequencies (χlf, χhf) and rock magnetic experiments (i.e., Curie curve analysis, Isothermal Remanent Magnetization, Hysteresis) are carried out on quaternary mangrove sediments … <title>Abstract</title> Magnetic susceptibility measurements at low and high frequencies (χlf, χhf) and rock magnetic experiments (i.e., Curie curve analysis, Isothermal Remanent Magnetization, Hysteresis) are carried out on quaternary mangrove sediments from the bank of Matla River, Sundarban, West Bengal, India. Magnetic investigations being simple, fast, cost-effective, and non-destructive, are utilized to gather extensive data as a proxy for the spatial distribution of pollution. The study emphasizes magnetic parameters, such as concentration-dependent factors (magnetic susceptibility, isothermal remanent magnetization) and feature-dependent factors (coercivity of remanence, magnetic susceptibility ratio), as indicators of pollution. This study aims to investigate the application of magnetic parameters to determine magnetic property enhancement within the mangrove sediments along Matla River and thereby evaluate anthropogenic activities. The analysis of variations of χlf and frequency-dependent susceptibilities (χfd and χfd%) indicate that the superparamagnetic (SP) grains dominate in the soil samples which mainly supports the magnetic susceptibility enhancement with few exceptions. The thermomagnetic curve identifies Curie temperature of the magnetic minerals and tracks magnetic carrier transformations during heating and cooling, showing both reversible and irreversible magnetization-temperature (J-T) behaviours. The Isothermal Remanent Magnetization (IRM) curve saturates at ~ 300 mT, characteristic of ferrimagnetic minerals like magnetite or maghemite, while some samples remain unsaturated at ~ 800 mT, suggesting high coercivity minerals like hematite or iron sulfides. Moving downstream, increasing coercivity indicates higher concentrations of these minerals. Hysteresis parameters (Mrs/Ms vs. Bcr/Bc) on a Day plot show samples within the Pseudo Single Domain (PSD) range, likely a mix of Single Domain (SD) and Multi Domain (MD) grains.

Limace.jl: A Julia package to compute hydromagnetic modes in spherical domains

2025-06-18

Felix Gerick | The Journal of Open Source Software

The geometry of intermittent and magnetospheric state changes pulsars

2025-06-18

Phrudth Jaroenjittichai , M. Kramer , P. Weltevrede +3 more | Astronomy and Astrophysics

Pulsars exhibit a variety of phenomena, including intermittency and magnetospheric state changes (MSC) -- moding, nulling, and profile -- which are thought to be related to changes in their magnetospheric … Pulsars exhibit a variety of phenomena, including intermittency and magnetospheric state changes (MSC) -- moding, nulling, and profile -- which are thought to be related to changes in their magnetospheric plasma. The variation in pulsar emission patterns has been attributed to changes in the flow of magnetospheric plasma above the polar cap, affecting both radio emission and pulsar spin-down ( This study aims to explore the link between these behaviours by investigating the geometry and spin-down characteristics of intermittent pulsars and MSC pulsars. We estimated the magnetic inclination angles for intermittent pulsars and a sample of MSC pulsars using the rotating vector model and pulse-width-period correlations. A 'plasma filling factor' was introduced to extend the model proposed by lst12a to MSC pulsars, with the aim of providing a unified framework for understanding these phenomena. Our results provide supporting evidence for a relationship between spin-down ratios and inclination angles that aligns with theoretical predictions. We determine the plasma filling factor explaining the observed spin-down variations for a number of pulsars. We also identify unusual emission height characteristics in PSR B1931+24 that suggest distinctive magnetospheric properties in intermittent pulsars. This work establishes a quantitative link between intermittent and MSC pulsars through a simple unified model of magnetospheric plasma depletion. Future observations of additional pulsars with known spin-down variations will be crucial for refining this model and deepening our understanding of pulsar magnetospheres.

