WorldWideScience

Sample records for geomagnetic field

  1. International Geomagnetic Reference Field

    DEFF Research Database (Denmark)

    Finlay, Chris; Maus, S.; Beggan, C. D.

    2010-01-01

    The eleventh generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2009 by the International Association of Geomagnetism and Aeronomy Working Group V‐MOD. It updates the previous IGRF generation with a definitive main field model for epoch 2005.0, a main field...

  2. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independe...... of the small-scale structure of the Earth’s lithospheric field....

  3. History of the geomagnetic field

    Science.gov (United States)

    Doell, Richard R.

    1969-01-01

    Direct measurements of the direction and strength of the earth's magnetic field have provided a knowledge of the field's form and behavior during the last few hundreds of years. For older times, however, it has been necessary to measure the magnetism of certain rocks to learn what the geomagnetic field was like. For example, when a lava flow solidifies (at temperatures near 1000??C) and cools through the Curie point of the magnetic minerals contained in it (around 500??C) it acquires a remanent magnetism that is (1) very weak, (2) very stablel, (3) paralle to the direction of the ambient geomagnetic field, and (4) proportional in intensity to the ambient field. Separating, by various analytical means, this magnetization from other 'unwanted' magnetizations has allowed paleomagnetists to study the historical and prehistorical behavior of the earth's field. It has been learned, for example, that the strength of the field was almost twice its present value 2000 years ago and that it has often completely reversed its polarity. Paleo-magnetists have also confirmed that most oceans are, geologically speaking, relatively new features, and that the continents have markedly changed their positions over the surface of the earth. ?? 1969 The American Institute of Physics.

  4. Geomagnetic Observations for Main Field Studies

    DEFF Research Database (Denmark)

    Matzka, Jürgen; Chulliat, A.; Mandea, M.

    2010-01-01

    Direct measurements of the geomagnetic field have been made for more than 400 years, beginning with individual determinations of the angle between geographic and magnetic North. This was followed by the start of continuous time series of full vector measurements at geomagnetic observatories and t...... for magnetic field measurements on ground and in space and covers geomagnetic observatories, repeat stations, automatic observatories, satellites and historic observations. Special emphasis is laid on the global network of geomagnetic observatories....... and the beginning of geomagnetic repeat stations surveys in the 19th century. In the second half of the 20th century, true global coverage with geomagnetic field measurements was accomplished by magnetometer payloads on low-Earth-orbiting satellites. This article describes the procedures and instruments...

  5. Differential rotation of geomagnetic field

    Institute of Scientific and Technical Information of China (English)

    WEI Zigang; XU Wenyao

    2003-01-01

    The latitudinal dependence of the westward drift in the main geomagnetic field is examined by using the correlation analysis of moving random pattern. The study reveals the characteristics in the differential rotation of the main field. The results show that the global geomagnetic field drifts westward with an average speed of 0.18°/a during 1900-2000. The westward drift rate is not symmetrical with respect to the equator. The maximum westward drift rate, 0.31°/a, occurs at the latitude --= -15°, forming a Rapid Westward Drift Belt (RDB) around this latitude. Going northward and southward from this belt, the drift rate decreases and reaches the minimum (0.12°/a) at --= 50° and the minimum (0.14°/a) at --= -56°, forming a Northern Hemisphere Slow Westward Drift Belt (N-SDB) and a Southern Hemisphere Slow Westward Drift Belt (S-SDB). Three phases can be detected in the evolution of the westward drift. In the first phase (1900-1940), the RDB dominates the global drift pattern. The westward drifts in this belt are much faster than those in other areas. In the second phase (1940-1960), the drift rates in the RDB are less than those in the first phase, while the drifts in the N-SDB and S-SDB are relatively large. In this phase, the differential rotation becomes less obvious. In the third phase (1960-2000), the westward drift in the RDB increases again and the differential rotation gradually becomes apparent.

  6. The geomagnetic main field and the geodynamo

    Science.gov (United States)

    Bloxham, Jeremy; Roberts, Paul H.

    1991-01-01

    Information available on the geomagnetic main field and the geodynamo is presented. Attention is given to the process of mapping the magnetic field, the last version of International Geomagnetic Reference Field Model, and maps of the magnetic field at the core-mantle boundary and their interpretation. Particular consideration is given to the existing geodynamo theories, with special relation given to the Braginsky and Meytlis theory of core turbulence in which the turbulence differs fundamentally from classical turbulence of Kolmogorov type.

  7. What happens when the geomagnetic field reverses?

    CERN Document Server

    Lemaire, Joseph F

    2012-01-01

    During geomagnetic field reversals the radiation belt high-energy proton populations become depleted. Their energy spectra become softer, with the trapped particles of highest energies being lost first, and eventually recovering after a field reversal. The radiation belts rebuild in a dynamical way with the energy spectra flattening on the average during the course of many millennia, but without ever reaching complete steady state equilibrium between successive geomagnetic storm events determined by southward turnings of the IMF orientation. Considering that the entry of galactic cosmic rays and the solar energetic particles with energies above a given threshold are strongly controlled by the intensity of the northward component of the interplanetary magnetic field, we speculate that at earlier epochs when the geomagnetic dipole was reversed, the entry of these energetic particles into the geomagnetic field was facilitated when the interplanetary magnetic field was directed northward. Unlike in other compleme...

  8. Centennial to millennial geomagnetic field variations

    Directory of Open Access Journals (Sweden)

    Muscheler Raimund

    2012-06-01

    Full Text Available Reconstructions of the geomagnetic field in the past represent a useful tool not only to investigate the geodynamo process, but also to estimate the effect of geomagnetic shielding for any studies on cosmogenic radionuclides and galactic cosmic rays. A number of new millennial-scale geomagnetic field reconstructions have been published over the last years, based on improved global archeo- and paleomagnetic data compilations. Here we review several spherical harmonic models and compare their dipole field predictions to reconstructions based on virtual axial dipole moments and virtual geomagnetic poles. Dipole intensity estimates from cosmogenic radionuclide production records, with suitable filtering to minimise the solar influence, have also been included in the comparison to provide independent information about variations in the strength of the geomagnetic field. However, due to differences among geomagnetic models and between 14C and 10Be production records this comparison is fairly inconclusive with respect to multi-centennial variations. Different geomagnetic dipole tilt reconstructions agree well for much of the Holocene, but dipole moment estimates still differ substantially. Recent spherical harmonic models for the past 3 and 10 kyrs have improved considerably compared to earlier versions. Nevertheless at present we recommend to test if any interpretation depends on the choice of model.

  9. The International Geomagnetic Reference Field, 2005

    Science.gov (United States)

    Rukstales, Kenneth S.; Love, Jeffrey J.

    2007-01-01

    This is a set of five world charts showing the declination, inclination, horizontal intensity, vertical component, and total intensity of the Earth's magnetic field at mean sea level at the beginning of 2005. The charts are based on the International Geomagnetic Reference Field (IGRF) main model for 2005 and secular change model for 2005-2010. The IGRF is referenced to the World Geodetic System 1984 ellipsoid. Additional information about the USGS geomagnetism program is available at: http://geomag.usgs.gov/

  10. Bats Use Geomagnetic Field: Behavior and Mechanism

    Science.gov (United States)

    Pan, Y.; Tian, L.; Zhang, B.; Zhu, R.

    2015-12-01

    It has been known that numerous animals can use the Earth's magnetic field for spatial orientation and long-distance navigation, nevertheless, how animals can respond to the magnetic field remain mostly ambiguous. The intensities of the global geomagnetic field varies between 23 and 66 μT, and the geomagnetic field intensity could drop to 10% during geomagnetic polarity reversals or geomagnetic excursions. Such dramatic changes of the geomagnetic field may pose a significant challenge for the evolution of magnetic compass in animals. For examples, it is vital whether the magnetic compass can still work in such very weak magnetic fields. Our previous experiment has demonstrated that a migratory bat (Nyctalus plancyi) uses a polarity compass for orientation during roosting when exposed to an artificial magnetic field (100 μT). Recently, we experimentally tested whether the N. plancyi can sense very weak magnetic fields that were even lower than those of the present-day geomagnetic field. Results showed: 1) the bats can sense the magnetic north in a field strength of present-day local geomagnetic field (51μT); 2) As the field intensity decreased to only 1/5th of the natural intensity (10 μT), the bats still responded by positioning themselves at the magnetic north. Notably, as the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 μT). Hence, N. plancyi is able to detect the direction of a magnetic field with intensity range from twice to 1/5th of the present-day field strength. This allows them to orient themselves across the entire range of present-day global geomagnetic field strengths and sense very weak magnetic fields. We propose that this high sensitivity might have evolved in bats as the geomagnetic field strength varied and the polarity reversed tens of times over the past fifty million years since the origin of bats. The physiological mechanisms underlying

  11. 10th Generation International Geomagnetic Reference Field

    Science.gov (United States)

    Maus, Stefan; Macmillan, Susan

    2005-04-01

    The International Association of Geomagnetism and Aeronomy (IAGA) released the 10th Generation International Geomagnetic Reference Field (IGRF) on 12 December 2004. This is the latest version of a standard mathematical description of the Earth's main magnetic field, and is used widely in studies of the Earth's deep interior, crust, ionosphere, and magnetosphere. The coefficients were finalized by a task force of IAGA, Division V, Working Group V-MOD: Geomagnetic Field Modeling. The IGRF is the product of a large collaborative effort between magnetic field modelers and the institutes around the world involved in collecting and disseminating magnetic field data from satellites and observatories. The IGRF is a series of mathematical models of the Earth's main field and its annual rate of change (secular variation). The sources of the main magnetic field are electric currents in the Earth and the magnetization of crustal rocks.

  12. International Geomagnetic Reference Field: the third generation.

    Science.gov (United States)

    Peddie, N.W.

    1982-01-01

    In August 1981 the International Association of Geomagnetism and Aeronomy revised the International Geomagnetic Reference Field (IGRF). It is the second revision since the inception of the IGRF in 1968. The revision extends the earlier series of IGRF models from 1980 to 1985, introduces a new series of definitive models for 1965-1976, and defines a provisional reference field for 1975- 1980. The revision consists of: 1) a model of the main geomagnetic field at 1980.0, not continuous with the earlier series of IGRF models together with a forecast model of the secular variation of the main field during 1980-1985; 2) definitive models of the main field at 1965.0, 1970.0, and 1975.0, with linear interpolation of the model coefficients specified for intervening dates; and 3) a provisional reference field for 1975-1980, defined as the linear interpolation of the 1975 and 1980 main-field models.-from Author

  13. Mathematical Properties Relevant to Geomagnetic Field Modeling

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Hulot, Gauthier; Olsen, Nils

    2010-01-01

    properties of those spatial mathematical representations are also discussed, especially in view of providing a formal justification for the fact that geomagnetic field models can indeed be constructed from ground-based and satellite-born observations, provided those reasonably approximate the ideal......Geomagnetic field modeling consists in converting large numbers of magnetic observations into a linear combination of elementary mathematical functions that best describes those observations.The set of numerical coefficients defining this linear combination is then what one refers...... be directly measured. In this chapter, the mathematical foundation of global (as opposed to regional) geomagnetic field modeling is reviewed, and the spatial modeling of the field in spherical coordinates is focussed. Time can be dealt with as an independent variable and is not explicitly considered...

  14. Mathematical Properties Relevant to Geomagnetic Field Modeling

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Hulot, Gauthier; Olsen, Nils

    2014-01-01

    properties of those spatial mathematical representations are also discussed, especially in view of providing a formal justification for the fact that geomagnetic field models can indeed be constructed from ground-based and satellite-born observations, provided those reasonably approximate the ideal situation......Geomagnetic field modeling consists in converting large numbers of magnetic observations into a linear combination of elementary mathematical functions that best describes those observations. The set of numerical coefficients defining this linear combination is then what one refers...... be directly measured. In this chapter, the mathematical foundation of global (as opposed to regional) geomagnetic field modeling is reviewed, and the spatial modeling of the field in spherical coordinates is focused. Time can be dealt with as an independent variable and is not explicitly considered...

  15. Satellite data for geomagnetic field modeling

    Science.gov (United States)

    Langel, R. A.; Baldwin, R. T.

    1992-06-01

    Satellite measurements of the geomagnetic fields began with the launch of Sputnik 3 in May of 1958 and have continued sporadically. Spacecraft making significant contributions to main field geomagnetism will be reviewed and the characteristics of their data discussed, including coverage, accuracy, resolution and data availability. Of particular interest are Vanguard 3; Cosmos 49, Ogo's -2, -4, and -6; Magsat; DE-2; and POGS. Spacecraft make measurements on a moving platfrom above the ionosphere as opposed to measurements from fixed observatories and surveys, both below the ionosphere. Possible future missions, such as Aristoteles and GOS are reviewed.

  16. Satellite Data for Geomagnetic Field Modeling

    Science.gov (United States)

    Langel, R. A.; Baldwin, R. T.

    1992-01-01

    Satellite measurements of the geomagnetic fields began with the launch of Sputnik 3 in May of 1958 and have continued sporadically. Spacecraft making significant contributions to main field geomagnetism will be reviewed and the characteristics of their data discussed, including coverage, accuracy, resolution and data availability. Of particular interest are Vanguard 3; Cosmos 49, Ogo's -2, -4, and -6; Magsat; DE-2; and POGS. Spacecraft make measurements on a moving platfrom above the ionosphere as opposed to measurements from fixed observatories and surveys, both below the ionosphere. Possible future missions, such as Aristoteles and GOS are reviewed.

  17. Interplanetary magnetic field and geomagnetic Dst variations.

    Science.gov (United States)

    Patel, V. L.; Desai, U. D.

    1973-01-01

    The interplanetary magnetic field has been shown to influence the ring current field represented by Dst. Explorer 28 hourly magnetic field observations have been used with the hourly Dst values. The moderate geomagnetic storms of 60 gammas and quiet-time fluctuations of 10 to 30 gammas are correlated with the north to south change of the interplanetary field component perpendicular to the ecliptic. This change in the interplanetary field occurs one to three hours earlier than the corresponding change in the Dst field.

  18. International Geomagnetic Reference Field: the seventh generation.

    Science.gov (United States)

    Barton, C. E.

    A seventh-generation revision of the International Geomagnetic Reference Field (IGRF) was adopted by the International Association of Geomagnetism and Aeronomy (IAGA) at the XXI General Assembly of the International Union of Geodesy and Geophysics in July 1995. The new spherical harmonic models adopted are based on weighted averages of candidate models submitted by NASA's Goddard Space Flight Center, the Russian Institute of Terrestrial Magnetism, Ionospheric, and Radio Wave Propagation - IZMIRAN, and jointly by the US Naval Oceanographic Office and the British Geological Survey. The revised IGRF specifies the Earth's main field from 1900 to 2000 and is declared to be definitive from 1945 to 1990. This paper lists the IGRF coefficients, describes the derivation of the new IGRF models, and examines aspects of the IGRF's accuracy, continuity, and behaviour during the 20th century.

  19. Geomagnetic field detection in rodents

    Energy Technology Data Exchange (ETDEWEB)

    Olcese, J.; Reuss, S.; Semm, P.

    1988-01-01

    In addition to behavioral evidence for the detection of earth-strength magnetic fields (MF) by rodents, recent investigations have revealed that electrophysiological and biochemical responses to MF occur in the pineal organ and retina of rodents. In addition, ferrimagnetic deposits have been identified in the ethmoidal regions of the rodent skull. These findings point to a new sensory phenomenon, which interfaces with many fields of biology, including neuroscience, psychophysics, behavioral ecology, chronobiology and sensory physiology.

  20. Trapping of strangelets in the geomagnetic field

    CERN Document Server

    Paulucci, L; Medina-Tanco, G A

    2007-01-01

    Strangelets coming from the interstellar medium (ISM) are an interesting target to experiments searching for evidence of this hypothetic state of hadronic matter. We entertain the possibility of a {\\it trapped} strangelet population, quite analogous to ordinary nuclei and electron belts. For a population of strangelets to be trapped by the geomagnetic field, these incoming particles would have to fulfill certain conditions, namely having magnetic rigidities above the geomagnetic cutoff and below a certain threshold for adiabatic motion to hold. We show in this work that, for fully ionized strangelets, there is a narrow window for stable trapping. An estimate of the stationary population is presented and the dominant loss mechanisms discussed. It is shown that the population would be substantially enhanced with respect to the ISM flux (up to two orders of magnitude) due to quasi-stable trapping.

  1. Could Geoneutrinos Interact With the Geomagnetic Field?

    CERN Document Server

    Quintero, C A B

    2015-01-01

    In the present paper, we consider the possibility of interaction between geoneutrinos and the geomagnetic field, by adopting an approach based on the Dirac's equation with a non-minimal coupling that accounts for the magnetic interaction of the massive neutrinos. In our approach, we see that the magnetic interaction is controlled by a dimensionless parameter, $f\\simeq 10^{-1}$, and we estimate the mean value of this interaction to be of the order of $10^{-14}\\ MeV^{2}$.

  2. The latitudinal distribution of the baseline geomagnetic field during the March 17, 2015 geomagnetic storm

    Science.gov (United States)

    Alberti, Tommaso; Piersanti, Mirko; Lepreti, Fabio; Vecchio, Antonio; De Michelis, Paola; Villante, Umberto; Carbone, Vincenzo

    2016-04-01

    Geomagnetic storms (GS) are global geomagnetic disturbances that result from the interaction between magnetized plasma that propagates from the Sun and plasma and magnetic fields in the near-Earth space plasma environment. The Dst (Disturbance Storm Time) global Ring Current index is still taken to be the definitive representation for geomagnetic storm and is used widely by researcher. Recent in situ measurements by satellites passing through the ring-current region (i.e. Van Allen probes) and computations with magnetospheric field models showed that there are many other field contributions on the geomagnetic storming time variations at middle and low latitudes. Appling the Empirical Mode Decomposition [Huang et al., 1998] to magnetospheric and ground observations, we detect the different magnetic field contributions during a GS and introduce the concepts of modulated baseline and fluctuations of the geomagnetic field. In this work, we apply this method to study the latitudinal distribution of the baseline geomagnetic field during the St. Patrick's Day Geomagnetic Storm 2015 in order to detect physical informations concerning the differences between high-latitude and equatorial ground measurements.

  3. Cosmic rays, geomagnetic field and climate changes

    Science.gov (United States)

    Shea, M.; Smart, D.

    The possibility of a connection between cosmic radiation and climate has intrigued scientists for the past several decades. The recent studies of Friis -Christensen and Svensmark has shown an observed variation of 3-4% of the global cloud cover between 1980 and 1995 that appeared to be directly correlated with the change in galactic cosmic radiation flux over the solar cycle. However, in studies of this type, not only the solar cycle modulation of cosmic radiation must be considered, but also the changes in the cosmic radiation impinging at the top of the atmosphere as a result of the long term evolution of the geomagnetic field. We present preliminary results of an on-going study of geomagnetic cutoff rigidities over a 400-year interval. These results show (1) the change in cutoff rigidity is sufficient large so that the change in cosmic radiation flux impacting the earth is approximately equal to the relative change in flux over a solar cycle, and (2) the changes in cutoff rigidity are non- uniform over the globe with both significant increases and decreases at mid-latitude locations.

  4. A domino model for geomagnetic field reversals

    CERN Document Server

    Mori, N; Ferriz-Mas, A; Wicht, J; Mouri, H; Nakamichi, A; Morikawa, M

    2011-01-01

    We solve the equations of motion of a one-dimensional planar Heisenberg (or Vaks-Larkin) model consisting of a system of interacting macro-spins aligned along a ring. Each spin has unit length and is described by its angle with respect to the rotational axis. The orientation of the spins can vary in time due to random forcing and spin-spin interaction. We statistically describe the behaviour of the sum of all spins for different parameters. The term "domino model" in the title refers to the interaction among the spins. We compare the model results with geomagnetic field reversals and find strikingly similar behaviour. The aggregate of all spins keeps the same direction for a long time and, once in a while, begins flipping to change the orientation by almost 180 degrees (mimicking a geomagnetic reversal) or to move back to the original direction (mimicking an excursion). Most of the time the spins are aligned or anti-aligned and deviate only slightly with respect to the rotational axis (mimicking the secular v...

  5. Evaluation of candidate geomagnetic field models for IGRF-12

    DEFF Research Database (Denmark)

    Thébault, Erwan; Finlay, Chris; Alken, Patrick

    2015-01-01

    Background: The 12th revision of the International Geomagnetic Reference Field (IGRF) was issued in December 2014 by the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group V-MOD (http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html). This revision comprises new spherical...

  6. The Egyptian geomagnetic reference field to the Epoch, 2010.0

    Directory of Open Access Journals (Sweden)

    H.A. Deebes

    2017-06-01

    The geomagnetic anomaly maps, the normal geomagnetic field maps with their corresponding secular variation maps, the normal geomagnetic field equations of the geomagnetic elements (EGRF and their corresponding secular variations equations, are outlined. The anomalous sites, as discovered from the anomaly maps are, only, mentioned. In addition, a correlation between the International Geomagnetic Reference Field (IGRF 2010.0 and the Egyptian Geomagnetic Reference Field (EGRF 2010 is indicated.

  7. Magnetic rotation imaging method to measure the geomagnetic field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A new imaging method for measuring the geomagnetic field based on the magnetic rotation effect is put forward. With the help of polarization property of the sunlight reflected from the ground and the magnetic rotation of the atmosphere, the geomagnetic field can be measured by an optical system installed on a satellite. According to its principle, the three-dimensional image of the geomagnetic field can be obtained. The measuring speed of this method is very high, and there is no blind spot and distortion. In this paper, the principle of this method is presented, and some key problems are discussed.

  8. Remote Sensing of Geomagnetic Field and Applications to Climate Prediction

    CERN Document Server

    Selvam, A M

    2000-01-01

    Observations show that geomagnetic field lines follow closely the atmosphericcirculation patterns and that geomagnetic field variations are precursors toclimate change . The exact mechanism for the observed close relationshipbetween global geomagnetic field and the tropospheric weather patterns is notclear. In this paper a universal theory of atmospheric eddy dynamics ispresented which shows that the global geomagnetic field, atmospheric electricfield and weather systems are manifestations of a semi permanent scaleinvariant hierarchical atmospheric eddy continuum. Quantitative equations arederived to show that the full continuum of atmospheric eddies exist as aunified whole and originate from buoyant energy supply from frictionalturbulence at the planetary surface . Large eddy growth occurs from turbulencescale by the universal period doubling route to chaos . The turbulent eddiesare carried upwards on the large eddy envelopes and vertical mixing occurs bythe turbulent eddy fluctuations resulting in downward ...

  9. Effects of geomagnetic activity on the mesospheric electric fields

    Directory of Open Access Journals (Sweden)

    A. M. Zadorozhny

    Full Text Available The results of three series of rocket measurements of mesospheric electric fields carried out under different geomagnetic conditions at polar and high middle latitudes are analysed. The measurements show a clear dependence of the vertical electric fields on geomagnetic activity at polar and high middle latitudes. The vertical electric fields in the lower mesosphere increase with the increase of geomagnetic indexes Kp and ∑Kp. The simultaneous increase of the vertical electric field strength and ion conductivity was observed in the mesosphere during geomagnetic disturbances. This striking phenomenon was displayed most clearly during the solar proton events of October, 1989 accompanied by very strong geomagnetic storm (Kp=8+. A possible mechanism of generation of the vertical electric fields in the mesosphere caused by gravitational sedimentation of charged aerosol particles is discussed. Simultaneous existence in the mesosphere of both the negative and positive multiply charged aerosol particles of different sizes is assumed for explanation of the observed V/m vertical electric fields and their behaviour under geomagnetically disturbed conditions.

    Keywords. Atmospheric composition and structure (aerosols and particles · Ionosphere (electric fields and currents · Meteorology and atmospheric dynamics (atmospheric electricity

  10. Globally strong geomagnetic field intensity circa 3000 years ago

    Science.gov (United States)

    Hong, Hoabin; Yu, Yongjae; Lee, Chan Hee; Kim, Ran Hee; Park, Jingyu; Doh, Seong-Jae; Kim, Wonnyon; Sung, Hyongmi

    2013-12-01

    High-fidelity geomagnetic field intensity determination was carried out using 191 baked fragments collected from 20 kilns or hearths with ages ranging between ∼1200 BC and ∼AD 1725 in South Korea. Geomagnetic field intensity variation displayed three narrow minima at ∼800-700 BC, ∼AD 700, and ∼AD 1600 and two maxima at ∼1200-1100 BC and ∼AD 1000-1100. In most time intervals, virtual axial dipole moment (VADM) variation is confined within 20% of the present VADM. However, geomagnetic field intensity circa 3000 yr ago is nearly 40% larger than the present value. Such high VADMs circa 3000 yr ago are in phase with those in other longitudinal bands in northern hemisphere centered at 5E (France), 30E (the Middle East) and 200E (Hawaii). Although strong geomagnetic field intensity circa 3000 yr ago is globally synchronous, the highest VADM occurs at slightly different time intervals in different locations. Hence it is possible that the globally strong geomagnetic field intensity circa 3000 yr ago reflects the migration of persistent hemispheric flux in northern hemisphere or an episode of geomagnetic field hemispheric asymmetry.

  11. Regional cosmic ray induced ionization and geomagnetic field changes

    Directory of Open Access Journals (Sweden)

    G. A. Kovaltsov

    2007-08-01

    Full Text Available Cosmic ray induced ionization (CRII is an important factor of outer space influences on atmospheric properties. Variations of CRII are caused by two different processes – solar activity variations, which modulate the cosmic ray flux in interplanetary space, and changes of the geomagnetic field, which affects the cosmic ray access to Earth. Migration of the geomagnetic dipole axis may greatly alter CRII in some regions on a time scale of centuries and longer. Here we present a study of CRII regional effects of the geomagnetic field changes during the last millennium for two regions: Europe and the Far East. We show that regional effects of the migration of the geomagnetic dipole axis may overcome global changes due to solar activity variations.

  12. Tsunami effects on the Z component of the geomagnetic field

    CERN Document Server

    Klausner, Virginia; Mendes, Odim; Papa, Andres R R

    2011-01-01

    The vertical component (Z) of the geomagnetic field observed by ground-based observatories of the INTERMAGNET network has been used to analyze the effects of the movement of electrically conducting sea water through the geomagnetic field due to a propagation of a tsumani. The purpose of this work is to study the geomagnetic variations induced by the tsunamis occurred at 26 December, 2004, 27 February, 2010 and 11 March, 2011. For each case study, we selected four magnetic stations belonging to the INTERMAGNET programme that were influenced or more direct affected by the tsumani. To detect these disturbances in the geomagnetic data, the discrete wavelet technique have been used in four levels of decomposition. We were able to detect the localized behavior of the geomagnetic variations induced by the movement of electrically conducting sea-water through the geomagnetic field, i. e., the identification of transients related to the tsunamis. As well, using the minutely magnetogram data, it was able to localize th...

  13. The 9th-Generation International Geomagnetic Reference Field

    Science.gov (United States)

    Macmillan, S.; Maus, S.; Bondar, T.; Chambodut, A.; Golovkov, V.; Holme, R.; Langlais, B.; Lesur, V.; Lowes, F.; Lühr, H.; Mai, W.; Mandea, M.; Olsen, N.; Rother, M.; Sabaka, T.; Thomson, A.; Wardinski, I.

    2003-12-01

    The International Association of Geomagnetism and Aeronomy has recently released the 9th-Generation International Geomagnetic Reference Field-the latest version of a standard mathematical description of the Earth's main magnetic field used widely in studies of the Earth's deep interior, its crust and its ionosphere and magnetosphere. The coefficients were recently finalized at the XXIII General Assembly of the International Union of Geophysics and Geodesy, held at Sapporo in Japan in 2003 July. The IGRF is the product of a huge collaborative effort between magnetic field modellers and the institutes involved in collecting and disseminating magnetic field data from satellites and from observatories and surveys around the world.

  14. The 10th generation international geomagnetic reference field

    Science.gov (United States)

    Maus, S.; Macmillan, S.; Chernova, T.; Choi, S.; Dater, D.; Golovkov, V.; Lesur, V.; Lowes, F.; Lühr, H.; Mai, W.; McLean, S.; Olsen, N.; Rother, M.; Sabaka, T.; Thomson, A.; Zvereva, T.; International Association of Geomagnetism, Aeronomy (IAGA), Division V, Working Group VMOD

    The International Association of Geomagnetism and Aeronomy (IAGA) on 12 December 2004 released the 10th generation International Geomagnetic Reference Field (IGRF)—the latest version of a standard mathematical description of the Earth's main magnetic field and used widely in studies of the Earth's deep interior, its crust, ionosphere and magnetosphere. The coefficients were finalised by a task force of IAGA. The IGRF is the product of a large collaborative effort between magnetic field modellers and the institutes involved in collecting and disseminating magnetic field data from satellites and observatories around the world.

  15. The 10th-Generation International Geomagnetic Reference Field

    Science.gov (United States)

    2005-06-01

    The International Association of Geomagnetism and Aeronomy (IAGA) on 2004 December 12 has released the 10th-Generation International Geomagnetic Reference Field-the latest version of a standard mathematical description of the Earth's main magnetic field used widely in studies of the Earth's deep interior, its crust, ionosphere and magnetosphere. The coefficients were finalized by a task force of IAGA. The IGRF is the product of a large collaborative effort between magnetic field modellers and the institutes involved in collecting and disseminating magnetic field data from satellites and observatories around the world.

  16. Intensity of the geomagnetic field in Europe for the last 3 ka: Influence of data quality on geomagnetic field modeling

    Science.gov (United States)

    Pavón-Carrasco, Francisco Javier; Gómez-Paccard, Miriam; Hervé, Gwenaël.; Osete, María. Luisa; Chauvin, Annick

    2014-06-01

    of the main challenges of paleomagnetic research is to obtain high-resolution geomagnetic field intensity reconstructions. For the last millennia, these reconstructions are mostly based on archeomagnetic data. However, the quality of the intensity data available in the databases is very variable, and the high scatter observed in the records clearly suggests that some of them might not be reliable. In this work we investigate how the geomagnetic field intensity reconstructions and, hence, our present knowledge of the geomagnetic field in the past, are affected by the quality of the data selected for modeling the Earth's magnetic field. For this purpose we rank the European archeointensity data in four quality categories following widely accepted paleomagnetic criteria based on the methodology used during the laboratory treatment of the samples and on the number of specimens retained to calculate the mean intensities. Four geomagnetic field regional models have been implemented by applying the revised spherical cap harmonic analysis to these four groups of input data. Geomagnetic field models strongly depend on the used data set. The model built using all the available data (without any preselection) appears to be the less accurate, indicating some internal inconsistencies of the data set. In addition, some features of this model are clearly dominated by the less reliable archeointensity data, suggesting that such features might not reflect real variations of the past geomagnetic field. On the contrary, the regional model built on selected high-quality intensity data shows a very consistent intensity pattern at the European scale, confirming that the main intensity changes observed in Europe in the recent history of the geomagnetic field occurred at the continental scale.

  17. Variability modes in core flows inverted from geomagnetic field models

    CERN Document Server

    Pais, Maria A; Schaeffer, Nathanaël

    2014-01-01

    We use flows that we invert from two geomagnetic field models spanning centennial time periods (gufm1 and COV-OBS), and apply Principal Component Analysis and Singular Value Decomposition of coupled fields to extract the main modes characterizing their spatial and temporal variations. The quasi geostrophic flows inverted from both geomagnetic field models show similar features. However, COV-OBS has a less energetic mean flow and larger time variability. The statistical significance of flow components is tested from analyses performed on subareas of the whole domain. Bootstrapping methods are also used to extract robust flow features required by both gufm1 and COV-OBS. Three main empirical circulation modes emerge, simultaneously constrained by both geomagnetic field models and expected to be robust against the particular a priori used to build them. Mode 1 exhibits three large robust vortices at medium/high latitudes, with opposite circulation under the Atlantic and the Pacific hemispheres. Mode 2 interesting...

  18. International Geomagnetic Reference Field: the 12th generation

    OpenAIRE

    2015-01-01

    International audience; 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, p...

  19. International Geomagnetic Reference Field: the 12th generation

    DEFF Research Database (Denmark)

    Thébault, Erwan; Finlay, Chris; Beggan, Ciarán D.

    2015-01-01

    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...... 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....

  20. Surface electric fields for North America during historical geomagnetic storms

    Science.gov (United States)

    Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.

    2013-01-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 “Quebec” storm and the 2003 “Halloween” storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  1. Analysis of geomagnetic secular variation during 1980-1985 and 1985- 1990, and geomagnetic models proposed for the 1991 revision of the International Geomagnetic Reference Field

    Science.gov (United States)

    Peddie, N.W.

    1992-01-01

    The secular variation of the main geomagnetic field during the periods 1980-1985 and 1985-1990 was analyzed in terms of spherical harmonics up to the eighth degree and order. Data from worldwide magnetic observatories and the Navy's Project MAGNET aerial surveys were used. The resulting pair of secular-variation models was used to update the Definitive Geomagnetic Reference Field (DGRF) model for 1980, resulting in new mainfield models for 1985.0 and 1990.0. These, along with the secular-variation model for 1985-1990, were proposed for the 1991 revision of the International Geomagnetic Reference Field (IGRF). -Author

  2. Evaluation of candidate geomagnetic field models for IGRF-11

    DEFF Research Database (Denmark)

    Finlay, Chris; Maus, S.; Beggan, C. D.

    2010-01-01

    The eleventh generation of the International Geomagnetic Reference Field (IGRF) was agreed in December 2009 by a task force appointed by the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group V-MOD. New spherical harmonic main field models for epochs 2005.0 (DGRF...... coefficients is also reported. Maps of differences in the vertical field intensity at Earth’s surface between the candidates and weighted mean models are presented. Candidates with anomalous aspects are identified and efforts made to pinpoint both troublesome coefficients and geographical regions where large...... vector satellite data is demonstrated; based on internal consistency DGRF-2005 has a formal root mean square vector field error over Earth’s surface of 1.0 nT. Difficulties nevertheless remain in accurately forecasting field evolution only five years into the future....

  3. A proposed International Geomagnetic Reference Field for 1965- 1985.

    Science.gov (United States)

    Peddie, N.W.; Fabiano, E.B.

    1982-01-01

    A set of spherical harmonic models describing the Earth's main magnetic field from 1965 to 1985 has been developed and is proposed as the next revision of the International Geomagnetic Reference Field (IGRF). A tenth degree and order spherical harmonic model of the main field was derived from Magsat data. A series of eighth degree and order spherical harmonic models of the secular variation of the main field was derived from magnetic observatory annual mean values. Models of the main field at 1965, 1970, 1975, and 1980 were obtained by extrapolating the main-field model using the secular variation models.-Authors spherical harmonic models Earth main magnetic field Magsat data

  4. An empirical model of the quiet daily geomagnetic field variation

    Science.gov (United States)

    Yamazaki, Y.; Yumoto, K.; Cardinal, M.G.; Fraser, B.J.; Hattori, P.; Kakinami, Y.; Liu, J.Y.; Lynn, K.J.W.; Marshall, R.; McNamara, D.; Nagatsuma, T.; Nikiforov, V.M.; Otadoy, R.E.; Ruhimat, M.; Shevtsov, B.M.; Shiokawa, K.; Abe, S.; Uozumi, T.; Yoshikawa, A.

    2011-01-01

    An empirical model of the quiet daily geomagnetic field variation has been constructed based on geomagnetic data obtained from 21 stations along the 210 Magnetic Meridian of the Circum-pan Pacific Magnetometer Network (CPMN) from 1996 to 2007. Using the least squares fitting method for geomagnetically quiet days (Kp ??? 2+), the quiet daily geomagnetic field variation at each station was described as a function of solar activity SA, day of year DOY, lunar age LA, and local time LT. After interpolation in latitude, the model can describe solar-activity dependence and seasonal dependence of solar quiet daily variations (S) and lunar quiet daily variations (L). We performed a spherical harmonic analysis (SHA) on these S and L variations to examine average characteristics of the equivalent external current systems. We found three particularly noteworthy results. First, the total current intensity of the S current system is largely controlled by solar activity while its focus position is not significantly affected by solar activity. Second, we found that seasonal variations of the S current intensity exhibit north-south asymmetry; the current intensity of the northern vortex shows a prominent annual variation while the southern vortex shows a clear semi-annual variation as well as annual variation. Thirdly, we found that the total intensity of the L current system changes depending on solar activity and season; seasonal variations of the L current intensity show an enhancement during the December solstice, independent of the level of solar activity. Copyright 2011 by the American Geophysical Union.

  5. International Geomagnetic Reference Field: the 12th generation

    Science.gov (United States)

    Thébault, Erwan; Finlay, Christopher C.; Beggan, Ciarán D.; Alken, Patrick; Aubert, Julien; Barrois, Olivier; Bertrand, Francois; Bondar, Tatiana; Boness, Axel; Brocco, Laura; Canet, Elisabeth; Chambodut, Aude; Chulliat, Arnaud; Coïsson, Pierdavide; Civet, François; Du, Aimin; Fournier, Alexandre; Fratter, Isabelle; Gillet, Nicolas; Hamilton, Brian; Hamoudi, Mohamed; Hulot, Gauthier; Jager, Thomas; Korte, Monika; Kuang, Weijia; Lalanne, Xavier; Langlais, Benoit; Léger, Jean-Michel; Lesur, Vincent; Lowes, Frank J.; Macmillan, Susan; Mandea, Mioara; Manoj, Chandrasekharan; Maus, Stefan; Olsen, Nils; Petrov, Valeriy; Ridley, Victoria; Rother, Martin; Sabaka, Terence J.; Saturnino, Diana; Schachtschneider, Reyko; Sirol, Olivier; Tangborn, Andrew; Thomson, Alan; Tøffner-Clausen, Lars; Vigneron, Pierre; Wardinski, Ingo; Zvereva, Tatiana

    2015-05-01

    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.

  6. De-noising Diurnal Variation Data in Geomagnetic Field Modelling

    Science.gov (United States)

    Onovughe, E.

    2017-01-01

    Ground based geomagnetic observatory series have been used to investigate and describe the residuals between a continuous geomagnetic field model and observed diurnal variation for noise-removal of signal due to external field of magnetospheric ring current sources. In all the observatories studied, the residuals in the X-direction consistently show the noisiest signal. Results show that the residuals in the X-direction correlates closely with the RC-index, suggesting an origin from unmodelled external field variation. Notable cross-correlation is also seen between the residuals and the RC-index at zero-lag. Removal/reduction of this unmodelled signal enhances resolution of fine-scale detail in diurnal variation studies.

  7. Basic Geomagnetic Network of the Republic of Croatia 2004 – 2012, with Geomagnetic Field Maps for 2009.5 epoch

    Directory of Open Access Journals (Sweden)

    Mario Brkić

    2013-12-01

    Full Text Available After more than half a century, scientific book Basic Geomagnetic Network of the Republic of Croatia 2004 – 2012, with Geomagnetic Field Maps for 2009.5 epoch describes the recent geomagnetic field on Croatian territory. A review of research in the past decade as well as the original solutions makes the book a document of contribution to geodesy and geomagnetism in Croatia.The book’s introduction gives an overview of two centuries of history and the strategic, security, economic and scientific significance of knowing the geomagnetic field on the Croatian territory. All the activities related to the updating of the geomagnetic information, which took place in the last decade, signified a big step toward the countries where geomagnetic survey is a mature scientific and technical discipline, and a scientific contribution to understanding of the nature of the Earth's magnetism.The declination, inclination and total intensity maps (along with the normal annual changes for the epoch 2009.5 are given in the Appendix. The book Basic Geomagnetic Network of the Republic of Croatia 2004 – 2012, with Geomagnetic Field Maps for 2009.5 epoch (ISBN 978-953-293-521-9 is published by the State Geodetic Administration of the Republic of Croatia. Beside editor in chief, M. Brkić, the authors are: E. Vujić, D. Šugar, E. Jungwirth, D. Markovinović, M. Rezo, M. Pavasović, O. Bjelotomić, M. Šljivarić, M. Varga and V. Poslončec-Petrić. The book contains 48 pages and 3 maps, and is published in 200 copies. CIP record is available in digital catalogue of the National and University Library in Zagreb under number 861937.

  8. The CHAOS-4 geomagnetic field model

    DEFF Research Database (Denmark)

    Olsen, Nils; Lühr, H.; Finlay, Chris;

    2014-01-01

    We present CHAOS-4, a new version in the CHAOS model series, which aims to describe the Earth's magnetic field with high spatial and temporal resolution. Terms up to spherical degree of at least n = 85 for the lithospheric field, and up to n = 16 for the time-varying core field are robustly deter...

  9. The CHAOS-4 Geomagnetic Field Model

    DEFF Research Database (Denmark)

    Olsen, Nils; Finlay, Chris; Lühr, H.

    We present CHAOS-4, a new version in the CHAOS model series, which aims at describing the Earth's magnetic field with high spatial resolution (terms up to spherical degree n=90 for the crustal field, and up to n=16 for the time-varying core field are robustly determined) and high temporal resolut...

  10. Geomagnetic field intensity in the middle jurassic - oligocene

    CERN Document Server

    Kurazhkovskii, A Yu; Klain, B I

    2014-01-01

    The present paper summarizes results of the studies on the intensity of geomagnetic field in the (167 - 23) Ma interval by sedimentary rocks of the Russian Plate and adjacent territories. The joint analysis of the data paleointensity obtained by sedimentary and thermomagnetized (from PINT12) rocks within this temporal interval is conducted. It is shown that the changes of the paleointensity were occurred chaotically. Alternating bursts and periods of quiet regime of the geomagnetic field are typical for intermittent processes and is a characteristic of the geological interval Jurassic-beginning of Paleogene. The distributions of the paleointensity corresponding to different intervals of geologic time were investigated. It is revealed that the cumulative distribution function (CDF) of the paleointensity values is best approximated by a power function. The indices of the power functions varied depending on geologic time intervals.The analysis of the paleomagnetic data suggests that the medium in which the geoma...

  11. Spurious behavior in volcanic records of geomagnetic field reversals

    Science.gov (United States)

    Carlut, Julie; Vella, Jerome; Valet, Jean-Pierre; Soler, Vicente; Legoff, Maxime

    2016-04-01

    Very large directional variations of magnetization have been reported in several lava flows recording a geomagnetic reversal. Such behavior could reflect real geomagnetic changes or be caused by artifacts due to post-emplacement alteration and/or non-ideal magnetic behavior. More recently, a high resolution paleomagnetic record from sediments pleads also for an extremely rapid reversal process during the last reversal. Assuming that the geomagnetic field would have moved by tens of degrees during cooling of moderate thickness lava flows implies brief episodes of rapid changes by a few degrees per day that are difficult to reconcile with the rate of liquid motions at the core surface. Systematical mineralogical bias is a most likely explanation to promote such behavior as recently reconsidered by Coe et al., 2014 for the rapid field changes recorded at Steens Mountain. We resampled three lava flows at La Palma island (Canarias) that are sandwiched between reverse polarity and normal polarity flows associated with the last reversal. The results show an evolution of the magnetization direction from top to bottom. Thermal demagnetization experiments were conducted using different heating and cooling rates. Similarly, continuous demagnetization and measurements. In both cases, we did not notice any remagnetization associated with mineralogical transformations during the experiments. Magnetic grain sizes do not show any correlation with the amplitude of the deviations. Microscopic observations indicate poor exsolution, which could suggests post-cooling thermochemical remagnetization processes.

  12. A study of geomagnetic field variations along the 80° S geomagnetic parallel

    Science.gov (United States)

    Lepidi, Stefania; Cafarella, Lili; Francia, Patrizia; Piancatelli, Andrea; Pietrolungo, Manuela; Santarelli, Lucia; Urbini, Stefano

    2017-01-01

    The availability of measurements of the geomagnetic field variations in Antarctica at three sites along the 80° S geomagnetic parallel, separated by approximately 1 h in magnetic local time, allows us to study the longitudinal dependence of the observed variations. In particular, using 1 min data from Mario Zucchelli Station, Scott Base and Talos Dome, a temporary installation during 2007-2008 Antarctic campaign, we investigated the diurnal variation and the low-frequency fluctuations (approximately in the Pc5 range, ˜ 1-7 mHz). We found that the daily variation is clearly ordered by local time, suggesting a predominant effect of the polar extension of midlatitude ionospheric currents. On the other hand, the pulsation power is dependent on magnetic local time maximizing around magnetic local noon, when the stations are closer to the polar cusp, while the highest coherence between pairs of stations is observed in the magnetic local nighttime sector. The wave propagation direction observed during selected events, one around local magnetic noon and the other around local magnetic midnight, is consistent with a solar-wind-driven source in the daytime and with substorm-associated processes in the nighttime.

  13. Geomagnetic Core Field Secular Variation Models

    DEFF Research Database (Denmark)

    Gillet, N.; Lesur, V.; Olsen, Nils

    2010-01-01

    We analyse models describing time changes of the Earth’s core magnetic field (secular variation) covering the historical period (several centuries) and the more recent satellite era (previous decade), and we illustrate how both the information contained in the data and the a priori information...... highlight the difficulty of resolving the time variability of the high degree secular variation coefficients (i.e. the secular acceleration), arising for instance from the challenge to properly separate sources of internal and of external origin. In addition, the regularisation process may also result...

  14. Chandler wobbles and the geomagnetic field

    Science.gov (United States)

    Flodmark, Stig; Davstad, K.

    1986-11-01

    Paleomagnetic motion of the magnetic pole is explained by angular momentum balance between the magnetic field, inner core, outer core, and mantle. The Chandler wobbles are explained as a nutation of the mantle and crust, caused by transfer of angular momentum between the core and mantle. Evidence is found for the atmosphere not to be fully responsible for the annual oscillation period of the Chandler wobbles. The main reasons for the principal periods of 12 and 14 months are found to be the flattenings of mantle and core, respectively. The fluid core rotates collectively, as a consequence of globally coworking long-distance electromagnetic coupling. Short-distance forces may locally displace fluid core material without essentially deforming its ellipsoid of inertia. The longitudinal polar drifts of the mantle and outer core are also explained by core-mantle interaction. The core is found to force the Chandler period on the mantle, and it has high wobbling energy in comparison with the mantle.

  15. Active experiments in the ionosphere and geomagnetic field variations

    Science.gov (United States)

    Sivokon, V. P.; Cherneva, N. V.; Khomutov, S. Y.; Serovetnikov, A. S.

    2014-11-01

    Variations of ionospheric-magnetospheric relation energy, as one of the possible outer climatology factors, may be traced on the basis of analysis of natural geophysical phenomena such as ionosphere artificial radio radiation and magnetic storms. Experiments on active impact on the ionosphere have been carried out for quite a long time in Russia as well. The most modern heating stand is located in Alaska; it has been used within the HAARP Program. The possibility of this stand to affect geophysical fields, in particular, the geomagnetic field is of interest.

  16. Quiet geomagnetic field representation for all days and latitudes

    Science.gov (United States)

    Campbell, W.H.; Schiffmacher, E.R.; Arora, B.R.

    1992-01-01

    Describes a technique for obtaining the quiet-time geomagnetic field variation expected for all days of the year and distribution of latitudes from a limited set of selected quiet days within a year at a discrete set of locations. A data set of observatories near 75??E longitude was used as illustration. The method relies upon spatial smoothing of the decomposed spectral components. An evaluation of the fidelity of the resulting model shows correlation coefficients usually above 0.9 at the lower latitudes and near 0.7 at the higher latitudes with variations identified as dependent upon season and field element. -from Authors

  17. Reversed polarity patches at the CMB and geomagnetic field reversal

    Institute of Scientific and Technical Information of China (English)

    XU; Wenyao(徐文耀); WEI; Zigang(魏自刚)

    2002-01-01

    The International Geomagnetic Reference Field models (IGRF) for 1900-2000 are used to calculate the geomagnetic field distribution in the Earth' interior from the ground surface to the core-mantle boundary (CMB) under the assumption of insulated mantle. Four reversed polarity patches, as one of the most important features of the CMB field, are revealed. Two patches with +Z polarity (downward) at the southern African and the southern American regions stand out against the background of -Z polarity (upward) in the southern hemisphere, and two patches of -Z polarity at the North Polar and the northern Pacific regions stand out against the +Z background in the northern hemisphere. During the 1900-2000 period the southern African (SAF) patch has quickly drifted westward at a speed of 0.2-0.3°/a; meanwhile its area has expanded 5 times, and the magnetic flux crossing the area has intensified 30 times. On the other hand, other three patches show little if any change during this 100-year period. Extending upward, each of the reversed polarity patches at the CMB forms a chimney-shaped "reversed polarity column" in the mantle with the bottom at the CMB. The height of the SAF column has grown rapidly from 200km in 1900 to 900km in 2000. If the column grows steadily at the same rate in the future, its top will reach to the ground surface in 600-700 years. And then a reversed polarity patch will be observed at the Earth's surface, which will be an indicator of the beginning of a magnetic field reversal. On the basis of this study, one can describe the process of a geomagnetic polarity reversal, the polarity reversal may be observed firstly in one or several local regions; then the areas of these regions expand, and at the same time, other new reversed polarity regions may appear. Thus several poles may exist during a polarity reversal.

  18. Continuous global geomagnetic field models for the past 3000 years

    Science.gov (United States)

    Korte, Monika; Constable, Catherine

    2003-11-01

    Several global geomagnetic field models exist for recent decades, but due to limited data availability models for several centuries to millennia are rare. We present a continuous spherical harmonic model for almost 3 millennia from 1000 b.c. to 1800 a.d., based on a dataset of directional archaeo- and paleomagnetic data and axial dipole constraints. The model, named Continuous Archaeomagnetic and Lake Sediment Geomagnetic Model for the last 3k years (CALS3K.1), can be used to predict both the field and secular variation. Comparisons and tests with synthetic data lead to the conclusion that CALS3K.1 gives a good general, large-scale representation of the geomagnetic field, but lacks small-scale structure due to the limited resolution of the sparse dataset. In future applications the model can be used for comparisons with additional, new data for that time span. For better resolved regions, the agreement of data with CALS3K.1 will provide an idea about the general compatibility of the data with the field and secular variation in that region of the world. For poorly covered regions and time intervals we hope to iteratively improve the model by comparisons with and inclusion of new data. Animations and additional snapshot plots of model predictions as well as the model coefficients and a FORTRAN code to evaluate them for any time can be accessed under http://www.mahi.ucsd.edu/cathy/Holocene/holocene.html. The whole package is also stored in the Earthref digital archive at http://www.earthref.org/...

  19. Assessment of extreme values in geomagnetic and geoelectric field variations for Canada

    Science.gov (United States)

    Nikitina, L.; Trichtchenko, L.; Boteler, D. H.

    2016-07-01

    Disturbances of the geomagnetic field produced by space weather events can have an impact on power systems and other critical infrastructure. To mitigate these risks it is important to determine the extreme values of geomagnetic activity that can occur. More than 40 years of 1 min magnetic data recorded at 13 Canadian geomagnetic observatories have been analyzed to evaluate extreme levels in geomagnetic and geoelectric activities in different locations of Canada. The hourly ranges of geomagnetic field variations and hourly maximum in rate of change of the magnetic variations have been used as measures of geomagnetic activity. Geoelectric activity is estimated by the hourly peak amplitude of the geoelectric fields calculated with the use of Earth resistivity models specified for different locations in Canada. A generalized extreme value distribution was applied to geomagnetic and geoelectric indices to evaluate extreme geomagnetic and geoelectric disturbances, which could happen once per 50 and once per 100 years with 99% confidence interval. Influence of geomagnetic latitude and Earth resistivity models on the results for the extreme geomagnetic and geoelectric activity is discussed. The extreme values provide criteria for assessing the vulnerability of power systems and other technology to geomagnetic activity for design or mitigation purposes.

  20. Magnetization of Steel Building Materials and Structures in the Natural Geomagnetic Field

    Directory of Open Access Journals (Sweden)

    E. Čermáková

    2005-01-01

    Full Text Available This paper presents the physical basis of the magnetic properties of ferromagnetic materials and shows their relationships with external geomagnetic field. It graphically processes the experimental data detected by an HMR magnetometer. Taking into account the natural geomagnetic field under the effects of steel U profiles, variations of the natural geomagnetic field in a steel structure building are indicated and the potential existence of Sick Building Syndrome (SBS in these types of buildings is pointed out. 

  1. DYNAMICS OF THE GEOMAGNETIC FIELD AND SUPERGRAVITY IN 112D

    Directory of Open Access Journals (Sweden)

    Trunev A. P.

    2016-05-01

    Full Text Available The paper deals with the problem of changing the polarity of the geomagnetic field as a problem of a unified field theory and supergravity in the 112D. Investigated centrally symmetric metric depends on the radial coordinate in the observable physical space of one of the worlds. The equation that relates the magnetic field of the planet with a gravitational field in 5D has been derived. The problem of changing the polarity of the magnetic field of the Earth discussed. The rapid change of the geomagnetic field polarity detected on the basis of paleomagnetic data is modeled as a movement on a hypersphere in the 112D, which corresponds to 110 corners. The simplest example of such a movement in the case of the three angles is the Euler model that describes the rigid body rotation. In this model, there are modes with a quick flip of the body while conservation of the angular momentum. If the body has a magnetic moment, when such a change occurs flip of the magnetic field. It is assumed that the central core of the earth is magnetized and surrounded by a number of satellites, each of which has a magnetic moment. Satellites interact with a central core and one another by means of gravity and through a magnetic field. The central core may sudden flip, as in the Euler model. It is shown that the duration of phase with constant polarity and upheaval time depends on the magnitude of the disturbance torque and core asymmetry. We discuss Einstein's hypothesis about the origin of the magnetic field when rotating the neutral masses. It is shown that the motion on a hypersphere in the 112D has the effect of a magnetic field due to the interaction of nucleons in nuclei. Such magnetic field is most evident for iron, cobalt and nickel - elements are consisting of the Earth's core

  2. Geomagnetic core field models in the satellite era

    DEFF Research Database (Denmark)

    Lesur, Vincent; Olsen, Nils; Thomson, Alan W. P.

    2011-01-01

    After a brief review of the theoretical basis and difficulties that modelers are facing, we present three recent models of the geomagnetic field originating in the Earth’s core. All three modeling approaches are using recent observatory and near-Earth orbiting survey satellite data. In each case ...... only up to degree 8 or 9. For higher time derivatives of core field models, only the very first degrees are robustly derived.......After a brief review of the theoretical basis and difficulties that modelers are facing, we present three recent models of the geomagnetic field originating in the Earth’s core. All three modeling approaches are using recent observatory and near-Earth orbiting survey satellite data. In each case...... the specific aims and techniques used by the modelers are described together with a presentation of the main results achieved. The three different modeling approaches are giving similar results. For a snap shot of the core magnetic field at a given epoch and observed at the Earth’s surface, the differences...

  3. Geomagnetic Field Variation during Winter Storm at Localized Southern and Northern High Latitude

    Indian Academy of Sciences (India)

    Babita Devi; Smita Dubey; Shailendra Saini; Rajni Devi; Rashmi Wahi; Ajay Dhar; S. K. Vijay; A. K. Gwal

    2008-03-01

    This paper presents the effect of geomagnetic storm on geomagnetic field components at Southern (Maitri) and Northern (Kiruna) Hemispheres. The Indian Antarctic Station Maitri is located at geom. long. 66.03° S; 53.21° E whereas Kiruna is located at geom. long. 67.52° N; 23.38° E. We have studied all the geomagnetic storms that occurred during winter season of the year 2004–2005. We observed that at Southern Hemisphere the variation is large as compared to the Northern Hemisphere. Geomagnetic field components vary when the interplanetary magnetic field is oriented in southward direction. Geomagnetic field components vary in the main phase of the ring current. Due to southward orientation of vertical component of IMF reconnection takes place all across the dayside that transports plasma and magnetic flux which create the geomagnetic field variation.

  4. Changes in cosmic ray cut-off rigidities due to secular variations of the geomagnetic field

    Directory of Open Access Journals (Sweden)

    A. Bhattacharyya

    Full Text Available An analytical expression is derived for the cutoff rigidity of cosmic rays arriving at a point in an arbitrary direction, when the main geomagnetic field is approximated by that of an eccentric dipole. This expression is used to determine changes in geomagnetic cutoffs due to secular variation of the geomagnetic field since 1835. Effects of westward drift of the quadrupole field and decrease in the effective dipole moment are seen in the isorigidity contours. On account of the immense computer time required to determine the cutoff rigidities more accurately using the particle trajectory tracing technique, the present formulation may be useful in estimating the transmission factor of the geomagnetic field in cosmic ray studies, modulation of cosmogenic isotope production by geomagnetic secular variation, and the contribution of geomagnetic field variation to long term changes in climate through cosmic ray related modulation of the current flow in the global electric circuit.

  5. Behavior of Plasma and Field Parameters and their Relationship with Geomagnetic Indices during Intense Geomagnetic Storms of Solar Cycle 23

    CERN Document Server

    Joshi, Navin Chandra; Pande, Seema; Pande, Bimal; Pandey, Kavita

    2010-01-01

    A correlative study between the geomagnetic indices and the peak values of various plasma and field parameters during rising, maximum and decay phases as well as during complete solar cycle 23 have been presented. We have also presented the lag/lead analysis between the maximum of Dst and peak values of plasma and field parameters and found that peak values of lag/lead time lies in the +/-10 hr interval. Three geomagnetic storms (GMSs) and associated solar sources observed during these phases of this solar cycle have also been studied and found that GMSs are associated with large flares and halo CMEs.

  6. A Gaussian Model for Simulated Geomagnetic Field Reversals

    CERN Document Server

    Wicht, Johannes

    2015-01-01

    Field reversals are the most spectacular changes in the geomagnetic field but remain little understood. Paleomagnetic data primarily constrain the reversal rate and provide few additional clues. Reversals and excursions are characterized by a low in dipole moment that can last for some 10kyr. Some paleomagnetic records also suggest that the field decreases much slower before an reversals than it recovers afterwards and that the recovery phase may show an overshoot in field intensity. Here we study the dipole moment variations in several extremely long dynamo simulation to statistically explored the reversal and excursion properties. The numerical reversals are characterized by a switch from a high axial dipole moment state to a low axial dipole moment state. When analysing the respective transitions we find that decay and growth have very similar time scales and that there is no overshoot. Other properties are generally similar to paleomagnetic findings. The dipole moment has to decrease to about 30% of its m...

  7. The geomagnetic field - An explanation for the microturbulence in coaxial gun plasmas

    Science.gov (United States)

    Mather, J. W.; Ahluwalia, H. S.

    1988-01-01

    The complexity introduced by the geomagnetic field in several regions of a coaxial gun plasma device is described. It is shown that the annihilation of the swept-up geomagnetic flux, trapped within the highly compressed turbulent plasma, provides an explanation for varied performance and experimental results. The results indicate that the device should be aligned along the direction of the local geomagnetic field or enclosed in a mu-metal shield.

  8. Signatures of core perturbations in geomagnetic field dynamics - preliminary results

    Science.gov (United States)

    Bury, Agata; Mizerski, Krzysztof

    2017-04-01

    Earth's magnetic field is continuously evolving in time. Research is carried out in order to understand it's characteristics and also to describe types of perturbations which can exist in the Earth's liquid core. The aim of this work is to analyze the geomagnetic ground observatory data for the occurrence of magnetohydrodynamic (MHD) waves described in literature traveling at the top of the Earth's liquid core. Hourly means data from 150 observatories collected from the World Data Center for Geomagnetism (WDC) were used in this work. Local topocentric magnetic field components: X (East), Y (North), Z (vertical), and also spherical coordinates: Br, Bθ, BΦ were analyzed. Hourly means were averaged to one day means and to one month means, missing values were interpolated by different methods. Fourier analysis and Empirical Mode Decomposition (EMD) method were applied to extract periods of oscillations visible in datasets. Similar analysis was also made for data generated from the IGRF12 model for comparison. The times associated with peaks within these data were identified for all components and plotted versus colatitude and longitude to find possible travelling perturbations. Possible candidates of MHD waves for future investigation will be presented.

  9. Geomagnetic core field models in the satellite era

    DEFF Research Database (Denmark)

    Lesur, Vincent; Olsen, Nils; Thomson, Alan W. P.

    2011-01-01

    After a brief review of the theoretical basis and difficulties that modelers are facing, we present three recent models of the geomagnetic field originating in the Earth’s core. All three modeling approaches are using recent observatory and near-Earth orbiting survey satellite data. In each case...... the specific aims and techniques used by the modelers are described together with a presentation of the main results achieved. The three different modeling approaches are giving similar results. For a snap shot of the core magnetic field at a given epoch and observed at the Earth’s surface, the differences...... only up to degree 8 or 9. For higher time derivatives of core field models, only the very first degrees are robustly derived....

  10. Electromagnetic Propulsion System for Spacecraft using Geomagnetic fields and Superconductors

    Science.gov (United States)

    Dadhich, Anang

    This thesis concentrates on developing an innovative method to generate thrust force for spacecraft in localized geomagnetic fields by various electromagnetic systems. The proposed electromagnetic propulsion system is an electromagnet, like normal or superconducting solenoid, having its own magnetic field which interacts with the planet's magnetic field to produce a reaction thrust force. The practicality of the system is checked by performing simulations in order the find the varying radius, velocity, and acceleration changes. The advantages, challenges, various optimization techniques, and viability of such a propulsion system in present day and future are discussed. The propulsion system such developed is comparable to modern MPD Thrusters and electric engines, and has various applications like spacecraft propulsion, orbit transfer and stationkeeping.

  11. Statistical analysis of extreme values for geomagnetic and geoelectric field variations for Canada

    Science.gov (United States)

    Nikitina, Lidia; Trichtchenko, Larisa; Boteler, David

    2016-04-01

    Disturbances of the geomagnetic field produced by space weather events cause variable geoelectric fields at Earth's surface which drive electric currents in power systems, resulting in hazardous impacts on electric power transmission. In extreme cases, as during the magnetic storm in March 13, 1989, this can result in burnt-out transformers and power blackouts. To make assessment of geomagnetic and geoelectric activity in Canada during extreme space weather events, extreme value statistical analysis has been applied to more than 40 years of magnetic data from the Canadian geomagnetic observatories network. This network has archived digital data recordings for observatories located in sub-auroral, auroral, and polar zones. Extreme value analysis was applied to hourly ranges of geomagnetic variations as an index of geomagnetic activity and to hourly maximum of rate-of-change of geomagnetic field. To estimate extreme geoelectric fields, the minute geomagnetic data were used together with Earth conductivity models for different Canadian locations to calculate geoelectric fields. The extreme value statistical analysis was applied to hourly maximum values of the horizontal geoelectric field. This assessment provided extreme values of geomagnetic and geoelectric activity which are expected to happen once per 50 years and once per 100 years. The results of this analysis are designed to be used to assess the geomagnetic hazard to power systems and help the power industry mitigate risks from extreme space weather events.

  12. Can the tardigrade Hypsibius dujardini survive in the absence of the geomagnetic field?

    Science.gov (United States)

    Erdmann, Weronika; Idzikowski, Bogdan; Kowalski, Wojciech; Szymański, Bogdan; Kosicki, Jakub Z; Kaczmarek, Łukasz

    2017-01-01

    Earth's geomagnetic field has undergone critical changes in the past. Studies on the influence of the magnetic field on Earth's organisms are crucial for the understanding of evolution of life on Earth and astrobiological considerations. Numerous studies conducted both on plants and animals confirmed the significant influence of the geomagnetic field on the metabolism of living organisms. Water bears (Tardigrada), which are a mong the most resistant animals due to their cryptobiotic abilities, show significant resistance to a number of environmental stressors, but the influence of the geomagnetic field on their fitness has not been addressed before. In our studies, we used eutardigrade Hypsibius dujardini to analyse whether isolation from the geomagnetic field had an effect on mortality. We found that Hypsibius dujardini specimens demonstrated relatively high mortality during anhydrobiosis, also in control groups exposed to the normal geomagnetic field. Moreover, similar mortality was observed in anhydrobiotic specimens isolated from the geomagnetic field. However, a significant difference was noted between tardigrade survival and the moment of their isolation from the geomagnetic field. In particular, tardigrade mortality substantially increased in absence of a magnetic field during the process of entering anhydrobiosis and returning to active life. Our results suggest that these processes rely on complex metabolic processes that are critically influenced by the geomagnetic field.

  13. Geomagnetism 4

    CERN Document Server

    Jacobs, John A

    2013-01-01

    Geomagnetism, Volume 4 focuses on the processes, methodologies, technologies, and approaches involved in geomagnetism, including electric fields, solar wind plasma, pulsations, and gravity waves.The selection first offers information on solar wind, magnetosphere, and the magnetopause of the Earth. Discussions focus on magnetopause structure and transfer processes, magnetosphere electric fields, geomagnetically trapped radiation, microstructure of the solar wind plasma, and hydro magnetic fluctuations and discontinuities. The text then examines geomagnetic tail, neutral upper atmosphere, and ge

  14. Solar Microwave and Geomagnetic Field Pulsations as Space Weather Factors

    Science.gov (United States)

    Snegirev, S. D.; Fridman, V. M.; Sheiner, O. A.

    The procedure of short-term prediction of main solar flares was created on the basis of temporal behavior of long-period microwave pulsations [Kobrin et al., 1997]. At the same time it was shown that before these flares one could observe long-period (T > 20 min) pulsations of geomagnetic field [Kobrin et al, 1985]. The resemblance between microwave and geomagnetic pulsations (duration and temporal behaviour) allows us to propose the common nature of these variations: the reflection of solar energy accumulation and instabilities in solar centers of activity. To be an important factor of Space Weather above mentioned pulsations can be useful for constructing the procedures to predict the near Earth's conditions. This work was supported by the Russian Foundation for Fundamental Research and Russian Federal Programm "Astronomy" (grant N 1.5.5.5). Kobrin M.M, Malygin V.I., Snegirev S.D. Plan. Space Sci., 33, N11, p. 1251 (1985). Kobrin M.M., Pakhomov V.V., Snegirev S.D., Fridman V.M., Sheiner O.A. Proc. Workshop `STPW-96', Tokyo: RCW, p. 200 (1997).

  15. Motility of magnetotactic bacteria/MTB to Geomagnetic fields

    Science.gov (United States)

    Hidajatullah-Maksoed, Fatahillah

    2016-03-01

    Bacteria with motility directed by a local geomagnetic fields have been observed in marine sediments'' discussed by R. Blakemore, 1975. Magnetotactic bacteria/MTB discovered in 1963 by Salvatore Bellini. For ``off-axis electron holography in the transmission electron microscope was used to correlates the physical & magnetic microstructure of magnetite nanocrystals in magnetotactic bacteria'' sought ``single-domain magnetite in hemopelagic sediments'' from JF Stolz. Otherwise, for potential source of bioproducts- product meant from result to multiplier -of magnetotactic bacteria[ACV Araujo, et.al, 2014 ] of marine drugs retrieved the `measurement of cellular chemotaxis with ECIS/Taxis, from KM Pietrosimone, 2012, whereas after ``earth magnetic field role on small living models'' are other interpretation of ``taxis'' as a movement of a cell instead usual ``tax'' for yew's taxus cuspidate, hired car & taxes in financial realms. Acknowledgements to HE. Mr. H. TUK SETYOHADI, Jl. Sriwijaya Raya 3, South-Jakarta, INDONESIA.

  16. The Egyptian geomagnetic reference field to the Epoch, 2010.0

    Science.gov (United States)

    Deebes, H. A.; Abd Elaal, E. M.; Arafa, T.; Lethy, A.; El Emam, A.; Ghamry, E.; Odah, H.

    2017-06-01

    The present work is a compilation of two tasks within the frame of the project ;Geomagnetic Survey & Detailed Geomagnetic Measurements within the Egyptian Territory; funded by the ;Science and Technology Development Fund agency (STDF);. The National Research Institute of Astronomy and Geophysics (NRIAG), has conducted a new extensive land geomagnetic survey that covers the whole Egyptian territory. The field measurements have been done at 3212 points along all the asphalted roads, defined tracks, and ill-defined tracks in Egypt; with total length of 11,586 km. In the present work, the measurements cover for the first time new areas as: the southern eastern borders of Egypt including Halayeb and Shlatin, the Quattara depresion in the western desert, and the new roads between Farafra and Baharia oasis. Also marine geomagnetic survey have been applied for the first time in Naser lake. Misallat and Abu-Simble geomagnetic observatories have been used to reduce the field data to the Epoch 2010. During the field measurements, whenever possible, the old stations occupied by the previous observers have been re-occupied to determine the secular variations at these points. The geomagnetic anomaly maps, the normal geomagnetic field maps with their corresponding secular variation maps, the normal geomagnetic field equations of the geomagnetic elements (EGRF) and their corresponding secular variations equations, are outlined. The anomalous sites, as discovered from the anomaly maps are, only, mentioned. In addition, a correlation between the International Geomagnetic Reference Field (IGRF) 2010.0 and the Egyptian Geomagnetic Reference Field (EGRF) 2010 is indicated.

  17. The unstable geomagnetic field during the last glacial

    Science.gov (United States)

    Nowaczyk, Norbert; Frank, Ute; Kind, Jessica; Plessen, Birgit; Arz, Helge

    2013-04-01

    Detailed stratigraphic analyses of a sediment composite record from three different sites in the southeastern Black Sea yielded a high-resolution, well-dated paleomagnetic record of the past 14 to 68 ka. Age constraints are provided by 16 AMS 14C ages, identification of the Campanian Ignimbrite tephra (39.28±0.11 ka), and by detailed tuning of sedimentologic parameters of the Black Sea sediments to the oxygen isotope record from the Greenland NGRIP ice core. Dansgaard-Oeschger events 3 through 18 are very well expressed in the Black Sea sedimentary records of Ca-content, oxygen isotopes as well as in records of ice-rafted detritus. Though hampered by some larger hiatusses at one site, and patchy contaminations by diagenetically formed greigite, the paleomagnetic composite record obtained from the preserved primary detrital magnetite phase reflects a highly dynamic geomagnetic field during the last glacial period. Relative variations of paleointensity inferred from the sediments' magnetisations were converted into a record of the virtual axial dipole moment (VADM). Thus, the Black Sea paleomagnetic record comprises evidence for the Norwegian-Greenland-Sea excursion at 64.5 ka (VADM = 1.5×1022 Am2), a full reversal of the geomagnetic field during the Laschamp excursion at 41 ka and several subsequent excursions with low northern virtual geomagnetic pole (VGP) latitudes, including the Mono Lake excursion at 34.5 ka (VADM = 3.0×1022 Am2). According to the derived age model, VGP positions during the Laschamp excursion persisted at high southern latitudes in Antarctica for an estimated 440 years, making the Laschamp excursion a short-lived event with fully reversed polarity directions. Recorded field reversals of the Laschamp excursion, lasting only an estimated ~250 years, are characterized by very low paleointensities with VADMs as low as 0.50×1022 Am2. The reversed phase of the Laschamp excursion is associated with a significant field recovery with a VADM of 2.0

  18. Uncertainties in field-line tracing in the magnetosphere. Part II: the complete internal geomagnetic field

    Directory of Open Access Journals (Sweden)

    K. S. C. Freeman

    Full Text Available The discussion in the preceding paper is restricted to the uncertainties in magnetic-field-line tracing in the magnetosphere resulting from published standard errors in the spherical harmonic coefficients that define the axisymmetric part of the internal geomagnetic field (i.e. gn0 ± δgn0. Numerical estimates of these uncertainties based on an analytic equation for axisymmetric field lines are in excellent agreement with independent computational estimates based on stepwise numerical integration along magnetic field lines. This comparison confirms the accuracy of the computer program used in the present paper to estimate the uncertainties in magnetic-field-line tracing that arise from published standard errors in the full set of spherical harmonic coefficients, which define the complete (non-axisymmetric internal geomagnetic field (i.e. gnm ± δgnm and hnm ± δhnm. An algorithm is formulated that greatly reduces the computing time required to estimate these uncertainties in magnetic-field-line tracing. The validity of this algorithm is checked numerically for both the axisymmetric part of the internal geomagnetic field in the general case (1 ≤ n ≤ 10 and the complete internal geomagnetic field in a restrictive case (0 ≤ m ≤ n, 1 ≤ n ≤ 3. On this basis it is assumed that the algorithm can be used with confidence in those cases for which the computing time would otherwise be prohibitively long. For the complete internal geomagnetic field, the maximum characteristic uncertainty in the geocentric distance of a field line that crosses the geomagnetic equator at a nominal dipolar distance of 2 RE is typically 100 km. The corresponding characteristic uncertainty for a field line that crosses the geomagnetic equator at a nominal dipolar distance of 6 RE is typically 500 km. Histograms and scatter plots showing the characteristic uncertainties associated with magnetic-field-line tracing in the magnetosphere are presented for a range of

  19. No alignment of cattle along geomagnetic field lines found

    CERN Document Server

    Hert, J; Pekarek, L; Pavlicek, A; 10.1007/s00359-011-0628-7

    2011-01-01

    This paper presents a study of the body orientation of domestic cattle on free pastures in several European states, based on Google satellite photographs. In sum, 232 herds with 3412 individuals were evaluated. Two independent groups participated in our study and came to the same conclusion that, in contradiction to the recent findings of other researchers, no alignment of the animals and of their herds along geomagnetic field lines could be found. Several possible reasons for this discrepancy should be taken into account: poor quality of Google satellite photographs, difficulties in determining the body axis, selection of herds or animals within herds, lack of blinding in the evaluation, possible subconscious bias, and, most importantly, high sensitivity of the calculated main directions of the Rayleigh vectors to some kind of bias or to some overlooked or ignored confounder. This factor could easily have led to an unsubstantiated positive conclusion about the existence of magnetoreception.

  20. Geomagnetic Field Reversals and Life on the Earth in Phanerozoic Time

    Science.gov (United States)

    Pechersky, D. M.

    2014-10-01

    Global paleomagnetic and biostratigraphic data are generalized. As a result it is found out that the direct connection between geomagnetic reversals, biozones and maxima of mass extinction of a biota is absent. At the same time it is noted close to a synchronous total picture of consistent changes of biozones and geomagnetic polarity. It is explained by the general source - the Earth's diurnal rotation. The reversal polarity of a geomagnetic field prevailed during the Phanerozoic that is agreed with the Earth's counterclockwise rotation. Change of polarity of a field, most likely, is connected with acceleration or deceleration of rotation speed of the internal core relative to the Earth's mantle. Lack of direct interrelation between changes in the biosphere and geomagnetic field indicate a lack of influence of a field on life evolution on Earth. It follows also from the fact that life on Earth developed from primitive unicellular forms to mammals and the man and diversity of biota was grew against a close condition of a geomagnetic field during ~2,5 billion years and irrespective of numerous geomagnetic reversals. Main conclusion: evolutionary development of life on Earth doesn't depend both on large changes of a geomagnetic field, and on the extreme catastrophic events conducting to mass extinction of a biota.

  1. Effect of March 9, 2016 Total Solar Eclipse on geomagnetic field variation

    Science.gov (United States)

    Ruhimat, Mamat; Winarko, Anton; Nuraeni, Fitri; Bangkit, Harry; Aris, M. Andi; Suwardi; Sulimin

    2016-11-01

    During solar eclipse, solar radiation to the Earth is blocked by the Moon. Thus, the ionization process in the ionosphere is disrupted, as well as the variation of geomagnetic field. The disturbance of geomagnetic field is caused by electric current in the E layer of the ionosphere. At low latitude, the current which is dominant in quiet day is the Sq currents. The blocking of solar radiation cause decrement in electron density in the blocked region. The aim of the research is to find the effect of total solar eclipse to the geomagnetic field. The measurement of the geomagnetic field variation during total solar eclipse on March 9, 2016 was carried out at the Meteorological station of BMKG in Ternate (0° 49' 45.20 "N; 127° 22' 54.00" E). By eliminating the geomagnetic disturbance that occurred in a daily geomagnetic field variation, the pattern of quiet day which is usually in a shape of smooth curve became affected. During the total solar eclipse on March 9, 2016 from 00:30 until 02:00 UT, we found that the geomagnetic field variation of the quiet day decreased by -5 nT.

  2. A theoretical model for mid- and low-latitude ionospheric electric fields in realistic geomagnetic fields

    Institute of Scientific and Technical Information of China (English)

    REN ZhiPeng; WAN WeiXing; WEI Yong; LIU LiBo; YU Tao

    2008-01-01

    The geomagnetic fields, which play important roles in the ionospheric dynamo, can greatly affect the global distribution of ionospheric electric fields, currents and other ionospheric electrodynamics phenomena. In the study of ionospheric electrodynamics phenomena, such as the longitudinal variations of ionospheric electric fields, the non-dipolar component of the geomagnetic fields must be taken into account. In this paper, we deduce a theoretical electric field model for ionospheric dynamo at midand low-latitude which adopt a modified magnetic apex coordinates system. In the new electric field model, the geomagnetic fields can be calculated from either the IGRF model or the dipole field model,and the neutral winds and conductivities are calculated based on empirical models. Then the dynamo equation for the electric potential is finally solved in terms of the line-by-line iteration method, and the ionospheric electric fields and currents are derived from the calculated potential. Our model can reproduce the main features of the ionospheric electrodynamics processes, so it will be a useful tool for the investigation of the upper atmosphere and ionosphere.

  3. Sources of the Geomagnetic Field and theModern Data That Enable Their Investigation

    DEFF Research Database (Denmark)

    Olsen, Nils; Hulot, Gauthier; Sabaka, Terence J.

    2010-01-01

    Abstract The geomagnetic field one canmeasure at the Earth’s surface or on board satellites is the sumof contributions frommany different sources.These sources have different physical origins and can be found both below (in the form of electrical currents and magnetized material) and above (only...... sets are available and analyzed in an adequate way, to produce the so-called geomagnetic field models.Here a general overview of the various sources that contribute to the observed geomagnetic field, and of the modern data that enable their investigation via such procedures is provided....

  4. Stochastic forecasting of the geomagnetic field from the COV-OBS.x1 geomagnetic field model, and candidate models for IGRF-12

    DEFF Research Database (Denmark)

    Gillet, Nicolas; Barrois, Olivier; Finlay, Chris

    2015-01-01

    filter algorithm. We show that the envelope of forecasts includes the observed secular variation of the geomagnetic field over 5-year intervals, even in the case of rapid changes. In a purpose of testing hypotheses about the core dynamics, this prototype method could be implemented to build the ‘state......We present the geomagnetic field model COV-OBS.x1, covering 1840 to 2020, from which have been derived candidate models for the IGRF-12. Towards the most recent epochs, it is primarily constrained by first differences of observatory annual means and measurements from the Oersted, Champ, and Swarm...... the ‘observations’ uncertainties in data assimilation schemes for the study of the outer core dynamics.We also present and illustrate a stochastic algorithm designed to forecast the geomagnetic field. The radial field at the outer core surface is advected by core motions governed by an auto-regressive process...

  5. The Swarm Initial Field Model for the 2014 geomagnetic field

    DEFF Research Database (Denmark)

    Olsen, Nils; Hulot, Gauthier; Lesur, Vincent;

    2015-01-01

    Data from the first year of ESA's Swarm constellation mission are used to derive the Swarm Initial Field Model (SIFM), a new model of the Earth's magnetic field and its time variation. In addition to the conventional magnetic field observations provided by each of the three Swarm satellites......, explicit advantage is taken of the constellation aspect by including East-West magnetic intensity gradient information from the lower satellite pair. Along-track differences in magnetic intensity provide further information concerning the North-South gradient. The SIFM static field shows excellent...... agreement (up to at least degree 60) with recent field models derived from CHAMP data, providing an initial validation of the quality of the Swarm magnetic measurements. Use of gradient data improves the determination of both the static field and its secular variation, with the mean misfit for East...

  6. A gaussian model for simulated geomagnetic field reversals

    Science.gov (United States)

    Wicht, Johannes; Meduri, Domenico G.

    2016-10-01

    Field reversals are the most spectacular events in the geomagnetic history but remain little understood. Here we explore the dipole behaviour in particularly long numerical dynamo simulations to reveal statistically significant conditions required for reversals and excursions to happen. We find that changes in the axial dipole moment behaviour are crucial while the equatorial dipole moment plays a negligible role. For small Rayleigh numbers, the axial dipole always remains strong and stable and obeys a clearly Gaussian probability distribution. Only when the Rayleigh number is increased sufficiently the axial dipole can reverse and its distribution becomes decisively non-Gaussian. Increased likelihoods around zero indicate a pronounced lingering in a new low dipole moment state. Reversals and excursions can only happen when axial dipole fluctuations are large enough to drive the system from the high dipole moment state assumed during stable polarity epochs into the low dipole moment state. Since it is just a matter of chance which polarity is amplified during dipole recovery, reversals and grand excursions, i.e. excursions during which the dipole assumes reverse polarity, are equally likely. While the overall reversal behaviour seems Earth-like, a closer comparison to palaeomagnetic findings suggests that the simulated events last too long and that grand excursions are too rare. For a particularly large Ekman number we find a second but less Earth-like type of reversals where the total field decays and recovers after a certain time.

  7. Steady induction effects in geomagnetism. Part 1C: Geomagnetic estimation of steady surficial core motions: Application to the definitive geomagnetic reference field models

    Science.gov (United States)

    Voorhies, Coerte V.

    1993-01-01

    In the source-free mantle/frozen-flux core magnetic earth model, the non-linear inverse steady motional induction problem was solved using the method presented in Part 1B. How that method was applied to estimate steady, broad-scale fluid velocity fields near the top of Earth's core that induce the secular change indicated by the Definitive Geomagnetic Reference Field (DGRF) models from 1945 to 1980 are described. Special attention is given to the derivation of weight matrices for the DGRF models because the weights determine the apparent significance of the residual secular change. The derived weight matrices also enable estimation of the secular change signal-to-noise ratio characterizing the DGRF models. Two types of weights were derived in 1987-88: radial field weights for fitting the evolution of the broad-scale portion of the radial geomagnetic field component at Earth's surface implied by the DGRF's, and general weights for fitting the evolution of the broad-scale portion of the scalar potential specified by these models. The difference is non-trivial because not all the geomagnetic data represented by the DGRF's constrain the radial field component. For radial field weights (or general weights), a quantitatively acceptable explication of broad-scale secular change relative to the 1980 Magsat epoch must account for 99.94271 percent (or 99.98784 percent) of the total weighted variance accumulated therein. Tolerable normalized root-mean-square weighted residuals of 2.394 percent (or 1.103 percent) are less than the 7 percent errors expected in the source-free mantle/frozen-flux core approximation.

  8. Regional Modelling of the Southern African Geomagnetic Field using Harmonic Splines

    CERN Document Server

    Geese, Anne; Lesur, Vincent; Mandea, Mioara

    2010-01-01

    Over the southern African region the geomagnetic field is weak and changes rapidly. For this area series of geomagnetic field measurements exist since the 1950s. We take advantage of the existing repeat station surveys and observatory annual means, and clean these data sets by eliminating jumps and minimising external field contributions in the original time series. This unique data set allows us to obtain a detailed view of the geomagnetic field behaviour in space and time by computing a regional model. For this, we use a system of representation similar to harmonic splines. Initially, the technique is systematically tested on synthetic data. After systematically testing the method on synthetic data, we derive a model for 1961 to 2001 that gives a detailed view of the fast changes of the geomagnetic field in this region.

  9. Variations of angular elements of the geomagnetic field in Europe during the last 24 centuries

    Science.gov (United States)

    Burakov, K. S.; Nachasova, I. E.

    2011-05-01

    The analysis of variations in angular elements of the geomagnetic field during the period since 350 B.C. to the present day according to the findings from the study of thermal magnetization of baked archaeological samples from England, France, and East Europe showed that the key feature in the behavior of the geomagnetic inclination in all three regions is a millennial variation. The trend in the behavior of the inclination of the geomagnetic field can be regarded as a manifestation of a variation with a characteristic time scale of several thousand years. Despite the general likeness of variations in inclination and declination of the ancient geomagnetic field, they also exhibit a noticeable dissimilarity. The paths of the virtual geomagnetic pole reconstructed from the variations of angular elements of the geomagnetic field in East Europe indicate that the geomagnetic polar motion is quasi-cyclic. The duration of the first cycle was about 1000 years, while the second cycle has not been completed due to the change of the motion to the opposite direction in the middle of the XVII century.

  10. On the slow time geomagnetic field modulation of galactic cosmic rays

    Science.gov (United States)

    Okpala, Kingsley

    2016-07-01

    Cosmic rays of galactic origin are modulated by both heliospheric and geomagnetic conditions. The mutual (and mutually exclusive) contribution of both heliospheric and geomagnetic conditions to galactic cosmic rays (GCR) modulation is still an open question. While the rapid-time association of the galactic cosmic ray variation with different heliophysical and geophysical phenomena has been well studied, not so much attention has been paid to slow-time variations especially with regards to local effects. In this work, we employed monthly means of cosmic ray count rates from two mid latitude (Hermanus and Rome), and two higher latitude (Inuvik and Oulu) neutron monitors (NM), and compared their variability with geomagnetic stations that are in close proximity to the NMs. The data spans 1966 to 2008 and covers four (4) solar cycles. The difference (DeltaCR)between the mean count rate of all days and the mean of the five quietest days for each month was compared with the Dst-related disturbance (DeltaH) derived from the nearby geomagnetic stations. Zeroth- and First- correlation between the cosmic ray parameters and geomagnetic parameters was performed to ascertain statistical association and test for spurious association. Our results show that solar activity is generally strongly correlated (>0.75) with mean strength of GCR count rate and geomagnetic field during individual solar cycles. The correlation between mean strength of cosmic ray intensity and Geomagnetic field strength is spurious and is basically moderated by the solar activity. The signature of convection driven disturbances at high latitude geomagnetic stations was evident during the declining phase of the solar cycles close to the solar minimum. The absence of this feature in the slow-time varying cosmic ray count rates in all stations, and especially in the mid latitude geomagnetic stations suggest that the local geomagnetic disturbance contributes much less in modulating the cosmic ray flux.

  11. High resolution geomagnetic field observations at Terra Nova bay, Antarctica

    Directory of Open Access Journals (Sweden)

    P. Palangio

    1996-06-01

    Full Text Available he preliminary results obtained from the analysis in the micropulsation frequency range of high time resolution magnetic field data recorded at the Antarctic Italian geomagnetic observatory at Terra Nova Bay for 11 consecutive days in February 1994 are reported. The spectral index over the whole Pcl-Pc5 frequency range is of the order of 3.5 and its value significantly increases beyond about 50 mHz. Spectral peaks in the Pc3 frequency range are common, especially during the daytime hours, and are probably due to the direct penetration of upstream waves in the cusp region. From the local time distribution of the micro pulsation power, a signifi - cant activity enhancement around the local magnetic noon emerges, in agreement with previous observations. The analysis of the signal polarisation characteristics in the horizontal plane shows a predominant CW polarisation in the Pcl-Pc3 frequency ranges with the major axis of the polarisation ellipse in the first quadrant.