Comments on ‘Magnetic fabrics of west coast dyke swarm from Deccan Volcanic Province’ by Lakshmi et al. (Environ. Earth Sci. 83, 465, August 2024)

2025-06-17

N. Basavaiah , K. Satyanarayana , J. N. Prasad | Environmental Earth Sciences

Heterogeneous density structure of seamounts: a sign count analysis of gravity anomalies

2025-06-17

Gyuha Hwang , Seung‐Sep Kim , Young-Tak Ko | Geosciences Journal

Influence of ENSO and SAM on the occurrence of absolute extremes and behavior of Ta, SST, and SIC anomalies in the western Antarctic Peninsula

2025-06-17

Daniela Montaño Bello , Nancy Villegas | Atmósfera

This study aims to improve the understanding of the interaction between El Niño-Southern Oscillation (ENSO) events and the phases of the Southern Annular Mode (SAM), as well as their influence … This study aims to improve the understanding of the interaction between El Niño-Southern Oscillation (ENSO) events and the phases of the Southern Annular Mode (SAM), as well as their influence on the western Antarctic Peninsula (WAP). Monthly series of air temperature (Ta), sea surface temperature (SST), and sea ice coverage (SIC) from 1981 to 2020 were analyzed at six representative points within the study area. Ta, SIC, and SST data were obtained from the ERA5 database. The Southern Oscillation Index (SOI) and Antarctic Oscillation Index (AAOI) were sourced from NOAA’s Climate Prediction Center. The spectral density of the anomaly series for each variable was calculated, and the characteristic cycles of SAM and ENSO were extracted. The most influential components driving the oscillations of the studied series were identified. A cross-correlation analysis was conducted between the anomaly components of Ta, SIC, and SST and those of SOI and AAOI. The results indicate that Ta series exhibit moderate positive correlations with SAM, particularly between the 5.2-year quasi-period of AAOI and the 4.4-year quasi period of Ta in the Drake Passage and Bransfield Strait. The SST series in Bransfield correlate with AAOI5.2, while the quasi-periods of 4.6 and 5.2 years in the Drake Passage correlate with SOI3.5. The SIC series show positive correlations with the 3.5-year quasi-period of SOI for lag times greater than one year, except in the Bransfield Strait. Extreme absolute Ta and SST events in the WAP region are strongly influenced by SAM and ENSO. It is concluded that the coupling of ENSO and SAM phases amplifies their effects on meteo-marine variables.

STUDY OF INDUCED POLARIZATION OF THE YASNOE GOLD OCCURRENCE (Taimyr peninsula) ON THE BASIS OF FIELD AND LABORATORY RESEARCH RESULTS

2025-06-16

G. Gurin | Russian Geology and Geophysics

Moon-Induced Differential Rotation in Earth’s Interior: A Comprehensive Conceptual Model

2025-06-16

Chil-Yeong Kim , Eun‐Kyoung Seo , You‐Soon Chang +1 more | Geosciences

This study presents a novel conceptual model to explain the differential rotation within Earth’s layers, a phenomenon observed through seismic wave studies but not fully understood. While geodynamo theory and … This study presents a novel conceptual model to explain the differential rotation within Earth’s layers, a phenomenon observed through seismic wave studies but not fully understood. While geodynamo theory and electromagnetic coupling models have been proposed to explain this phenomenon, our model offers an alternative perspective focusing on the Moon’s tidal forces. Our model proposes that the Moon’s tidal forces play a crucial role in this process, acting as a braking mechanism on Earth’s rotation. We hypothesize that these tidal forces initially decelerate the Earth’s crust and mantle, with this effect sequentially transmitted to deeper layers. A key aspect of our model is the role of the liquid outer core in mediating this process. We suggest that the liquid state of the outer core delays the transmission of tidal friction, resulting in differential rotation between layers in contact with it. This delay mechanism provides a potential explanation for the observed rotational differences between the mantle and core. Our model demonstrates that about 66,000 years after the Moon’s formation, the tidal force slowed the crust–mantle rotation by approximately 5.5 degrees per year more than the core. Furthermore, we estimate that the frictional heat generated at the boundaries of differential rotation is about 0.3478 TW. At this rate, the outer core temperature would increase by approximately 13.4 K per billion years. This thermal effect may have significant implications for the long-term evolution of Earth’s core, potentially slowing its cooling rate and maintaining its liquid state. Our model thus provides a new perspective on the interplay between lunar tidal forces, Earth’s internal structure, and its thermal evolution, offering insights into the complex dynamics of our planet’s interior.