  12. The quasi-biennial variation in the geomagnetic field: a global characteristics analysis

    Science.gov (United States)

    Ou, Jiaming; Du, Aimin

    2016-04-01

    The periodicity of 1.5-3 years, namely the quasi-biennial oscillation (QBO), has been identified in the solar, geophysical, and atmospheric variability. Sugiura (1976) investigated the observatory annual means over 1900-1970 and confirmed the QBO in the geomagnetic field. At present, studying the quasi-biennial oscillation becomes substantial for separating the internal/external parts in the geomagnetic observations. For the internal field, two typical periodicities, namely the 6-year oscillation in the geomagnetic secular acceleration (SA) and the geomagnetic jerk (occurs in 1-2 years), have close period to the QBO. Recently, a global quasi-biennial fluctuation was identified in the geomagnetic core field model (Silva et al., 2012). Silva et al. speculated this 2.5 years signal to either external source remaining in the core field model or consequence of the methods used to construct the model. As more high-quality data from global observatories are available, it is a good opportunity to characterize the geomagnetic QBO in the global range. In this paper, we investigate the QBO in the observatory monthly geomagnetic field X, Y, and Z components spanning 1985-2010. We employ the observatory hourly means database from the World Data Center for Geomagnetism (WDC) for the investigation. Wavelet analysis is used to detect and identify the QBO, while Fast Fourier Transform (FFT) analysis to obtain the statistics of the QBO. We apply the spherical harmonic analysis on QBO's amplitude, in order to quantify and separate internal and external sources. Three salient periods respectively at 2.9, 2.2, and 1.7 years, are identified in the amplitude spectrum over 1988-2008. The oscillation with the period of ~2.2 years is most prominent in all field components and further studied. In the X component the QBO is attenuated towards the polar regions, while in the Z component the amplitude of QBO increases with increasing of the geomagnetic latitude. At the high latitudes, the QBO

  13. The 1995 revision of the joint US/UK geomagnetic field models - I. Secular variation

    Science.gov (United States)

    Macmillan, S.; Barraclough, D.R.; Quinn, J.M.; Coleman, R.J.

    1997-01-01

    We present the methods used to derive mathematical models of global secular variation of the main geomagnetic field for the period 1985 to 2000. These secular-variation models are used in the construction of the candidate US/UK models for the Definitive Geomagnetic Reference Field at 1990, the International Geomagnetic Reference Field for 1995 to 2000, and the World Magnetic Model for 1995 to 2000 (see paper II, Quinn et al., 1997). The main sources of data for the secular-variation models are geomagnetic observatories and repeat stations. Over the areas devoid of these data secular-variation information is extracted from aeromagnetic and satellite data. We describe how secular variation is predicted up to the year 2000 at the observatories and repeat stations, how the aeromagnetic and satellite data are used, and how all the data are combined to produce the required models.

  14. Full vector spherical harmonic analysis of the Holocene geomagnetic field

    Science.gov (United States)

    Richardson, Marcia

    High-quality time-series paleomagnetic measurements have been used to derive spherical harmonic models of Earth's magnetic field for the past 2,000 years. A newly-developed data compilation, PSVMOD2.0 consists of time-series directional and intensity records that significantly improve the data quality and global distribution used to develop previous spherical harmonic models. PSVMOD2.0 consists of 185 paleomagnetic time series records from 85 global sites, including 30 full-vector records (inclination, declination and intensity). It includes data from additional sites in the Southern Hemisphere and Arctic and includes globally distributed sediment relative paleointensity records, significantly improving global coverage over previous models. PSVMOD2.0 records have been assessed in a series of 7 regional intercomparison studies, four in the Northern Hemisphere and 3 in the southern hemisphere. Comparisons on a regional basis have improved the quality and chronology of the data and allowed investigation of spatial coherence and the scale length associated with paleomagnetic secular variation (PSV) features. We have developed a modeling methodology based on nonlinear inversion of the PSVMOD2.0 directional and intensity records. Models of the geomagnetic field in 100-year snapshots have been derived for the past 2,000 with the ultimate goal of developing models spanning the past 8,000 years. We validate the models and the methodology by comparing with the GUFM1 historical models during the 400-year period of overlap. We find that the spatial distribution of sites and quality of data are sufficient to derive models that agree with GUFM1 in the large-scale characteristics of the field. We use the the models derived in this study to downward continue the field to the core-mantle boundary and examine characteristics of the large-scale structure of the magnetic field at the source region. The derived models are temporally consistent from one epoch to the next and exhibit

  15. Ultra-high geomagnetic field reversal frequency around the Precambrian-Cambrian transition ?

    Science.gov (United States)

    Pavlov, V.; Gallet, Y.; Shatsillo, A.; Kouznetsov, N.

    2014-12-01

    Magnetostratigraphic investigations carried out in Siberia have shown that the middle Cambrian was marked by an extremely high geomagnetic field reversal frequency of about 7 to 10 rev./Myr. The results available for the Lower Cambrian are more uncertain but they may indicate an even higher reversal frequency, which could thus reveal a very unstable nature of the geomagnetic field at this time. Recent magnetostratigraphic results also suggest that the geomagnetic reversal frequency has been extraordinarily high at the end of the Precambrian, thus in agreement with the Lower Cambrian data. We will present a review of these data, and will further describe new results we have obtained from Late Ediacaran-Nemakit-Daldynian sections of the south-western Siberian platform (Enisey range, Teya and Chapa rivers valleys). All these data provide consistent evidences for an ultra-high geomagnetic field reversal frequency, and thus for the exceptional nature of the geomagnetic field, around the Precambrian-Cambrian transition. We will also discuss a number of hypotheses which could explain a temporary destabilization of the geomagnetic field.

  16. Fourier power spectra of the geomagnetic field for circular paths on the Earth's surface.

    Science.gov (United States)

    Alldredge, L.R.; Benton, E.R.

    1986-01-01

    The Fourier power spectra of geomagnetic component values, synthesized from spherical harmonic models, have been computed for circular paths on the Earth's surface. They are not found to be more useful than is the spectrum of magnetic energy outside the Earth for the purpose of separating core and crustal sources of the geomagnetic field. The Fourier power spectra of N and E geomagnetic components along nearly polar great circle paths exhibit some unusual characteristics that are explained by the geometric perspective of Fourier series on spheres developed by Yee. -Authors

  17. Features of Pc5 pulsations in the geomagnetic field, auroral luminosity, and Riometer absorption

    Science.gov (United States)

    Belakhovsky, V. B.; Pilipenko, V. A.; Samsonov, S. N.; Lorentsen, D.

    2016-01-01

    Simultaneous morning Pc5 pulsations ( f ~ 3-5 mHz) in the geomagnetic field, aurora intensities (in the 557.7 and 630.0 nm oxygen emissions and the 471.0 nm nitrogen emission), and riometer absorption, were studied based on the CARISMA, CANMOS, and NORSTAR network data for the event of January 1, 2000. According to the GOES-8 satellite observations, these Pc5 geomagnetic pulsations are observed as incompressible Alfvén waves with toroidal polarization in the magnetosphere. Although the Pc5 pulsation frequencies in auroras, the geomagnetic field, and riometer absorption are close to one another, stable phase relationships are not observed between them. Far from all trains of geomagnetic Pc5 pulsations are accompanied by corresponding auroral pulsations; consequently, geomagnetic pulsations are primary with respect to auroral pulsations. Both geomagnetic and auroral pulsations propagate poleward, and the frequency decreases with increasing geomagnetic latitude. When auroral Pc5 pulsations appear, the ratio of the 557.7/630.0 nm emission intensity sharply increases, which indicates that auroral pulsations result from not simply modulated particle precipitation but also an additional periodic acceleration of auroral electrons by the wave field. A high correlation is not observed between Pc5 pulsations in auroras and the riometer absorption, which indicates that these pulsations have a common source but different generation mechanisms. Auroral luminosity modulation is supposedly related to the interaction between Alfvén waves and the region with the field-aligned potential drop above the auroral ionosphere, and riometer absorption modulation is caused by the scattering of energetic electrons by VLF noise pulsations.

  18. Quasi-biennial oscillations in the geomagnetic field: Their global characteristics and origin

    DEFF Research Database (Denmark)

    Ou, Jiaming; Du, Aimin; Finlay, Chris

    2017-01-01

    of second-order derivatives of the geomagnetic X, Y, and Z components reveals salient QBO signals at periods of 1.3, 1.7, 2.2, 2.9, and 5.0 years, with the most prominent peak at 2.2 years. The signature of geomagnetic QBO is generally stronger in the X and Z components and with larger amplitudes...... of crucial importance in studies of rapid core field variations. In this paper, we document the global characteristics of the geomagnetic QBO, using ground-based data collected by geomagnetic observatories between 1985 and 2010, and reexamine the origin of the signals. Fast Fourier transform analysis...... on geomagnetically disturbed days. The amplitude of the QBO in the X component decreases from the equator to the poles, then shows a local maximum at subauroral and auroral zones. The QBO in the Z component enhances from low latitudes toward the polar regions. At high latitudes (poleward of 50°) the geomagnetic QBO...

  19. Proterozoic low orbital obliquity and axial-dipolar geomagnetic field from evaporite palaeolatitudes.

    Science.gov (United States)

    Evans, David A D

    2006-11-02

    Palaeomagnetism of climatically sensitive sedimentary rock types, such as glacial deposits and evaporites, can test the uniformitarianism of ancient geomagnetic fields and palaeoclimate zones. Proterozoic glacial deposits laid down in near-equatorial palaeomagnetic latitudes can be explained by 'snowball Earth' episodes, high orbital obliquity or markedly non-uniformitarian geomagnetic fields. Here I present a global palaeomagnetic compilation of the Earth's entire basin-scale evaporite record. Magnetic inclinations are consistent with low orbital obliquity and a geocentric-axial-dipole magnetic field for most of the past two billion years, and the snowball Earth hypothesis accordingly remains the most viable model for low-latitude Proterozoic ice ages. Efforts to reconstruct Proterozoic supercontinents are strengthened by this demonstration of a consistently axial and dipolar geomagnetic reference frame, which itself implies stability of geodynamo processes on billion-year timescales.

  20. Proterozoic low orbital obliquity and axial-dipolar geomagnetic field from evaporite palaeolatitudes

    Science.gov (United States)

    Evans, David A. D.

    2006-11-01

    Palaeomagnetism of climatically sensitive sedimentary rock types, such as glacial deposits and evaporites, can test the uniformitarianism of ancient geomagnetic fields and palaeoclimate zones. Proterozoic glacial deposits laid down in near-equatorial palaeomagnetic latitudes can be explained by `snowball Earth' episodes, high orbital obliquity or markedly non-uniformitarian geomagnetic fields. Here I present a global palaeomagnetic compilation of the Earth's entire basin-scale evaporite record. Magnetic inclinations are consistent with low orbital obliquity and a geocentric-axial-dipole magnetic field for most of the past two billion years, and the snowball Earth hypothesis accordingly remains the most viable model for low-latitude Proterozoic ice ages. Efforts to reconstruct Proterozoic supercontinents are strengthened by this demonstration of a consistently axial and dipolar geomagnetic reference frame, which itself implies stability of geodynamo processes on billion-year timescales.

  1. A geomagnetic field model for the Holocene based on archaeomagnetic and lava flow data

    Science.gov (United States)

    Pavón-Carrasco, Francisco Javier; Osete, María Luisa; Torta, Joan Miquel; De Santis, Angelo

    2014-02-01

    We propose a new geomagnetic field model for the Holocene period based on archaeomagnetic and lava flow data, avoiding the use of lake sediment data. The source of data comes from the GEOMAGIA50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 yr. The model, called SHA.DIF.14k, allows us to analyse the behaviour of the geomagnetic field for the last 14 000 yr: from 12 000 BC to 1900 AD. For the model construction we use the spherical harmonic analysis in space and the penalized cubic B-splines in time. Both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core-mantle boundary (CMB) to assure the convergence of the model. For the last 3 ka, the model predictions agree with those given by the global model ARCH3k.1 and the European model SCHA.DIF.3k. For older epochs, the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the Holocene. For the last 9 ka, the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 BC and 3000 BC, and the well-known continuous decreasing trend of the geomagnetic field strength for the last millennium and a half. A general view of the time-average evolution of the geomagnetic field flux lobes at the CMB for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum. This lobe vanishes when the dipolar field is decreasing. The north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5.1 km/yr and 3.7 km/yr respectively. The model shows that the geomagnetic field can be averaged as axial dipolar in ˜2000 yr within an error of 5°, the typical uncertainty of the palaeomagnetic studies. Finally, and following the recent definition of archaeomagnetic jerks, we found 8 critical events in the

  2. On the seismogenic increase of the ratio of the ULF geomagnetic field components

    Science.gov (United States)

    Masci, Fabrizio

    2011-07-01

    Following the paper by Fraser-Smith et al. (1990), many scientists have focused their research on the ULF geomagnetic field pulsations in the hope of finding possible anomalous signals caused by the seismic activity. Thereafter, many papers have reported ULF geomagnetic field polarization ratio increases which have been claimed to be related to the occurrence of moderate and strong earthquakes. Even if there is no firm evidence of correlation between the polarization ratio increase and seismic events, these publications maintain that these "anomalous" increases are without doubt precursors of pending earthquakes. Furthermore, several researchers suggest that these seismogenic signals may be considered a promising approach towards the possibility of developing short-term earthquake prediction capabilities based on electromagnetic precursory signatures. On the contrary, a part of the scientific community emphasizes the lack of validation of claimed seismogenic anomalies and doubt their association with the seismic activity. Since earthquake prediction is a very important topic of social importance, the authenticity of earthquake precursors needs to be carefully checked. The aim of this paper is to investigate the reliability of the ULF magnetic polarization ratio changes as an earthquakes' precursor. Several polarization ratio increases of the geomagnetic field, which previous researchers have claimed to have a seismogenic origin, are put into question by a qualitative investigation. The analysis takes into account both the temporal evolution of the geomagnetic field polarization ratio reported in previous papers, and the global geomagnetic activity behaviour. Running averages of the geomagnetic index Kp are plotted onto the original figures from previous publications. Moreover, further quantitative analyses are also reported. Here, nine cases are investigated which include 17 earthquakes. In seven cases it is shown that the suggested association between the

  3. A new method for distortion magnetic field compensation of a geomagnetic vector measurement system

    Science.gov (United States)

    Liu, Zhongyan; Pan, Mengchun; Tang, Ying; Zhang, Qi; Geng, Yunling; Wan, Chengbiao; Chen, Dixiang; Tian, Wugang

    2016-12-01

    The geomagnetic vector measurement system mainly consists of three-axis magnetometer and an INS (inertial navigation system), which have many ferromagnetic parts on them. The magnetometer is always distorted by ferromagnetic parts and other electric equipments such as INS and power circuit module within the system, which can lead to geomagnetic vector measurement error of thousands of nT. Thus, the geomagnetic vector measurement system has to be compensated in order to guarantee the measurement accuracy. In this paper, a new distortion magnetic field compensation method is proposed, in which a permanent magnet with different relative positions is used to change the ambient magnetic field to construct equations of the error model parameters, and the parameters can be accurately estimated by solving linear equations. In order to verify effectiveness of the proposed method, the experiment is conducted, and the results demonstrate that, after compensation, the components errors of measured geomagnetic field are reduced significantly. It demonstrates that the proposed method can effectively improve the accuracy of the geomagnetic vector measurement system.

  4. Did Open Solar Magnetic Field Increase during the Last 100 Years: A Reanalysis of Geomagnetic Activity

    CERN Document Server

    Mursula, K; Karinen, A

    2004-01-01

    Long-term geomagnetic activity presented by the aa index has been used to show that the heliospheric magnetic field has more than doubled during the last 100 years. However, serious concern has been raised on the long-term consistency of the aa index and on the centennial rise of the solar magnetic field. Here we reanalyze geomagnetic activity during the last 100 years by calculating the recently suggested IHV (Inter-Hour Variability) index as a measure of local geomagnetic activity for seven stations. We find that local geomagnetic activity at all stations follows the same qualitative long-term pattern: an increase from early 1900s to 1960, a dramatic dropout in 1960s and a (mostly weaker) increase thereafter. Moreover, at all stations, the activity at the end of the 20th century has a higher average level than at the beginning of the century. This agrees with the result based on the aa index that global geomagnetic activity, and thereby, the open solar magnetic field has indeed increased during the last 100...

  5. LPM Showers in the Atmosphere Taking into Account the Geomagnetic Field

    Science.gov (United States)

    Vankov, H.; Stanev, T.; Inoue, N.; Misaki, A.; Kawaguchi, S.; Konishi, E.

    2003-07-01

    It has become a common knowledge that a correct calculation of the development of air showers initiated by UHE (> 5 × 1019 eV) primary photons should take into account the interactions in the geomagnetic field before entering the atmosphere and the Landau-Pomeranchuk-Migdal effect (LPM) in the atmosphere. We show that the geomagnetic field has also a noticeable effect on the UHE electromagnetic shower development in the atmosphere and has to be accounted for in precise calculations of the shower characteristic.

  6. The 1995 revision of the joint US/UK geomagnetic field models. II: Main field

    Science.gov (United States)

    Quinn, J.M.; Coleman, R.J.; Macmillan, S.; Barraclough, D.R.

    1997-01-01

    This paper presents the 1995 main-field revision of the World Magnetic Model (WMM-95). It is based on Project MAGNET high-level (??? 15,000 ft.) vector aeromagnetic survey data collected between 1988 and 1994 and on scalar total intensity data collected by the Polar Orbiting Geomagnetic Survey (POGS) satellite during the period 1991 through 1993. The spherical harmonic model produced from these data describes that portion of the Earth's magnetic field generated internal to the Earth's surface at the 1995.0 Epoch. When combined with the spherical harmonic model of the Earth's secular variation described in paper I, the Earth's main magnetic field is fully characterized between the years 1995 and 2000. Regional magnetic field models for the conterminous United States, Alaska and, Hawaii were generated as by-products of the global modeling process.

  7. The Distribution of Geomagnetic Field Components on the Southern Part of the Korean Peninsula for Epoch 2010.0

    Directory of Open Access Journals (Sweden)

    Mutaek Lim

    2011-05-01

    Full Text Available NGII(National Geography Information Institute of Korea consigned KIGAM(Korea Institute of Geoscience & Mineral Resources to do absolute geomagnetic measurements on 32 geomagnetic repeat stations evenly distributed on the southern part of Korean Peninsula in the year 2010 and to produce geomagnetic field components' distribution maps for the year 2010.0. The result of the processing of the measured data, i. e., the geomagnetic field components' distribution, shows a near similarity with that calculated from IGRF-11 although the latter was processed without any real geomagnetic data measured on the Korean Peninsula as an input. This implies that we installed the repeat stations on sites with good geomagnetic conditions and that our result in accordance with the IGRF represents well the regional distribution trend, i. e., it is dominated by relatively long wavelength components.

  8. Interrelation of geomagnetic storms and earthquakes: Insight from lab experiments and field observations

    Science.gov (United States)

    Ruzhin, Yuri; Kamogawa, Masashi; Novikov, Victor

    Investigations of possible relations between variations of geomagnetic field and seismicity, including Sq-variations and geomagnetic storms, are overviewed and discussed. There are many papers demonstrating positive correlations between geomagnetic field variations and subsequent earthquake occurrence that allows to authors to talk about triggering impact on earthquake source provided by ionospheric disturbances [e.g., 1]. Nevertheless, there is another opinion on negligible impact of geomagnetic disturbances on the earthquake source supported by statistical analysis of correlation between variations of geomagnetic field and global and regional seismicity. In general, the both points of view on this problem are based on statistical research without detailed consideration of possible physical mechanisms which may be involved into the supposed earthquake triggering, or very rough estimations of possible increase of stresses in the faults under critical (near-to-failure) state were made. It is clear that verification of hypothesis of earthquake triggering by geomagnetic storms should be based on physical mechanisms of generation of additional stresses in the earthquake source or some secondary mechanisms resulted in change of the fault properties. Recently it was shown that the fluids may play very important role in the electromagnetic earthquake triggering [2], and the secondary triggering mechanism should be considered when the fluid migrating into the fault under electromagnetic action may provide fault weakening up to the earthquake triggering threshold. At the same time, depending on fault orientation, local hydrological structure of the crust around the fault, location of fluid reservoirs, etc. it may be possible that the fluid migration from the fault may provide the fault strengthening, and in this case the impact of variation of geomagnetic field may provide an opposite effect, and earthquake will not occur. In so doing, it is useless to apply only

  9. Long-term variations of solar magnetic fields derived from geomagnetic data

    CERN Document Server

    Georgieva, K; Nagovitsyn, Yu A

    2013-01-01

    Sunspots are dark spots on the solar surface associated with strong magnetic fields. The number, area, and brightness of sunspots are supposed to reflect the intensity of the solar magnetic fields and are often used as proxies for their long-term variations. However, the correlations between the sunspot parameters and solar magnetic fields are not constant, and the causes and the time profiles of the variations in these correlations are not quite clear. Therefore, the sunspot data alone cannot be used as proxy for deriving the variations of the sunspot magnetic fields for periods when no instrumental measurements are available. But the Earth is a sort of a probe reacting to interplanetary disturbances which are manifestation of the solar magnetic fields, so records of the geomagnetic activity can be used as diagnostic tools for reconstructing past solar magnetic fields evolution. In the present study we combine sunspot and geomagnetic data to estimate the long-term variations of sunspot magnetic fields.

  10. Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes

    Science.gov (United States)

    Doumbia, Vafi; Boka, Kouadio; Kouassi, Nguessan; Didier Franck Grodji, Oswald; Amory-Mazaudier, Christine; Menvielle, Michel

    2017-01-01

    In this study we examined the influences of geomagnetic activity on the Earth surface electric field variations at low latitudes. During the International Equatorial Electrojet Year (IEEY) various experiments were performed along 5° W in West Africa from 1992 to 1995. Among other instruments, 10 stations equipped with magnetometers and telluric electric field lines operated along a meridian chain across the geomagnetic dip equator from November 1992 to December 1994. In the present work, the induced effects of space-weather-related geomagnetic disturbances in the equatorial electrojet (EEJ) influence area in West Africa were examined. For that purpose, variations in the north-south (Ex) and east-west (Ey) components of telluric electric field were analyzed, along with that of the three components (H, D and Z) of the geomagnetic field during the geomagnetic storm of 17 February 1993 and the solar flare observed on 4 April 1993. The most important induction effects during these events are associated with brisk impulses like storm sudden commencement (ssc) and solar flare effect (sfe) in the geomagnetic field variations. For the moderate geomagnetic storm that occurred on 17 February 1993, with a minimum Dst index of -110 nT, the geo-electric field responses to the impulse around 11:00 LT at LAM are Ex = 520 mV km-1 and Ey = 400 mV km-1. The geo-electric field responses to the sfe that occurred around 14:30 LT on 4 April 1993 are clearly observed at different stations as well. At LAM the crest-to-crest amplitude of the geo-electric field components associated with the sfe are Ex = 550 mV km-1 and Ey = 340 mV km-1. Note that the sfe impact on the geo-electric field variations decreases with the increasing distance of the stations from the subsolar point, which is located at about 5.13° N on 4 April. This trend does not reflect the sfe increasing amplitude near the dip equator due the high Cowling conductivity in the EEJ belt.

  11. Evaluation of a new paleosecular variation activity index as a diagnostic tool for geomagnetic field variations

    Science.gov (United States)

    Panovska, Sanja; Constable, Catherine

    2015-04-01

    Geomagnetic indices like Dst, K and A, have been used since the early twentieth century to characterize activity in the external part of the modern geomagnetic field and as a diagnostic for space weather. These indices reflect regional and global activity and serve as a proxy for associated physical processes. However, no such tools are yet available for the internal geomagnetic field driven by the geodynamo in Earth's liquid outer core. To some extent this reflects limited spatial and temporal sampling for longer timescales associated with paleomagnetic secular variation, but recent efforts in both paleomagnetic data gathering and modeling activity suggest that longer term characterization of the internal geomagnetic weather/climate and its variability would be useful. Specifically, we propose an index for activity in paleosecular variation, useful as both a local and global measure of field stability during so-called normal secular variation and as a means of identifying more extreme behavior associated with geomagnetic excursions and reversals. To date, geomagnetic excursions have been identified by virtual geomagnetic poles (VGPs) deviating more than some conventional limit from the geographic pole (often 45 degrees), and/or by periods of significant intensity drops below some critical value, for example 50% of the present-day field. We seek to establish a quantitative definition of excursions in paleomagnetic records by searching for synchronous directional deviations and lows in relative paleointensity. We combine paleointensity variations with deviations from the expected geocentric axial dipole (GAD) inclination in a single parameter, which we call the paleosecular variation (PSV) activity index. This new diagnostic can be used on any geomagnetic time series (individual data records, model predictions, spherical harmonic coefficients, etc.) to characterize the level of paleosecular variation activity, find excursions, or even study incipient reversals

  12. Dependence of time derivative of horizontal geomagnetic field on sunspot number and aa index

    National Research Council Canada - National Science Library

    Falayi, Elijah O; Rabiu, Babatunde A

    2013-01-01

    This work investigated an interrelationship between the monthly means of time derivatives of horizontal geomagnetic field, dH/dt, sunspot number, R z , and aa index for the period of substorms (from −90 to −1800 nT...

  13. Geodynamo simulations: tools to understand and forecast the geomagnetic field evolution

    Science.gov (United States)

    Aubert, Julien

    2016-04-01

    The past two decades have seen an extensive development of numerical geodynamo simulations as tools to understand the mechanisms through which the magnetic field of internal origin of our planet is generated. Though these are still run at parameter regimes far from that of the Earth's core, the similarity of their output with the various observables of the field, secular variation, and underlying core flows has strengthened the prospect to use these simulations as analysis and forecasting tools for the geomagnetic field evolution. In this presentation, I will report on recent progress in geomagnetic data assimilation, an emerging discipline which blends together the high-quality satellite data such as these obtained by the Swarm mission, and state-of-the art numerical geodynamo simulation with an Earth-like output. The outcome of data assimilation is an estimate of the internal geodynamo structure, which sheds light into the mechanisms currently responsible for the geomagnetic dipole decay and the extension of the South Atlantic geomagnetic anomaly. Starting from such estimates obtained at present, ensemble-based techniques akin to those used in meteorology can help to estimate how the present field will evolve in the future. For the next century, our operational forecasts predict a further dipole decay of about 1 microtesla at Earth's surface, together with a similar deepening and a westward motion of the South Atlantic anomaly.

  14. Sources of the Geomagnetic Field and the Modern Data That Enable Their Investigation

    DEFF Research Database (Denmark)

    Olsen, Nils; Hulot, Gauthier; Sabaka, Terence J.

    2014-01-01

    The geomagnetic field one can measure at the Earth’s surface or on board satellites is the sum of contributions from many different sources. These sources have different physical origins and can be found both below (in the form of electrical currents and magnetized material) and above (only in th...

  15. The intensity of the time-averaged geomagnetic field: the last 5 Myr

    NARCIS (Netherlands)

    Juarez, M.T.; Tauxe, Lisa

    2002-01-01

    The existing database for paleointensity estimates of the ancient geomagnetic field contains more than 1500 data points collected through decades of effort. Despite the huge amount of work put into obtaining these data, there remains a strong bias in the age and global distribution of the data towar

  16. Variations in the intensity of the geomagnetic field in Siberia during the last 13000 years

    Science.gov (United States)

    Nachasova, I. E.; Burakov, K. S.; Pilipenko, O. V.

    2015-01-01

    The thermal magnetization of the samples from the archaeological sites in Siberia is studied. The magnetization of the collected samples was studied using the authors' modification of the Thellier method amended by the magnetic anisotropy and chemical alterations. Resulting from the study of the burned material from the Kazachka site, the time series of the geomagnetic field intensity in Siberia spanning the time interval from 10000 to 1000 B.C. is obtained. These data are unique in terms of the duration and representativeness. For the first time, the main variation in the intensity of the geomagnetic field is traced by studying the magnetization of the samples from a single archeological site. The pattern of the variations in the intensity of the geomagnetic field in Siberia from 11000 B.C. to 2000 A.D., which is reconstructed from the data of the Kazachka, Ust-Karenga, and some other sites of Cis-Baikalia, indicates that the characteristics time of the long-period oscillation in the intensity of the geomagnetic field is about 8000 years. It also suggests the existence of rapid variations superimposed on the main oscillation.

  17. Solar Flares and Variation of Local Geomagnetic Field: Measurements by the Huancayo Observatory over 2001-2010

    Science.gov (United States)

    Carlos Reyes, Rafael E.; Gárate Ayesta, Gabriel A.; Reyes Navarro, Felipe A.

    2017-02-01

    We study the local variation of the geomagnetic field measured by the Huancayo Geomagnetic Observatory, Peru, during 2001-2010. Initially, we sought to relate the SFI values, stored daily in the NOAA's National Geophysical Data Center, with the corresponding geomagnetic index; however, no relation was observed. Nonetheless, subsequently, a comparison between the monthly geomagnetic-activity index and the monthly SFI average allowed observing a temporal correlation between these average indices. This correlation shows that the effect of the solar flares does not simultaneously appear on the corresponding magnetic indices. To investigate this, we selected the most intense X-class flares; then, we checked the magnetic field disturbances observed in the Huancayo Geomagnetic Observatory magnetograms. We found some disturbances of the local geomagnetic field in the second and third day after the corresponding solar flare; however, the disturbance strength of the local geomagnetic field is not correlated with the X-class of the solar flare. Finally, there are some disturbances of the local geomagnetic field that are simultaneous with the X-class solar flares and they show a correlation with the total flux of the solar flare.

  18. Geological support for the Umbrella Effect as a link between geomagnetic field and climate

    Science.gov (United States)

    Kitaba, Ikuko; Hyodo, Masayuki; Nakagawa, Takeshi; Katoh, Shigehiro; Dettman, David L.; Sato, Hiroshi

    2017-01-01

    The weakening of the geomagnetic field causes an increase in galactic cosmic ray (GCR) flux. Some researchers argue that enhanced GCR flux might lead to a climatic cooling by increasing low cloud formation, which enhances albedo (umbrella effect). Recent studies have reported geological evidence for a link between weakened geomagnetic field and climatic cooling. However, more work is needed on the mechanism of this link, including whether the umbrella effect is playing a central role. In this research, we present new geological evidence that GCR flux change had a greater impact on continental climate than on oceanic climate. According to pollen data from Osaka Bay, Japan, the decrease in temperature of the Siberian air mass was greater than that of the Pacific air mass during geomagnetic reversals in marine isotope stages (MIS) 19 and 31. Consequently, the summer land-ocean temperature gradient was smaller, and the summer monsoon was weaker. Greater terrestrial cooling indicates that a reduction of insolation is playing a key role in the link between the weakening of the geomagnetic field and climatic cooling. The most likely candidate for the mechanism seems to be the increased albedo of the umbrella effect. PMID:28091595

  19. Magnetic Field Perturbations from Currents in the Dark Polar Regions During Quiet Geomagnetic Conditions

    Science.gov (United States)

    Friis-Christensen, E.; Finlay, C. C.; Hesse, M.; Laundal, K. M.

    2017-02-01

    In the day-side sunlit polar ionosphere the varying and IMF dependent convection creates strong ionospheric currents even during quiet geomagnetic conditions. Observations during such times are often excluded when using satellite data to model the internal geomagnetic main field. Observations from the night-side or local winter during quiet conditions are, however, also influenced by variations in the IMF. In this paper we briefly review the large scale features of the ionospheric currents in the polar regions with emphasis on the current distribution during undisturbed conditions. We examine the distribution of scalar measurements of the magnetic field intensity minus predictions from a geomagnetic field model. These `residuals' fall into two main categories. One category is consistently distributed according to the well-known ionospheric plasma convection and its associated Birkeland currents. The other category represent contributions caused by geomagnetic activity related to the substorm current wedge around local magnetic midnight. A new observation is a strong IMF By control of the residuals in the midnight sector indicating larger ionospheric currents in the substorm current wedge in the northern polar region for By > 0 and correspondingly in the southern hemisphere for By < 0.

  20. Geological support for the Umbrella Effect as a link between geomagnetic field and climate

    Science.gov (United States)

    Kitaba, Ikuko; Hyodo, Masayuki; Nakagawa, Takeshi; Katoh, Shigehiro; Dettman, David L.; Sato, Hiroshi

    2017-01-01

    The weakening of the geomagnetic field causes an increase in galactic cosmic ray (GCR) flux. Some researchers argue that enhanced GCR flux might lead to a climatic cooling by increasing low cloud formation, which enhances albedo (umbrella effect). Recent studies have reported geological evidence for a link between weakened geomagnetic field and climatic cooling. However, more work is needed on the mechanism of this link, including whether the umbrella effect is playing a central role. In this research, we present new geological evidence that GCR flux change had a greater impact on continental climate than on oceanic climate. According to pollen data from Osaka Bay, Japan, the decrease in temperature of the Siberian air mass was greater than that of the Pacific air mass during geomagnetic reversals in marine isotope stages (MIS) 19 and 31. Consequently, the summer land-ocean temperature gradient was smaller, and the summer monsoon was weaker. Greater terrestrial cooling indicates that a reduction of insolation is playing a key role in the link between the weakening of the geomagnetic field and climatic cooling. The most likely candidate for the mechanism seems to be the increased albedo of the umbrella effect.

  1. Some effects of quiet geomagnetic field changes upon values used for main field modeling

    Science.gov (United States)

    Campbell, W.H.

    1987-01-01

    The effects of three methods of data selection upon the assumed main field levels for geomagnetic observatory records used in main field modeling were investigated for a year of very low solar-terrestrial activity. The first method concerned the differences between the year's average of quiet day field values and the average of all values during the year. For H these differences were 2-3 gammas, for D they were -0.04 to -0.12???, for Z the differences were negligible. The second method of selection concerned the effects of the daytime internal Sq variations upon the daily mean values of field. The midnight field levels when the Sq currents were a minimum deviated from the daily mean levels by as much as 4-7 gammas in H and Z but were negligible for D. The third method of selection was designed to avoid the annual and semi-annual quiet level changes of field caused by the seasonal changes in the magnetosphere. Contributions from these changes were found to be as much as 4-7 gammas in quiet years and expected to be greater than 10 gammas in active years. Suggestions for improved methods of improved data selection in main field modeling are given. ?? 1987.

  2. Annual Variations of the Geomagnetic Field in the Earth's Polar Regions

    Science.gov (United States)

    Ou, Jiaming; Du, Aimin

    2017-04-01

    The annual variations of the geomagnetic field play an important role in the coupling processes between the solar wind, magnetosphere and ionosphere. The annual variation is a well-established feature of the geomagnetic field, and usually is applied for modeling the conductivity of the lower mantle [Parkinson, 1983], and for long-term space weather forecasting [Bartels, 1932; Malin and Mete Isikara, 1976; Gonzalez et al., 1994]. Considerable effort has been devoted toward understanding the causes of the geomagnetic field variations, but the suggested physical mechanisms differ widely. The annual variation is relatively weak in many magnetic indices, but it has a distinct signature in the geomagnetic components. Thus, we use the components for this analysis. The components have a positive peak in northern summer and a negative dip in winter [Vestine, 1954]. Vestine [1954] suggested that the annual variation is caused by an ionospheric dynamo in which electric currents in the ionosphere are generated by meridional winds. The winds blow from north-to-south during northern summer, and south-to-north in northern winter. Malin and Mete Isikara [1976], using near-midnight geomagnetic data, concluded that the annual variation results from a latitudinal movement of the auroral electrojet or the ring current. Stauning [2011] derived of the seasonal variation of the quiet daily variations and examined the influence of the sector structure of the interplanetary magnetic field. Ziegger and Mursula [1998] have suggested a third mechanism: that the cause is related to an asymmetric solar wind speed distribution across the heliographic equator. In this paper, we study the annual variation problem using long-term magnetic observation and ionospheric conductivity. The sunlight incident on the ionosphere will be calculated. Although a global analysis is done, particular focus will be placed on the polar regions. This study covers the interval 1990-2010, and the cause of the well

  3. Mapping of steady-state electric fields and convective drifts in geomagnetic fields - Part 2: The IGRF

    Science.gov (United States)

    Walker, A. D. M.

    2016-01-01

    A method of mapping electric fields along geomagnetic field lines is applied to the IGRF (International Geomagnetic Reference Field) model. The method involves integrating additional sets of first order differential equations simultaneously with those for tracing a magnetic field line. These provide a measure of the rate of change of the separation of two magnetic field lines separated by an infinitesimal amount. From the results of the integration Faraday's law is used to compute the electric field as a function of position along the field line. Examples of computations from a software package developed to implement the method are presented. This is expected to be of use in conjugate studies of magnetospheric phenomena such as SuperDARN (Super Dual Auroral Radar) observations of convection in conjugate hemispheres, or comparison of satellite electric field observations with fields measured in the ionosphere.

  4. The geomagnetic field intensity variations in the Iberian Peninsula during the last millennium

    Science.gov (United States)

    Nachasova, I. E.; Akimova, S. V.

    2015-09-01

    The pattern of variations in the intensity of the geomagnetic field starting from the middle of the sixth millennium B.C. is reconstructed from the data about the intensity of the ancient geomagnetic field in the region of the Iberian Peninsula provided by the archaeomagnetic studies of ceramics from archaeological monuments. In this time interval, the intensity of the field widely varies from ~30 to ~90 µT. The smooth variation of the field is superimposed by the variations with characteristic times from thousands to hundreds of years. The intensity variations can be subdivided into two groups: rather sharp variations with a characteristic duration of about 200 years and smooth quasi-harmonic fluctuations with a duration of a few hundred years.

  5. Estimating ionospheric currents by inversion from ground-based geomagnetic data and calculating geoelectric fields for studies of geomagnetically induced currents

    Science.gov (United States)

    de Villiers, J. S.; Pirjola, R. J.; Cilliers, P. J.

    2016-09-01

    This research focuses on the inversion of geomagnetic variation field measurements to obtain the source currents in the ionosphere and magnetosphere, and to determine the geoelectric fields at the Earth's surface. During geomagnetic storms, the geoelectric fields create geomagnetically induced currents (GIC) in power networks. These GIC may disturb the operation of power systems, cause damage to power transformers, and even result in power blackouts. In this model, line currents running east-west along given latitudes are postulated to exist at a certain height above the Earth's surface. This physical arrangement results in the fields on the ground being composed of a zero magnetic east component and a nonzero electric east component. The line current parameters are estimated by inverting Fourier integrals (over wavenumber) of elementary geomagnetic fields using the Levenberg-Marquardt technique. The output parameters of the model are the ionospheric current strength and the geoelectric east component at the Earth's surface. A conductivity profile of the Earth is adapted from a shallow layered-Earth model for one observatory, together with a deep-layer model derived from satellite observations. This profile is used to obtain the ground surface impedance and therefore the reflection coefficient in the integrals. The inputs for the model are a spectrum of the geomagnetic data for 31 May 2013. The output parameters of the model are spectrums of the ionospheric current strength and of the surface geoelectric field. The inverse Fourier transforms of these spectra provide the time variations on the same day. The geoelectric field data can be used as a proxy for GIC in the prediction of GIC for power utilities. The current strength data can assist in the interpretation of upstream solar wind behaviour.

  6. Geomagnetism applications

    Science.gov (United States)

    Campbell, Wallace H.

    1995-01-01

    The social uses of geomagnetism include the physics of the space environment, satellite damage, pipeline corrosion, electric power-grid failure, communication interference, global positioning disruption, mineral-resource detection, interpretation of the Earth's formation and structure, navigation, weather, and magnetoreception in organisms. The need for continuing observations of the geomagnetic field, together with careful archiving of these records and mechanisms for dissemination of these data, is emphasized.

  7. Shielding of the Geomagnetic Field Alters Actin Assembly and Inhibits Cell Motility in Human Neuroblastoma Cells

    OpenAIRE

    Wei-Chuan Mo; Zi-Jian Zhang; Dong-Liang Wang; Ying Liu; Bartlett, Perry F.; Rong-Qiao He

    2016-01-01

    Accumulating evidence has shown that absence of the geomagnetic field (GMF), the so-called hypomagnetic field (HMF) environment, alters the biological functions in seemingly non-magnetosensitive cells and organisms, which indicates that the GMF could be sensed by non-iron-rich and non-photo-sensing cells. The underlying mechanisms of the HMF effects on those cells are closely related to their GMF sensation but remain poorly understood so far. Previously, we found that the HMF represses expres...

  8. The Geomagnetic Field and Correlations with Multiple Sclerosis: A Possible Etiology of Disease

    Science.gov (United States)

    Wade, Brett

    Multiple sclerosis (MS) is a complex autoimmune disease that results in a demyelinating process of the central nervous system. It is the most common, progressive, neurological disease affecting young adults, and there is no cure. A curious feature of MS is its distinct global prevalence with high rates of occurrence between 40 and 60 degrees latitude. While genetics may partially explain this phenomenon, studies have shown that the influence of genetics is modest. Many non-genetic variables, such as viruses, vitamin D, smoking, diet, hormones, etc., have been shown to be related to the expression of MS but none of these variables have been determined to be necessarily strong enough to exclude other factors. The geomagnetic field, which is a non-uniform, three dimensional entity which protects all living things from ionizing radiation, is suggested in this research to be related to global MS prevalence. This study hypothesized that either the total field, the vertical field, or the horizontal field strength of the geomagnetic field will be correlated with MS. Using secondary sources of prevalence studies (N=131) and geomagnetic data, the results supported all three hypotheses with the strongest correlation being an inverse relationship between the horizontal field and MS (r = -.607). The explanation for the inverse relationship being most strongly correlated with MS prevalence is explained by the fact that the horizontal aspect of the geomagnetic field has a protective effect from incoming cosmic radiation. Chronic exposure to high levels of background radiation can have deleterious health effects. This research suggests that living in areas of a weak horizontal field increases a person's exposure to ionizing radiation and therefore increases the risk for developing MS. While it was not the intention of this research, it became clear that an explanation which explained the results of this research and also attempted to unify the mechanisms of all non

  9. Geomagnetic Secular Variation in Texas over the Last 17,000 Years: High-Intensity Geomagnetic Field 'Spike' Observed at ca. 3000 cal BP

    Science.gov (United States)

    Bourne, M. D.; Feinberg, J. M.; Waters, M. R.; Stafford, T. W., Jr.; Forman, S. L.; Lundelius, E. L.

    2015-12-01

    By observing the fluctuations in direction and intensity of the Earth's magnetic field through time, we increase our understanding of the fluid motions in the Earth's outer core that sustain the geomagnetic field, the geodynamo. Recent archaeomagnetic studies in the Near East have proposed extremely rapid increases - 'spikes' - in geomagnetic field intensity ca. 3000 years ago that have proved problematic for our current understanding of core-flow. However, until now, these geomagnetic spikes had not been observed outside of the Near East, where they have been found in metallurgical slag and mud brick walls. We present a new fully-oriented, geomagnetic secular variation and relative palaeointensity (RPI) record for the last 17,000 years from Hall's Cave, Texas. Sediment washed into the cave has formed a continuous stratigraphic sequence that is at least 3.5 m thick. Within the stable, cool climate of the cave, pedogenic and bioturbation processes are almost non-existent, thereby limiting post-depositional physical and geochemical alteration of the magnetic record. The sub-aerial and subterranean setting of the sedimentary sequence in Hall's Cave enabled us to collect oriented palaeomagnetic cubes from an excavated section through the sequence. The palaeomagnetic samples yielded high-quality vectors. An age model for the sequence, determined using 57 AMS 14C-dates on individual bones from microvertebrate, was combined with the palaeomagnetic data to construct a secular variation record. The record is in broad agreement with predictions by Holocene field models for the site's location. However, at ca. 3000 years ago, the RPI data indicate an almost four-fold increase in geomagnetic field intensity lasting several hundred years and contemporaneous with the more short-lived, decadal-scale spikes reported from the Near East. Evidence for this extreme intensity event outside of the Near East has major implications for our current understanding of core-dynamics.

  10. Multi-proxy identification of the Laschamp geomagnetic field excursion in Lake Pupuke, New Zealand

    Science.gov (United States)

    Nilsson, Andreas; Muscheler, Raimund; Snowball, Ian; Aldahan, Ala; Possnert, Göran; Augustinus, Paul; Atkin, Daniel; Stephens, Tom

    2011-11-01

    We present palaeomagnetic and cosmogenic radionuclide records of the Laschamp geomagnetic excursion in Lake Pupuke, a maar lake in Auckland, New Zealand. Laschamp was identified by a combination of relative palaeointensity, 10Be and 14C data from the lake sediments and represents the first such record from the Southern Hemisphere. Despite the high organic carbon content, which causes relatively weak natural remanent magnetisations, the geomagnetic intensity minimum associated with the Laschamp excursion is identifiable as a relative palaeointensity minimum that is synchronous with (i) a peak in 10Be concentration and (ii) an anomaly in Δ 14C. The Lake Pupuke time scale, provided by 14C data calibrated with INTCAL09, places the 10Be maximum at the same time as a 10Be maximum in Greenland ice cores when secured to the GICC05 time scale. The central age of the Laschamp geomagnetic excursion in Lake Pupuke as defined by the 10Be prediction peak is c. 41 kyr, which confirms its global application as a palaeomagnetic isochron. Anomalous palaeomagnetic directional data at c. 32 kyr in the Lake Pupuke sediments may represent the Mono Lake geomagnetic excursion, but tephra layers caused by frequent eruptions in the Auckland volcanic field during this excursion probably disrupted the palaeointensity signal. The study highlights the value of combining traditional palaeomagnetic methods with measurements of cosmogenic radionuclides in the quest for accurate and precise geochronologies during MIS3, a time of rapid global climate change.

  11. Morphology of the southern African geomagnetic field derived from observatory and repeat station survey observations: 2005-2014

    Science.gov (United States)

    Kotzé, P. B.; Korte, M.

    2016-02-01

    Geomagnetic field data from four observatories and annual field surveys between 2005 and 2015 provide a detailed description of Earth's magnetic field changes over South Africa, Namibia and Botswana on time scales of less than 1 year. The southern African area is characterized by rapid changes in the secular variation pattern and lies in close proximity to the South Atlantic Anomaly (SAA) where the geomagnetic field intensity is almost 30 % weaker than in other regions at similar latitudes around the globe. Several geomagnetic secular acceleration (SA) pulses (geomagnetic jerks) around 2007, 2010 and 2012 could be identified over the last decade in southern Africa. We present a new regional field model for declination and horizontal and vertical intensity over southern Africa (Southern African REGional (SAREG)) which is based on field survey and observatory data and covering the time interval from 2005 to 2014, i.e. including the period between 2010 and 2013 when no low Earth-orbiting vector field satellite data are available. A comparative evaluation between SAREG and global field models like CHAOS-5, the CHAMP, Orsted and SAC-C model of the Earth's magnetic field and International Geomagnetic Reference Field (IGRF-12) reveals that a simple regional field model based on a relatively dense ground network is able to provide a realistic representation of the geomagnetic field in this area. We particularly note that a global field model like CHAOS-5 does not always indicate similar short-period patterns in the field components as revealed by observatory data, while representing the general secular variation reasonably well during the time interval without near-Earth satellite vector field data. This investigation further shows the inhomogeneous occurrence and distribution of secular variation impulses in the different geomagnetic field components and at different locations in southern African.

  12. A model of the geomagnetic field and its secular variation for epoch 2000 estimated from Orsted data

    DEFF Research Database (Denmark)

    Olsen, Nils

    2002-01-01

    The availability of high-precision geomagnetic measurements from satellites such as Orsted and CHAMP opens a new era in geomagnetic field research. However, in order to take full advantage of the improved data accuracy it is necessary to refine the usual way of deriving field models from satellite...... as measured simultaneously by globally distributed geomagnetic observatories. In addition, the observatory data are used to constrain secular variation. The model is estimated using an iteratively reweighted least-squares method with Huber weights to account for the non-Gaussian data error distribution...

  13. The intensity of the time-averaged geomagnetic field: the last 5 Myr

    OpenAIRE

    Juarez, M.T.; Tauxe, Lisa

    2002-01-01

    The existing database for paleointensity estimates of the ancient geomagnetic field contains more than 1500 data points collected through decades of effort. Despite the huge amount of work put into obtaining these data, there remains a strong bias in the age and global distribution of the data toward very young results from a few locations. Also, few of the data meet strict criteria for reliability and most are of unknown quality. In order to improve the age and spatial distribution of the pa...

  14. Separation of variations of the geomagnetic field into normal and anomalous parts on a bounded territory

    Science.gov (United States)

    Zhdanov, M. S.; Plotnikov, S. V.

    1981-12-01

    A method based on convolution integrals is developed for separating geomagnetic variations into normal and anomalous parts. It is shown for a number of typical models of normal geoelectric section that the kernels of the integral transforms have the form of spatial windows which fluctuate (depending on the variation period) from several tens to several hundreds of kilometers. This indicates the possibility of separating fields specified on a bounded territory into normal and anomalous parts.

  15. Regional estimation of geomagnetically induced currents based on the local magnetic or electric field

    Directory of Open Access Journals (Sweden)

    Viljanen Ari

    2015-01-01

    Full Text Available Previous studies have demonstrated a close relationship between the time derivative of the horizontal geomagnetic field vector (dH/dt and geomagnetically induced currents (GIC at a nearby location in a power grid. Similarly, a high correlation exists between GIC and the local horizontal geoelectric field (E, typically modelled from a measured magnetic field. Considering GIC forecasting, it is not feasible to assume that detailed prediction of time series will be possible. Instead, other measures summarising the activity level over a given period are preferable. In this paper, we consider the 30-min maximum of dH/dt or E as a local activity indicator (|dH/dt|30 or |E|30. Concerning GIC, we use the sum of currents through the neutral leads at substations and apply its 30-min maximum as a regional activity measure (GIC30. We show that |dH/dt|30 at a single point yields a proxy for GIC activity in a larger region. A practical consequence is that if |dH/dt|30 can be predicted at some point then it is also possible to assess the expected GIC level in the surrounding area. As is also demonstrated, |E|30 and GIC30 depend linearly on |dH/dt|30, so there is no saturation with increasing geomagnetic activity contrary to often used activity indices.

  16. Uncertainties in field-line tracing in the magnetosphere. Part I: the axisymmetric part of the internal geomagnetic field

    Directory of Open Access Journals (Sweden)

    J. Comer

    Full Text Available The technique of tracing along magnetic field lines is widely used in magnetospheric physics to provide a "magnetic frame of reference'' that facilitates both the planning of experiments and the interpretation of observations. The precision of any such magnetic frame of reference depends critically on the accurate representation of the various sources of magnetic field in the magnetosphere. In order to consider this important problem systematically, a study is initiated to estimate first the uncertainties in magnetic-field-line tracing in the magnetosphere that arise solely from the published (standard errors in the specification of the geomagnetic field of internal origin. Because of the complexity in computing these uncertainties for the complete geomagnetic field of internal origin, attention is focused in this preliminary paper on the uncertainties in magnetic-field-line tracing that result from the standard errors in just the axisymmetric part of the internal geomagnetic field. An exact analytic equation exists for the magnetic field lines of an arbitrary linear combination of axisymmetric multipoles. This equation is used to derive numerical estimates of the uncertainties in magnetic-field-line tracing that are due to the published standard errors in the axisymmetric spherical harmonic coefficients (i.e. gn0 ± δgn0. Numerical results determined from the analytic equation are compared with computational results based on stepwise numerical integration along magnetic field lines. Excellent agreement is obtained between the analytical and computational methods in the axisymmetric case, which provides great confidence in the accuracy of the computer program used for stepwise numerical integration along magnetic field lines. This computer program is then used in the following paper to estimate the uncertainties in magnetic-field-line tracing in the magnetosphere that arise from the published standard errors in the full set of spherical

  17. Studies of the influence of the geomagnetic field on the sensitivity of gamma-ray observatories

    Energy Technology Data Exchange (ETDEWEB)

    Krause, Maria

    2011-02-15

    Cherenkov Telescope Array (CTA) will be a ground-based high energy gamma radiation detector. This radiation is detected by the measurement of particle showers in the atmosphere. The questions of the origin of the cosmic radiation, the functional principle of cosmic particle accelerators in the area of black holes or the nature of the dark matter are in the scientific goals of CTA. At the moment the instrument is in the planning phase and first results will probably be in 2014. The site of the instrument has an immediate influence on the sensitivity e.g. due to the weather, the height above sea level. Several possible sites for CTA are being considered at the moment including Namibia, Argentina, Canary Islands and Mexico. The geomagnetic field affects the development of showers and distorts the images of the air shower in the telescope. The aim of this work is to quantify the influence of the strength and the direction of the geomagnetic field at the different possible locations on the sensitivity of CTA using Monte Carlo simulations of particle showers. Firstly, we simulated the lateral distribution at the twelve sites. The geomagnetic field of the sites was obtained from the National Geographic Data Center (NGDC). To study the influence of the Earth's magnetic field, we held the altitude of the sites constant at 2000 m. Hence, we could choose two sites per hemisphere which could be potential candidates for the Cherenkov Telescope Array: BeaufortWest (South Africa), El Leoncito (Argentina), La Palma (Canary Islands) and San Pedro Martir (Mexico). To compare the results with a site which is already known, we chose the observatory H.E.S.S. in Namibia. After the study of the energy thresholds and the effective areas we decided in favour of two sites, one in the southern and one in the northern hemisphere. Considering the influence of the geomagnetic field on the predictions, the southern observatory should be in Beaufort West in South Africa. The northern array

  18. The null magnetic field as reference for the study of geomagnetic directional effects in animals and man.

    Science.gov (United States)

    Beischer, D. E.

    1971-01-01

    Techniques for producing very low and zero magnetic fields are considered, giving attention to the compensation of the geomagnetic field by a Helmholtz coil system, approaches utilizing the shielding power of highly permeable alloys, and the complete exclusion of the geomagnetic field with the aid of a superconductive shield. Animal experiments in low magnetic fields are discussed, together with the exposure of man to 'null' magnetic fields and the Josephson junction as a possible biosensor of magnetic fields. It is found that neither the functions nor the behavior of man changes significantly during a two-week exposure to magnetic fields below 50 gammas.

  19. Magnetic Field Perturbations from Currents in the Dark Polar Regions During Quiet Geomagnetic Conditions

    DEFF Research Database (Denmark)

    Friis-Christensen, Eigil; Finlay, Chris; Hesse, M.

    2017-01-01

    In the day-side sunlit polar ionosphere the varying and IMF dependent convection creates strong ionospheric currents even during quiet geomagnetic conditions. Observations during such times are often excluded when using satellite data to model the internal geomagneticmain field. Observations from...... the night-side or local winter during quiet conditions are, however, also influenced by variations in the IMF. In this paper we briefly review the large scale features of the ionospheric currents in the polar regions with emphasis on the current distribution during undisturbed conditions. We examine....... The other category represent contributions caused by geomagnetic activity related to the substorm current wedge around local magnetic midnight. A new observation is a strong IMF By control of the residuals in the midnight sector indicating larger ionospheric currentsin the substorm current wedge...

  20. The signature of the 2011 Tohoku mega earthquake on the geomagnetic field measurements in Japan

    Directory of Open Access Journals (Sweden)

    E.M. Takla

    2013-12-01

    Full Text Available On 11 March 2011 at 05:46:23 UTC, a mega earthquake (EQ with magnitude (Mw 9.0 [The 2011 Tohoku Earthquake] occurred at a depth of about 24 km near the East coast of Honshu Island, Japan as a result of a thrust faulting on or near the subduction plate boundary between the Pacific and North American plates. Geomagnetic data from MAGDAS and Geospatial Information Authority of Japan (GSI networks have been analyzed to examine the signature of the 2011 Tohoku earthquake on the geomagnetic field measurements in Japan. Results of data analysis indicate about 5 nT increase in the total geomagnetic field intensity in the vicinity of the epicenter of 2011Tohoku EQ compared with other reference stations. Moreover, the annual range of the Z-component daily variations tends to decrease near the epicenter before the occurrence of the Tohoku EQ. Concerning the ULF emissions; the Pc 3 amplitude ratio (ZPc3/HPc3 near the epicenter at the Onagawa [ONW] station showed a good correlation with other remote reference stations before the Tohoku EQ but it started to decrease with no correlation to other stations a few weeks before the 2011 Tohoku EQ. On the other hand, the Pc 3 amplitude ratio at ONW station showed a clear anti-correlation compared with reference stations after the 2011 Tohoku EQ.

  1. Geomagnetic Field Variations as Determined from Bulgarian Archaeomagnetic Data. Part II: The Last 8000 Years

    Science.gov (United States)

    Kovacheva, Mary; Jordanova, Neli; Karloukovski, Vassil

    The knowledge about past secular variations of the geomagnetic field is achieved on the basis of archaeomagnetic researches of which the Bulgarian studies form an extended data set. In Part I (Kovacheva and Toshkov, 1994), the methodology used in the Sofia palaeomagnetic laboratory was described and the secular variation curves for the last 2000 years were shown. In Part II (this paper), the basic characteristics of the prehistoric materials used in the archaeomagnetic studies are emphasised, particularly in the context of the rock magnetic studies used in connection with palaeointensity determinations. The results of magnetic anisotropy studies of the prehistoric ovens and other fired structures are summarised, including the anisotropy correction of the palaeointensity results for prehistoric materials, different from bricks and pottery. Curves of the direction and intensity of the geomagnetic field during the last 8000 years in Bulgaria are given. The available directional and intensity values have been used to calculate the variation curve of the virtual dipole moment (VDM) for the last 8000 years based on different time interval averages. The path of virtual geomagnetic pole (VGP) positions is discussed.

  2. Noise reduction by magnetostatic coupling in geomagnetic-field sensors

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Chong-Jun; Li, Min; Li, Jian-Wei [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Ding, Lei [School of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China); Teng, Jiao, E-mail: cjzhao.ustb@gmail.com [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guang-Hua [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2014-11-15

    A new magnetoresistive (MR) thin film with a structure of “antiferromagnetic layer/pinned soft magnetic layer/non-magnetic MgO spacer layer/sensitive NiFe layer” was designed. The barber-pole MR elements with a Wheatstone bridge circuit were fabricated using photolithographic methods. The testing results show that, in comparison to the element with a typical structure of Ta/NiFe/Ta, the fabricated MR element shows significant reduction in the Barkhausen noise and the 1/f noise and good magnetic stability while maintaining high magnetic field sensitivity. This element with improved signals can be attributed to the magnetostatic coupling between the pinned soft magnetic layer and the sensitive NiFe layer, which can act as a small stabilizing field, leading to the coherent rotation of magnetic moment in the sensitive NiFe layer. - Highlights: • A new MR film with the structure of “IrMn/NiFe/MgO/NiFe” was designed. • The elements with a Wheatstone bridge circuit were fabricated using photolithography. • A reduced noisy and good magnetic stable signal was achieved. • The magnetostatic coupling can act as a small stabilizing field. • Coherent rotation of the magnetic moment happened in the sensing NiFe layer.

  3. NOAA/NGDC candidate models for the 12th generation International Geomagnetic Reference Field

    Science.gov (United States)

    Alken, Patrick; Maus, Stefan; Chulliat, Arnaud; Manoj, Chandrasekharan

    2015-05-01

    The International Geomagnetic Reference Field (IGRF) is a model of the geomagnetic main field and its secular variation, produced every 5 years from candidate models proposed by a number of international research institutions. For this 12th generation IGRF, three candidate models were solicited: a main field model for the 2010.0 epoch, a main field model for the 2015.0 epoch, and the predicted secular variation for the five-year period 2015 to 2020. The National Geophysical Data Center (NGDC), part of the National Oceanic and Atmospheric Administration (NOAA), has produced three candidate models for consideration in IGRF-12. The 2010 main field candidate was produced from Challenging Minisatellite Payload (CHAMP) satellite data, while the 2015 main field and secular variation candidates were produced from Swarm and Ørsted satellite data. Careful data selection was performed to minimize the influence of magnetospheric and ionospheric fields. The secular variation predictions of our parent models, from which the candidate models were derived, have been validated against independent ground observatory data.

  4. Bulgarian Geomagnetic Reference Field (BulGRF) for 2015.0 and secular variation prediction model up to 2020

    Science.gov (United States)

    Metodiev, Metodi; Trifonova, Petya

    2017-09-01

    The Bulgarian Geomagnetic Reference Field (BulGRF) for 2015.0 epoch and its secular variation model prediction up to 2020.0 is produced and presented in this paper. The main field model is based on the well-known polynomial approximation in latitude and longitude of the geomagnetic field elements. The challenge in our modelling strategy was to update the absolute field geomagnetic data from 1980.0 up to 2015.0 using secular measurements unevenly distributed in time and space. As a result, our model gives a set of six coefficients for the horizontal H, vertical Z, total field F, and declination D elements of the geomagnetic field. The extrapolation of BulGRF to 2020 is based on an autoregressive forecasting of the Panagyurishte observatory annual means. Comparison of the field values predicted by the model with Panagyurishte (PAG) observatory annual mean data and two vector field measurements performed in 2015 shows a close match with IGRF-12 values and some difference with the real (measured) values, which is probably due to the influence of crustal sources. BulGRF proves to be a reliable alternative to the global geomagnetic field models which together with its simplicity makes it a useful tool for reducing magnetic surveys to a common epoch carried out over the Bulgarian territory up to 2020.

  5. The electric field in northern England and southern Scotland: implications for geomagnetically induced currents

    Science.gov (United States)

    McKay, A. J.; Whaler, K. A.

    2006-11-01

    Magnetotelluric (MT) data, in the form of MT tensors, are used to estimate directly the size and spatial distribution of the electric field in northern England and southern Scotland with the aim of predicting the flow of geomagnetically induced currents (GIC) in power networks in the region. MT and Geomagnetic Deep Sounding data from a number of different field campaigns, at a period of 750 s, are employed. The MT data are cast in the form of telluric vectors, which allow a joint hypothetical event analysis (HEA) of both Geomagnetic Deep Sounding and MT data. This analysis reveals qualitatively the pervasive effects of electric field distortion in the region. Two approaches are taken to understand how the spatial structure of the regional electromagnetic field is affected by local distortions, and what the origin of these distortions might be. The dimensionality, and form of electric field distortion, of the MT tensors is investigated using the Weaver et al. and Bahr classification schemes, and by examining the misfit of a galvanic distortion model as a function of rotation angle. At sites where the galvanic distortion model is found to be appropriate the regional MT tensors are recovered using tensor decomposition techniques. It is found that recovering the regional MT response reconciles the geometry of induced currents implied by the MT data with that of the Magnetic Variation anomalies. Lilley's central impedances are used to calculate rotationally invariant effective telluric responses. In the Southern Uplands the magnitude of the effective telluric response is approximately 0.25-0.5 mV km-1 nT-1, but as the Southern Uplands Fault is approached it rises steadily to 3 mV km-1 nT-1. In the Midland Valley, the effective telluric response is approximately 0.5 mV km-1 nT-1 which rises steadily to 2.5 mV km-1 nT-1 as the Southern Uplands and Highland Boundary Faults are approached to the southeast and northwest, respectively. Therefore, the increase in the magnitude

  6. Big Data Analytics for Modelling and Forecasting of Geomagnetic Field Indices

    Science.gov (United States)

    Wei, H. L.

    2016-12-01

    A massive amount of data are produced and stored in research areas of space weather and space climate. However, the value of a vast majority of the data acquired every day may not be effectively or efficiently exploited in our daily practice when we try to forecast solar wind parameters and geomagnetic field indices using these recorded measurements or digital signals, probably due to the challenges stemming from the dealing with big data which are characterized by the 4V futures: volume (a massively large amount of data), variety (a great number of different types of data), velocity (a requirement of quick processing of the data), and veracity (the trustworthiness and usability of the data). In order to obtain more reliable and accurate predictive models for geomagnetic field indices, it requires that models should be developed from the big data analytics perspective (or it at least benefits from such a perspective). This study proposes a few data-based modelling frameworks which aim to produce more efficient predictive models for space weather parameters forecasting by means of system identification and big data analytics. More specifically, it aims to build more reliable mathematical models that characterise the relationship between solar wind parameters and geomagnetic filed indices, for example the dependent relationship of Dst and Kp indices on a few solar wind parameters and magnetic field indices, namely, solar wind velocity (V), southward interplanetary magnetic field (Bs), solar wind rectified electric field (VBs), and dynamic flow pressure (P). Examples are provided to illustrate how the proposed modelling approaches are applied to Dst and Kp index prediction.

  7. Regional modelling of the Geomagnetic Field in Europe for the last 8000 years

    Science.gov (United States)

    Pavon-Carrasco, Francisco Javier; Osete, Maria Luisa; Miquel Torta, J.

    2010-05-01

    From a selected compilation of sedimentary and archaeomagnetic data a new low-degree regional geomagnetic model for the European Continent valid for the period 6000 BC to 1000 BC has been developed. This model provides information about the direction (declination and inclination) and intensity of the Earth's Magnetic Field in Europe during 5000 years, from 6000 BC to 1000 BC. By connecting it with our SCHA.DIF.3K previous model valid from 1000 BC to 1900 AD and the IGRF, we furnish continuous geomagnetic field information for the last 8000 years. The new model is called SCHA.DIF.8K. It has been developed using the Revised Spherical Cap Harmonic Analysis in 2 Dimensions technique (R-SCHA2D, Thébault, 2008, GJI) and the norm of the Earth's Magnetic Field to constrain the inversion problem. The size of the cap is 22°. The maximum degree of the expansion is 2. The linearization problem has been solved using the truncation Taylor's series applied to the expressions of the relationship between the declination, inclination and intensity data and the Cartesian component of the geomagnetic field. As initial or reference we used the Geocentric Axial Dipole field. In time, we used the classical sliding overlapping window method. The size of the window was set to 100 years shifted 50 years. We have compared the model's prediction with the input data and with the global CALS7K.2 model. The regional model shows a better fitting to the input data than the global model, especially for the intensity data.

  8. A method to solve the aircraft magnetic field model basing on geomagnetic environment simulation

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chunsheng; Zhou, Jian-jun; Yang, Zhen-yu

    2015-06-15

    In aeromagnetic survey, it is difficult to solve the aircraft magnetic field model by flying for some unman controlled or disposable aircrafts. So a model solving method on the ground is proposed. The method simulates the geomagnetic environment where the aircraft is flying and creates the background magnetic field samples which is the same as the magnetic field arose by aircraft’s maneuvering. Then the aircraft magnetic field model can be solved by collecting the magnetic field samples. The method to simulate the magnetic environment and the method to control the errors are presented as well. Finally, an experiment is done for verification. The result shows that the model solving precision and stability by the method is well. The calculated model parameters by the method in one district can be used in worldwide districts as well. - Highlights: • A method to solve the aircraft magnetic field model on the ground is proposed. • The method solves the model by simulating dynamic geomagnetic environment as in the real flying. • The way to control the error of the method was analyzed. • An experiment is done for verification.

  9. Improving our knowledge of the rapid geomagnetic field intensity variation observed in Europe around 800 AD

    Science.gov (United States)

    Gómez-Paccard, M.; Chauvin, A.; Lanos, P.; Dufresne, P.; Kovacheva, M.; Hill, M. J.; Beamud, E.; Gutiérrez-Lloret, S.; Cañavate, V.; Blain, S.; Bouvier, A.; Oberlin, C.; Guibert, P.; Sapin, C.; Pringent, D.

    2011-12-01

    Available European data indicate that during the past 2500 years there have been periods of rapid intensity geomagnetic fluctuations interspersed with periods of little change. The challenge now is to precisely describe these rapid changes. The aim of this study is to obtain an improved description of the sharp geomagnetic intensity change that took place in Western Europe around 800 yrs AD as well as to investigate if this peak is observed at a continental scale. For this purpose 13 precisely dated early medieval Spanish pottery fragments, 4 archeological French kilns and a 3 collections of bricks used for the construction of different historical buildings from France and with ages ranging between 330 to 1290 AD have been studied. The material collected has been dated by archeological/historical constraints together with radiocarbon,thermoluminiscence (TL) and archeomagentic analysis. From classical Thellier experiments including TRM anisotropy and cooling rate corrections upon archeointensity estimates and conducted on 164 specimens (119 of them giving reliable results) ten new high-quality mean intensities have been obtained. The new intensity data together with a selection of the most reliable data from Western Europe have been relocated to the latitude of Paris and confirm the existence of an intensity maxima of ~85 μT centred at ~850 AD and related to intensity changes up to 20 μT per century. The results also indicate that a previous abrupt intensity change (reaching a maximum value of ~ 90 μT) took place in Western Europe around 650 AD. A selection of high-quality intensity data from Bulgaria, Italy and Greece indicate a very similar intensity trend for Eastern Europe. Although available data indicate that the duration of such periods of high intensities may be of less than one century more data are needed to infer the exact duration of these maximums. A comparison between the selected data and regional and global geomagnetic field models indicates that

  10. Evaluation of models proposed for the 1991 revision of the International Geomagnetic Reference Field

    Science.gov (United States)

    Peddie, N.W.

    1992-01-01

    The 1991 revision of the International Geomagnetic Reference Field (IGRF) comprises a definitive main-field model for 1985.0, a main-field model for 1990.0, and a forecast secular-variation model for the period 1990-1995. The five 1985.0 main-field models and five 1990.0 main-field models that were proposed have been evaluated by comparing them with one another, with magnetic observatory data, and with Project MAGNET aerial survey data. The comparisons indicate that the main-field models proposed by IZMIRAN, and the secular-variation model proposed jointly by the British Geological Survey and the US Naval Oceanographic Office, should be assigned relatively lower weight in the derivation of the new IGRF models. -Author

  11. Can Core Flows inferred from Geomagnetic Field Models explain the Earth's Dynamo?

    CERN Document Server

    Schaeffer, Nathanaël; Pais, Maria Alexandra

    2015-01-01

    We test the ability of velocity fields inferred from geomagnetic secular variation data to produce the global magnetic field of the Earth. Our kinematic dynamo calculations use quasi-geostrophic (QG) flows inverted from geomagnetic field models which, as such, incorporate flow structures that are Earth-like and may be important for the geodynamo. Furthermore, the QG hypothesis allows straightforward prolongation of the flow from the core surface to the bulk. As expected from previous studies, we check that a simple quasi-geostrophic flow is not able to sustain the magnetic field against ohmic decay. Additional complexity is then introduced in the flow, inspired by the action of the Lorentz force. Indeed, on centenial timescales, the Lorentz force can balance the Coriolis force and strict quasi-geostrophy may not be the best ansatz. When the columnar flow is modified to account for the action of the Lorentz force, magnetic field is generated for Elsasser numbers larger than 0.25 and magnetic Reynolds numbers l...

  12. High field strength following the Kauai R-N geomagnetic reversal

    Energy Technology Data Exchange (ETDEWEB)

    Paul, H.A. (Occidental College, Los Angeles, CA (United States). Dept. of Geology)

    1993-04-01

    The paleomagnetism of superposed lava flows on Kauai, Hawaii shows that the ancient geomagnetic field was unusually strong following a reverse-to-normal polarity transition that occurred about 4 million years ago. Paleointensities were determined by a standard experimental procedure (Thelliers' method) that recreates the process of remanence acquisition in volcanic rocks. This experiment makes it possible to infer the strength of the geomagnetic field present with each lava flow formed, thus producing an accurate picture of the ancient field's behavior after the reversal. Samples from 10 volcanic units yielded virtual dipole moments (VDMs) ranging from 7.4 [times] 10[sup 22] Am[sup 2] to 14.5 [times] 10[sup 22] Am[sup 2] with an average of 11.1[times]10[sup 22] Am[sup 2]. This value is high in comparisons to the average VDM for the past 5 m.y., approximately 8.7[times]10[sup 22] Am[sup 2]. In contrast to the highly variable dipole moment observed following a 15 m.y. old reversal at Steen s Mountain, Oregon, the field following the Kauai transition was relatively steady. Surprisingly, the maximum dipole moments following the two reversals were nearly equal. This similarity hints that high field strength may be a systematic feature of the geodynamo immediately following a polarity reversal.

  13. A northern hemisphere geomagnetic field model for the last 14ka

    Science.gov (United States)

    Pavon-Carrasco, Fco Javier; Osete, Maria Luisa; Miquel Torta, Joan; de Santis, Angelo

    2013-04-01

    In this work, we propose a first regional geomagnetic field model for the Northern Hemisphere based on archaeomagnetic and lava flow data. The regional model, called scha.dif.14k, allows us to analyse the low degree of the geomagnetic field secular variation for the last 14000 years: from 12000 BC to 1900 AD. The inversion process of the declination, inclination and intensity palaeomagnetic data was carried out iteratively, using the spherical cap harmonic analysis (SCHA) up to degree K = 4 in space and penalized cubic B-spline in time with a knot point of 100 years for the whole time interval. Three starting models have been tested: a) A constant axial dipole field, b) a time-dependent axial dipole field and c) a time-dependent inclined dipole field. The last two starting models were estimated by using directly the archaeomagnetic data. These starting models have been perturbed in order to obtain a regional model with a higher spatial and temporal variability. We have compared the model with the recent published palaeosecular variation curves and with the global model for the Holocene: CALS10K.1b. Our model fits reasonably well the different palaeosecular variation curves and improves the prediction of the CALS10K.1b global model.

  14. Magnetic and Electric Fields Produced in the Sea During Geomagnetic Disturbances

    Science.gov (United States)

    Boteler, D. H.; Pirjola, R. J.

    - To understand geomagnetic effects on systems with long conductors it is necessary to know the electric field those systems experience. For surface conductors such as power systems and pipelines this can easily be calculated from the magnetic field variations at the surface using the surface impedance of the earth. However, for calculating the electric fields in pipelines and submarine cables at the seafloor it is necessary to take account of the attenuating effect of the conducting seawater. Assuming that the fields are vertically propagating plane waves, we derive the transfer functions between the electric and magnetic fields at the seafloor and the magnetic field variations at the sea surface. These transfer functions are then used, with surface magnetic field data, to determine the power spectra of the seafloor magnetic and electric fields in a shallow sea (depth 100 m) and in the deep ocean (depth 5 km) for different values of the Kp magnetic activity index . For the period range considered (2 min to 3 hrs) the spectral characteristics of the seafloor magnetic and electric fields for a 100 m deep sea are very similar to those of the surface fields. For the deep ocean the seafloor spectra show a faster decrease in spectral density with increasing frequency compared to the surface fields. The results obtained are shown to be consistent with seafloor observations. Assessment of the seafloor electric fields produced by different levels of geomagnetic activity can be useful in the design of the power feed equipment for submarine cables and cathodic protection for undersea pipelines.

  15. POGO satellite orbit corrections: an opportunity to improve the quality of the geomagnetic field measurements?

    Science.gov (United States)

    Stockmann, Reto; Christiansen, Freddy; Olsen, Nils; Jackson, Andrew

    2015-06-01

    We present an attempt to improve the quality of the geomagnetic field measurements from the Polar Orbiting Geophysical Observatory (POGO) satellite missions in the late 1960s. Inaccurate satellite positions are believed to be a major source of errors for using the magnetic observations for field modelling. To improve the data, we use an iterative approach consisting of two main parts: one is a main field modelling process to obtain the radial field gradient to perturb the orbits and the other is the state-of-the-art GPS orbit modelling software BERNESE to calculate new physical orbits. We report results based on a single-day approach showing a clear increase of the data quality. That single-day approach leads, however, to undesirable orbital jumps at midnight. Furthermore, we report results obtained for a much larger data set comprising almost all of the data from the three missions. With this approach, we eliminate the orbit discontinuities at midnight but only tiny quality improvements could be achieved for geomagnetically quiet data. We believe that improvements to the data are probably still possible, but it would require the original tracking observations to be found.

  16. Limitations in paleomagnetic data and modelling techniques and their impact on Holocene geomagnetic field models

    DEFF Research Database (Denmark)

    Panovska, S.; Korte, M.; Finlay, Chris;

    2015-01-01

    Characterization of geomagnetic field behaviour on timescales of centuries to millennia is necessary to understand the mechanisms that sustain the geodynamo and drive its evolution. As Holocene paleomagnetic and archeomagnetic data have become more abundant, strategies for regularized inversion...... of modern field data have been adapted to produce numerous timevarying global field models. We evaluate the effectiveness of several approaches to inversion and data handling, by assessing both global and regional properties of the resulting models. Global Holocene field models cannot resolve Southern...... hemisphere regional field variations without the use of sediments. A standard data set is used to construct multiple models using two different strategies for relative paleointensity calibration and declination orientation and a selection of starting models in the inversion procedure. When data uncertainties...

  17. [Initial growth processes in seeds in magnetic fields, strengthened or weakened in relation to the geomagnetic field].

    Science.gov (United States)

    Es'kov, E K; Rodionov, Iu A

    2010-01-01

    The effects of modifications of magnetic fields, simulating anomalies of natural magnetism of the Earth, were studied in the seeds of peas and winter wheat. It has been shown that strengthening or weakening of the geomagnetic field inhibits water absorption and initial growth processes. The influence of magnetic fields on the orientation of rootlets and development of plantlets is determined. The connection between the magnetic susceptibility of seeds and content of heavy metals in them is established, which obviously concerns the magnetic susceptibility and magnetotropism in plants.

  18. A more realistic estimate of the variances and systematic errors in spherical harmonic geomagnetic field models

    DEFF Research Database (Denmark)

    Lowes, F.J.; Olsen, Nils

    2004-01-01

    Most modern spherical harmonic geomagnetic models based on satellite data include estimates of the variances of the spherical harmonic coefficients of the model; these estimates are based on the geometry of the data and the fitting functions, and on the magnitude of the residuals. However......, led to quite inaccurate variance estimates. We estimate correction factors which range from 1/4 to 20, with the largest increases being for the zonal, m = 0, and sectorial, m = n, terms. With no correction, the OSVM variances give a mean-square vector field error of prediction over the Earth's surface...

  19. Study of the solar wind coupling to the time difference horizontal geomagnetic field

    Directory of Open Access Journals (Sweden)

    P. Wintoft

    2005-07-01

    Full Text Available The local ground geomagnetic field fluctuations (Δ B are dominated by high frequencies and 83% of the power is located at periods of 32 min or less. By forming 10-min root-mean-square (RMS of Δ B a major part of this variation is captured. Using measured geomagnetic induced currents (GIC, from a power grid transformer in Southern Sweden, it is shown that the 10-min standard deviation GIC may be computed from a linear model using the RMS Δ X and Δ Y at Brorfelde (BFE: 11.67° E, 55.63° N, Denmark, and Uppsala (UPS: 17.35° E, 59.90° N, Sweden, with a correlation of 0.926±0.015. From recurrent neural network models, that are driven by solar wind data, it is shown that the log RMS Δ X and Δ Y at the two locations may be predicted up to 30 min in advance with a correlation close to 0.8: 0.78±0.02 for both directions at BFE; 0.81±0.02 and 0.80±0.02 in the X- and Y-directions, respectively, at UPS. The most important inputs to the models are the 10-min averages of the solar wind magnetic field component Bz and velocity V, and the 10-min standard deviation of the proton number density σn. The average proton number density n has no influence.

    Keywords. Magnetospheric physics (Solar wind - magnetosphere interactions – Geomagnetism and paleomagnetism (Rapid time variations

  20. ANOMALOUS CHANGES OF THE GEOMAGNETIC FIELD VERTICAL COMPONENT IN KAMCHATKA

    Directory of Open Access Journals (Sweden)

    Smirnov, S.E.

    2016-11-01

    Full Text Available Statistical estimates of the effect in the electric field of the surface layer of the atmosphere parameters, such as time of the beginning, time of a maximum, its intensity and duration, were obtained. It was shown experimentally that the diurnal variation maximum of atmospheric electric field intensity is associated with air temperature height distribution. Power spectra of time variations of electric field intensity in the near ground atmosphere and of the horizontal component of geomagnetic field were under study. It was shown that there are oscillations with the periods of T _ 2, 0–2,5 hours in the power spectra of these parameters during a day. A possible mechanism of generation of these oscillations was proposed. It is associated with vortex motion of convective cells arising during the sunrise in the atmosphere exchange layer.

  1. A study on severe geomagnetic storms and earth’s magnetic field H variations, Sunspots and formation of cyclone

    Directory of Open Access Journals (Sweden)

    M.V.Subramanian

    2016-10-01

    Full Text Available For our study, we have selected ten severe geomagnetic storms. Which occurred during the years 1994 to 2015. Here great geomagnetic storm of Dst index from -422 nT to -17 nT are taken. These storms are significant not only because of the extremely high magnetic activity but also due to their great impact on the geomagnetosphere. We have studied the relation between severe geomagnetic storms with Earth’s magnetic field in horizontal component (H constant and also studied the relation between Dst index with sunspots number. The H constant data from Kyoto data centre and Dst index, Ap index, Kp index from OMNI data centre. We have found that the Dst is at very lowest level in this storm period, Ap index Kp index are increased in severe geomagnetic storm period and H Constant is at very lowest level in storm period. We have found that geomagnetic storms were induced to form the cyclones within 29 days. The Sunspots numbers are increased to induce to geomagnetic storm within 5 – 15 days

  2. A New Geomagnetic Field Model for the last 2k years based on high quality archaeomagnetic and volcanic data

    Science.gov (United States)

    Campuzano, Saioa A.; Gómez-Paccard, Miriam; Pavón-Carrasco, Francisco Javier; Osete, María Luisa

    2016-04-01

    The knowledge of the ancient Earth's magnetic field is crucial to understand its origin and future evolution. In this context, the palaeomagnetic studies provide useful information about the past geomagnetic field registered in rocks, lava flows, sediments or archaeological materials. The continuous upgrade of the palaeomagnetic database during the last decade has allowed the generation of global geomagnetic field models based on different palaeomagnetic data and techniques (such as the SHA.DIF.14K, ARCH3K.1, CALS3K.4b, pfm9k.1a models, among others). Some recent studies have pointed out that the archaeointensity database might not be reliable enough, by observing high scatter in the records. Here, we present a new global geomagnetic model for the last 2000 years, SHAQ2K, based on high quality archaeomagnetic and volcanic intensity data. For this purpose we classify the palaeointensity data in two quality categories following widely accepted palaeomagnetic criteria based on the methodology used during the laboratory treatment of the samples and on the number of specimens finally used to calculate the mean intensities. Respect to the modelling process, we use the spherical harmonic analysis in space and cubic b-splines in time, also applying a spatial and temporal regularization which minimizes the energy of the geomagnetic field at the core-mantle boundary. The implications of the differences between this new model and other previously published global geomagnetic models are discussed.

  3. Artificial reproduction of magnetic fields produced by a natural geomagnetic storm increases systolic blood pressure in rats

    Science.gov (United States)

    Martínez-Bretón, J. L.; Mendoza, B.; Miranda-Anaya, M.; Durán, P.; Flores-Chávez, P. L.

    2016-04-01

    The incidence of geomagnetic storms may be associated with changes in circulatory physiology. The way in which the natural variations of the geomagnetic field due to solar activity affects the blood pressure are poorly understood and require further study in controlled experimental designs in animal models. In the present study, we tested whether the systolic arterial pressure (AP) in adult rats is affected by simulated magnetic fields resembling the natural changes of a geomagnetic storm. We exposed adult rats to a linear magnetic profile that simulates the average changes associated to some well-known geomagnetic storm phases: the sudden commencement and principal phase. Magnetic stimulus was provided by a coil inductor and regulated by a microcontroller. The experiments were conducted in the electromagnetically isolated environment of a semi-anechoic chamber. After exposure, AP was determined with a non-invasive method through the pulse on the rat's tail. Animals were used as their own control. Our results indicate that there was no statistically significant effect in AP when the artificial profile was applied, neither in the sudden commencement nor in the principal phases. However, during the experimental period, a natural geomagnetic storm occurred, and we did observe statistically significant AP increase during the sudden commencement phase. Furthermore, when this storm phase was artificially replicated with a non-linear profile, we noticed a 7 to 9 % increase of the rats' AP in relation to a reference value. We suggested that the changes in the geomagnetic field associated with a geomagnetic storm in its first day could produce a measurable and reproducible physiological response in AP.

  4. Artificial reproduction of magnetic fields produced by a natural geomagnetic storm increases systolic blood pressure in rats

    Science.gov (United States)

    Martínez-Bretón, J. L.; Mendoza, B.; Miranda-Anaya, M.; Durán, P.; Flores-Chávez, P. L.

    2016-11-01

    The incidence of geomagnetic storms may be associated with changes in circulatory physiology. The way in which the natural variations of the geomagnetic field due to solar activity affects the blood pressure are poorly understood and require further study in controlled experimental designs in animal models. In the present study, we tested whether the systolic arterial pressure (AP) in adult rats is affected by simulated magnetic fields resembling the natural changes of a geomagnetic storm. We exposed adult rats to a linear magnetic profile that simulates the average changes associated to some well-known geomagnetic storm phases: the sudden commencement and principal phase. Magnetic stimulus was provided by a coil inductor and regulated by a microcontroller. The experiments were conducted in the electromagnetically isolated environment of a semi-anechoic chamber. After exposure, AP was determined with a non-invasive method through the pulse on the rat's tail. Animals were used as their own control. Our results indicate that there was no statistically significant effect in AP when the artificial profile was applied, neither in the sudden commencement nor in the principal phases. However, during the experimental period, a natural geomagnetic storm occurred, and we did observe statistically significant AP increase during the sudden commencement phase. Furthermore, when this storm phase was artificially replicated with a non-linear profile, we noticed a 7 to 9 % increase of the rats' AP in relation to a reference value. We suggested that the changes in the geomagnetic field associated with a geomagnetic storm in its first day could produce a measurable and reproducible physiological response in AP.

  5. Variation of surface electric field during geomagnetic disturbed period at Maitri, Antarctica

    Indian Academy of Sciences (India)

    N Jeni Victor; C Panneerselvam; C P Anil Kumar

    2015-12-01

    The paper discusses on the variations of the atmospheric vertical electric field measured at sub-auroral station Maitri (70°75′S, 11°75′E), and polar station Vostok (78.5°S, 107°E) during the geomagnetic disturbances on 25–26 January 2006. Diurnal variation of surface electric field measured at Maitri shows a similar variation with worldwide thunderstorm activity, whereas the departure of the field is observed during disturbed periods. This part of the field corresponds to the magnetospheric/ionospheric (an additional generator in the polar regions) voltage generators. Solar wind parameters and planetary indices represent the temporal variation of the disturbances, and digital fluxgate magnetometer variation continuously monitored to trace the auroral movement at Maitri. We have observed that the electrojet movement leaves its signature on vertical and horizontal components of the DFM in addition; the study infers the position of auroral current wedge with respect to Maitri. To exhibit the auroral oval, OVATION model is obtained with the aid of DMSP satellite and UV measurements. It is noted that the Maitri is almost within the auroral oval during the periods of disturbances. To examine the simultaneous changes in the vertical electric field associated with this magnetic disturbance, the dawn–dusk potential is studied for every UT hours; the potential was obtained from Weimer model and SuperDARN radar. The comparison reveals the plausible situation for the superposition of dawn–dusk potential on surface electric field over Maitri. This observation also shows that the superposition may not be consistent with the phase of the electrojet. Comparison of surface electric field at Maitri and Vostok shows that the parallel variation exhibits with each other, but during the period of geomagnetic disturbances, the influence is not much discerned at Vostok.