Log-periodic signatures prior to volcanic eruptions: evidence from 34 events

2025-06-16

Qinghua Lei , Didier Sornette | Earth and Planetary Science Letters

Control of Gravitational Potential Energy on the Distribution of Off‐Rift Volcanic Activity in the Turkana Depression, East African Rift

2025-06-14

Giacomo Corti , Ameha Muluneh , D. Sarah Stamps +5 more | Geophysical Research Letters

Abstract The distribution and alignment of volcanism in continental rifts is controlled by regional extensional stresses modulated by several factors such as structural inheritance, volcano edifice loading, and rift architecture. … Abstract The distribution and alignment of volcanism in continental rifts is controlled by regional extensional stresses modulated by several factors such as structural inheritance, volcano edifice loading, and rift architecture. These interactions result in complex characteristics of rift‐related volcanic features, which may be difficult to interpret considering the different controlling processes. The Turkana Depression (East Africa) exemplifies these complexities, showing an anomalous location of volcanic fields (outside the area of ongoing extension), with variable vent orientation. We analyze vent distribution in the Turkana Depression and calculate the stresses resulting from Gravitational Potential Energy (GPE). Our results show that West to East variations in topography and (subordinately) crustal thickness give rise to extensional GPE‐related stresses East of Lake Turkana, where recent off‐rift volcanism is localized. Within each different volcanic field, local GPE‐related stresses control the arrangement of volcanic vents, which therefore do not respond to the regional (plate motion‐driven) stress field.

Strong link between Earth’s oxygen level and geomagnetic dipole revealed since the last 540 million years

2025-06-13

Weijia Kuang , R. Kopparapu , Joshua Krissansen‐Totton +1 more | Science Advances

Earth is the only known rocky planet to support complex life forms that use oxygen and to have a strong intrinsic magnetic field in much of its history, prompting speculation … Earth is the only known rocky planet to support complex life forms that use oxygen and to have a strong intrinsic magnetic field in much of its history, prompting speculation that Earth’s magnetic field and habitability are related on geological timescales. We search for possible observational evidence for such a relationship by examining evolutions of the virtual geomagnetic axial dipole moment and the atmospheric oxygen level over the past 540 million years. We find that both exhibit strong linearly increasing trends, coupled with a large surge in magnitude between 330 and 220 million years ago. Our time series analysis and statistical tests show that both are highly correlated, with the maximum correlation reached when there is no time lag between the two. Our findings suggest unexpected strong connections between the geophysical processes in Earth’s deep interior, the surface redox budget, and biogeochemical cycling.

Magmatic intrusions in real time

2025-06-13

Leilei Wu | Nature Physics

Spatio-temporal disturbances of the Earth’s magnetic field along the Struve Geodetic Arc