  6. Applying "domino" model to study dipolar geomagnetic field reversals and secular variation

    Science.gov (United States)

    Peqini, Klaudio; Duka, Bejo

    2014-05-01

    Aiming to understand the physical processes underneath the reversals events of geomagnetic field, different numerical models have been conceived. We considered the so named "domino" model, an Ising-Heisenberg model of interacting magnetic spins aligned along a ring [Mazaud and Laj, EPSL, 1989; Mori et al., arXiv:1110.5062v2, 2012]. We will present here some results which are slightly different from the already published results, and will give our interpretation on the differences. Following the empirical studies of the long series of the axial magnetic moment (dipolar moment or "magnetization") generated by the model varying all model parameters, we defined the set of parameters that supply the longest mean time between reversals. Using this set of parameters, a short time series (about 10,000 years) of axial magnetic moment was generated. After de-noising the fluctuation of this time series, we compared it with the series of dipolar magnetic moment values supplied by CALS10K.1b model for the last 10000 years. We found similar behavior of the both series, even if the "domino" model could not supply a full explanation of the geomagnetic field SV. In a similar way we will compare a 14000 years long series with the dipolar magnetic moment obtained by the model SHA.DIF.14k [Pavón-Carrasco et al., EPSL, 2014].

  7. Electromagnetic panel deployment and retraction using the geomagnetic field in LEO satellite missions

    Science.gov (United States)

    Inamori, Takaya; Sugawara, Yoshiki; Satou, Yasutaka

    2015-12-01

    Increasingly, spacecraft are installed with large-area structures that are extended and deployed post-launch. These extensible structures have been applied in several missions for power generation, thermal radiation, and solar propulsion. Here, we propose a deployment and retraction method using the electromagnetic force generated when the geomagnetic field interacts with electric current flowing on extensible panels. The panels are installed on a satellite in low Earth orbit. Specifically, electrical wires placed on the extensible panels generate magnetic moments, which interfere with the geomagnetic field. The resulting repulsive and retraction forces enable panel deployment and retraction. In the proposed method, a satellite realizes structural deployment using simple electrical wires. Furthermore, the satellite can achieve not only deployment but also retraction for avoiding damage from space debris and for agile attitude maneuvers. Moreover, because the proposed method realizes quasi-static deployment and the retraction of panels by electromagnetic forces, low impulsive force is exerted on fragile panels. The electrical wires can also be used to detect the panel deployment and retraction and generate a large magnetic moment for attitude control. The proposed method was assessed in numerical simulations based on multibody dynamics. Simulation results shows that a small cubic satellite with a wire current of 25 AT deployed 4 panels (20 cm × 20 cm) in 500 s and retracted 4 panels in 100 s.

  8. Regional geomagnetic field modelling: the contribution of the Istituto Nazionale di Geofisica

    Directory of Open Access Journals (Sweden)

    A. Meloni

    1997-06-01

    Full Text Available Models of the geomagnetic field are mathematical expressions able to represent the Earth's magnetic field space and time variations. Time variations on the long term basis are represented by the so-called secular variation. This paper describes and reviews recent activities of the Italian group at the Istituto Nazionale di Geofisica in regional magnetic field modelling. The models are introduced starting from the classical technique of Spherical Harmonic Analysis (SHA undertaken for the first time by Gauss, the polynomial analysis and the regional harmonic analysis, specifically introduced as a regional analogue of SHA. In this last group the recent techniques of Spherical Cap Harmonic Analysis (SCHA, Translated Origin Spherical Cap Analysis (TOSCA and Adjusted Spherical Cap Harmonic Analysis (ASHA are also described and discussed.

  9. The role of high-resolution geomagnetic field models for investigating ionospheric currents at low Earth orbit satellites

    Science.gov (United States)

    Stolle, Claudia; Michaelis, Ingo; Rauberg, Jan

    2016-07-01

    Low Earth orbiting geomagnetic satellite missions, such as the Swarm satellite mission, are the only means to monitor and investigate ionospheric currents on a global scale and to make in situ measurements of F region currents. High-precision geomagnetic satellite missions are also able to detect ionospheric currents during quiet-time geomagnetic conditions that only have few nanotesla amplitudes in the magnetic field. An efficient method to isolate the ionospheric signals from satellite magnetic field measurements has been the use of residuals between the observations and predictions from empirical geomagnetic models for other geomagnetic sources, such as the core and lithospheric field or signals from the quiet-time magnetospheric currents. This study aims at highlighting the importance of high-resolution magnetic field models that are able to predict the lithospheric field and that consider the quiet-time magnetosphere for reliably isolating signatures from ionospheric currents during geomagnetically quiet times. The effects on the detection of ionospheric currents arising from neglecting the lithospheric and magnetospheric sources are discussed on the example of four Swarm orbits during very quiet times. The respective orbits show a broad range of typical scenarios, such as strong and weak ionospheric signal (during day- and nighttime, respectively) superimposed over strong and weak lithospheric signals. If predictions from the lithosphere or magnetosphere are not properly considered, the amplitude of the ionospheric currents, such as the midlatitude Sq currents or the equatorial electrojet (EEJ), is modulated by 10-15 % in the examples shown. An analysis from several orbits above the African sector, where the lithospheric field is significant, showed that the peak value of the signatures of the EEJ is in error by 5 % in average when lithospheric contributions are not considered, which is in the range of uncertainties of present empirical models of the EEJ.

  10. DYNAMICS OF THE GEOMAGNETIC FIELD AND REVERSALS IN THE SATELLITE MODEL

    Directory of Open Access Journals (Sweden)

    Trunev A. P.

    2016-09-01

    Full Text Available The article deals with the problem of changing the polarity of the geomagnetic field in the satellite model. It is assumed that the central core of the earth magnetized and surrounded by a number of satellites, each of which has a magnetic moment. Satellites interact with a central core and one another by means of gravity and through a magnetic field. It is shown that satellites distributed in orbit around a central core in such a system. It displays two models, one of which on the outer orbit satellites interact with each other and with a central body - the core and satellites, located on the inner orbit. The central body can make sudden upheavals in the fall at the core of one or more satellites, which leads to the excitation of vibrations in the satellite system, located on the outer orbit. It is shown that the duration of phase with constant polarity and upheaval time depends on the magnitude of the disturbance torque and core asymmetry. The second model contains two magnets subsystems and the central core. The rapid change of the geomagnetic field polarity detected on the basis of paleomagnetic data is modeled based on the Euler theory describing the rigid body rotation. In this model, there are modes with a quick flip of the body while maintaining the angular momentum. If the body has a magnetic moment, when there is a change coup magnetic field polarity. This leads to the excitation of vibrations in the satellite subsystems that are on the inner and outer orbits. Numerical simulation of the dynamics of the system consisting of the core and 10-13 satellites was run to determine the period of constant polarity magnetic field

  11. Plasma and Magnetic Field Characteristics of Solar Coronal Mass Ejections in Relation to Geomagnetic Storm Intensity and Variability

    CERN Document Server

    Liu, Ying D; Wang, Rui; Yang, Zhongwei; Zhu, Bei; Liu, Yi A; Luhmann, Janet G; Richardson, John D

    2015-01-01

    The largest geomagnetic storms of solar cycle 24 so far occurred on 2015 March 17 and June 22 with $D_{\\rm st}$ minima of $-223$ and $-195$ nT, respectively. Both of the geomagnetic storms show a multi-step development. We examine the plasma and magnetic field characteristics of the driving coronal mass ejections (CMEs) in connection with the development of the geomagnetic storms. A particular effort is to reconstruct the in situ structure using a Grad-Shafranov technique and compare the reconstruction results with solar observations, which gives a larger spatial perspective of the source conditions than one-dimensional in situ measurements. Key results are obtained concerning how the plasma and magnetic field characteristics of CMEs control the geomagnetic storm intensity and variability: (1) a sheath-ejecta-ejecta mechanism and a sheath-sheath-ejecta scenario are proposed for the multi-step development of the 2015 March 17 and June 22 geomagnetic storms, respectively; (2) two contrasting cases of how the CM...

  12. Paleointensity of the geomagnetic field in the Cretaceous (from Cretaceous rocks of Mongolia)

    Science.gov (United States)

    Shcherbakova, V. V.; Kovalenko, D. V.; Shcherbakov, V. P.; Zhidkov, G. V.

    2011-09-01

    A representative collection of Cretaceous rocks of Mongolia is used for the study of the magnetic properties of the rocks and for determination of the paleodirections and paleointensities H anc of the geomagnetic field. The characteristic NRM component in the samples is recognized in the temperature interval from 200 to 620-660°C. The values of H anc are determined by the Thellier-Coe method with observance of all present-day requirements regarding the reliability of such kind of results. Comparison of data in the literature on paleointensity in the Cretaceous superchron and in the Miocene supports the hypothesis of the inverse correlation between the average intensity of the paleofield and the frequency of geomagnetic reversals. The increase in the average intensities is accompanied by an appreciable increase in the variance of the virtual dipole moment (VDM). We suggest that the visible increase in the average VDM value in the superchron is due to the greater variability of VDM in this period compared to the Miocene.

  13. Reconstructing the Geomagnetic Field in West Africa: First Absolute Intensity Results from Burkina Faso

    Science.gov (United States)

    Kapper, Lisa; Donadini, Fabio; Serneels, Vincent; Tema, Evdokia; Goguitchaichvili, Avto; Julio Morales, Juan

    2017-01-01

    We present absolute geomagnetic intensities from iron smelting furnaces discovered at the metallurgical site of Korsimoro, Burkina Faso. Up to now, archaeologists recognized four different types of furnaces based on different construction methods, which were related to four subsequent time periods. Additionally, radiocarbon ages obtained from charcoal confine the studied furnaces to ages ranging from 700–1700 AD, in good agreement with the archaeologically determined time periods for each type of furnace. Archaeointensity results reveal three main groups of Arai diagrams. The first two groups contain specimens with either linear Arai diagrams, or slightly curved diagrams or two phases of magnetization. The third group encompasses specimens with strong zigzag or curvature in their Arai diagrams. Specimens of the first two groups were accepted after applying selection criteria to guarantee the high quality of the results. Our data compared to palaeosecular variation curves show a similar decreasing trend between 900–1500 AD. However, they reveal larger amplitudes at around 800 AD and 1650 AD than the reference curves and geomagnetic field models. Furthermore, they agree well with archaeomagnetic data from Mali and Senegal around 800 AD and with volcanic data around 1700 AD. PMID:28350006

  14. Preliminary study on the source field mode of geomagnetic six-month-period variations

    Institute of Scientific and Technical Information of China (English)

    陈伯舫; 冯戬云

    1997-01-01

    The monthly means of north component X of geomagnetic field from 16 observatories during 1984-1988 were analyzed using the Sompi spectral analysis technique. Most of these observatories are located in China. The analysis of the semiannual variations indicates that the latitude has no apparent effect on the X component. This clearly implies that the source field mode of semiannual variations cannot simply be described by using the P°1 mode. Using the P°1 mode to estimate the inductive scale length C in the semiannual period, the value of C at each observatory would be biased significantly. The purpose of this study is to find which kind of modes is optimal for estimating the values of C corresponding to the semiannual variations. The results show that a composite mode, involving five terms P°n(n = 1,....,5), might be a reasonable and acceptable one.

  15. A novel autonomous real-time position method based on polarized light and geomagnetic field

    Science.gov (United States)

    Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen

    2015-04-01

    Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance.

  16. A novel autonomous real-time position method based on polarized light and geomagnetic field.

    Science.gov (United States)

    Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen

    2015-04-08

    Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance.

  17. On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

    Science.gov (United States)

    Kauristie, K.; Morschhauser, A.; Olsen, N.; Finlay, C. C.; McPherron, R. L.; Gjerloev, J. W.; Opgenoorth, H. J.

    2016-12-01

    We present a review on geomagnetic indices describing global geomagnetic storm activity (Kp, am, Dst and dDst/dt) and on indices designed to characterize high latitude currents and substorms (PC and AE-indices and their variants). The focus in our discussion is in main field modelling, where indices are primarily used in data selection criteria for weak magnetic activity. The publicly available extensive data bases of index values are used to derive joint conditional Probability Distribution Functions (PDFs) for different pairs of indices in order to investigate their mutual consistency in describing quiet conditions. This exercise reveals that Dst and its time derivative yield a similar picture as Kp on quiet conditions as determined with the conditions typically used in internal field modelling. Magnetic quiescence at high latitudes is typically searched with the help of Merging Electric Field (MEF) as derived from solar wind observations. We use in our PDF analysis the PC-index as a proxy for MEF and estimate the magnetic activity level at auroral latitudes with the AL-index. With these boundary conditions we conclude that the quiet time conditions that are typically used in main field modelling ( PC-300 nT) can take place, when these criteria prevail. Although AE-indices have been designed to probe electrojet activity only in average conditions and thus their performance is not optimal during weak activity, we note that careful data selection with advanced AE-variants may appear to be the most practical way to lower the elevated RMS-values which still exist in the residuals between modeled and observed values at high latitudes. Recent initiatives to upgrade the AE-indices, either with a better coverage of observing stations and improved baseline corrections (the SuperMAG concept) or with higher accuracy in pinpointing substorm activity (the Midlatitude Positive Bay-index) will most likely be helpful in these efforts.

  18. NGDC/GFZ candidate models for the 10th generation International Geomagnetic Reference Field

    Science.gov (United States)

    Maus, Stefan; McLean, Susan; Dater, David; Lühr, Hermann; Rother, Martin; Mai, Wolfgang; Choi, Sungchan

    2005-12-01

    Following the call for candidates for the 10th generation IGRF, we produced and submitted three main field and three secular variation candidate models. The candidates are derived from parent models which use a standard quadratic parameterisation in time of the internal Gauss coefficients. External magnetospheric fields are represented by combined parameterisations in Solar Magnetic (SM) and in Geocentric Solar Magnetospheric (GSM) coordinates. Apart from the daily and annual variations caused by these external fields, the model also accounts for induction by Earth rotation in a non-axial external field. The uncertainties of our candidates are estimated by comparing independent models from CHAMP and Èrsted data. The root mean square errors of our main field candidates, for the internal field to spherical harmonic degree 13, are estimated to be less than 8 nT at the Earth's surface. Our secular variation candidates are estimated to have root mean square uncertainties of 12 nT per year. A hind-cast analysis of the geomagnetic field for earlier epochs shows that our secular acceleration estimates from post-2000 satellite data are inconsistent with pre-2000 acceleration in the field. This could confirm earlier reports of a jerk around 2000.0, with a genuine change in the secular acceleration.

  19. The Liverpool Geomagnetic Polarity Reversal : New evidences for a complex magnetic field behavior during reversals.

    Science.gov (United States)

    Camps, P.; Perrin, M.; Hoffman, K. A.; Singer, B. S.

    2009-04-01

    We carried out a detailed and continuous paleomagnetic re-sampling of the reversed-to-normal Eocene -36 Ma- geomagnetic transition recorded in the Liverpool (NSW, Australia) volcanic range [Hoffman, 1986]. Our main objective was to obtain a precise description of the variation in the paleofield vector (direction and absolute intensity) as the geomagnetic field reverses. With more than 30 transitional directions documented, the Liverpool reversal is, along with the Miocene record -16.2 Ma- of the Steens Mountain (Oregon, USA) [Mankinen et al., 1985] and the Matuyama-Brunhes -780 Ka- record of Hawaii [Coe et al, 2004], among the best example of a transition record from a volcanic sequence. The Liverpool polarity reversal shows a complex path of the Virtual Geomagnetic poles between the initial (reverse) and final (normal) polarities. Two loops in the trajectory of VGPs before the actual polarity switch are documented [Hoffman, 1986]. Such swings preceding the reversal seems to be a common characteristic of reversal since similar features are described on the Steens Mountain [Jarboe et al., 2007] and a long period of instability, estimated to 18 ka, is now well established prior to the Matuyama-Brunhes reversal [Singer et al., 2005]. In the present study, we found an additional swing through the reversed polarity yielding a complex R-T-R-T-R-T-R-T-N path for VGPs to achieve the reversal process. During the sampling campaign, we did not find evidence for significant hiatus in the eruptive activity such as soil horizons or sediments. We do not believe either that some part of the volcanic sequence be duplicate by the presence of tectonic faults. Hence, we think that the three excursions and the actual reversal belong to a single phenomenon. In order to strengthen this conclusion, precise Ar/ Ar will be performed. Twelve flows (5 of transitional and 7 of reversed polarity, respectively) all located in the lower half part of the Liverpool record, yielded paleointensity

  20. Tango in the Mid-Jurassic: 10,000-Yr Geomagnetic Field Reversals

    Science.gov (United States)

    Steiner, M.

    2001-12-01

    A continuous magnetostratigraphic signature of Layer 2A from Jurassic Quiet Zone (JQZ) oceanic crust now is known from two separate paleo-magnetic data sets. Measurement/demagnetization along the length of the entire core at 5-cm intervals generated ~100,000 data points, whereas a suite of 472 discrete samples also were taken from throughout the core. Both data sets display the same magnetization pattern, a series of repeated sinusoidal inclination changes downhole. Six inter-vals of maximum inclination (three positive, three negative) are obser-ved. Maximum inclination intervals of +/-40° are separated by regions of smoothly varying intermediate inclination values. Despite lack of azmuithal orientation of the core, downhole magnetic logging (Larson et al., in prep.) shows full ~360° directional change in the magnetization vector. Therefore, the maximum inclination regions represent polarity intervals of the geomagnetic field, and six polarity intervals in stacked sequence are contained in the upper 400 m thickness of Layer 2A at this site. The time duration spanned by these six reversals was estimated from recent seismic studies of young ocean crustal construction on the East Pacific Rise (EPR). Estimates of completion of construction of Layer 2A within 1-3 km from the rise crest and typical EPR half-spreading rates of 5-8 cm/yr suggest that the studied 400 m of ocean crust represents 37,000-60,000 years. The fast construction of EPR crust implies that the Middle Jurassic geomagnetic field was reversing at a phenomenal rate of 5000-10,000 years. These data establish that the `quiet' signature in the oldest portion of the lineated magnetic anomaly patterns in the ocean crust is due to exceedingly rapid reversals of the geomagnetic field, because succes-sive, superposed opposite-polarity magnetic signatures will essentially cancel one another out at the sea surface. The width of the 'quiet' magnetic signature in the western Pacific Ocean implies that the 5000

  1. Geomagnetic field intensity and quantitative paleorainfall reconstruction from Chinese loess using 10Be and magnetic susceptibility

    Science.gov (United States)

    Beck, W.; zhou, W.; Li, C.; Wu, Z.; White, L.; Xian, F.

    2011-12-01

    7Be is produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols, usually encapsulated in rain or snow. Numerous studies have shown that its flux to the ground is proportional to rainfall amount. Unfortunately, with a half life of only a few weeks, this observation has little relevance for reconstruction past rainfall amounts in paleosoils. Fortunately, 7Be has a long-lived sister isotope (10Be) with a half life of ~1.5 Ma which can be used for such purposes. There are a number of complications, however. First, 10Be atmospheric production rate changes when the geomagnetic field intensity changes. Secondly, 10Be half life is long enough that 10Be which fell to the ground attached to dust some time in the past can become resuspended, meaning that there are two sources of 10Be, one meteoric, and the other recycled aeolian dust. Fortunately, we have found a method to deconvolute this knotty situation and have applied it to soils of the Chinese Loess Plateau, allowing us to reconstruct records of both geomagnetic field intensity and paleorainfall. To do so, we use the additional parameters magnetic susceptibility and coercivity to help define the inherited amount of each component, and to define what fraction of the variations in 10Be are associated with magnetic field fluctuations, versus that linked to rainfall variations. We also use a sediment age/depth model to convert 10Be concentration to 10Be flux, and finally, we use the modern 7Be vs. rainfall relationship and 10Be/7Be atmospheric production rate ratio to calculate quantitative paleorainfall rates. We have used these techniques to generate several such records ranging from the Holocene to MIS13 (Circa 525 ka BP), and will compare some of these to U-series dated speleothem records of δ18O.

  2. Fast geomagnetic field intensity variations between 1400 and 400 BCE: New archaeointensity data from Germany

    Science.gov (United States)

    Hervé, Gwenaël; Faβbinder, Jörg; Gilder, Stuart A.; Metzner-Nebelsick, Carola; Gallet, Yves; Genevey, Agnès; Schnepp, Elisabeth; Geisweid, Leonhard; Pütz, Anja; Reuβ, Simone; Wittenborn, Fabian; Flontas, Antonia; Linke, Rainer; Riedel, Gerd; Walter, Florian; Westhausen, Imke

    2017-09-01

    Thirty-five mean archaeointensity data were obtained on ceramic sherds dated between 1400 and 400 BCE from sites located near Munich, Germany. The 453 sherds were collected from 52 graves, pits and wells dated by archaeological correlation, radiocarbon and/or dendrochronology. Rock magnetic analyses indicate that the remanent magnetization was mainly carried by magnetite. Data from Thellier-Thellier experiments were corrected for anisotropy and cooling rate effects. Triaxe and multispecimen (MSP-DSC) protocols were also measured on a subset of specimens. Around 60% of the samples provide reliable results when using stringent criteria selection. The 35 average archaeointensity values based on 154 pots are consistent with previous data and triple the Western Europe database between 1400 and 400 BCE. A secular variation curve for central-western Europe, built using a Bayesian approach, shows a double oscillation in geomagnetic field strength with intensity maxima of ∼70 μT around 1000-900 BCE and another up to ∼90 μT around 600-500 BCE. The maximum rate of variation was ∼0.25 μT/yr circa 700 BCE. The secular variation trend in Western Europe is similar to that observed in the Middle East and the Caucasus except that we find no evidence for hyper-rapid field variations (i.e. geomagnetic spikes). Virtual Axial Dipole Moments from Western Europe, the Middle East and central Asia differ by more than 2·1022 A·m2 prior to 600 BCE, which signifies a departure from an axial dipole field especially between 1000 and 600 BCE. Our observations suggest that the regional Levantine Iron Age anomaly has been accompanied by an increase of the axial dipole moment together with a tilt of the dipole.

  3. A simple model for reconstructing geomagnetic field intensity with (10)~Be production rate and its application in Loess studies

    Institute of Scientific and Technical Information of China (English)

    J.; Warren; BECK

    2008-01-01

    A simple model for reconstructing the paleomagnetic field intensity with (10)~Be production rate was used for the first time in Loess (10)~Be studies of Luochuan profile. Using the LGM (Last Glacial Maxmium) method, the climatic effects and geomagnetic modulation effects on loess (10)~Be was separated and in turn the 80 ka geomagnetic excursion sequence reconstructed, of which the globally remarkable geomagnetic excursion events such as the Laschamp (42 ka), Mono Lake (32 ka) during the Last Glacial period were revealed and the paleo-geomagnetic intensity curve from Loess (10)~Be over the past 80 ka was quantitatively reconstructed. The reconstructed paleo-intensity fits well with the paleo-intensity curves (SINT200 and NAPIS75), which indicates the significance of global criterion of the (10)~Be paleo- intensity curve and the future direction of loess (10)~Be tracing studies. Results show the irregular vari-ability of the East Asian monsoon precipitation in Loess Plateau is the main cause that has resulted in the ambiguity of the geomagnetic modulation of the (10)~Be record in the loess, and the intrinsic source component of the loess (10)~Be and inherited fraction of magnetic susceptibility (SUS) are characterized by the "quasi-homogeneous distribution" manner.

  4. Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

    Science.gov (United States)

    Yamazaki, Y.; Maute, A.

    2017-03-01

    A record of the geomagnetic field on the ground sometimes shows smooth daily variations on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are caused by electric currents of several μ A/m2 flowing on the sunlit side of the E-region ionosphere at about 90-150 km heights. We review advances in our understanding of the geomagnetic daily variation and its source ionospheric currents during the past 75 years. Observations and existing theories are first outlined as background knowledge for the non-specialist. Data analysis methods, such as spherical harmonic analysis, are then described in detail. Various aspects of the geomagnetic daily variation are discussed and interpreted using these results. Finally, remaining issues are highlighted to provide possible directions for future work.

  5. Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

    Science.gov (United States)

    Yamazaki, Y.; Maute, A.

    2016-09-01

    A record of the geomagnetic field on the ground sometimes shows smooth daily variations on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are caused by electric currents of several μA/m2 flowing on the sunlit side of the E-region ionosphere at about 90-150 km heights. We review advances in our understanding of the geomagnetic daily variation and its source ionospheric currents during the past 75 years. Observations and existing theories are first outlined as background knowledge for the non-specialist. Data analysis methods, such as spherical harmonic analysis, are then described in detail. Various aspects of the geomagnetic daily variation are discussed and interpreted using these results. Finally, remaining issues are highlighted to provide possible directions for future work.

  6. An active time-optimal control for space debris deorbiting via geomagnetic field

    Science.gov (United States)

    Amiri Atashgah, M. A.; Gazerpour, Hamid; Lavaei, Abolfazl; Zarei, Yaser

    2017-02-01

    This paper is concerned with an approach for active removing of space debris by electrodynamic tether (EDT) systems in a time-optimal maneuver. In this regard, a collector-emitter system is comprised of the insulated EDT in order to generate the required electric current over a virtual circuit once the induced electric current is adopted as control force producer. To this end, a simulation program is initially developed, during which dynamic and mathematical models of the EDT as well as the geomagnetic field are encompassed, respectively. This toolset is first utilized for prediction of orbital characteristics during the deorbit process; and subsequently, using the direct transcription method, the time-optimal problem is well solved. The efficacy of the suggested technique is verified through extensive simulations once all hard constraints of the underlying problem are well satisfied. In short, while the altitude varies from 1413 to 200 km, the optimized deorbit time would reduce about 17 days.

  7. Pc5 geomagnetic field fluctuations at discrete frequencies at a low latitude station

    Directory of Open Access Journals (Sweden)

    U. Villante

    Full Text Available A statistical analysis of the geomagnetic field fluctuations in the Pc5 frequency range (1–5 mHz at a low latitude station (L = 1.6 provides further evidence for daytime power peaks at discrete frequencies. The power enhancements, which become more pronounced during high solar wind pressure conditions, may be interpreted in terms of ground signatures of magnetospheric cavity/waveguide compressional modes driven by solar wind pressure pulses. In this sense, the much clearer statistical evidence for afternoon events can be related to corotating structures mainly impinging the postnoon magnetopause. A comparison with results obtained for the same time intervals from previous investigations at higher latitudes and in the Earth’s magnetosphere confirms the global character of the observed modes.

    Key words. Magnetospheric physics (MHD waves and instabilities; solar wind-magnetospheric interactions

  8. Seasonal effect on the diurnal variation of the geomagnetic field registered in Huancayo Observatory

    CERN Document Server

    Rosales, Domingo

    2016-01-01

    In this article we study the seasonal effect on the diurnal variation of the geomagnetic field registered in the Huancayo Observatory, located in the Magnetic Equator, which is driven by "ionospheric currents" and its counterpart induced by "telluric currents". Huancayo Observatory has the highest amplitude in the diurnal variation, because of being in the Magnetic Equator and under the "Equatorial Electrojet". We present the pattern of seasonal variation in diurnal variation of components X, Y and Z, the same as confirmed by previous works since 1940. The effect of solar activity cycle of about 11 years in the diurnal variation is also confirmed; it is observed that amplitudes are greater in the maximum of solar activity.

  9. Geomagnetic field and altitude effects on the performance of future IACT arrays

    CERN Document Server

    Szanecki, M; Sobczyńska, D; Niedźwiecki, A; Sitarek, J; Bednarek, W

    2014-01-01

    The performance of IACT's arrays is sensitive to the altitude and geomagnetic field (GF) of the observatory site. Both effects play important role in the region of the sub-TeV gamma-ray measurements. We investigate the influence of GF on detection rates and the energy thresholds for five possible locations of the future CTA observatory using the Monte Carlo simulations. We conclude that the detection rates of gamma rays and the energy thresholds of the arrays can be fitted with linear functions of the altitude and the component of the GF perpendicular to the shower axis core. These results can be directly extrapolated for any possible localization of the CTA. In this paper we also show the influence of both geophysical effects on the images of shower and gamma/hadron separation.

  10. Re-Evaluation of Geomagnetic Field Observation Data at Syowa Station, Antarctica

    Directory of Open Access Journals (Sweden)

    K Takahashi

    2013-05-01

    Full Text Available The Japanese Antarctic Research Expedition has conducted geomagnetic observations at Syowa Station, Antarctica, since 1966. Geomagnetic variation data measured with a fluxgate magnetometer are not absolute but are relative to a baseline and show drift. To enhance the importance of the geomagnetic data at Syowa Station, therefore, it is necessary to correct the continuous variation data by using absolute baseline values acquired by a magnetic theodolite and proton magnetometer. However, the database of baseline values contains outliers. We detected outliers in the database and then converted the geomagnetic variation data to absolute values by using the reliable baseline values.

  11. RBSPICE measurement of ion loss during the 2015 March storm: Adiabatic response to the geomagnetic field change

    Science.gov (United States)

    Soto-Chavez, A. R.; Lanzerotti, L. J.; Gerrard, A.; Kim, H.; Bortnik, J.; Manweiler, J. W.

    2016-10-01

    A strongly energy-dependent ring current ion loss was measured by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on the Van Allen Probes A spacecraft in the local evening sector during the 17 March 2015 geomagnetic storm. The ion loss is found to be energy dependent where only ions with energies measured above ˜ 150 keV have a significant drop in intensity. At these energies the ion dynamics are principally controlled by variations of the geomagnetic field which, during magnetic storms, exhibits large-scale variations on time scales from minutes to hours. Here we show that starting from ˜19:10 UTC on 17 March the geomagnetic field increased from 220 to 260 nT on a time scale of about an hour as captured by RBSPICE-A close to spacecraft apogee, L = 6.1 and magnetic local time (MLT) = 21.85 h (GSM coordinates X =- 4.89, Y = 3.00, and Z =- 0.73). We demonstrate the relationship between this large geomagnetic field increase and the dropouts of the ≳ 150 keV ring current ions.

  12. An Approach to Model Earth Conductivity Structures with Lateral Changes for Calculating Induced Currents and Geoelectric Fields during Geomagnetic Disturbances

    Directory of Open Access Journals (Sweden)

    Bo Dong

    2015-01-01

    Full Text Available During geomagnetic disturbances, the telluric currents which are driven by the induced electric fields will flow in conductive Earth. An approach to model the Earth conductivity structures with lateral conductivity changes for calculating geoelectric fields is presented in this paper. Numerical results, which are obtained by the Finite Element Method (FEM with a planar grid in two-dimensional modelling and a solid grid in three-dimensional modelling, are compared, and the flow of induced telluric currents in different conductivity regions is demonstrated. Then a three-dimensional conductivity structure is modelled and the induced currents in different depths and the geoelectric field at the Earth’s surface are shown. The geovoltages by integrating the geoelectric field along specific paths can be obtained, which are very important regarding calculations of geomagnetically induced currents (GIC in ground-based technical networks, such as power systems.

  13. Solar and geomagnetic activity effects on mid-latitude F-region electric fields

    Directory of Open Access Journals (Sweden)

    V. V. Kumar

    2008-09-01

    Full Text Available Diurnal patterns of average F-region ionospheric drift (electric field and their dependence on solar and geomagnetic activity have been defined using digital ionosonde Doppler measurements recorded at a southern mid-latitude station (Bundoora 145.1° E, 37.7° S geographic, 49° S magnetic. A unique database consisting of 300 907 drift velocities was compiled, mostly using one specific mode of operation throughout 1632 days of a 5-year interval (1999–2003. The velocity magnitudes were generally larger during the night than day, except during the winter months (June–August, when daytime velocities were enhanced. Of all years, the largest drifts tended to occur during the high speed solar wind streams of 2003. Diurnal patterns in the average quiet time (AE<75 nT meridional drifts (zonal electric field peaked at up to ~6 m s−1 poleward (0.3 mV m−1 eastward at 03:30 LST, reversing in direction at ~08:30 LST, and gradually reaching ~10 m s−1 equatorward at ~13:30 LST. The quiet time zonal drifts (meridional electric fields displayed a clear diurnal pattern with peak eastward flows of ~10 m s−1 (0.52 mV m−1 equatorward at 09:30 LST and peak westward flows around midnight of ~18 m s−1 (0.95 mV m−1 poleward. As the AE index increased, the westward drifts increased in amplitude and they extended over a greater fraction of the day. The perturbation drifts changed in a similar way with decreasing Dst except the daytime equatorward flows strengthened with increasing AE index, whereas they became weak for Dst<−60 nT. The responses in all velocity components to changing solar flux values were small, but net poleward perturbations during the day were associated with large solar flux values (>192×10−22 W m−2 Hz−1. These results help to more fully quantify the response of the mid

  14. Elimination of the geomagnetic field stimulates the proliferation of mouse neural progenitor and stem cells

    Directory of Open Access Journals (Sweden)

    Jing-Peng Fu

    2016-08-01

    Full Text Available Abstract Living organisms are exposed to the geomagnetic field (GMF throughout their lifespan. Elimination of the GMF, resulting in a hypogeomagnetic field (HMF, leads to central nervous system dysfunction and abnormal development in animals. However, the cellular mechanisms underlying these effects have not been identified so far. Here, we show that exposure to an HMF (<200 nT, produced by a magnetic field shielding chamber, promotes the proliferation of neural progenitor/stem cells (NPCs/NSCs from C57BL/6 mice. Following seven-day HMF-exposure, the primary neurospheres (NSs were significantly larger in size, and twice more NPCs/NSCs were harvested from neonatal NSs, when compared to the GMF controls. The self-renewal capacity and multipotency of the NSs were maintained, as HMF-exposed NSs were positive for NSC markers (Nestin and Sox2, and could differentiate into neurons and astrocyte/glial cells and be passaged continuously. In addition, adult mice exposed to the HMF for one month were observed to have a greater number of proliferative cells in the subventricular zone. These findings indicate that continuous HMF-exposure increases the proliferation of NPCs/NSCs, in vitro and in vivo. HMF-disturbed NPCs/NSCs production probably affects brain development and function, which provides a novel clue for elucidating the cellular mechanisms of the bio-HMF response.

  15. Satellite Geomagnetism

    DEFF Research Database (Denmark)

    Olsen, Nils; Stolle, Claudia

    2012-01-01

    Observations of Earth’s magnetic field from space began more than 50 years ago. A continuous monitoring of the field using low Earth orbit (LEO) satellites, however, started only in 1999, and three satellites have taken highprecision measurements of the geomagnetic field during the past decade...... ability to characterize and understand the many sources that contribute to Earth’s magnetic field. In this review, we summarize investigations of Earth’s interior and environment that have been possible through the analysis of high-precision magnetic field observations taken by LEO satellites........ The unprecedented time-space coverage of their data opened revolutionary new possibilities for monitoring, understanding, and exploring Earth’s magnetic field. In the near future, the three-satellite constellation Swarm will ensure continuity of such measurement and provide enhanced possibilities to improve our...

  16. Wp index: A new substorm index derived from high-resolution geomagnetic field data at low latitude

    DEFF Research Database (Denmark)

    Nose, M.; Iyemori, T.; Wang, L.

    2012-01-01

    Geomagnetic field data with high time resolution (typically 1 s) have recently become more commonly acquired by ground stations. Such high time resolution data enable identifying Pi2 pulsations which have periods of 40-150 s and irregular (damped) waveforms. It is well-known that pulsations...... of this type are clearly observed at mid-and low-latitude ground stations on the nightside at substorm onset. Therefore, with 1-s data from multiple stations distributed in longitude around the Earth's circumference, substorm onset can be regularly monitored. In the present study we propose a new substorm...... index, the Wp index (Wave and planetary), which reflects Pi2 wave power at low-latitude, using geomagnetic field data from 11 ground stations. We compare the Wp index with the AE and ASY indices as well as the electron flux and magnetic field data at geosynchronous altitudes for 11 March 2010. We find...

  17. Continuous record of geomagnetic field intensity between 4.7 and 2.7 Ma from downhole measurements

    Science.gov (United States)

    Thibal, J.; Pozzi, J.-P.; Barthès, V.; Dubuisson, G.

    1995-12-01

    A continuous record of the geomagnetic field intensity from 4.7 to 2.7 Ma has been obtained, together with a precise magnetostratigraphy, from downhole magnetic measurements at Site 884 of ODP Leg 145 in the North Pacific. The record confirms the saw-tooth pattern of geomagnetic field intensity proposed by Valet et Meynadier [10]. Reversals are characterized by a steep intensity decrease followed by a quick regeneration. Over each polarity interval, rapid variations are superimposed over a progressive decrease in the mean intensity. We find that the duration of each polarity interval is inversely proportional to the mean rate of decrease in the field intensity over this period, and thus this duration seems to be pre-determined.

  18. Parallel Computation of Spatio-Temporal Variations of Geomagnetic Field Using One-Minute Time Resolution Dataset

    Directory of Open Access Journals (Sweden)

    Felix Ale

    2012-11-01

    Full Text Available This work presents a novel method for analyzing spatio-temporal variations of geomagnetic field using parallel computing. One-minute resolution geomagnetic dataset of 1996 was obtained from INTERMAGNET global network of 64 observatory stations. In effect, large and three dimensional arrays of geomagnetic observations are to be processed. Thus, sequential and parallel algorithms were developed using MATLAB 2012a, interfaced with the well-known kriging method for efficient geostatistical data gridding and mapping of solar quiet (Sq daily variations. The runtime of the sequential algorithm on a processor took 18.5 minutes while the corresponding parallel algorithm took 2.95 minutes using eight Intel Xeon E5410 2.33GHz processors in parallel. The efficiency profile of the model is logarithmic in nature. This was further optimized using quadratic polynomial interpolation. The results show that 13 processors will process the Sq in less than one minute, thus providing effective near real-time observation of Space weather. In addition, the foci of the generated finer Sq(H plots revealed temporal variability that is consistently maximized at local noon at every location on this geomagnetic environment as demonstrated in the 2D visual display.

  19. Shielding of the Geomagnetic Field Alters Actin Assembly and Inhibits Cell Motility in Human Neuroblastoma Cells.

    Science.gov (United States)

    Mo, Wei-Chuan; Zhang, Zi-Jian; Wang, Dong-Liang; Liu, Ying; Bartlett, Perry F; He, Rong-Qiao

    2016-03-31

    Accumulating evidence has shown that absence of the geomagnetic field (GMF), the so-called hypomagnetic field (HMF) environment, alters the biological functions in seemingly non-magnetosensitive cells and organisms, which indicates that the GMF could be sensed by non-iron-rich and non-photo-sensing cells. The underlying mechanisms of the HMF effects on those cells are closely related to their GMF sensation but remain poorly understood so far. Previously, we found that the HMF represses expressions of genes associated with cell migration and cytoskeleton assembly in human neuroblastoma cells (SH-SY5Y cell line). Here, we measured the HMF-induced changes on cell morphology, adhesion, motility and actin cytoskeleton in SH-SY5Y cells. The HMF inhibited cell adhesion and migration accompanied with a reduction in cellular F-actin amount. Moreover, following exposure to the HMF, the number of cell processes was reduced and cells were smaller in size and more round in shape. Furthermore, disordered kinetics of actin assembly in vitro were observed during exposure to the HMF, as evidenced by the presence of granule and meshed products. These results indicate that elimination of the GMF affects assembly of the motility-related actin cytoskeleton, and suggest that F-actin is a target of HMF exposure and probably a mediator of GMF sensation.

  20. The ionospheric response to perturbation electric fields during the onset phase of geomagnetic storms

    Energy Technology Data Exchange (ETDEWEB)

    Jakowski, N.; Jungstand, A. (Deutsche Forschungsanstalt fuer Luft- and Raumfahrt, Neustrelitz (Germany)); Schlegel, K.; Kohl, H.; Rinnert, K. (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany))

    1992-07-01

    The generation and propagation of ionospheric storms are studied by analyzing EISCAT radar, and vertical sounding and total electron content data obtained under different geophysical conditions. Both case studies as well as the average storm pattern of percentage deviations of different ionospheric parameters from their corresponding reference values such as total electron content, F2-layer critical frequency, F2 layer critical height, and slab thickness indicate the action of a perturbation electric field during the first few hours of the onset of geomagnetic storms. Considering the onset phase of the storm on July 28-29, 1987 evidence has been found that high latitude electric fields may penetrate to lower latitudes before the ring current has developed. Different mechanisms are assumed to be responsible for daytime and nightime behaviour, respectively. The negative phase propagates equatorward with velocities in the order of 70-350 m/s following a strong heating of the thermosphere and ionosphere due to the auroral electrojet. 24 refs., 10 figs.

  1. Latitude-dependence and dispersion of the westward drift in the geomagnetic field

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The main geomagnetic field models of IGRF1900---2000 are used to study the latitude-dependence of the westward drift in the main field. The results show that the latitude-dependence exists in the magnetic components with different wavelengths (m=l-10). The globai-average westward drift rate of the component of m=l is 0.189°/a with the maximum of 0.295°/a at latitudes 40°-45°. The component of m=2 has an average drift rate of 0.411°/a with the maximum of 1.305°/a at latitude -60°. As for the components with further shorter wavelengths, the drift is generally restricted in a limited latitude range, and has many smaller drift rates. This latitude-dependence of westward drift can not be explained by rigid rotation of the earth's core. The results of this note also show that there is a negative dispersion in the westward drift, namely the components of long wavelengths drift faster than those of short wavelengths.This dispersion feature is not in agreement with Hide's MHD model. It is likely needed to find a new mechanism for explaining the observed feature of dispersion.

  2. Effects of geomagnetic disturbances in daytime variations of the atmospheric electric field in polar regions

    Science.gov (United States)

    Kleimenova, N. G.; Kubicki, M.; Odzimek, A.; Malysheva, L. M.; Gromova, L. I.

    2017-05-01

    We have studied the influence of daytime polar substorms (geomagnetic bays under the IMF Bz > 0) on variations of the vertical gradient of the atmospheric electric field potential ( Ez) observed at the Polish Hornsund Station (Svalbard, Norway). Only the observations of Ez under "fair weather" conditions were used, i.e. in the absence of strong wind, precipitations, low cloud cover, etc. We studied more than 20 events of daytime polar substorms registered by the Scandinavian chain of IMAGE magnetometers in 2010-2014 during the "fair weather" periods at the Hornsund Station. Analysis of the observations showed that Ez significantly deviates from the its background variations during daytime, as a rule, when the Hornsund Station is in the region of projection of the daytime auroral oval, the position of which was determined from OVATION data. It was shown that the development of a daytime polar substorm leads to fluctuating enhance of Ez values. It was found that Ez surges are accompanied by intensification of field-aligned electric currents outflowing from the ionosphere, which were calculated from the data of low-orbit communication satellites of the AMPERE project.

  3. TS07D Empirical Geomagnetic Field Model as a Space Weather Tool

    Science.gov (United States)

    Sharp, N. M.; Stephens, G. K.; Sitnov, M. I.

    2011-12-01

    Empirical modeling and forecasting of the geomagnetic field is a key element of the space weather research. A dramatic increase in the number of data available for the terrestrial magnetosphere required a new generation of empirical models with large numbers of degrees of freedom and sophisticated data-mining techniques. A set of the corresponding data binning, fitting and visualization procedures known as the TS07D model is now available at \\url{http://geomag_field.jhuapl.edu/model/} and it is used for detailed investigation of storm-scale phenomena in the magnetosphere. However, the transformation of this research model into a practical space weather application, which implies its extensive running for validation and interaction with other space weather codes, requires its presentation in the form of a single state-of-the-art code, well documented and optimized for the highest performance. To this end, the model is implemented in the Java programming language with extensive self-sufficient library and a set of optimization tools, including multi-thread operations that assume the use of the code in multi-core computers and clusters. The results of the new code validation and optimization of its binning, fitting and visualization parts are presented as well as some examples of the processed storms are discussed.

  4. Influence of the Geomagnetic Field on the IACT detection technique for possible sites of CTA observatories

    CERN Document Server

    Szanecki, Michał; Sobczyńska, Dorota; Niedźwiecki, Andrzej; Sitarek, Julian; Bednarek, Włodzimierz

    2013-01-01

    We investigate the influence of the geomagnetic field (GF) on the Imaging Air Cherenkov Telescope technique for two northern (Tenerife and San Pedro Martir) and three southern (Salta, Leoncito and Namibia (the H.E.S.S.-site)) site candidates for Cherenkov Telescope Array (CTA) observatories. We use the CORSIKA and sim_telarray programs for Monte Carlo simulations of gamma ray showers, hadronic background and the telescope response. We focus here on gamma ray measurements in the low energy, sub-100 GeV, range. Therefore, we only consider the performance of arrays of several large telescopes. Neglecting the GF effect, we find (in agreement with previous studies) that such arrays have lower energy thresholds, and larger collection areas below 30 GeV, when located at higher altitudes. We point out, however, that in the considered ranges of altitudes and magnetic field intensities, 1800-3600 m a.s.l. and 0-40 \\mu T, respectively, the GF effect has a similar magnitude to this altitude effect. We provide the trigger...

  5. Interplanetary drivers of daytime penetration electric field into equatorial ionosphere during CIR-induced geomagnetic storms

    Science.gov (United States)

    Yeeram, Thana

    2017-05-01

    Observations based on the magnetometer data of the response of the daytime equatorial electric field to the geomagnetic storms induced by corotating interaction regions (CIRs) during 2007-2010 reveal many events of striking long duration of multiple short-lived prompt penetration electric fields (PPEFs). The PPEFs essentially occurred in the main phase of the storms, which are associated with the ring current and magnetic reconnection of the southward z-component of the interplanetary magnetic field (IMF Bz) in relation to the Alfvén waves. The behaviors of the electric field penetration during the storms are consistent with the shielding theory. Particularly, the PPEF is found to be complex due to transient variations in the solar wind dynamic pressure (SWDP) and the IMF Bz in the CIRs. The PPEF is temporary suppressed for about an hour under a shock in association with a drop in the SWDP. The interplanetary electric field Ey is the main driver of the PPEFs, when the solar wind speed, SWDP, and the symmetric ring current are nearly constant, even in the recovery phase. The PPEF is allowed under the condition of high and variable SWDP. The shocks with a northward IMF Bz shield the PPEFs when the SWDP is nearly constant. The partial ring current is strongest in the large and northward IMF Bz, where the shielding effect is greater than the undershielding caused by the large SWDP. The results may provide an important step to study equatorial and low latitude ionospheric electrodynamics in the solar minimum conditions.

  6. Latitude-independent Pc5 Geomagnetic Pulsations Associated With Field Line Resonance

    Science.gov (United States)

    Sung, S.; Kim, K.; Lee, D.; Cattell, C. A.; Andre, M.; Khotyaintsev, Y. V.

    2004-12-01

    The latitude-independent Pc5 pulsations with a spectral peak at ˜2.8 mHz were observed with IMAGE and SAMNET magnetometer array in the morning sector (0700-1000 local time) on April 29 (Day 119), 2001. The spectral amplitude had a local peak at ˜67° geomagnetic latitude, where a sudden phase change of ˜180° appeared. A vortical equivalent ionospheric current structure centered at latitude between 67° and 71° was observed during the Pc5 pulsations and the rotational sense of the current vortex was reversed for one cycle of the pulsation. During the interval of the enhancement of the Pc5 pulsations, the POLAR spacecraft in the morning side crossed near the magnetic shell (L ˜ 8) corresponding to the latitude where the spectral amplitude was maximum, and observed ˜2.8 mHz pulsations in the radial electric field and compressional magnetic field components. Since the toroidal mode Alfvén waves in the magnetosphere are characterized by an electric field perturbation in the radial direction, the simultaneous presence of the pulsations in both components indicates that a field line resonance (FLR) was driven by compressional Pc5 pulsations. Using solar wind data, we conformed that the compressional Pc5 pulsations at POLAR occurred during an interval of enhanced solar wind dynamic pressure. From the analysis of the ground magnetometer data and POLAR data, we suggest that latitude independent ground magnetic perturbations are caused by the vortical equivalent current generated by FLR-associated field-aligned currents.

  7. Spatial and Temporal Variations in the Geomagnetic Field Determined From the Paleomagnetism of Sediment Cores From Scientific Ocean Drilling

    Science.gov (United States)

    Acton, G.

    2014-12-01

    Quantifying the spatial and temporal variations of the main geomagnetic field at Earth's surface is important for understanding underlying geodynamo processes and conditions near the core-mantle boundary. Much of the geomagnetic variability, known as secular variation, occurs on timescales of tens of years to many thousands of years, requiring the use of paleomagnetic observations to derive continuous records of the ancient field, referred to as paleosecular variation (PSV) records. Marine depositional systems where thick sedimentary sections accumulate at high sedimentation rates provide some of the best locations for obtaining long continuous PSV records that can reveal both the short- and long-term changes in the field. Scientific ocean drilling has been successful at recovering many such sections and the paleomagnetic records from these reveal how the amplitude of PSV differs between sites and through time. In this study, several such records cored during Ocean Drilling Program (ODP), Integrated Ocean Drilling Program (IODP), and other cruises from high, mid, and low latitudes will be used to quantify time intervals of low and high PSV, to examine time-average properties of the field, to map spatial variations in the angular dispersion of the virtual geomagnetic pole (VGP), and to assess whether the spatial variation in angular dispersion changes with time.

  8. ULF fluctuations of the geomagnetic field and ionospheric sounding measurements at low latitudes during the first CAWSES campaign

    Directory of Open Access Journals (Sweden)

    U. Villante

    2006-07-01

    Full Text Available We present an analysis of ULF geomagnetic field fluctuations at low latitudes during the first CAWSES campaign (29 March-3 April 2004. During the whole campaign, mainly in the prenoon sector, a moderate Pc3-4 pulsation activity is observed, clearly related to interplanetary upstream waves. On 3 April, in correspondence to the Earth's arrival of a coronal mass ejection, two SIs are observed whose waveforms are indicative of a contribution of the high-latitude ionospheric currents to the low-latitude ground field. During the following geomagnetic storm, low frequency (Pc5 waves are observed at discrete frequencies. Their correspondence with the same frequencies detected in the radial components of the interplanetary magnetic field and solar wind speed suggests that Alfvénic solar wind fluctuations may act as direct drivers of magnetospheric fluctuations. A cross-phase analysis, using different pairs of stations, is also presented for identifying field line resonant frequencies and monitoring changes in plasmaspheric mass density. Lastly, an analysis of ionospheric vertical soundings, measured at the Rome ionosonde station (41.8° N, 12.5° E, and vertical TEC measurements deduced from GPS signals within an European network shows the relation between the ULF resonances in the inner magnetosphere and thermal plasma density variations during geomagnetically quiet conditions, in contrast to various storm phases at the end of the CAWSES campaign.

  9. On the seismogenic increase of the ratio of the ULF geomagnetic field components

    OpenAIRE

    Masci, Fabrizio

    2011-01-01

    Abstract Highlights ? The reliability of magnetic ratio changes as earthquake precursors are investigated. ? Nine cases are considered which include seventeen earthquakes. ? In the analysis running averages of the ?Kp geomagnetic index are taken into account. ? These increases are actually caused by the normal geomagnetic activity variation. Abstract Following the paper by Fraser-Smith et al. (1990), many scientists have focused their research on the ULF ge...

  10. Decadal to millennial scale geomagnetic field variations in the Levantine archaeointensity curve (LAC): methodology and applications

    Science.gov (United States)

    Shaar, Ron; Tauxe, Lisa; Ron, Hagai; Agnon, Amotz; Ben-Yosef, Erez; Finkelstein, Israel; Zuckerman, Sharon; Levy, Thomas E.

    2014-05-01

    Recovering the absolute intensity of the geomagnetic field on historical and archaeological timescale (archaeointensity) in a sufficient resolution is a fundamental effort in the paleomagnetic research. However, it is a complicated task hampered by some serious methodological difficulties. First, paleointensity experiments should be carefully designed using sufficient number of specimens, and accurate correction for remanence anisotropy, cooling rate effects, and non-linear TRM (NLT). Second, the basic assumption of the paleointensity method - that the natural remanence magnetization (NRM) is a stable thermoremanent magnetization (TRM) carried by single domain (SD) like particles - is hard to test using non-destructive methods. Third, the interpretation of the experimental results is non-unique leading to uncertainty in the final paleointensity calculation. These experimental difficulties compound with dating problems, which are not always easy to overcome. Here, we address each of the issues pointed above in order to construct a high-resolution archaeointensity curve of the Levant using a comprehensive dataset consisting of more than 2000 specimens from over 400 samples. The experimental difficulties are overcome by applying the same treatments to all specimens: Thellier-type IZZI protocol with pTRM checks every second step, and additional anisotropy, cooling rate, and NLT experiments. To ensure consistency, comparability, and objectivity of the interpretations we apply an automatic data analysis technique using a recently published open code computer program (PmagPy Thellier-GUI). We use strict selection criteria for the specimens/samples level and for the correction to screen out any unreliable data. For transparency, we make all the raw data, which include over 80,000 individual measurements, available in the MagIC database for the use of other researchers. We treat the dating problems by assigning a six-level quality scale (form controversial to excellent

  11. The correlation between geomagnetic field reversals, Hawaiian volcanism, and the motion of the Pacific plate

    Directory of Open Access Journals (Sweden)

    W. Dong

    1996-06-01

    Full Text Available The correlation between geomagnetic field reversals and volcanism is investigated, according to the speculated consequence on volcanoes of the transient electric currents in the geodynamo, through Joule's heating, before and after every reversal event. We evaluate the temporal variation during the last ~ 70 Ma both of the magma emplacement rate Q(t from the Hawaii hot spot, and of the speed v(t of the Pacific plate, by means of the observed volumes of islands and seamounts along the Hawaii/Emperor Seamounts chain, and their respective radiometric datings. Results confirm expectations. A justification of the volcanic crises that lead to the generation of the large igneous provinces during the last ~ 250 Ma also emerged. We describe in detail the complex pattern of the timings of the different effects. Joule's power is generally responsible for ~ 75-80% of magmatism, and friction power only for ~ 20-25%; but, on some occasions almost ~ 100% is fuelled by friction alone. The visco-elastic coupling between lithosphere and asthenosphere results ~ 96% viscous, and ~ 4% elastic.

  12. Steady flows at the top of earth's core derived from geomagnetic field models

    Science.gov (United States)

    Voorhies, Coerte V.

    1986-01-01

    Select models of the main geomagnetic field and its secular variation are extrapolated to the base of an insulating mantle and used to estimate the adjacent fluid motion of a perfectly conducting outer core. The assumption of steady motion provides formally unique solutions and is tested along with that of no upwelling. The hypothesis of no upwelling is found to be substantially worse than that of steady motion. Although the actual motion is not thought to be steady, the large-scale secular variation at the top of the core can be adequately described by a large-scale, combined toroidal-poloidal circulation which is steady for intervals of at least a decade or two. The derived flows include a bulk westward drift but are complicated by superimposed jets, gyres, and surface divergence indicative of vigorous vertical motion at depth. The circulation pattern and key global properties including rms speed, upwelling, and westward drift are found to be fairly insensitive to variations in modeling parameters.

  13. Geomagnetic Field Variability in the Western Canadian Arctic Since the Last Deglaciation

    Science.gov (United States)

    St-Onge, G.; Lise-Pronovost, A.; Barletta, F.; Channell, J. E.; Brachfeld, S. A.; Polyak, L. V.; Darby, D. A.; Rochon, A.; Scott, D. B.

    2009-12-01

    Several piston cores (HLY0501-05JPC, -06JPC, -08JPC and 2004-804-803, -124, -250, -650, -750) were recently collected in the western Canadian Arctic and Arctic Alaskan margin as part of major international scientific programs such as CASES (Canadian Arctic Shelf Exchange Study), ArcticNet and HOTRAX (Healy-Oden Trans Arctic Expedition). Due to the seafloor imaging and subbottom profiling capabilities of the deployed ice-breakers (CCGS Amundsen and USCCG Healy), the coring sites were carefully selected for high sediment accumulation areas not affected by mass wasting events nor by ice scouring. The sedimentological, physical and magnetic properties of these piston cores in conjunction with AMS-14C dating reveal that these cores span the last deglaciation to the present with sedimentation rates as high as 350 cm/ka. Here we highlight key paleomagnetic secular variations and relative paleointensity findings from selected cores collected off the Arctic Alaskan margin, the Mackenzie delta and in the Amundsen Gulf in order to synthesize geomagnetic field variability in the western Canadian Arctic since the last deglaciation.

  14. The Effect of Extremely Low Frequency Alternating Magnetic Field on the Behavior of Animals in the Presence of the Geomagnetic Field

    Directory of Open Access Journals (Sweden)

    Natalia A. Belova

    2015-01-01

    Full Text Available It is known that the geomagnetic field can influence animal migration and homing. The magnetic field detection by animals is known as magnetoreception and it is possible due to two different transduction mechanisms: the first one through magnetic nanoparticles able to respond to the geomagnetic field and the second one through chemical reactions influenced by magnetic fields. Another behavior is the magnetic alignment where animals align their bodies to the geomagnetic field. It has been observed that magnetic alignment of cattle can be disrupted near electric power lines around the world. Experimentally, it is known that alternating magnetic fields can influence living beings, but the exact mechanism is unknown. The parametric resonance model proposes a mechanism to explain that effect on living beings and establishes that, in the presence of a constant magnetic field, molecules associated with biochemical reactions inside cells can absorb resonantly alternating magnetic fields with specific frequencies. In the present paper, a review is made about animal magnetoreception and the effects of alternating magnetic fields in living beings. It is suggested how alternating magnetic fields can interfere in the magnetic alignment of animals and a general conclusion is obtained: alternating magnetic field pollution can affect the magnetic sensibility of animals.

  15. Holocene geomagnetic field intensity variations: Contribution from the low latitude Canary Islands site

    Science.gov (United States)

    Kissel, C.; Laj, C.; Rodriguez-Gonzalez, A.; Perez-Torrado, F.; Carracedo, J. C.; Wandres, C.

    2015-11-01

    New absolute paleomagnetic intensity (PI) are investigated from 37 lava flows located at Tenerife and Gran Canaria (Canary Islands). They complete previously published directional results from the same flows and therefore allow to examine the time variations of the full geomagnetic vector. Twenty-eight flows are radiocarbon dated between 1706 AD and about 13 200 BC and one is historical. Eight other flows are not dated but they have stratigraphic links with the dated flows and archeomagnetic ages had been attributed to them based on their paleomagnetic directions. Various mineralogical analyses were conducted, giving access to the nature of the magnetic minerals and to their grain size. We performed the original Thellier and Thellier paleointensity (PI) experiments with a success rate of about 65% coupling this experiment with the strict set of selection criteria PICRIT-03. The mean PIs at the flow level are based on 3 to 12 independent PI determinations except for one site in which only one reliable determination could be obtained. The data indicate some variability in the local field intensity with a prominent PI peak centered around 600 BC and reaching 80 μT (VADM 16 ×1022 Am2), documented for the first time in this region. Combined with the published data obtained from western Africa, Spain, Portugal, Morocco and the Azores within a 2000 km-radius around the Canary Islands, our data allow to construct a curve illustrating the Earth magnetic field intensity fluctuations for Southwestern Europe/Western Africa. This curve, compared to the one produced for the Middle East and one calculated for Central Asia shows that maximum intensity patches have a very large geographical extent. They do not yet appear clearly in the models of variations of the dipolar field intensity.

  16. AN UPDATE OF ITALIAN ARCHEAOINTENSITY DATA AND GEOMAGNETIC FIELD STRENGTH VARIATION DURING THE LAST THREE MILLENNIA

    Science.gov (United States)

    Tema, E.; Goguitchaichrili, A.

    2009-12-01

    Beside of the impressive cultural heritage and the abundant archaeological sites, Italian archaeointensity data are still sparse. We present here a new compilation and analysis of existing absolute intensity data in order to estimate the variation of the Earth’s magnetic field over the past three millennia. The current dataset consists of 140 intensity data mainly belonging to southern Italy. Vesuvius and Etna contribute 83 per cent of total while only 17 per cent comes from archaeological material. The time distribution is also irregular with the majority of determinations concentrated at the last four centuries. Still, older periods are very poorly covered. All data have been reduced at the latitude of Viterbo (42.45° N, 12.03° E) and plotted versus time. Data coming from historical volcanic eruptions show important discrepancies while those coming from archaeological material are still not sufficiently numerous to reliably describe the fine characteristics of geomagnetic field intensity variations. In order to increase the representativity of the data, archaeointensity results from nearby regions (approximately 700 km and 900 km radius from Viterbo) have been considered. The 700 km circle dataset still remains poor with only 20 additional data added. In contrast, the 900 km dataset includes 122 more archaeointensity data mainly coming from France, Switzerland, Czech Republic, Slovakia, Hungary, Greece and Bulgaria that partially fill the gap between 4-7th centuries BC and 3-4th and 9-11th AD for which no Italian data are available. A preliminary Italian intensity secular variation curve has been calculated by using sliding windows of 100 years shifted by 50 years. The results have been compared with regional and global models predictions. Clearly more Italian archaeointensity data are still needed in order to draw a robust Italian intensity secular variation curve that could be used for archaeomagnetic dating in combination with directional data.

  17. An intense SFE and SSC event in geomagnetic H, Y and Z fields at the Indian chain of observatories

    Directory of Open Access Journals (Sweden)

    S. Alex

    Full Text Available Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent sudden commencement (SSC of geomagnetic storm at 1518 h on 17 June 1991. The solar flare effects (SFE registered on the magnetograms appear to be an augmentation of the ionospheric current system existing at the start time of the flare. An equatorial enhancement in ΔH due to SFE is observed to be similar in nature to the latitudinal variation of SQ (H at low latitude. ΔY registered the largest effect at 3.6° dip latitude at the fringe region of the electrojet. ΔZ had positive amplitudes at the equatorial stations and negative at stations north of Hyderabad. The SSC amplitude in the H component is fairly constant with latitude, whereas the Z component again showed larger positive excursions at stations within the electrojet belt. These results are discussed in terms of possible currents of internal and external origin. The changes in the Y field strongly support the idea that meridional current at an equatorial electrojet station flows in the ionospheric dynamo, E.

  18. Geomagnetically Induced Currents: Principles

    Science.gov (United States)

    Oliveira, Denny M.; Ngwira, Chigomezyo M.

    2017-10-01

    The geospace, or the space environment near Earth, is constantly subjected to changes in the solar wind flow generated at the Sun. The study of this environment variability is called Space Weather. Examples of effects resulting from this variability are the occurrence of powerful solar disturbances, such as coronal mass ejections (CMEs). The impact of CMEs on the Earth's magnetosphere very often greatly perturbs the geomagnetic field causing the occurrence of geomagnetic storms. Such extremely variable geomagnetic fields trigger geomagnetic effects measurable not only in the geospace but also in the ionosphere, upper atmosphere, and on and in the ground. For example, during extreme cases, rapidly changing geomagnetic fields generate intense geomagnetically induced currents (GICs). Intense GICs can cause dramatic effects on man-made technological systems, such as damage to high-voltage power transmission transformers leading to interruption of power supply, and/or corrosion of oil and gas pipelines. These space weather effects can in turn lead to severe economic losses. In this paper, we supply the reader with theoretical concepts related to GICs as well as their general consequences. As an example, we discuss the GIC effects on a North American power grid located in mid-latitude regions during the 13-14 March 1989 extreme geomagnetic storm. That was the most extreme storm that occurred in the space era age.

  19. Computation and analysis of the geomagnetic field model in China and its adjacent area for 2003

    Institute of Scientific and Technical Information of China (English)

    GU Zuo-wen; AN Zhen-chang; GAO Jin-tian; ZHAN Zhi-jia; YAO Tong-qi; HAN Wei; CHEN Bin

    2006-01-01

    Based on the geomagnetic data at 135 stations and 35 observatories in China in 2003, the Taylor polynomial model and the spherical cap harmonic model in China and its adjacent area for 2003 were established. In the model calculation, the truncation order of the model and the influences of the boundary restriction on the model calculation were carefully analyzed. The results show that the geomagnetic data used are precise and reliable, and the selection of the truncation order is reasonable. The Taylor polynomial model and the spherical cap harmonic model in China and its adjacent area established in this paper are consistent very well.

  20. A cooling event during the last geomagnetic polarity reversal: synchronous occurrence with a large decrease in field intensity

    Science.gov (United States)

    Kitaba, I.; Hyodo, M.; Katoh, S.; Matsushita, M.

    2009-12-01

    The discovery of a correlation between galactic cosmic ray flux and cloud cover suggests that climate change can be caused by variation in cosmic ray flux which is strongly modulated by the geomagnetic field intensity. This study uses a detailed climate record of the Matuyama-Brunhes (MB) magnetic polarity transition to examine a link between geomagnetic field intensity and climate in geologic time. The record is based on palynological data obtained from a sediment core from Osaka Bay with a 200 year resolution. From marine oxygen isotope stage (MIS) 20 to 18, climate variability is well correlated with glacial-interglacial precession cycles, except for a cooling event that occurred at the highest point of the MIS 19 sea-level highstand. In early MIS 19, the proportion of the warm-temperate evergreen broad-leaved taxon Quercus (Cyclobalanopsis) gradually increased as sea level rose, indicating a progressive warming. However, after ~2 kyr of warming a cooling began with an abrupt reduction in Quercus (Cyclobalanopsis) and an increase in Fagus (cool-temperate deciduous broad-leaved taxon). The cooling persisted for about 4 kyr coincident with the sea-level highstand 19.3, and was followed by a rapid warming. A thermal maximum occurred 6 kyr after 19.3 and 11-12 kyr after an insolation peak. These time lags cannot be interpreted as a delayed vegetational response, as this is typically 500 yr or less. After the thermal maximum, Quercus (Cyclobalanopsis) gradually decreased from 19.2 to 19.1, but the temperature estimated from the vegetation was still warmer than at the sea-level highstand 19.3. This observation conflicts with the pattern of sea-level estimated from oxygen isotope values, which indicates that sea level at MIS 19.1 was about 20 m lower than that at 19.3. This cooling event, during the highest sea level highstand contrasts with the climates of MISs 21, 11 and 1 when the thermal maximum coincided with the highest sea-levels. Detailed relative

  1. Large geomagnetic field anomalies revealed in Bronze to Iron Age archeomagnetic data from Tel Megiddo and Tel Hazor, Israel

    Science.gov (United States)

    Shaar, Ron; Tauxe, Lisa; Ron, Hagai; Ebert, Yael; Zuckerman, Sharon; Finkelstein, Israel; Agnon, Amotz

    2016-05-01

    Geomagnetic field measurements from the past few centuries show heightened secular variation activity in the southern hemisphere associated with the south Atlantic anomaly (SAA). It is uncertain whether geomagnetic anomalies at a similar scale have existed in the past owing to limited coverage and uncertainties in the paleomagnetic database. Here we provide new evidence from archaeological sources in the Levant suggesting a large positive northern hemisphere anomaly, similar in magnitude to the SAA during the 9th-8th centuries BCE, called ;Levantine Iron Age anomaly;. We also report an additional geomagnetic spike in the 8th century. The new dataset comprises 73 high precision paleointensity estimates from ca. 3000 BCE to 732 BCE, and five directional measurements between the 14th and the 9th centuries BCE. Well-dated pottery and cooking ovens were collected from twenty archaeological strata in two large contemporaneous stratigraphical mounds (tells) in Israel: Tel Megiddo and Tel Hazor. The new data are combined with previously published data and interpreted automatically using the PmagPy Thellier GUI program. The Tel Megiddo and Tel Hazor data sets demonstrate excellent internal consistency and remarkable agreement with published data from Mesopotamia (Syria). The data illustrate the evolution of an extreme geomagnetic high that culminated in at least two spikes between the 11th and the 8th centuries BCE (Iron Age in the Levant). The paleomagnetic directional data of the 9th century BCE show positive inclination anomalies, and deviations of up to 22° from the averaged geocentric axial dipole (GAD) direction. From comparison of the Levantine archaeomagnetic data with IGRF model for 2015 we infer the ;Levantine Iron Age anomaly; between the 10th and the 8th centuries BCE is a local positive anomaly. The eastward extent of the anomaly is currently unknown.

  2. The separation of the geomagnetic field originated in the core, in the asthenosphere, and in the crust

    Directory of Open Access Journals (Sweden)

    X. Q. Gao

    1999-06-01

    Full Text Available The separation of the field produced by different internal sources can be accomplished by means of the so-called spatial spectrum of the geomagnetic field of internal origin. It is shown how such a rationale, when suitably interpreted, allows to recognize the field that is originated by electric currents that flow either on the Inner-Core Boundary (ICB, or on the Core-Mantle Boundary (CMB, or on the Asthenosphere-Lithosphere Boundary (ALB. It appears crucial, however, to rely on satellite measurements alone, because ground-based and ship- and air-borne records are severely perturbed by the crustal field. Therefore, it is shown, on the basis of a critical reconsideration of a few key-papers in the literature, that the best approach is to avoid mixing together all kinds of measurements. Satellite data are best suited for recognizing the dynamo field, while ground-based, ship- and air-borne records, which are measured much closer to crustal sources, are best suited, after subtraction of the satellite-derived dynamo field, for inferring the geomagnetic anomalies that are to be associated with crustal sources alone.

  3. New archaeointensity results from archaeological sites and variation of the geomagnetic field intensity for the last 7 millennia in Greece

    Science.gov (United States)

    De Marco, E.; Spatharas, V.; Gómez-Paccard, M.; Chauvin, A.; Kondopoulou, D.

    In this study six new intensity determinations are presented, obtained from five well dated archaeological sites, located in northern Greece and in Paros, Cyclades Islands. The fired structures consisted of ceramic and pottery kilns belonging to the Hellenistic, Roman and Byzantine periods. Between 8 and 21 samples of highly fired baked clays, tiles and bricks were taken, homogeneously distributed over the structures. The samples were analysed using the classical Thellier method, providing the past intensities and directions of the geomagnetic field recorded at each site. The intensity values have been corrected for anisotropy of thermal remanent magnetisation and cooling rate effects. Differences in the mean archaeointensities per site ranging from 1% to 11%, before and after TRM anisotropy and cooling rate corrections, were obtained. The new results indicate a decrease of 20% of the geomagnetic field strength in Greece, during the last four centuries BC. In order to compare our results with previously published data, a catalogue of archaeo- and palaeointensity results for the Aegean area has been established, covering the last 7 millennia. It consists of 336 data from Greece, western Turkey and Former Yugoslavia, collected from various authors. Weighting factors have been applied to these data, that then have been treated with a hierarchical Bayesian modelling, and a geomagnetic field intensity variation curve for Greece was constructed. A good agreement is observed when comparing the curve for Greece with the Bulgarian secular variation curve (SVC) for intensity. Satisfactory coincidence is also found with the archaeointensity data from Mesopotamia. Despite the presence of some time gaps, a more precise secular variation intensity curve has been constructed for Greece which, combined with a forthcoming directional SVC, will help for dating purposes.

  4. Mechanisms of Geomagnetic Field Influence on Gene Expression Using Influenza as a Model System: Basics of Physical Epidemiology

    Directory of Open Access Journals (Sweden)

    Andriy Ponomarenko

    2010-03-01

    Full Text Available Recent studies demonstrate distinct changes in gene expression in cells exposed to a weak magnetic field (MF. Mechanisms of this phenomenon are not understood yet. We propose that proteins of the Cryptochrome family (CRY are "epigenetic sensors" of the MF fluctuations, i.e., magnetic field-sensitive part of the epigenetic controlling mechanism. It was shown that CRY represses activity of the major circadian transcriptional complex CLOCK/BMAL1. At the same time, function of CRY, is apparently highly responsive to weak MF because of radical pairs that periodically arise in the functionally active site of CRY and mediate the radical pair mechanism of magnetoreception. It is known that the circadian complex influences function of every organ and tissue, including modulation of both NF-κB- and glucocorticoids- dependent signaling pathways. Thus, MFs and solar cycles-dependent geomagnetic field fluctuations are capable of altering expression of genes related to function of NF-κB, hormones and other biological regulators. Notably, NF-κB, along with its significant role in immune response, also participates in differential regulation of influenza virus RNA synthesis. Presented data suggests that in the case of global application (example—geomagnetic field, MF-mediated regulation may have epidemiological and other consequences.

  5. Holocene geomagnetic field variations from low latitude site: contribution from the Canary Islands

    Science.gov (United States)

    Kissel, Catherine; Laj, Carlo; Rodriguez-Gonzalez, Alejandro; Perez-Torrado, Francisco; Carrracedo, Juan-Carlos; Wandres, Camille

    2016-04-01

    Full geomagnetic vector information was retrieved from 37 lava flows (corresponding to 38 sites because one flow was sampled at two different localities) located in Tenerife and Gran Canaria (Canary Islands). Twenty-eight flows are dated between 1706 AD and about 13200 BC and one is historical. Eight other non-dated flows have stratigraphic links with the dated flows and at the end, our study allowed us to attribute to them archeomagnetic ages based on their paleomagnetic characteristics. Various mineralogical analyses were conducted, giving access to the nature and grain size of the magnetic minerals. Full stepwise (about 13 steps) thermal and AF demagnetizations were conducted on more than 400 samples to determine the paleomagnetic directions. The individual MAD values are on the average about 2° and the mean precision parameter at the flow scale (alpha95) is 4.2°. For paleointensities (PI), we performed the original Thellier and Thellier experiments with a success rate of about 65%, coupling it with the strict set of selection criteria PICRIT-03. The mean PIs at the flow level are based on 3 to 12 independent PI determinations except for one site in which only one reliable determination could be obtained. The obtained data are unique in this area over the 1000-14000 BC period and they are complementary to the dataset obtained in the Canary Islands for the last 500 years. Over the last 3 kyr, they indicate some variability in the local field intensity with a prominent PI peak centered around 600 BC and reaching 80 μT (VADM 16 x 10 ^22 Am ^2), documented by four different flows and associated to significantly easterly deviated declinations. The directional data are rather consistent with the most recent models proposed for that area but the obtained PI indicate that models largely underestimate the paleointensities. Combined with published data obtained from western Africa, Spain, Portugal, Morocco and the Azores within a 2000 km-radius around the Canary

  6. International geomagnetic reference field 1980: a report by IAGA Division I working group.

    Science.gov (United States)

    Peddie, N.W.

    1982-01-01

    Describes the recommendations of the working group, which suggested additions to IGRF because of the cumulative effect of the inevitable uncertainties in the secular variation models which had led to unacceptable inaccuracies in the IGRF by the late 1970's. The recommendations were accepted by the International Association of Geomagnetism and Aeronomy on August 15, 1981 at the 4th Scientific Assembly, Edinburgh. An extended table sets out spherical harmonic coefficients of the IGRF 1980.-R.House

  7. New evidence of a fast secular variation of the geomagnetic field 1000 BCE: archaeomagnetic study of Bavarian potteries

    Science.gov (United States)

    Hervé, G.; Gilder, S.; Fassbinder, J.; Metzler-Nebelsick, C.; Schnepp, E.; Geisweid, L.; Putz, A.; Reuss, S.; Riedel, G.; Westhausen, I.; Wittenborn, F.

    2016-12-01

    This study presents new archaeointensity results obtained on 350 pottery sherds from 45 graves and pits from 12 sites around Munich (Germany). The features are dated between 1400 and 400 BCE by ceramic and metallic artifacts, radiocarbon and dendrochronology. We collected only red- or partly red-colored sherds in order to minimize mineralogical alteration during laboratory experiments. Rock magnetism analyses show that the remanent magnetization is mainly carried by titanomagnetite. Archaeointensities were determined using the Thellier-Thellier protocol with corrections of TRM anisotropy and cooling rate on one to three specimens per sherd. The experiments were completed using Triaxe and multispecimen (MSP-DSC) methods. Around 60 per cent of the sherds provide reliable results, allowing the computation of 35 mean archaeointensity values. This quadruples the number of previously published data in Western Europe. The secular variation of the geomagnetic field strength is low from 1400 to 1200 BCE with intensities close to 50 µT then the intensity increased to 70 µT around 1000-900 BCE. After a minimum 50 µT near 750 BCE, the intensity increased again to 90 µT at 650 BCE. This high secular variation rate (0.4 µT/year) is especially apparent in the sherds from a fountain dated between 750 and 650 BCE. Next, the intensity remained high until 400 BCE before rapidly decreasing to 200 BCE. As the sharp change in geomagnetic direction around 800 BCE is not contemporaneous with an intensity high, this period is probably not characterized by an archaeomagnetic jerk. The trend of secular variation with two intensity maxima is similar to the one observed in the Near East. The Virtual Axial Dipole Moments of the two regions are approximately the same after 700 BCE, but before they are systematically 1-2 × 1022 Am2 higher in the Near East. This difference may be a further proof of a geomagnetic field anomaly in this area 1000 BCE, yet there is no evidence for a geomagnetic

  8. Holocene records of geomagnetic field behavior from a north-south transect along the western Antarctic Peninsula

    Science.gov (United States)

    Brachfeld, S. A.; Shah, D. P.; St-Onge, M.; St-Onge, G.

    2013-12-01

    (-77°) values for each site, with a temporal wavelength of approximately 1000 years. The Holocene intensity of the geomagnetic field in this region was highest during the last 3000 years, broadly similar to patterns observed in the Northern Hemisphere. The records will be stacked in order to generate a regional reference curve for the Antarctic Peninsula. Moreover, these sites have the potential to fill a spatial gap in the distribution of paleomagnetic records that are used in geomagnetic field models.

  9. Dipolar geomagnetic field and low orbital obliquity during the last two billion years: Evidence from paleomagnetism of evaporite basins

    Science.gov (United States)

    Evans, D. A.

    2006-05-01

    Paleomagnetism of climatically sensitive sedimentary rock types, such as glacial deposits and evaporites, can test the uniformitarianism of ancient geomagnetic fields and paleoclimatic zones. Precambrian glacial deposits laid down in near-equatorial paleomagnetic latitudes indicate a paleoclimatic paradox that can be explained either by Snowball Earth episodes, or high orbital obliquity, or dramatically non-uniformitarian geomagnetic fields. Here I present the first global paleomagnetic compilation of the Earth's entire basin-scale evaporite record. Evaporation exceeds precipitation in today's subtropical desert belts, generally within a zone of 15-35° from the equator. Assuming a geocentric axial dipole (GAD) magnetic field for Cenozoic- Mesozoic time, evaporite basins of the past 250 Myr have a volume-weighted mean paleolatitude of 23±4°, also squarely within the subtropics. Carboniferous-Permian evaporites have an indistinguishable weighted-mean paleolatitude of 22±4°, which does not change significantly when recently hypothesized octupolar field components are included in the calculations. Early Paleozoic (including late Ediacaran) evaporites are lower-latitude (weighted mean 10±5°), but detailed analyses of individual examples show this cannot be attributed solely to nondipolar field components or sedimentary inclination biases; the cause may be due to particular paleogeographic effects on regional tropical climates, or incomplete sampling by the paleomagnetic data. Proterozoic (pre-Ediacaran) evaporite basins have a volume- weighted mean inclination of 33±4°, which would correspond to a mean paleolatitude of 18±3° for a pure GAD field. This latter mean is indistinguishable, within error, from the Cenozoic-Mesozoic mean and demonstrates the success of the GAD model as a first-order description of the geomagnetic field for the last two billion years. Also, general circulation climate models of a high-obliquity Earth predict either no strong zonal

  10. Intensity of the geomagnetic field in western Europe over the past 2000 years: New data from ancient French pottery

    Science.gov (United States)

    Genevey, AgnèS.; Gallet, Yves

    2002-11-01

    We studied 14 groups of French pottery fragments dated between the 4th and 16th centuries. The potsherds were analyzed using the [1959] method, revised by [1967]. Intensity values were corrected for thermoremanent magnetization (TRM) anisotropy and cooling rate dependence of TRM acquisition. We first analyzed modern ceramics produced following ancient techniques and fired in a wood-burning kiln inside of which field intensity was measured. The recovered mean intensity is within ˜3% of the expected value, which proves the reliability of our experimental procedure. Thermal experiments carried out at rapid and slow cooling rates clearly indicate that the cooling rate correction is critical in archeointensity studies. Our data indicate that large variations in intensity occurred in France over the last 2000 years. Two relative maxima in intensity are observed, one between the 8th and 10th centuries and the second between the 14th and 15th centuries. Similarities are observed between the archeointensity data from France and Ukraine, yielding some evidence for eastward drift of geomagnetic sources between western and eastern Europe from A.D. 800 to A.D. 1700. We also show that the dipole moment evolution proposed by [1982] and [2000] for the last two millennia is likely biased toward higher values, mainly because of the absence of correction for the cooling rate dependence of TRM acquisition in most published archeointensity studies. We finally underline a possible relationship, valid at least in western Europe, between changes in direction and intensity of the geomagnetic field.

  11. New archaeomagnetic direction results from China and their constraints on palaeosecular variation of the geomagnetic field in Eastern Asia

    Science.gov (United States)

    Cai, Shuhui; Tauxe, Lisa; Deng, Chenglong; Qin, Huafeng; Pan, Yongxin; Jin, Guiyun; Chen, Xuexiang; Chen, Wei; Xie, Fei; Zhu, Rixiang

    2016-11-01

    We carried out an archaeomagnetic directional study on 38 oriented samples (bricks and baked clays) collected from four archaeological locations at three provinces in China. The ages of our samples, spanning from ˜3000 BCE to ˜1300 CE, were constrained using a combination of archaeological context, radiocarbon dating and stratigraphic information. Rock magnetic results demonstrate that the main magnetic minerals of the studied samples are magnetite and/or hematite in single domain and superparamagnetic states. A total of 20 new reliable archaeodirectional data from 12 independent sites are obtained after thermal demagnetization experiments. These are the first set of archaeodirectional data in China produced since the 1990s. The published data are largely from the past 2 kyr and data from older time periods are rare. Our new data, especially those from period older than 3 ka, fill many gaps of the presently published dataset and will provide strong constraints on palaeosecular variation of the geomagnetic field in Eastern Asia and on the improvement of global models. Quite a few inflection points in the direction of the geomagnetic field are recorded in Eastern Asia over the past 10 kyr and some of them synchronize with the maximums or minimums of the palaeointensity. The palaeosecular variation rates are very low (based on present data distribution) before 2000 BCE and then start to increase and fluctuate afterward, which is generally consistent with the pattern of palaeointensity variations in this area.

  12. Low-frequency (0.7-7.4 mHz geomagnetic field fluctuations at high latitude: frequency dependence of the polarization pattern

    Directory of Open Access Journals (Sweden)

    L. Cafarella

    2001-06-01

    Full Text Available A statistical analysis of the polarization pattern of low-frequency geomagnetic field fluctuations (0.7-7.4 mHz covering the entire 24-h interval was performed at the Antarctic station Terra Nova Bay (80.0°S geomagnetic latitude throughout 1997 and 1998. The results show that the polarization pattern exhibits a frequency dependence, as can be expected from the frequency dependence of the latitude where the coupling between the magnetospheric compressional mode and the field line resonance takes place. The polarization analysis of single pulsation events shows that wave packets with different polarization sense, depending on frequency, can be simultaneously observed.

  13. Low-frequency (0.7-7.4 mHz) geomagnetic field fluctuations at high latitude. Frequency dependence of the polarization pattern

    Energy Technology Data Exchange (ETDEWEB)

    Lepidi, S.; Cafarella, L. [Istituto Nazionale di Geofisica e Vulcanologia, L' Aquila (Italy); Francia, P. [L' Aquila Univ., L' Aquila (Italy). Dipt. di Fisica

    2001-06-01

    A statistical analysis of the polarization pattern of low-frequency geomagnetic field fluctuations (0.7-7.4 m Hz) covering the entire 24-h interval was performed at the Antarctic station Terra Nova Bay (80.0{sup 0}S geomagnetic latitude) throughout 1997 and 1998. The results show that the polarization pattern exhibits a frequency dependence, as can be expected from the frequency dependence of the latitude where the coupling between the magnetospheric compressional mode and the field line resonance takes place. The polarization analysis of single pulsation events shows that wave packets with different polarization sense, depending on frequency, can be simultaneously observed.

  14. Comparison Of The Global Analytic Models Of The Main Geomagnetic Field With The Stratospheric Balloon Magnetic Data 335

    Science.gov (United States)

    Tsvetkov, Yu.; Filippov, S.; Frunze, A.

    2013-12-01

    Three global analytical models of a main geomagnetic field constructed by satellite data are used: model IGRF, Daily Mean Spherical Harmonic Models (DMSHM), and model EMM/2010, and also scalar data of geomagnetic field and its gradients, received in stratospheric balloon gradient magnetic surveys at altitudes of ~30 km. At these altitudes the regional magnetic field is formed from all sources of the Earth's crust. It enables to receive along lengthy routes of surveys the fullest data on regional and longwave-lenght magnetic anomalies. Model DMSHM is used at extracting of magnetic anomalies for elimination of a secular variation up to significant value 0,2 nT. The model can be constructed within the limits of ± 1 months from the moment stratospheric balloon surveys with beneficial day terms with magnetic activity up to Kp MFE equal ±5 нТл. It is possible at presence acting for the period of stratospheric balloon magnetic survey of the satellite, for example, Swarm. On stratospheric balloon data it is shown, that model EMM/2010 unsatisfactorily displays MFE at altitude of 30 km. Hence, the qualitative model of the constant (main and anomaly) magnetic field cannot be constructed only with use of satellite and ground data. The improved model constant MFE, constructed according to satellite and stratospheric balloon magnetic surveys, developed up to a degree and the order m=n=720, will have a reliable data about regional crust magnetic field, hence, and about deep magnetic structure of the Earth's crust. The use gradient magnetic surveys aboard stratospheric balloons allows to find the places alternating approximately through 3000 km in which there are no magnetic anomalies. In these places probably to supervise satellite magnetic models for a range of altitude of 20-40 km, timed to stratospheric balloon magnetic surveys.

  15. The paleomagnetism of single silicate crystals: Recording geomagnetic field strength during mixed polarity intervals, superchrons, and inner core growth

    Science.gov (United States)

    Tarduno, J. A.; Cottrell, R. D.; Smirnov, A. V.