2025-06-09

М.І. Оrlyuk , А. Romenets , А. В. Марченко +1 more | Geofizicheskiy Zhurnal

In 1816-1855, astronomer Friedrich Georg Wilhelm von Struve made the first topographic measurements along a 2822 km long segment of the meridian stretching from northern Norway (70°40′N) to southern Odesa … In 1816-1855, astronomer Friedrich Georg Wilhelm von Struve made the first topographic measurements along a 2822 km long segment of the meridian stretching from northern Norway (70°40′N) to southern Odesa Region (45°19′N) to determine the exact size and shape of the planet. This segment of the meridian is a good testing ground for studying the geomagnetic aspect of solar-terrestrial interactions, as both the main magnetic field of the Earth and the anomalous magnetic field at surface and ionospheric heights change significantly within its boundaries. The article presents the results of a study of the nature of the magnetic storm on May 10-13, 2024, depending on the module and anomalies of the geomagnetic field induction module along the Struve Geodesic Arc. To characterize the Earth's internal magnetic field, digital maps of the induction module and anomalies at heights of 5 and 100 km were developed, and to characterize the magnetic storm, the results of observations of variations in the northern, eastern, and vertical components of the geomagnetic field induction module in 7 magnetic observatories were used. For each observatory, we calculated the induction modulus of the internal magnetic field Bi, the modulus of the main magnetic field (core field) BIGRF, the amplitude and mean value of the geomagnetic field variation, as well as the variation of the parameter ΔD, which reflects the ratio of the anomaly of the geomagnetic field induction modulus to the BIGRF field. According to the results of statistical analysis, the dependence of the amplitude of the external geomagnetic field variations and their average values on the modulus of the main magnetic field of the Earth BIGRF was revealed (R2AõB/BIGPH = 0.96 and R2õB_average/BIGPH = 0.7, respectively). A slightly lower correlation dependence was observed for the Bx component of the geomagnetic field and BIGRF (R2Bx/BIGRF=0.89). The amplitude of variation of the spatio-temporal perturbation of the geomagnetic field δ(ΔD) is also characterized by a high correlation dependence on the BIGRF module (R2Aδ(ΔD)/BIGPH= 0.96) and naturally increases depending on the latitude of the observatory, from 273 nT at the SUA observatory to 2240 nT at the SOD observatory. The revealed regularity is confirmed by a stronger manifestation of the magnetic storm on May 10-13, 2024 and a shift of its maximum disturbances by 4 degrees to the south compared to the magnetic storm of November 29-31, 2003, during which the BIGRF field induction module for the northern part of the STRUVE GEODETIC ARC increased by 830÷930 nT. The connection between the maximum manifestation of the geomagnetic storm and regional magnetic anomalies on the Earth's surface and their superposition at an altitude of 100 km was revealed. The connection between the maximum manifestation of the geomagnetic storm and regional magnetic anomalies on the Earth's surface and their superposition at an altitude of 100 km is revealed. The maximum magnitude of the magnetic disturbance is recorded at the Pello station, which is located in the region of the maximum anomalous magnetic field (more than 90 nT at an altitude of 100 km), in contrast to the Mikkelvik station ‒ in the zone of the minimum geomagnetic field, which is partially confirmed by the variation of ΔB anomalies due to the magnetization of their sources by the variation of the external field. The most probable reason for the connection between the amplitude of external field variations and the modulus of the main magnetic field of the BIGRF and the anomalous magnetic field ΔB is their effect on the formation of ionospheric currents.

Geomagnetic Excursions Recorded in North Atlantic IODP Expedition 395C Sites U1555 and U1563

2025-06-01

Anita Di Chiara , S. Satolli , Sarah Friedman +7 more | Geochemistry Geophysics Geosystems

Abstract By studying deep‐sea drilled records from the North Atlantic Ocean, several magnetic instabilities of short duration, such as the Iceland Basin (188 ka), the Björn (1,255 ka) and the … Abstract By studying deep‐sea drilled records from the North Atlantic Ocean, several magnetic instabilities of short duration, such as the Iceland Basin (188 ka), the Björn (1,255 ka) and the Gardar (1,460 ka) excursions, were discovered. These records have contributed to our understanding of Earth's magnetic field and are the foundation of the Geomagnetic Instability Time Scale (GITS) in the Quaternary. Here, we present the magnetostratigraphy from Sites U1555 (0 to ∼2.7 Ma) and U1563 (0 to ∼5.2 Ma) drilled during the International Ocean Discovery Program Expedition 395C on the eastern side of the modern Mid‐Atlantic Ridge (∼60°N, 20–30°W). Shipboard paleomagnetic and microfossil data provided a preliminary age model, extending the regional record to 3.4 Ma. The Virtual Geomagnetic Pole latitudes from archive halves, corroborated with data from discrete samples, were used to build a high‐resolution magnetostratigraphy, which contained the expected Brunhes and Matuyama Chrons and their respective Subchrons. We also identified most of the magnetic events reported in the GITS, including the less well‐documented ones, such as Osaka, Kamitzukara, Huckleberry Ridge, Reunion, Gardar, Halawa and L4 events. The high‐resolution magnetostratigraphy from Sites U1555 and U1563 is compared with two previous legacy sites and contributes toward an increasingly robust GITS, expanding its use as a correlation and dating tool.