    2006-03-01

    The basic features of the geomagnetic reversal chronology of the last 160 million years are well established. The relationship between this history and other features of the field, however, has been elusive. The determination of past field strength (paleointensity) is especially challenging. Commonly accepted results have come from analyses of bulk samples of lava. Historic lavas have been shown to faithfully record the past field strength when analyzed using the Thellier double-heating method. Data from older lavas, however, tend to show effects of in situ and laboratory-induced alteration. Here we review an alternative approach. Single plagioclase crystals can contain minute magnetic inclusions, 50-350 nm in size, that are potential high-fidelity field recorders. Thellier experiments using plagioclase feldspars from an historic lava on Hawaii provide a benchmark for the method. Rock magnetic data from older lavas indicate that the feldspars are less susceptible to experimental alteration than bulk samples. This resistance is likely related to the lack of clays. In addition, magnetic minerals are sheltered by the encasing silicate matrix from natural alteration that can otherwise transform the well-defined thermoremanent magnetization into an irresolute chemical remanent magnetization. If there is a relationship between geomagnetic reversal frequency and paleointensity, it should be best expressed during superchrons, intervals with few (or no) reversals. Thellier data sets based on single plagioclase crystals from lavas erupted during the Cretaceous Normal Polarity Superchron (~83-120 million years ago) suggest a strong (>12 × 1022 Am2), stable field, consistent with an inverse relationship between reversal frequency and paleointensity. Superchrons may represent times when the pattern of core-mantle boundary heat flux allows the geodynamo to operate at peak efficiency, as suggested in some numerical models. Thellier data from single plagioclase crystals formed

  16. The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory

    CERN Document Server

    Abreu, P; Ahn, E J; Albuquerque, I F M; Allard, D; Allekotte, I; Allen, J; Allison, P; Castillo, J Alvarez; Alvarez-Muñiz, J; Ambrosio, M; Aminaei, A; Anchordoqui, L; Andringa, S; Antičić, T; Anzalone, A; Aramo, C; Arganda, E; Arqueros, F; Asorey, H; Assis, P; Aublin, J; Ave, M; Avenier, M; Avila, G; Bäcker, T; Balzer, M; Barber, K B; Barbosa, A F; Bardenet, R; Barroso, S L C; Baughman, B; Bäuml, J; Beatty, J J; Becker, B R; Becker, K H; Bellétoile, A; Bellido, J A; BenZvi, S; Berat, C; Bertou, X; Biermann, P L; Billoir, P; Blanco, F; Blanco, M; Bleve, C; Blümer, H; Boháčová, M; Boncioli, D; Bonifazi, C; Bonino, R; Borodai, N; Brack, J; Brogueira, P; Brown, W C; Bruijn, R; Buchholz, P; Bueno, A; Burton, R E; Caballero-Mora, K S; Caramete, L; Caruso, R; Castellina, A; Catalano, O; Cataldi, G; Cazon, L; Cester, R; Chauvin, J; Cheng, S H; Chiavassa, A; Chinellato, J A; Chou, A; Chudoba, J; Clay, R W; Coluccia, M R; Conceição, R; Contreras, F; Cook, H; Cooper, M J; Coppens, J; Cordier, A; Coutu, S; Covault, C E; Creusot, A; Criss, A; Cronin, J; Curutiu, A; Dagoret-Campagne, S; Dallier, R; Dasso, S; Daumiller, K; Dawson, B R; de Almeida, R M; De Domenico, M; De Donato, C; de Jong, S J; De La Vega, G; Junior, W J M de Mello; Neto, J R T de Mello; De Mitri, I; de Souza, V; de Vries, K D; Decerprit, G; del Peral, L; del Río, M; Deligny, O; Dembinski, H; Dhital, N; Di Giulio, C; Diaz, J C; Castro, M L Díaz; Diep, P N; Dobrigkeit, C; Docters, W; D'Olivo, J C; Dong, P N; Dorofeev, A; Anjos, J C dos; Dova, M T; D'Urso, D; Dutan, I; Ebr, J; Engel, R; Erdmann, M; Escobar, C O; Espadanal, J; Etchegoyen, A; Luis, P Facal San; Tapia, I Fajardo; Falcke, H; Farrar, G; Fauth, A C; Fazzini, N; Ferguson, A P; Ferrero, A; Fick, B; Filevich, A; Filipčič, A; Fliescher, S; Fracchiolla, C E; Fraenkel, E D; Fröhlich, U; Fuchs, B; Gaior, R; Gamarra, R F; Gambetta, S; García, B; Gámez, D García; Garcia-Pinto, D; Gascon, A; Gemmeke, H; Gesterling, K; Ghia, P L; Giaccari, U; Giller, M; Glass, H; Gold, M S; Golup, G; Albarracin, F Gomez; Berisso, M Gómez; Gonçalves, P; Gonzalez, D; Gonzalez, J G; Gookin, B; Góra, D; Gorgi, A; Gouffon, P; Gozzini, S R; Grashorn, E; Grebe, S; Griffith, N; Grigat, M; Grillo, A F; Guardincerri, Y; Guarino, F; Guedes, G P; Guzman, A; Hague, J D; Hansen, P; Harari, D; Harmsma, S; Harton, J L; Haungs, A; Hebbeker, T; Heck, D; Herve, A E; Hojvat, C; Hollon, N; Holmes, V C; Homola, P; Hörandel, J R; Horneffer, A; Hrabovský, M; Huege, T; Insolia, A; Ionita, F; Italiano, A; Jarne, C; Jiraskova, S; Josebachuili, M; Kadija, K; Kampert, K H; Karhan, P; Kasper, P; Kégl, B; Keilhauer, B; Keivani, A; Kelley, J L; Kemp, E; Kieckhafer, R M; Klages, H O; Kleifges, M; Kleinfeller, J; Knapp, J; Koang, D -H; Kotera, K; Krohm, N; Krömer, O; Kruppke-Hansen, D; Kuehn, F; Kuempel, D; Kulbartz, J K; Kunka, N; La Rosa, G; Lachaud, C; Lautridou, P; Leão, M S A B; Lebrun, D; Lebrun, P; de Oliveira, M A Leigui; Lemiere, A; Letessier-Selvon, A; Lhenry-Yvon, I; Link, K; López, R; Agüera, A Lopez; Louedec, K; Bahilo, J Lozano; Lu, L; Lucero, A; Ludwig, M; Lyberis, H; Maccarone, M C; Macolino, C; Maldera, S; Mandat, D; Mantsch, P; Mariazzi, A G; Marin, J; Marin, V; Maris, I C; Falcon, H R Marquez; Marsella, G; Martello, D; Martin, L; Martinez, H; Bravo, O Martínez; Mathes, H J; Matthews, J; Matthews, J A J; Matthiae, G; Maurizio, D; Mazur, P O; Medina-Tanco, G; Melissas, M; Melo, D; Menichetti, E; Menshikov, A; Mertsch, P; Meurer, C; Mićanović, S; Micheletti, M I; Miller, W; Miramonti, L; Molina-Bueno, L; Mollerach, S; Monasor, M; Ragaigne, D Monnier; Montanet, F; Morales, B; Morello, C; Moreno, E; Moreno, J C; Morris, C; Mostafá, M; Moura, C A; Mueller, S; Muller, M A; Müller, G; Münchmeyer, M; Mussa, R; Navarra, G; Navarro, J L; Navas, S; Necesal, P; Nellen, L; Nelles, A; Neuser, J; Nhung, P T; Niemietz, L; Nierstenhoefer, N; Nitz, D; Nosek, D; Nožka, L; Nyklicek, M; Oehlschläger, J; Olinto, A; Oliva, P; Olmos-Gilbaja, V M; Ortiz, M; Pacheco, N; Selmi-Dei, D Pakk; Palatka, M; Pallotta, J; Palmieri, N; Parente, G; Parizot, E; Parra, A; Parsons, R D; Pastor, S; Paul, T; Pech, M; Pȩkala, J; Pelayo, R; Pepe, I M; Perrone, L; Pesce, R; Petermann, E; Petrera, S; Petrinca, P; Petrolini, A; Petrov, Y; Petrovic, J; Pfendner, C; Phan, N; Piegaia, R; Pierog, T; Pieroni, P; Pimenta, M; Pirronello, V; Platino, M; Ponce, V H; Pontz, M; Privitera, P; Prouza, M; Quel, E J; Querchfeld, S; Rautenberg, J; Ravel, O; Ravignani, D; Revenu, B; Ridky, J; Riggi, S; Risse, M; Ristori, P; Rivera, H; Rizi, V; Roberts, J; Robledo, C; de Carvalho, W Rodrigues; Rodriguez, G; Martino, J Rodriguez; Rojo, J Rodriguez; Rodriguez-Cabo, I; Rodríguez-Frías, M D; Ros, G; Rosado, J; Rossler, T; Roth, M; Rouillé-d'Orfeuil, B; Roulet, E; Rovero, A C; Rühle, C; Salamida, F; Salazar, H; Salina, G; Sánchez, F; Santo, C E; Santos, E; Santos, E M; Sarazin, F; Sarkar, B; Sarkar, S; Sato, R; Scharf, N; Scherini, V; Schieler, H; Schiffer, P; Schmidt, A; Schmidt, F; Scholten, O; Schoorlemmer, H; Schovancova, J; Schovánek, P; Schröder, F; Schulte, S; Schuster, D; Sciutto, S J; Scuderi, M; Segreto, A; Settimo, M; Shadkam, A; Shellard, R C; Sidelnik, I; Sigl, G; Lopez, H H Silva; Śmiałkowski, A; Šmída, R; Snow, G R; Sommers, P; Sorokin, J; Spinka, H; Squartini, R; Stanic, S; Stapleton, J; Stasielak, J; Stephan, M; Strazzeri, E; Stutz, A; Suarez, F; Suomijärvi, T; Supanitsky, A D; Šuša, T; Sutherland, M S; Swain, J; Szadkowski, Z; Szuba, M; Tamashiro, A; Tapia, A; Tartare, M; Taşcău, O; Ruiz, C G Tavera; Tcaciuc, R; Tegolo, D; Thao, N T; Thomas, D; Tiffenberg, J; Timmermans, C; Tiwari, D K; Tkaczyk, W; Peixoto, C J Todero; Tomé, B; Tonachini, A; Travnicek, P; Tridapalli, D B; Tristram, G; Trovato, E; Tueros, M; Ulrich, R; Unger, M; Urban, M; Galicia, J F Valdés; Valiño, I; Valore, L; Berg, A M van den; Varela, E; Cárdenas, B Vargas; Vázquez, J R; Vázquez, R A; Veberič, D; Verzi, V; Vicha, J; Videla, M; Villaseñor, L; Wahlberg, H; Wahrlich, P; Wainberg, O; Walz, D; Warner, D; Watson, A A; Weber, M; Weidenhaupt, K; Weindl, A; Westerhoff, S; Whelan, B J; Wieczorek, G; Wiencke, L; Wilczyńska, B; Wilczyński, H; Will, M; Williams, C; Winchen, T; Winnick, M G; Wommer, M; Wundheiler, B; Yamamoto, T; Yapici, T; Younk, P; Yuan, G; Yushkov, A; Zamorano, B; Zas, E; Zavrtanik, D; Zavrtanik, M; Zaw, I; Zepeda, A; Silva, M Zimbres; Ziolkowski, M

    2011-01-01

    We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than $60^\\circ$, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the ~2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for.

  17. Evaluation of the Applicability of the Chapman-Miller Method on Variation of the Geomagnetic Total Intensity Field in Taiwan from 1988 to 2007

    Directory of Open Access Journals (Sweden)

    Chieh-Hung Chen

    2009-01-01

    Full Text Available The solar (S and lunar (L variations of geomagnetic fields at the horizontal (H, declination (D, and the downward vertical component data (Z are modeled by the Chap man-Miller method with four order harmonics. In this paper, we compare S and L variations of the geomagnetic total intensity field using a consistent method with 3-component data for seasonal variations (summer, winter, and equinox for three distinct phases during the years 1988 - 2007. The results show that consistency in the S and L variations for geomagnetic total intensity indicates normal stations and discrepancies are occurred due to data quality. In application, consistent results also prove that the function of the magnetometers at TW was normal and that large anomalies were certainly in existence during the Chia-Yi earthquake.

  18. The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory

    Science.gov (United States)

    Pierre Auger Collaboration; Abreu, P.; Aglietta, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antičić, T.; Anzalone, A.; Aramo, C.; Arganda, E.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Bäcker, T.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Bäuml, J.; Beatty, J. J.; Becker, B. R.; Becker, K. H.; Bellétoile, A.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brogueira, P.; Brown, W. C.; Bruijn, R.; Buchholz, P.; Bueno, A.; Burton, R. E.; Caballero-Mora, K. S.; Caramete, L.; Caruso, R.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chudoba, J.; Clay, R. W.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; Decerprit, G.; del Peral, L.; del Río, M.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Fajardo Tapia, I.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Ferrero, A.; Fick, B.; Filevich, A.; Filipčič, A.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Fröhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; García, B.; García Gámez, D.; Garcia-Pinto, D.; Gascon, A.; Gemmeke, H.; Gesterling, K.; Ghia, P. L.; Giaccari, U.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gonçalves, P.; Gonzalez, D.; Gonzalez, J. G.; Gookin, B.; Góra, D.; Gorgi, A.; Gouffon, P.; Gozzini, S. R.; Grashorn, E.; Grebe, S.; Griffith, N.; Grigat, M.; Grillo, A. F.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Guzman, A.; Hague, J. D.; Hansen, P.; Harari, D.; Harmsma, S.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hojvat, C.; Hollon, N.; Holmes, V. C.; Homola, P.; Hörandel, J. R.; Horneffer, A.; Horvath, P.; Hrabovský, M.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jarne, C.; Jiraskova, S.; Josebachuili, M.; Kadija, K.; Kampert, K. H.; Karhan, P.; Kasper, P.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kelley, J. L.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Koang, D.-H.; Kotera, K.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuehn, F.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; Lautridou, P.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Lemiere, A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, J.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Mertsch, P.; Meurer, C.; Mićanović, S.; Micheletti, M. I.; Miller, W.; Miramonti, L.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Morris, C.; Mostafá, M.; Moura, C. A.; Mueller, S.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nhung, P. T.; Niemietz, L.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Nyklicek, M.; Oehlschläger, J.; Olinto, A.; Oliva, P.; Olmos-Gilbaja, V. M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Parsons, R. D.; Pastor, S.; Paul, T.; Pech, M.; Pękala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrinca, P.; Petrolini, A.; Petrov, Y.; Petrovic, J.; Pfendner, C.; Phan, N.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Ponce, V. H.; Pontz, M.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rivera, H.; Rizi, V.; Roberts, J.; Robledo, C.; Rodrigues de Carvalho, W.; Rodriguez, G.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodriguez-Cabo, I.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Rouillé-d'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Rühle, C.; Salamida, F.; Salazar, H.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarkar, S.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Schmidt, F.; Scholten, O.; Schoorlemmer, H.; Schovancova, J.; Schovánek, P.; Schröder, F.; Schulte, S.; Schuster, D.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Silva Lopez, H. H.; Śacute; Smiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Stanic, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Strazzeri, E.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Šuša, T.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Tamashiro, A.; Tapia, A.; Tartare, M.; Taşąu, O.; Tavera Ruiz, C. G.; Tcaciuc, R.; Tegolo, D.; Thao, N. T.; Thomas, D.; Tiffenberg, J.; Timmermans, C.; Tiwari, D. K.; Tkaczyk, W.; Todero Peixoto, C. J.; Tomé, B.; Tonachini, A.; Travnicek, P.; Tridapalli, D. B.; Tristram, G.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van den Berg, A. M.; Varela, E.; Vargas Cárdenas, B.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Wahlberg, H.; Wahrlich, P.; Wainberg, O.; Walz, D.; Warner, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Westerhoff, S.; Whelan, B. J.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Winnick, M. G.; Wommer, M.; Wundheiler, B.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zimbres Silva, M.; Ziolkowski, M.

    2011-11-01

    We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than 60°, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the ~ 2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for.

  19. Effect of long-term geomagnetic field deprivation on the concentration of some elements in the hair of laboratory rats.

    Science.gov (United States)

    Tombarkiewicz, Barbara

    2008-07-01

    The aim of the study was to determine the effect of long-term geomagnetic field (GMF) deprivation on the concentration of selected elements in the hair of laboratory rats. A total of 32 Wistar laboratory rats were divided into four equal groups (males and females) kept under hypomagnetic conditions (GMF vertical component below 20nT) and two control groups (males and females) kept free of field disturbances (GMF vertical component approx. 38000nT). At the beginning and at 7 months of the experiment, hair was taken from the dorsal part of all rats and analysed using atomic emission spectrometry for the concentration of selected magnetic elements (Fe, Ni, Co, Cr, Mn and Cu). Long-term GMF deprivation was found to affect the concentration of Fe, Mn, Cu and Cr, but had no significant effect on the concentration of Co or Ni in the hair of the analysed rats.

  20. Relative paleointensity of the geomagnetic field during the past 0.8 Ma from Nihewan Basin, Hebei Province, China

    Institute of Scientific and Technical Information of China (English)

    WANG Yong; CHI Zhenqing; LEE Tehquei; MIN Longrui; CHU Huiyan

    2004-01-01

    We conducted a detailed rock magnetic study on upper 80 m of Jing'erwa core from the Nihewan basin. The results indicate that the sediments from Jing'erwa core are suitable for relative paleointensity study, and anhysteretic remanent magnetization (ARM) can be used as the normalization parameter of the natural remanent magnetization (NRM). Our relative paleointensity data of upper 80 m of Jing'erwa core provide a continuous record of the intensity variation during the last 0.8 Ma, which correlates well with the results from marine sediments cores in the Pacific Ocean. This means that the sediments records are reliable for relative paleointensity of Earth's magnetic field, and suggests that these sediments have recorded the real changes of geomagnetic field, which would provide a new method for regional stratigraphic correlation.

  1. Geomagnetic field variations in Western Europe from 1500 BC to 200 AD. Part II: New intensity secular variation curve

    Science.gov (United States)

    Hervé, Gwenaël; Chauvin, Annick; Lanos, Philippe

    2013-05-01

    In order to extend the secular variation curve (SVC) of archaeointensity in Western Europe to the first millennium BC, we studied 24 kilns and hearths in place, two displaced hearths and six sets of pottery sherds from French archaeological sites. Archaeological artefacts, radiocarbon and dendrochronology dated the acquisition of the thermoremanent magnetization (TRM) carried by the studied objects. Rock magnetism experiments suggest that the main carrier of the magnetization is a Ti-poor titanomagnetite. Archaeointensity was determined by the Thellier-Thellier classical protocol with pTRM-checks. A strict criteria set was applied to select only the most reliable results with linear NRM-TRM diagrams (55% of total specimens). This study demonstrates that pottery sherds with two TRMs give reliable archaeointensities in the low-temperature interval, if the NRM-TRM diagram is adequately adjusted. Eighteen new mean archaeointensities (14 corrected from the anisotropy of TRM and 16 from cooling rate) were computed. The comparison with previously published Western Europe paleointensities show a strong dispersion between data primarily due to their variable quality. Western Europe data were weighted following the archaeointensity protocol, the number of specimens per site and the type of studied materials, in order to better highlight the secular variation of archaeointensity during the first millennium BC. The SVC, built with sliding windows of 160 years shifted every 50 years, presents (at Paris) a maximum of 90 μT around 800 BC and a minimum of 60 μT around 250 BC. These archaeointensity maximum and minimum correspond to cusps of the geomagnetic field direction in Western Europe. This new curve is consistent with Mesopotamian and Eastern Europe data. The archaeointensity secular variation in Western Europe predicted by global geomagnetic models CALS3k.4, ARCH3k.1 and ARCH3k_cst.1 is smoother than our SVC. We used our directional dataset (Hervé et al., 2013) to build

  2. Geomagnetic Observations and Models

    CERN Document Server

    Mandea, Mioara

    2011-01-01

    This volume provides comprehensive and authoritative coverage of all the main areas linked to geomagnetic field observation, from instrumentation to methodology, on ground or near-Earth. Efforts are also focused on a 21st century e-Science approach to open access to all geomagnetic data, but also to the data preservation, data discovery, data rescue, and capacity building. Finally, modeling magnetic fields with different internal origins, with their variation in space and time, is an attempt to draw together into one place the traditional work in producing models as IGRF or describing the magn

  3. A directional Secular Variation Curve for Greece for the last 4500 years: Comparison with regional and global geomagnetic field models

    Science.gov (United States)

    de Marco, E.; Tema, E.; Lanos, P.; Kondopoulou, D.

    2009-12-01

    A total of 64 Greek archaeomagnetic directional data have been used for the establishment of the variation of the Earth’s magnetic field in Greece over the past 4500 years. Most of the data come from archaeological material but some data from Santorini lava flows are also included. The data ages range from Minoan times (~2500 BC) up to the last century with a gap around 10th to 6th century BC. All data have been relocated to Athens (37.97° N, 23.72° E) using the virtual geomagnetic pole method. Data coming from direct measurements available in Greece for the last four centuries have been also added. The secular variation (SV) curves for declination and inclination have been obtained using hierarchical Bayesian modelling. For comparison, the dataset has been also analysed using the bi-variate moving average window technique with 150 years time window shifted by 75 years. The obtained smoothed curves accompanied by a 95 % confidence envelope are compared with archaeomagnetic data from Mediterranean area and with SV curves from nearby countries. The Greek curves have also been compared with the predictions of the SCHA.DIF.3K regional and the CALS7K and ARCH3K global geomagnetic field models. Despite the differences recognised between these models, the Greek archaeomagnetic SV curve is in reasonably good agreement with their basic trends. The proposed directional SV curve can contribute, together with the intensity SV curve previously published for Greece, to the reliable archaeomagnetic dating of Greek artefacts based on the full description of the Earth’s magnetic field (declination, inclination, intensity). It is clear that the continuous update of the dataset with new results from well-dated archaeological material will increase the precision of the SV curve, especially for the time periods poorly covered by data.

  4. [Reaction of circadian rhythms of the lymphoid system to deep screening from geomagnetic fields of the earth].

    Science.gov (United States)

    Borodin, Iu I; Letiagin, A Y

    1990-02-01

    C57B1/6 inbred mice were placed in hypomagnetic condition during 14 days constantly. Degree of relaxation of geomagnetic field was 10(4). The increase of the number of eosinophil granulocytes was discovered in peripheral blood of mice. Measures of circadian rhythms of blood's absolute lymphocytosis, absolute number of cells in bone marrow, thymus, spleen and inguinal lymph nodes were safe. Adaptation of lymphoid system to hypomagnetic condition was manifested by desynchronization of circadian rhythmicity on the basis of different sensitivity of lymphoid organs, that realized in strengthening of ultradian rhythms with periods of 15 hours. There are indirect data, that show the increase of speed and/or volume of recirculation of lymphoid cells.

  5. The Geomagnetic Field Recorded in Sediments of the Tuzla Section (the Krasnodar Territory, Russia) over the Time Interval 120-70 ka

    DEFF Research Database (Denmark)

    Pilipenko, Olga; Abrahamsen, N.; Trubikhin, V. M.

    2007-01-01

    of the variation in the geomagnetic field inclination reveal an anomalous direction dated at ~110 ka which coincides with a similar anomalous direction in the Eltigen section (Ukraine) correlating with the Blake paleomagnetic event. The significant correlation between the time series NRM0.015/SIRM0.015 (Tuzla...

  6. Geomagnetic field variations in Western Europe from 1500BC to 200AD. Part I: Directional secular variation curve

    Science.gov (United States)

    Hervé, Gwenaël; Chauvin, Annick; Lanos, Philippe

    2013-05-01

    To improve the geomagnetic field secular variation curve (SVC) of Western Europe during protohistoric times, archaeomagnetic directions of 39 archaeological kilns or hearths from France were investigated. The dating of each archaeological structure was established with archaeological or chronometric methods. Thirty-seven of these structures are dated from the first millennium BC, one from the end of the second millennium BC and the last one from the fourth millennium BC. Thermomagnetic curves, unblocking temperatures and coercivities suggest that the main carrier of the remanent magnetization is a Ti-poor titanomagnetite. Archaeodirections were obtained by alternating field and thermal demagnetizations on almost 900 specimens. The anisotropy tensor of thermoremanent magnetization was determined for 35 structures and 22 mean archaeodirections were corrected for anisotropy. The new archaeodirections are very consistent with previously published data. A new directional SVC was built using bivariate statistics with selected Western Europe data located within 1000 km of Paris. Selection criteria include the number of samples, the dating reliability and the accuracy of the mean archaeodirection. Resulting secular variation between 1500BC and 0AD mainly shows large changes in declination, while inclinations are bracketed between ˜65° and ˜75°. The declinations show a strong maximum with values ˜30-35° around 800-750BC, followed by a sharp decrease to values around 0° at 500BC and close to -7° around 250BC. The main features of the secular variation from 1500BC to 0AD appear to be a dominant westward drift and two major changes around 800 and 250BC. Compared to the global and regional geomagnetic models, the new reference data are better fitted by ARCH3k_cst.1 and SCHA.DIF.3k than by ARCH3k.1 and CALS3k.4 models. The strong variation of the archaeodirection between 1000 and 500BC makes archaeomagnetism very useful for dating purposes.

  7. NOAA/NGDC candidate models for the 11th generation International Geomagnetic Reference Field and the concurrent release of the 6th generation POMME magnetic model

    OpenAIRE

    2010-01-01

    The International Geomagnetic Reference Field (IGRF) is updated every five years based on candidate model submissions by research institutions worldwide. In the call for the 11th generation of IGRF, candidates were requested for the definitive main field in 2005, the predicted main field in 2010, and the predicted secular variation from 2010 to 2015. The NOAA/NGDC candidate models for IGRF-11 were produced from parent models parameterized in the same way as the 6th generation of our Pomme mag...

  8. Geomagnetic field intensity in the eastern Mediterranean region in the second half of the 1st millennium BC and the beginning of our era

    Science.gov (United States)

    Nachasova, I. E.; Burakov, K. S.; Il'Ina, T. A.

    2007-12-01

    The magnetization of ceramic material manufactured in the eastern Mediterranean is studied. Data on the variation in geomagnetic field intensity in the time interval from the fourth-quarter of the 6th century BC through the 2nd century AD are obtained. The main tendency of the variation in the field intensity until approximately the middle of this interval is its decrease, after which the average intensity level varied insignificantly over the three next centuries. Variations with characteristic times of a few tens to a few hundreds of years are superimposed on the smooth variation in the field intensity approximated by a sinusoid with a period of 1600 yr. The data obtained in this work confirm the previously derived conclusion that short-term intensity variations have been permanently present in the geomagnetic field in the recent millennia.

  9. Paleosecular variations of geomagnetic field from the Last Glacial Maximum to the Holocene in the north of South China Sea

    Science.gov (United States)

    Yang, X.; Huang, W.; Liu, Q.

    2012-12-01

    The high-resolution geomagnetic field records from the Last Glacial Maximum to the Holocene, which possessed of a notable climate change, were scarce in the global area. In this abstract, two gravity piston cores ZSQD2 (114.16oE, 19.58oN, ~190 cm in length, water depth 681m) and ZSQD34 (114.74oE, 19.05oN, ~184 cm in length, water depth 1820 m), situated in the north of South China Sea, were selected to study the secular variations of geomagnetic field in this area. Radiocarbon ages of G.sacculifer suggest that the deposition rate varied with 56.1 cm/kyr and 3.7 cm/kyr during the Last Glacial and the Holocene, respectively. Rock magnetic results indicate that the pseudo-single domain magnetite with low coercivity dominate the properties of sediments. The characteristic remanent magnetization (ChRM) values are evaluated using the 5-8 AF steps when MAD values are generally <5. Constrained by the radiocarbon chronology, the secular variation curves since ~18 cal. kyr can be constructed using the ChRM directions and NRM/ARM ratios (as a proxy of relative intensity). Comparing the Holocene SV with that from terrestrial lakes in Southern China, similar shape corroborates the reliability of records and uniform pattern of non-dipole magnetic field. Two significant features on SV curves present the geomagnetic field characteristics from ~17 cal. kyr to the early Holocene. One is that the direction variations lag behind the relative intensity on the millennium time scale. Such as a major direction shift occurred around 13 cal. kyr while the relative intensity low was about 14 cal. kyr. Another feature is the fast and frequent wiggles both in direction and intensity between ~17 to ~14.5 cal. kyr. During this period, two significant negative inclination anomalies occurred at ~16.4 and ~15.4 cal. kyr associated with low intensity, respectively. Nevertheless, the corresponding declinations did not show the reversed features although they had also some slight fluctuations. The

  10. Variations in the geomagnetic field strength in the 5th 3rd centuries BC in the eastern Mediterranean (according to narrowly dated ceramics)

    Science.gov (United States)

    Nachasova, I. E.; Burakov, K. S.; Il'Ina, T. A.

    2008-06-01

    The magnetization of ceramics from the eastern Mediterranean dated within a short period (mostly shorter than ±20 years) has been studied, which made it possible to specify the geomagnetic field variations on the time interval 5th 3rd centuries BC. The 11-year time series of the geomagnetic field strength values has been constructed. The field strength changes have been considered, which indicated that the centennial variation with a characteristic time of ˜130 years (according to the obtained data) is observed on this time interval as well as during the last two millennia. The ceramic material from the Mayskaya Gora archeological site (Taman), the preparation succession of which was established based on the shape of pottery but the problem of absolute dating was not solved, has been dated.

  11. Early Oligocene geomagnetic field behavior from ODP Site 1128: Complex records of short-period polarity events

    Science.gov (United States)

    Molina-Garza, R. S.; Fuller, M. D.

    2001-12-01

    At Site 1128, in the Great Australian Bight, Leg 182 of the Ocean Drilling Program recovered a thick (~350 m) section of Upper Eocene and Lower Oligocene marine calcareous clays. Shipboard measurements established a magnetostratigraphy that can unambiguously be correlated to chrons C13n to C10n of the global polarity time scale (GPTS), and a less complete record of chrons C17n to C15r (due to poor core recovery). Correlation to the GPTS is further supported by available biostratigraphic data. For the Lower Oligocene sequence, average sedimentation rate is estimated at ~4 cm/kyr. The sediments recovered thus allow to test for the completeness and reliability of the geomagnetic field polarity during the Early Oligocene. The original shipboard long-core measurements suggested the presence of additional short polarity events or geomagnetic field excursions during chrons C13n, C12r, C11r, and C11n. In order to examine the reliability of the record and the nature of possible short-polarity events, we obtained discrete samples from the entire sequence at ~1 m intervals, with a closer sample spacing in critical intervals (~10 cm). The natural remanence of these sediments is normally simple. After removing a small soft overprint, the magnetization decays towards the origin with distributed coercivities and distributed unblocking temperatures. Demagnetization behavior and other rock magnetic data indicate that the remanence resides primarily in a cubic phase such as magnetite or maghemite, with a small contribution from hematite. Discrete samples from chron C12r did not reproduce the long-core record for two of the supposed events, single samples suggest the presence of short events or cryptochrons near the base of both C13n and C12r, and multiple samples suggest the existence of short-period normal polarity events during C11r and near the top of C12r. The records of these events are, however, complex. Demagnetization results indicate that the magnetization consists of an

  12. The origin of polarity asymmetries in the history of the geomagnetic field

    Science.gov (United States)

    Levy, E. H.

    1987-01-01

    The behavior of magnetohydrodynamic stationary modes in the presence of an imposed weak magnetic field originating separately from the dynamo is studied. A rare class of stationary states is found that exhibit high sensitivity to the presence of weak imposed fields. The amplitude of the difference between the total fields of opposite polarity is much larger than the amplitude of the imposed nondynamo fields. It is proposed that Earth's magnetic field operates in such a mode, highly sensitive to the presence of an ambient field. An argument is given to explain why the terrestrial dynamo should choose to operate in one of these rare states. Implications are discussed for the general mechanism of dynamo magnetic field equilibrium in planets.

  13. Archaeointensity results spanning the past 6 kiloyears from eastern China and implications for extreme behaviors of the geomagnetic field

    Science.gov (United States)

    Cai, Shuhui; Jin, Guiyun; Tauxe, Lisa; Deng, Chenglong; Qin, Huafeng; Pan, Yongxin; Zhu, Rixiang

    2017-01-01

    Variations of the Earth’s geomagnetic field during the Holocene are important for understanding centennial to millennial-scale processes of the Earth’s deep interior and have enormous potential implications for chronological correlations (e.g., comparisons between different sedimentary recording sequences, archaeomagnetic dating). Here, we present 21 robust archaeointensity data points from eastern China spanning the past ˜6 kyr. These results add significantly to the published data both regionally and globally. Taking together, we establish an archaeointensity reference curve for Eastern Asia, which can be used for archaeomagnetic dating in this region. Virtual axial dipole moments (VADMs) of the data range from a Holocene-wide low of ˜27 to “spike” values of ˜166 ZAm2 (Z: 1021). The results, in conjunction with our recently published data, confirm the existence of a decrease in paleointensity (DIP) in China around ˜2200 BCE. These low intensities are the lowest ever found for the Holocene and have not been reported outside of China. We also report a spike intensity of 165.8 ± 6.0 ZAm2 at ˜1300 BCE (±300 y), which is either a prelude to or the same event (within age uncertainties) as spikes first reported in the Levant.

  14. Relative paleointensity of the geomagnetic field during the past 200 ka from the West Philippine Sea and its chronological significance

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Our rock magnetic analysis of core Ph05 from the West Philippine Sea demonstrates that the core preserves a strong, stable remanent magnetization and meets the magnetic mineral criteria for relative paleointensity (RPI) analyses. The magnetic minerals in the sequence are dominated by pseudosingle-domain magnetite, and the concentration of magnetic minerals is at the same scale. Both the conventional normalizing method and the pseudo-Thellier method were used in conjunction with the examination of the rock magnetic properties and natural remanent magnetization. Susceptibility (χ), anhysteretic remnant magnetization (ARM) and saturation isothermal remnant magnetization (SIRM) were used as the natural remanent magnetization normalizer. However, coherence analysis indicated that only ARM is more suitable for paleointensity reconstruction. The age model of core is established based on oxygen isotope data and AMS14C data, which is consistent with the age model estimated from RPI records. The relative paleointensity data provide a continuous record of the intensity variation during the last 200 ka, which correlates well with the global references RPI stacks. Several prominent low paleointensity values are identified and are correlated to the main RPI minima in the SINT-200 record, suggesting that the sediments have recorded the real changes of geomagnetic field.

  15. Relative paleointensity of the geomagnetic field during the past 200 ka from the West Philippine Sea and its chronological significance

    Institute of Scientific and Technical Information of China (English)

    MENG QingYong; LI AnChun; LI TieGang; JIANG FuOing; ZHOU XiaoJing

    2009-01-01

    Our rock magnetic analysis of core Ph05 from the West Philippine Sea demonstrates that the core preserves a strong, stable remanent magnetization and meets the magnetic mineral criteria for relative paleointensity (RPI) analyses. The magnetic minerals in the sequence are dominated by pseudosingle-domain magnetite, and the concentration of magnetic minerals is at the same scale. Both the conventional normalizing method and the pseudo.Thellier method were used in conjunction with the examination of the rock magnetic properties and natural remanent magnetization. Susceptibility (X), anhysteretic remnant magnetization (ARM) and saturation isothermal remnant magnetization (SIRM) were used as the natural remanent magnetization normalizer. However, coherence analysis indicated that only ARM is more suitable for paleointensity reconstruction. The age model of core is established based on oxygen isotope data and AMS14C data, which is consistent with the age model estimated from RPI records. The relative paleointensity data provide a continuous record of the intensity variation during the last 200 ka, which correlates well with the global references RPI stacks. Several prominent low paleointensity values are identified and are correlated to the main RPI minima in the SINT-200 record, suggesting that the sediments have recorded the real changes of geomagnetic field.

  16. Challenges Handling Magnetospheric and Ionospheric Signals in Internal Geomagnetic Field Modelling

    Science.gov (United States)

    Finlay, C. C.; Lesur, V.; Thébault, E.; Vervelidou, F.; Morschhauser, A.; Shore, R.

    2016-09-01

    Measurements of the Earth's magnetic field collected by low-Earth-orbit satellites such as Swarm and CHAMP, as well as at ground observatories, are dominated by sources in the Earth's interior. However these measurements also contain significant contributions from more rapidly-varying current systems in the ionosphere and magnetosphere. In order to fully exploit magnetic data to probe the physical properties and dynamics of the Earth's interior, field models with suitable treatments of external sources, and their associated induced signals, are essential. Here we review the methods presently used to construct models of the internal field, focusing on techniques to handle magnetospheric and ionospheric signals. Shortcomings of these techniques often limit the quality, as well as spatial and temporal resolution, of internal field models. We document difficulties in using track-by-track analysis to characterize magnetospheric field fluctuations, differences in internal field models that result from alternative treatments of the quiet-time ionospheric field, and challenges associated with rapidly changing, but spatially correlated, magnetic signatures of polar cap current systems. Possible strategies for improving internal field models are discussed, many of which are described in more detail elsewhere in this volume.

  17. On polar daily geomagnetic variation

    Directory of Open Access Journals (Sweden)

    Paola De Michelis

    2015-11-01

    Full Text Available The aim of this work is to investigate the nature of the daily magnetic field perturbations produced by ionospheric and magnetospheric currents at high latitudes. We analyse the hourly means of the X and Y geomagnetic field components recorded by a meridian chain of permanent geomagnetic observatories in the polar region of the Northern Hemisphere during a period of four years (1995-1998 around the solar minimum. We apply a mathematical method, known as natural orthogonal component (NOC, which is capable of characterizing the dominant modes of the geomagnetic field daily variability through a set of empirical orthogonal functions (EOFs. Using the first two modes we reconstruct a two-dimensional equivalent current representation of the ionospheric electric currents, which contribute substantially to the geomagnetic daily variations. The obtained current structures resemble the equivalent current patterns of DP2 and DP1. We characterize these currents by studying their evolution with the geomagnetic activity level and by analysing their dependence on the interplanetary magnetic field. The obtained results support the idea of a coexistence of two main processes during all analysed period although one of them, the directly driven process, represents the dominant component of the geomagnetic daily variation.

  18. Challenges Handling Magnetospheric and Ionospheric Signals in Internal Geomagnetic Field Modelling

    DEFF Research Database (Denmark)

    Finlay, Chris; Lesur, V.; Thébault, E.;

    2016-01-01

    -by-track analysis to characterize magnetospheric field fluctuations, differences in internal field models that result from alternative treatments of the quiet-time ionospheric field, and challenges associated with rapidly changing, but spatially correlated, magnetic signatures of polar cap current systems. Possible......Measurements of the Earth’s magnetic field collected by low-Earth-orbit satellites such as Swarm and CHAMP, as well as at ground observatories, are dominated by sources in the Earth’s interior. However these measurements also contain significant contributions from more rapidly-varying current...... systems in the ionosphere and magnetosphere. In order to fully exploit magnetic data to probe the physical properties and dynamics of the Earth’s interior, field models with suitable treatments of external sources, and their associated induced signals, are essential. Here we review the methods presently...

  19. Adiabatic Hamiltonian of charged particle motion in a dipole field. [geomagnetic trapping

    Science.gov (United States)

    Chen, A. J.; Stern, D. P.

    1975-01-01

    The Hamiltonian for a dipole field is developed, and the result is expressed by an analytic approximation accurate to within about 1%. This allows extension of results derived for equatorial particles to particles with arbitrary pitch angles; in particular, it makes available even in the presence of electric fields orthogonal to the magnetic field a function K that is preserved by the bounce-averaged motion. This function provides at once the equations of drift paths in (alpha, beta) or of their projections onto the equatorial plane; the derivation of a pacing function that times the progress of particles along such drift paths is also described.

  20. NGDC/GFZ candidate models for the 10th generation International Geomagnetic Reference Field

    OpenAIRE

    2005-01-01

    Following the call for candidates for the 10th generation IGRF, we produced and submitted three main field and three secular variation candidate models. The candidates are derived from parent models which use a standard quadratic parameterisation in time of the internal Gauss coefficients. External magnetospheric fields are represented by combined parameterisations in Solar Magnetic (SM) and in Geocentric Solar Magnetospheric (GSM) coordinates. Apart from the daily and annual variations cause...

  1. Role of the Hermanus Magnetic Observatory in geomagnetic-field research

    CSIR Research Space (South Africa)

    Sutcliffe, PR

    1995-08-01

    Full Text Available of AlfvSn waves in a cold, collisionless, magnetized plasma. A simple plasma model consisting only of H +, the concentration of which is assumed to vary along a field line according to the inverse power of the radial... plasma mass den- sity on that field line relative to the others and that oxygen ions play a significant role. Factors which may have contributed to the lower plasma mass density are the lower rate of production of O...

  2. Structural and temporal requirements for geomagnetic field reversal deduced from lava flows.

    Science.gov (United States)

    Singer, Brad S; Hoffman, Kenneth A; Coe, Robert S; Brown, Laurie L; Jicha, Brian R; Pringle, Malcolm S; Chauvin, Annick

    2005-03-31

    Reversals of the Earth's magnetic field reflect changes in the geodynamo--flow within the outer core--that generates the field. Constraining core processes or mantle properties that induce or modulate reversals requires knowing the timing and morphology of field changes that precede and accompany these reversals. But the short duration of transitional field states and fragmentary nature of even the best palaeomagnetic records make it difficult to provide a timeline for the reversal process. 40Ar/39Ar dating of lavas on Tahiti, long thought to record the primary part of the most recent 'Matuyama-Brunhes' reversal, gives an age of 795 +/- 7 kyr, indistinguishable from that of lavas in Chile and La Palma that record a transition in the Earth's magnetic field, but older than the accepted age for the reversal. Only the 'transitional' lavas on Maui and one from La Palma (dated at 776 +/- 2 kyr), agree with the astronomical age for the reversal. Here we propose that the older lavas record the onset of a geodynamo process, which only on occasion would result in polarity change. This initial instability, associated with the first of two decreases in field intensity, began approximately 18 kyr before the actual polarity switch. These data support the claim that complete reversals require a significant period for magnetic flux to escape from the solid inner core and sufficiently weaken its stabilizing effect.

  3. The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Abreu, P.; /Lisbon, IST; Aglietta, M.; /IFSI, Turin; Ahn, E.J.; /Fermilab; Albuquerque, I.F.M.; /Sao Paulo U.; Allard, D.; /APC, Paris; Allekotte, I.; /Centro Atomico Bariloche; Allen, J.; /New York U.; Allison, P.; /Ohio State U.; Alvarez Castillo, J.; /Mexico U., ICN; Alvarez-Muniz, J.; /Santiago de Compostela U.; Ambrosio, M.; /Naples U. /INFN, Naples /Nijmegen U., IMAPP

    2011-11-01

    We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than 60{sup o}, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the {approx} 2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for. In this work, we have identified and quantified a systematic uncertainty affecting the energy determination of cosmic rays detected by the surface detector array of the Pierre Auger Observatory. This systematic uncertainty, induced by the influence of the geomagnetic field on the shower development, has a strength which depends on both the zenith and the azimuthal angles. Consequently, we have shown that it induces distortions of the estimated cosmic ray event rate at a given energy at the percent level in both the azimuthal and the declination distributions, the latter of which mimics an almost dipolar pattern. We have also shown that the induced distortions are already at the level of the statistical uncertainties for a number of events N {approx_equal} 32 000 (we note that the full Auger surface detector array collects about 6500 events per year with energies above 3 EeV). Accounting for these effects is thus essential with regard to the correct interpretation of large scale anisotropy measurements taking explicitly profit from the declination distribution.

  4. Paleointensity and paleodirection of the geomagnetic field in the middle Miocene: Evidence from late cenozoic volcanites of primorye

    Science.gov (United States)

    Shcherbakova, V. V.; Shcherbakov, V. P.; Bretshtein, Yu. S.; Zhidkov, G. V.

    2010-12-01

    We present the results of analyzing a representative collection of the middle Miocene 12.4-10.0 Ma basalts that compose the volcanic cover of the Shufan and Sovgavan plateaus, namely the Nikolo-L'vovsk (NL) and Sovetskaya Gavan (SG) volcanic fields. Preliminary data are obtained about the relicts of some volcanic edifices within the West and East Sikhote-Alin volcanic belts, namely the Shishlovskii, Malyshevo, and Truzhenik objects. It is established that the volcanic rocks from these localities are characterized by similar petrologic and magnetic properties. Thermal cleaning of the samples is carried out, and the coordinates of the paleomagnetic pole are determined as Λ = 190.2°E, Φ = 71.3°N for basalts of the Nokolo-L'vovsk area and Λ = 180.4°E, Φ = 71.9°N for rocks from the Sovgavan locality. These values are consistent with the data for coeval volcanics from other regions of Eurasia. Reliable determinations of the paleointensity H pal for a representative collection of samples were obtained using the Thellier method. The corresponding values of the virtual dipole moment (VDM) are almost half its present-day value. The analysis of the Miocene VDM values available from the world database revealed a low average field 5.06 × 1022 Am2 characterized by high variance σ = 2.13 × 1022 Am2 at that time. The similarity of VDM values for the Miocene characterized by frequent inversions and for the Cretaceous Superchron supports the hypothesis of the lack of a correlation between the VDM values and the frequency of geomagnetic inversions.

  5. Archaeomagnetism of a Mediaeval brass melting &working site near Dinant (Belgium) and the suitability of firebricks as geomagnetic field recorders

    Science.gov (United States)

    Hus, J.; Geeraerts, R.; Plumier, J.

    2003-04-01

    Field directional archaeomagnetic data from several kilns, unearthed in a brass melting and working site in Bouvignes-sur-Meuse (Dinant, Namur province) in Belgium during a rescue excavation, confirm the archaeological dating as 15th century A.D. for the main site activities.The archaeomagnetic dates, obtained using reference secular variation curves for France and Great Britain, lead to better time constraints for the cessation of kiln operations. Refractory bricks (firebricks), which are used for their chemical and thermal properties, and in particular for their resistance to high temperatures and temperature changes, are not unusual in metal melting &working sites. In the examined site, circular-, square- and oval-shaped kilns, lined with firebricks, were present. The firebricks, which are very porous and coarse-grained, possess a very stable remanent magnetisation and revealed to be suitable geomagnetic field recorders. In the square-shaped kiln two stable magnetisation components could be isolated in the firebricks: a low-temperature component acquired below 420 C, yielding an age near the middle of the 15th century A.D. and a high-temperature component with non-coherent directions. Although the firebricks from the oval-shaped kiln have a very stable, single-component remanent magnetisation, very large non-random deviations in remanence direction in function of the relative azimuth from the centre of the kiln, or with the position of the bricks in the kiln wall, were found. Several hypothesis for the origin of the deviations were tested: anisotropy, refraction and the presence of a local disturbing magnetic source.

  6. The CHAOS-3 geomagnetic field model and candidates for the 11th generation IGRF

    Science.gov (United States)

    Olsen, N.; Mandea, M.; Sabaka, T. J.; Tøffner-Clausen, L.

    2010-10-01

    As a part of the 11th generation IGRF defined by IAGA, we propose a candidate model for the DGRF 2005, a candidate model for IGRF 2010 and a candidate model for the mean secular variation between 2010 and 2015. These candidate models, the derivation of which is described in the following, are based on the latest model in the CHAOS model series, called "CHAOS-3". This model is derived from more than 10 years of satellite and ground observatory data. Maximum spherical harmonic degree of the static field is n = 60. The core field time changes are expressed by spherical harmonic expansion coefficients up to n = 20, described by order 6 splines (with 6-month knot spacing) spanning the time interval 1997.0-2010.0. The third time derivative of the squared magnetic field intensity is regularized at the core-mantle boundary. No spatial regularization is applied.

  7. Latitudinal and longitudinal behavior of the geomagnetic field during a disturbed period: A case study using wavelet techniques

    Science.gov (United States)

    Klausner, Virginia; Domingues, Margarete Oliveira; Mendes, Odim; da Costa, Aracy Mendes; Papa, Andres Reinaldo Rodriguez; Gonzalez, Arian Ojeda

    2016-11-01

    Coronal mass ejections are the primary cause of the highly disturbed conditions observed in the magnetosphere. Momentum and energy from the solar wind are transferred to the Earth's magnetosphere mainly via magnetic reconnection which produces open field lines connecting the Earth magnetic field to the solar wind. Magnetospheric currents are coupled to the ionosphere through field-aligned currents. This particular characteristic of the magnetosphere-ionosphere interconnection is discussed here on the basis of the energy transfer from high (auroral currents) to low-latitudes (ring current). The objective of this work is to examine how the conditions during a magnetic storm can affect the global space and time configuration of the ring current, and, how these processes can affect the region of the South Atlantic Magnetic Anomaly. The H- or X-components of the Earth's magnetic field were examined using a set of six magnetometers approximately aligned around the geographic longitude at about 10 °, 140 ° and 295 ° from latitudes of 70 ° N to 70 ° S and aligned throughout the equatorial region, for the event of October 18-22, 1998. The investigation of simultaneous observations of data measured at different locations makes it possible to determine the effects of the magnetosphere-ionosphere coupling, and, it tries to establish some relationships among them. This work also compares the responses of the aligned magnetic observatories to the responses in the South Atlantic Magnetic Anomaly region. The major contribution of this paper is related to the applied methodology of the discrete wavelet transform. The wavelet coefficients are used as a filter to extract the information in high frequencies of the analyzed magnetogram. They also better represent information about the injections of energy and, consequently, the disturbances of the geomagnetic field measured on the ground. As a result, we present a better way to visualize the correlation between the X- or H

  8. Improving geomagnetic field models for the period 1980-1999 using Ørsted data

    Science.gov (United States)

    Ultré-Guérard, P.; Jault, D.; Alexandrescu, M.; Achache, J.

    1998-08-01

    The Danish satellite Ørsted is due to be launched in 1998, and should provide, for the first time since the Magsat mission (1979-1980), a dense and global coverage of the Earth's surface with vector measurements of the magnetic field. In this paper, we compare the expected error in the main field models computed for the 1970-1999 time interval using observatory data, with or without the a priori information given by the knowledge of the field at both Magsat and Ørsted epochs. This work is based on the reasonable hypothesis that the main field models derived from Ørsted data will be as accurate as the Magsat models. The a priori information given by the Magsat and Ørsted models is based on a linear behaviour of the rate-of-change of the field throughout this period, plus a noise level which can be estimated as a function of time and degree from past field changes. The expected error in the models computed for the 1980-1999 period with a priori information appears to be significantly smaller than the expected error in the models computed without this information. This result is related to the heterogeneous distribution of the observatories over the Earth surface. Consequently, when the Ørsted data is available, improved models can be computed for the 1980-1999 period particularly in regions without observatory data. This method with a priori information may allow the use of the same set of observatories throughout the entire period. Indeed, our method alleviates the requirement of a very dense data distribution.

  9. On the usage of geomagnetic indices for data selection in internal field modelling

    DEFF Research Database (Denmark)

    Kauristie, K.; Morschhauser, A.; Olsen, Nils

    2017-01-01

    conditions. This exercise reveals that Dst and its time derivative yield a similar picture as Kp on quiet conditions as determined with the conditions typically used in internal field modelling. Magnetic quiescense at high latitudes is typically searched with the help of Merging Electric Field (MEF...... and observed values at high latitudes. Recent initiatives to upgrade the AE-indices, either with a better coverage of observing stations and improved baseline corrections (the Super-MAG concept) or with higher accuracy in pinpointing substorm activity (the Midlatitude Positive Bay -index) will most likely...

  10. Paleomagnetism and 40Ar/39Ar geochronology of the Plio-Pleistocene Boring Volcanic Field: Implications for the geomagnetic polarity time scale and paleosecular variation

    Science.gov (United States)

    Hagstrum, Jonathan T.; Fleck, Robert J.; Evarts, Russell C.; Calvert, Andrew T.

    2017-01-01

    Paleomagnetic directions and 40Ar/39Ar ages have been determined for samples of lava flows from the same outcrops, where possible, for 84 eruptive units ranging in age from 3200 ka to 60 ka within the Boring Volcanic Field (BVF) of the Pacific Northwest, USA. This study expands upon our previous results for the BVF, and compares the combined results with the current geomagnetic polarity time scale (GPTS). Lava flows with transitional directions were found within the BVF at the Matuyama-Brunhes and Jaramillo-Matuyama polarity boundaries, and replicate ages corresponding to these and other boundaries have been newly ascertained. Although the BVF data generally agree with GPTS chronozone boundaries, they indicate that onset of the Gauss-Matuyama transition and Olduvai subchron occurred significantly earlier than given in the current time scale calibration. Additional comparisons show that the BVF results are consistent with recent statistical models of geomagnetic paleosecular variation.

  11. Review Article: On the relation between the seismic activity and the Hurst exponent of the geomagnetic field at the time of the 2000 Izu swarm

    Directory of Open Access Journals (Sweden)

    F. Masci

    2013-09-01

    Full Text Available Many papers document the observation of earthquake-related precursory signatures in geomagnetic field data. However, the significance of these findings is ambiguous because the authors did not adequately take into account that these signals could have been generated by other sources, and the seismogenic origin of these signals have not been validated by comparison with independent datasets. Thus, they are not reliable examples of magnetic disturbances induced by the seismic activity. Hayakawa et al. (2004 claim that at the time of the 2000 Izu swarm the Hurst exponent of the Ultra-Low-Frequency (ULF: 0.001–10 Hz band of the geomagnetic field varied in accord with the energy released by the seismicity. The present paper demonstrates that the behaviour of the Hurst exponent was insufficiently investigated and also misinterpreted by the authors. We clearly show that during the Izu swarm the changes of the Hurst exponent were strongly related to the level of global geomagnetic activity and not to the increase of the local seismic activity.

  12. Review "On the relation between the seismic activity and the Hurst exponent of the geomagnetic field at the time of the 2000 Izu swarm"

    Directory of Open Access Journals (Sweden)

    F. Masci

    2013-03-01

    Full Text Available Many papers document the observation of earthquake-related precursory signatures in geomagnetic field data. However, the significance of these findings is ambiguous because the authors did not adequately take into account that these signals could have been generated by other sources, and the seismogenic origin of these signals have not been validated by comparison with independent datasets. Thus, they are not reliable examples of magnetic disturbances induced by the seismic activity. Hayakawa et al. (2004 claim that at the time of the 2000 Izu swarm the Hurst exponent of the Ultra-Low-Frequency (ULF: 0.001–10 Hz band of the geomagnetic field varied in accord with the energy released by the seismicity. The present paper demonstrates that the behaviour of the Hurst exponent was insufficiently investigated and also misinterpreted by the authors. We clearly show that during the Izu swarm the changes of the Hurst exponent were strongly related to the level of global geomagnetic activity and not to the increase of the local seismic activity.

  13. First-principles modeling of geomagnetically induced electromagnetic fields and currents from upstream solar wind to the surface of the Earth

    Directory of Open Access Journals (Sweden)

    A. Pulkkinen

    2007-05-01

    Full Text Available Our capability to model the near-space physical phenomena has gradually reached a level enabling module-based first-principles modeling of geomagnetically induced electromagnetic fields and currents from upstream solar wind to the surface of the Earth. As geomagnetically induced currents (GIC pose a real threat to the normal operation of long conductor systems on the ground, such as high-voltage power transmission systems, it is quite obvious that success in accurate predictive modeling of the phenomenon would open entirely new windows for operational space weather products.

    Here we introduce a process for obtaining geomagnetically induced electromagnetic fields and currents from the output of global magnetospheric MHD codes. We also present metrics that take into account both the complex nature of the signal and possible forecasting applications of the modeling process. The modeling process and the metrics are presented with the help of an actual example space weather event of 24–29 October 2003. Analysis of the event demonstrates that, despite some significant shortcomings, some central features of the overall ionospheric current fluctuations associated with GIC can be captured by the modeling process. More specifically, the basic spatiotemporal morphology of the modeled and "measured" GIC is quite similar. Furthermore, the presented user-relevant utility metrics demonstrate that MHD-based modeling can outperform simple GIC persistence models.

  14. CHAOS-2-a geomagnetic field model derived from one decade of continuous satellite data

    DEFF Research Database (Denmark)

    Olsen, Nils; Mandea, M.; Sabaka, T.J.

    2009-01-01

    coefficients up to n = 20 are described by order 5 splines (with 6-month knot spacing) spanning the years from 1997.0 to 2009.5. Compared to its predecessors, the temporal regularization of the CHAOS-2 model is also modified. Indeed, second and higher order time derivatives of the core field are damped...

  15. POGO satellite orbit corrections: an opportunity to improve the quality of the geomagnetic field measurements?

    DEFF Research Database (Denmark)

    Stockmann, Reto; Christiansen, Freddy; Olsen, Nils

    2015-01-01

    modelling. To improve the data, we use aniterative approach consisting of two main parts: one is a main field modelling process to obtain the radial fieldgradient to perturb the orbits and the other is the state-of-the-art GPS orbit modelling software BERNESE to calculatenew physical orbits. We report...

  16. Stochastic dynamics of magnetic nanoparticles and a mechanism of biological orientation in the geomagnetic field

    CERN Document Server

    Binhi, V N

    2004-01-01

    The rotations of microscopic magnetic particles, magnetosomes, embedded into the cytoskeleton are considered. A great number of magnetosomes are shown to possess two stable equilibrium positions, between which there occur transitions under the influence of thermal disturbances. The random rotations attain the value of order of radian. The rate of the transitions and the probability of magnetosomes to stay in the different states depend on magnetic field direction with respect to an averaged magnetosome's orientation. This effect explains the ability of migrant birds to faultless orientation in long-term passages in the absence of the direct visibility of optical reference points. The sensitivity to deviation from an `ideal' orientation is estimated to be 1-2 degrees. Possible participation of magnetosomes in biological effects caused by microwave electromagnetic fields is discussed.

  17. Pre-Columbian mural paintings from Mesoamerica as geomagnetic field recorders

    Science.gov (United States)

    Goguitchaichvili, A.; Soler, A. M.; Zanella, E.; Chiari, G.; Lanza, R.; Urrutia-Fucugauchi, J.; Gonzalez, T.

    2004-06-01

    This paper reports a reconnaissance archeomagnetic study of mural paintings in various pre-Columbian sites in Mexico. The magnetic measurements of the pigments show that at least four murals (sites: Cacaxtla, Cholula and Templo Mayor) retain a remanent magnetization carried by a mixture of magnetite and minor hematite grains. In most specimens, a characteristic remanent magnetization is successfully isolated by alternating field demagnetization. The mean directions are reasonably well determined for each mural and within the range of secular variation during the last centuries. Studied Mesoamerican murals apparently retain the direction of the magnetic field at the time they were painted and therefore are an invaluable source of information concerning its secular variation. The archeomagnetic study of pre-Columbian mural paintings opens new alternatives to drawing a reliable reference master curve for the region and may largely contribute to the Mesoamerican absolute chronology.

  18. Evaluation of candidate geomagnetic field models for the 10th generation of IGRF

    Science.gov (United States)

    Maus, Stefan; Macmillan, Susan; Lowes, Frank; Bondar, Tatjana

    2005-12-01

    The recent satellite magnetic missions, combined with high quality ground observatory measurements, have provided excellent data for main field modelling. Four different groups submitted seven main-field and eight secular-variation candidate models for IGRF-10. These candidate models were evaluated using several different strategies. Comparing models with independent data was found to be difficult. Valuable information was gained by mapping model differences, computing root mean square differences between all pairs of models and between models and the common mean, and by studying power spectra and azimuthal distributions of coefficient power. The resulting adopted IGRF main-field model for 2005.0, an average of three selected candidate models, is estimated to have a formal root mean square error over the Earth's surface of only 5 nT, though it is likely that the actual error is somewhat larger than this. Due to the inherent uncertainty in secular variation forecasts, the corresponding error of the adopted secular-variation model for 2005.0-2010.0, an average of four selected candidate models, is estimated at 20 nT/a.

  19. Accurate Predictions of Mean Geomagnetic Dipole Excursion and Reversal Frequencies, Mean Paleomagnetic Field Intensity, and the Radius of Earth's Core Using McLeod's Rule

    Science.gov (United States)

    Voorhies, Coerte V.; Conrad, Joy

    1996-01-01

    The geomagnetic spatial power spectrum R(sub n)(r) is the mean square magnetic induction represented by degree n spherical harmonic coefficients of the internal scalar potential averaged over the geocentric sphere of radius r. McLeod's Rule for the magnetic field generated by Earth's core geodynamo says that the expected core surface power spectrum (R(sub nc)(c)) is inversely proportional to (2n + 1) for 1 less than n less than or equal to N(sub E). McLeod's Rule is verified by locating Earth's core with main field models of Magsat data; the estimated core radius of 3485 kn is close to the seismologic value for c of 3480 km. McLeod's Rule and similar forms are then calibrated with the model values of R(sub n) for 3 less than or = n less than or = 12. Extrapolation to the degree 1 dipole predicts the expectation value of Earth's dipole moment to be about 5.89 x 10(exp 22) Am(exp 2)rms (74.5% of the 1980 value) and the expected geomagnetic intensity to be about 35.6 (mu)T rms at Earth's surface. Archeo- and paleomagnetic field intensity data show these and related predictions to be reasonably accurate. The probability distribution chi(exp 2) with 2n+1 degrees of freedom is assigned to (2n + 1)R(sub nc)/(R(sub nc). Extending this to the dipole implies that an exceptionally weak absolute dipole moment (less than or = 20% of the 1980 value) will exist during 2.5% of geologic time. The mean duration for such major geomagnetic dipole power excursions, one quarter of which feature durable axial dipole reversal, is estimated from the modern dipole power time-scale and the statistical model of excursions. The resulting mean excursion duration of 2767 years forces us to predict an average of 9.04 excursions per million years, 2.26 axial dipole reversals per million years, and a mean reversal duration of 5533 years. Paleomagnetic data show these predictions to be quite accurate. McLeod's Rule led to accurate predictions of Earth's core radius, mean paleomagnetic field

  20. The magnetic properties of baked clays and their implications for past geomagnetic field intensity determinations

    Science.gov (United States)

    Kostadinova-Avramova, M.; Kovacheva, M.

    2013-12-01

    Burnt clays provide a vital source of information about the archaeomagnetic field but their magnetic properties, and the dependency of these on thermal history, are diverse, complex and poorly understood. Here, we attempt to shed light on this problem through the investigation of artificial clay samples prepared from three different clay types repeatedly heated in known magnetic field to two different temperatures (400 and 700 °C). Combined rock-magnetic and X-ray analyses were carried out to obtain information about the mineralogical content and magnetic properties of the diverse raw and heated clays, and also their evolution during the course of multiple heating/cooling treatments. The magnetic behaviour of the three clay types evolved significantly during the course of being repeatedly heated to both 400 and 700 °C. Phyllosilicates containing iron-substitutions in their matrix apparently played an important role in supplying iron- oxides during the heatings and the iron oxides themselves underwent progressive oxidation. The samples heated to the higher temperature exhibited more ideal magnetic behaviour but even those heated only to 400 °C achieved magnetic stabilization after multiple heatings. After 10 reheating treatments, samples heated to both peak temperatures yielded reliable palaeointensity results and a grand mean intensity value Fa = 48.57 ± 1.19 μT which differs by less than 2 μT (or about 3 per cent) from the known intensity of the inducing field. The results confirm that the thermoremanent magnetization produced as a result of multiple heatings even to moderate temperature in the antiquity can give reliable palaeointensity determination. They also highlight that materials from repeatedly used baked clay structures (kilns, hearths, etc.) may be far more appropriate for archaeointensity study than singly baked clay structures (destruction layers, floor plasters, etc.).

  1. Simulations of a quasi-Taylor state geomagnetic field including polarity reversals on the Earth Simulator.

    Science.gov (United States)

    Takahashi, Futoshi; Matsushima, Masaki; Honkura, Yoshimori

    2005-07-15

    High-resolution, low-viscosity geodynamo simulations have been carried out on the Earth Simulator, one of the fastest supercomputers, in a dynamic regime similar to that of Earth's core, that is, in a quasi-Taylor state. Our dynamo models exhibit features of the geodynamo not only in spatial and temporal characteristics but also in dynamics. Polarity reversals occurred when magnetic flux patches at high latitudes moved poleward and disappeared; patches with reversed field at low and mid-latitudes then moved poleward.

  2. Geomagnetic field variations during the last 400 kyr in the western equatorial Pacific: Paleointensity-inclination correlation revisited

    Science.gov (United States)

    Yamazaki, T.; Kanamatsu, T.; Mizuno, S.; Hokanishi, N.; Gaffar, E. Z.

    2008-12-01

    A paleomagnetic study was conducted on four piston cores newly obtained from the West Caroline Basin in the western equatorial Pacific in order to investigate variations in paleointensity and inclination during the last 400 kyr. An inclination-intensity correlation was previously reported in this region using giant piston cores, but the quality of the paleomagnetic data of the younger end, the last ca. 300 kyr, was needed to be checked because the upper part of the giant piston cores could suffer from perturbation by oversampling. Age control is based on the oxygen-isotope ratios for one core and inter-core correlation using relative paleointensity for other cores. The mean inclinations of the four cores show negative inclination anomalies ranging from -5.2 to -11.2 degree. The western equatorial Pacific is documented as a region of a large negative inclination anomalies, and the observed values are comparable to those expected from the time-averaged field (TAF) models [Johnson and Constable, 1997; Hatakeyama and Kono, 2002]. Stacked curves of paleointensity and inclination were constructed from the four cores. It was confirmed that geomagnetic variations on the order of 10 to 100 kyrs occur in inclination as well as paleointensity. A cross-correlation analysis showed that significant in-phase correlation occurs between intensity and inclination for periods longer than about 25 kyr, and power spectra of both paleointensity and inclination variations have peaks at ~100 kyr periods. The regional paleointensity stack with higher resolution than the Sint-800 stack [Guyodo and Valet, 1999] should be useful for paleointensity-assisted chronostratigraphy.

  3. Full-Vector Geomagnetic Field Records for the Late Quaternary from El Hierro and the Eifel

    Science.gov (United States)

    Monster, M.; de Groot, L. V.; Dekkers, M. J.; van Galen, J. P.; Kuiper, K.; Langemeijer, J.; Wiarda, L. R.

    2015-12-01

    Twenty-eight flows in the age range of c. 100 to c. 500 ka were sampled on the island of El Hierro (Canary Islands, Spain) and twelve in the Eifel (Germany). All sites from the Eifel had been previously dated, whereas the ages of the El Hierro flows were approximated by stratigraphic and directional coherency with a dated section c. 4 km to the north-east. Additionally, seven flows were dated using the ThermoFisher Helix multi-collector mass spectrometer at VU University Amsterdam (the Netherlands). The rocks were subjected to standard rock magnetic and palaeomagnetic experiments. Palaeodirections were obtained using both thermal and alternating-field demagnetisation techniques. Apart from two sites that appear to have been struck by lightning, all sites yielded reliable palaeodirections. Absolute palaeointensities were obtained using three different methods: IZZI-Thellier, the multispecimen protocol and the calibrated pseudo-Thellier technique. Nineteen sites from El Hierro and all twelve sites from the Eifel passed the selection criteria for one or more of these methods, with the pseudo-Thellier technique having the highest success rate (c. 35% for El Hierro and 55% for the Eifel). The palaeointensities obtained for El Hierro were mostly between 20 and 40 μT and for the Eifel between 20 and 50 μT, both with a tendency to be somewhat low compared to the present-day field of c. 39 μT and c. 49 μT, respectively. The pseudo-Thellier and multispecimen methods generally yielded lower palaeointensities than IZZI-Thellier, but no clear trend was visible.

  4. Statistical analysis of geomagnetic field intensity differences between ASM and VFM instruments onboard Swarm constellation

    Science.gov (United States)

    De Michelis, Paola; Tozzi, Roberta; Consolini, Giuseppe

    2017-02-01

    From the very first measurements made by the magnetometers onboard Swarm satellites launched by European Space Agency (ESA) in late 2013, it emerged a discrepancy between scalar and vector measurements. An accurate analysis of this phenomenon brought to build an empirical model of the disturbance, highly correlated with the Sun incidence angle, and to correct vector data accordingly. The empirical model adopted by ESA results in a significant decrease in the amplitude of the disturbance affecting VFM measurements so greatly improving the vector magnetic data quality. This study is focused on the characterization of the difference between magnetic field intensity measured by the absolute scalar magnetometer (ASM) and that reconstructed using the vector field magnetometer (VFM) installed on Swarm constellation. Applying empirical mode decomposition method, we find the intrinsic mode functions (IMFs) associated with ASM-VFM total intensity differences obtained with data both uncorrected and corrected for the disturbance correlated with the Sun incidence angle. Surprisingly, no differences are found in the nature of the IMFs embedded in the analyzed signals, being these IMFs characterized by the same dominant periodicities before and after correction. The effect of correction manifests in the decrease in the energy associated with some IMFs contributing to corrected data. Some IMFs identified by analyzing the ASM-VFM intensity discrepancy are characterized by the same dominant periodicities of those obtained by analyzing the temperature fluctuations of the VFM electronic unit. Thus, the disturbance correlated with the Sun incidence angle could be still present in the corrected magnetic data. Furthermore, the ASM-VFM total intensity difference and the VFM electronic unit temperature display a maximal shared information with a time delay that depends on local time. Taken together, these findings may help to relate the features of the observed VFM-ASM total intensity

  5. Progress in Studies of Geomagnetic Navigation of Animals

    Institute of Scientific and Technical Information of China (English)

    Tian Lanxiang; Pan Yongxin; Lin Wei; Wang Yinan; Zhang Shuyi

    2005-01-01

    @@ The geomagnetic field may play a key role in orientation and navigation of many long-distance migratory animals. Taking homing and migrating birds as examples, this paper reviews recent progress in studies of geomagnetic "compass" of animals.Moreover, we propose to address two aspects in future geomagnetic orientation research: ( 1 ) what are the true components of the "map"? (2) What are the magneto-receptors and which brain areas acquire and process the geomagnetic field information ?

  6. A model of the geomagnetic field and its secular variation for epoch 2000 estimated from Orsted data

    DEFF Research Database (Denmark)

    Olsen, Nils

    2002-01-01

    as measured simultaneously by globally distributed geomagnetic observatories. In addition, the observatory data are used to constrain secular variation. The model is estimated using an iteratively reweighted least-squares method with Huber weights to account for the non-Gaussian data error distribution...

  7. New parameterization of external and induced fields in geomagnetic field modeling, and a candidate model for IGRF 2005

    DEFF Research Database (Denmark)

    Olsen, Nils; Sabaka, T.J.; Lowes, F.

    2005-01-01

    When deriving spherical harmonic models of the Earth's magnetic field, low-degree external field contributions are traditionally considered by assuming that their expansion coefficient q(1)(0) varies linearly with the D-st-index, while induced contributions are considered assuming a constant ratio...

  8. Recent geomagnetic secular variation from Swarm and ground observatories as estimated in the CHAOS-6 geomagnetic field model

    DEFF Research Database (Denmark)

    Finlay, Chris; Olsen, Nils; Kotsiaros, Stavros

    2016-01-01

    , under the region of northern South America, and at high northern latitudes under Alaska and Siberia. Surprisingly, there is also evidence for significant SA in the central Pacific region, for example near Hawaii where radial field SA is observed on either side of a jerk in 2014. On the other hand...... of the Earth's magnetic field between 1999.0 and 2016.5. We present details of the secular variation (SV) and secular acceleration (SA) from CHAOS-6 at Earth's surface and downward continued to the core surface. At Earth's surface, we find evidence for positive acceleration of the field intensity in 2015 over......, jets at low latitudes, for example close to 40 degrees W, that may be responsible for localized SA oscillations. In addition to scalar data from Orsted, CHAMP, SAC-C and Swarm, and vector data from Orsted, CHAMP and Swarm, CHAOS-6 benefits from the inclusion of along-track differences of scalar...

  9. 基于PASCO实验平台的地球磁场测量%Measurement and Study of the Geomagnetic Field Based on the PASCO Experimental Platform

    Institute of Scientific and Technical Information of China (English)

    李爽; 刘立英; 张砚霖; 侯胜益

    2012-01-01

    基于PASCO实验平台的软件和计算机接口,利用高灵敏度磁场传感器对地球磁场的强度及磁倾角等相关参量进行测量与分析。实验结果表明,该测量方法操作简单,精确度较高,实用性很强。通过轻松的实验过程对地球磁场等不易感知的弱磁场有了一个清晰直观的认识。%Based on the PASCO experimental platform and data studio software,magnetic field intensity and related parameters of the geomagnetic field are measured and studied using high sensitivity magnetic field sensor.It implies that the experimental method is practicable,while the results are precision.Through the simple experimental process,we have a clear understanding to the geomagnetic field,which is usually difficult to be shown and perceived as typical weak magnetic field.

  10. The statistical model for the secondary quick reversals during the geomagnetic pole transition

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A statistical model for the quick reversals during a geomagnetic pole transition is put forward by combining the modern geomagnetic field and paleomagnetic field. The decrease of geomagnetic intensity determines the reversals, and the quick reversals are possibly caused by the interaction between g01 and the other geomagnetic components.

  11. The statistical model for the secondary quick reversals during the geomagnetic pole transition

    Institute of Scientific and Technical Information of China (English)

    刘青松; 朱日祥; 潘永信; 郭斌

    2000-01-01

    A statistical model for the quick reversals during a geomagnetic pole transition is put forward by combining the modern geomagnetic field and paleomagnetic field. The decrease of geomagnetic intensity determines the reversals, and the quick reversals are possibly caused by the interaction between g10 and the other geomagnetic components.

  12. Geomagnetic field: Conclusions

    Digital Repository Service at National Institute of Oceanography (India)

    Gorodnitsky, A.M.; Subrahmanyam, A.S.

    stream_size 1 stream_content_type text/plain stream_name Mem_Geol_Soc_India_1998_39_38.pdf.txt stream_source_info Mem_Geol_Soc_India_1998_39_38.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 ...

  13. On the distribution function of the geomagnetic field intensity according to the model of a giant Gaussian process and empirical data

    Science.gov (United States)

    Shcherbakov, V. P.; Khokhlov, A. V.; Sycheva, N. K.

    2015-09-01

    The quadrature formula is obtained for the distribution function (DF) of the intensity of the geomagnetic field B and the corresponding virtual axial dipole moment VADM in the model of the Giant Gaussian Process (GGP). The predictions of this model are compared, up to a high degree of detail, with the empirical data for the Brunhes Epoch, which are contained in the global databases (GDB) for paleointensity. With a fixed latitude φ, the DFs f B ( B, φ) and f VADM(VADM, φ) are close to Gaussian within the first approximation. At the same time, the global DF f B ( B) has a high coefficient of asymmetry a = 0.35 since the mean of this function is latitude-dependent. In contrast, the global DF f VADM(VADM) has far lower asymmetry a = 0.16, since its mean barely varies with latitude. The comparison between the distribution histograms of VADM according to the PINT GDB data for the Brunhes Epoch and the results calculated by the BGP model shows that the empirical data and the calculations by the GGP model noticeably differ in the interval of the small VADM. Specifically, the histogram based on PINT GDB data shows a significant predominance of these data compared to the model predictions. At the same time, the same data fairly well agree with the GGP model in directions. This contradiction is probably accounted for by the underestimation of the paleointensity values in the experiments by the Thellier method if the rock carries chemical magnetization instead of thermal remanent magnetization. An alternative explanation suggests a short drop in the geomagnetic dynamo power associated with a simultaneous decrease in both the mean value of the axial dipole and in the variances of all the other terms of the spherical expansion of the geomagnetic field (i.e., quadrupole, octupole, and other components).

  14. Hazards of geomagnetic storms

    Science.gov (United States)

    Herzog, D.C.

    1992-01-01

    Geomagnetic storms are large and sometimes rapid fluctuations in the Earth's magnetic field that are related to disturbances on the Sun's surface. Although it is not widely recognized, these transient magnetic disturbances can be a significant hazard to people and property. Many of us know that the intensity of the auroral lights increases during magnetic storms, but few people realize that these storms can also cause massive power outages, interrupt radio communications and satellite operations, increase corrosion in oil and gas pipelines, and lead to spuriously high rejection rates in the manufacture of sensitive electronic equipment. 

  15. Was the Devonian geomagnetic field dipolar or multipolar? Palaeointensity studies of Devonian igneous rocks from the Minusa Basin (Siberia) and the Kola Peninsula dykes, Russia

    Science.gov (United States)

    Shcherbakova, V. V.; Biggin, A. J.; Veselovskiy, R. V.; Shatsillo, A. V.; Hawkins, L.; Shcherbakov, V. P.; Zhidkov, G. V.

    2017-02-01

    Defining variations in the behaviour of the geomagnetic field through geological time is critical to understanding the dynamics of Earth's core and its response to mantle convection and planetary evolution. Furthermore, the question of whether the axial dipole dominance of the recent palaeomagnetic field persists through the whole of Earth's history is fundamental to determining the reliability of palaeogeographic reconstructions and the efficacy of the magnetosphere in shielding Earth from solar wind radiation. Previous palaeomagnetic directional studies have suggested that the palaeofield had a complex configuration in the Devonian period (419-359 Ma). Here we present new palaeointensity determinations from rocks aged between 408 and 375 Ma from the Minusa Basin (southern Siberia), and the Kola Peninsula to investigate the strength of the field during this enigmatic period. Palaeointensity experiments were performed using the thermal Thellier, microwave Thellier, and Wilson methods on 165 specimens from 25 sites. Six out of eight successful sites from the Minusa Basin and all four successful sites from the Kola Peninsula produced extremely low palaeointensities (uniformitarian view of the palaeomagnetic field: field intensities of nearly an order of magnitude lower than Neogene values (except during relatively rare geomagnetic excursions and reversals) together with the widespread appearance of strange directions found in the Devonian suggest that the Earth's field during this time may have had a dominantly multipolar geometry. A persistent, low intensity multipolar magnetic field and associated diminished magnetosphere would increase the impact of solar particles on the Earth's magnetosphere, ionosphere and atmosphere with potential major implications for Earth's climate and biosphere.

  16. Geomagnetic Principal Magnetic Storms

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The abbreviations used for observatory names are as follows: GEOMAGNETIC OBSERVATORIES Code Station Geomagnetic Latitude ABG Alibag AMS Martin de Vivie. These data...

  17. "Double low-points" anomaly in daily variation of vertical component of geomagnetic field before the MS8.0 Wenchuan earthquake

    Institute of Scientific and Technical Information of China (English)

    Jiuchang Hu; Wei Liu; Minrui Guo; Hua Zheng

    2009-01-01

    The "double low-points" anomaly in daily variation of vertical geomagnetic component was observed on May 9, 2008 at 13 geomagnetic observatories belonging to the geomagnetic observatory network center of China Earthquake Administration. These observatories distribute roughly on three belts with the intersection in western Sichuan. On May 12, three days after the anomaly appearance, the great MS8.0 Wenchuan earthquake occurred. The "double low-points" anomaly in daily variation of vertical geomagnetic component is an anomalous phenomenon of regional geomagnetism, which does exist objectively. The possible cause is the change of extrinsic eddy current system resulting in geomagnetic daily quiet variation (Sq), or the delay of several hours between the intrinsic and the extrinsic eddy current systems. The relationship between the "double low-points" anomaly of daily geomagnetic variation and the earthquake reveals that the former possibly reflects the accelera-tive alteration of earthquake gestation in the deep Earth.

  18. NOAA/NGDC candidate models for the 11th generation International Geomagnetic Reference Field and the concurrent release of the 6th generation Pomme magnetic model

    Science.gov (United States)

    Maus, S.; Manoj, C.; Rauberg, J.; Michaelis, I.; Lühr, H.

    2010-10-01

    The International Geomagnetic Reference Field (IGRF) is updated every five years based on candidate model submissions by research institutions worldwide. In the call for the 11th generation of IGRF, candidates were requested for the definitive main field in 2005, the predicted main field in 2010, and the predicted secular variation from 2010 to 2015. The NOAA/NGDC candidate models for IGRF-11 were produced from parent models parameterized in the same way as the 6th generation of our Pomme magnetic model. All models were based on CHAMP satellite measurements, while Ørsted satellite measurements were used for model validation. The internal field in Pomme-6 is described by a 2nd degree Taylor time series of spherical harmonic expansion coefficients of a scalar magnetic potential. Magnetic fields of ionospheric origin are avoided by careful data selection. Instead of co-estimating magnetospheric fields, we subtract a magnetospheric field model estimated previously from a more extensive data set covering all local times. From comparison with Örsted measurements and general considerations of magnetic field predictability, we attribute a root mean square (RMS) uncertainty of 1.3 nT to our candidate model for the main field in 2005, 2.5 nT to the predicted main field in 2010 and 26 nT/a to the predicted secular variation from 2010 to 2015.

  19. A study on the main periodicities in interplanetary magnetic field Bz component and geomagnetic AE index during HILDCAA events using wavelet analysis

    Science.gov (United States)

    Souza, A. M.; Echer, E.; Bolzan, M. J. A.; Hajra, R.

    2016-11-01

    The interplanetary and geomagnetic characteristics of High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events are studied using wavelet analysis technique. The Morlet wavelet transform was applied to the 1 min interplanetary magnetic field (IMF) Bz component and the geomagnetic AE index during HILDCAA events. We have analyzed the AE data for the events occurring between 1975 and 2011, and the IMF Bz data (both in GSE and GSM) for the events between 1995 and 2011. We analyzed the scalograms and the global wavelet spectrum of the parameters. For 50% of all HILDCAA events, the main periodicities of the AE index are generally between 4 and 12 h. For the Bz component, the main periodicities were found to be less than 8 h for 56% of times in GSM system and for 54% of times in GSE system. It is conjectured that the periodicities might be associated with the Alfvén waves which have typical periods between 1 and 10 h. The results are discussed in the light of self organized criticality theory where the physical events have the capacity of releasing a considerable amount of energy in a short interval of time.

  20. Are changes of the geomagnetic field intensity related to changes of the tropical Pacific sea-level pressure during the last 50 years?

    Science.gov (United States)

    Vieira, Luis Eduardo Antunes; da Silva, Ligia Alves; Guarnieri, Fernando LuíS.

    2008-08-01

    The influence of solar variability into the lower atmospheric regions has been suggested on different atmospheric parameters in different time scales. However, a plausible mechanism to explain these observations remains unclear. Although it is widely accepted that the climate change over the past 50 years is attributed to human influence, we present the case that local climate change in the tropical Pacific may be due to changes in the Earth's magnetic field strength. The changes in the tropical Pacific circulation have been observed during the last 50 years, and they are attributed to the increase of the global surface temperature. However, a geomagnetic modulation of the net radiative flux in the southern tropical Pacific was recently suggested. Moreover, comparisons of long-term reconstructions of the Northern Hemisphere surface temperature and solar activity proxies indicated that the existence of a geomagnetic signal in climate data would support a direct link between solar variability and their effects on climate. Here we show that in the tropical Pacific the sea-level pressure, which is a component of the Walker circulation, could be related to the magnetospheric, ionospheric, and upper-atmosphere processes which may propagate downward to the lower atmosphere. Furthermore, we show that the changes in sea-level pressure and the Walker circulation are correlated to the westward drift of the magnetic anomaly. We compare the region averaged monthly values of the sea-level pressure in the tropical Pacific with those of the magnetic field intensity near the surface for the last 50 years. We find that the sea-level pressure in the tropical Pacific is increasing as the magnetic field intensity is decreasing. The correlation coefficient of the sea-level pressure 36-month running means versus the magnetic field intensity is 0.96. We anticipate our investigation to be a starting point for a more sophisticated investigation of the coupling between the space weather

  1. Solar dynamo and geomagnetic activity

    CERN Document Server

    Georgieva, Katya

    2010-01-01

    The correlation between geomagnetic activity and the sunspot number in the 11-year solar cycle exhibits long-term variations due to the varying time lag between the sunspot-related and non-sunspot related geomagnetic activity, and the varying relative amplitude of the respective geomagnetic activity peaks. As the sunspot-related and non-sunspot related geomagnetic activity are caused by different solar agents, related to the solar toroidal and poloidal fields, respectively, we use their variations to derive the parameters of the solar dynamo transforming the poloidal field into toroidal field and back. We find that in the last 12 cycles the solar surface meridional circulation varied between 5 and 20 m/s (averaged over latitude and over the sunspot cycle), the deep circulation varied between 2.5 and 5.5 m/s, and the diffusivity in the whole of the convection zone was ~10**12 m2/s. In the last 12 cycles solar dynamo has been operating in moderately diffusion dominated regime in the bulk of the convection zone....

  2. Time-variation update for geomagnetic navigation reference map based on secular variation model of main geomagnetic field%基于主磁场长期变化模型的地磁导航基准图时变修正

    Institute of Scientific and Technical Information of China (English)

    孙渊; 张金生; 王仕成; 乔玉坤; 张盈

    2011-01-01

    Secular variation of main geomagnetic field is an important factor that influences the time-validity of geomagnetic navigation reference map. A method is proposed to update the variation using a model-predicted value. The secular variation model of main geomagnetic field is used to solve the time-variation problem of near-space geomagnetic navigation reference map. Secular variation model of the earth's main geomagnetic field is modeled based on WMM2010, and depending on this model, the secular variation model of near-space in China (30 km above sea level) is modeled. Calculated secular variation rates of geomagnetic components are used to update the time-variation. Experiment results indicate that the matching probability of updated map can reach more than 90%, and the effect is better when the time-interval is longer. The updated reference map by the secular variation model of main geomagnetic field has good adaptability.%地球主磁场长期变化是影响地磁导航基准图时效性的一个重要因素.提出一种以模型预测值对基准图进行时变修正的方法,利用主磁场长期变化模型解决临近空间地磁导航基准图的时变修正问题.基于WMM2010建立地球主磁场长期变化模型,在此基础上建立中国地区临近空间(海拔高度30 km)的主磁场长期变化模型,利用该模型计算出的地磁场分量长期变化率对基准图时变进行修正.仿真实验结果表明,修正后的地磁导航基准图的匹配概率可以达到90%以上,相比修正前有显著提高,且修正前后间隔时间越长效果越明显.利用主磁场长期变化模型修正后的地磁导航基准图具有良好的适配性.

  3. New archeointensity data from French Early Medieval pottery production (6th-10th century AD). Tracing 1500 years of geomagnetic field intensity variations in Western Europe

    Science.gov (United States)

    Genevey, Agnès; Gallet, Yves; Jesset, Sébastien; Thébault, Erwan; Bouillon, Jérôme; Lefèvre, Annie; Le Goff, Maxime

    2016-08-01

    Nineteen new archeointensity results were obtained from the analysis of groups of French pottery fragments dated to the Early Middle Ages (6th to 10th centuries AD). They are from several medieval ceramic production sites, excavated mainly in Saran (Central France), and their precise dating was established based on typo-chronological characteristics. Intensity measurements were performed using the Triaxe protocol, which takes into account the effects on the intensity determinations of both thermoremanent magnetization anisotropy and cooling rate. Intensity analyses were also carried out on modern pottery produced at Saran during an experimental firing. The results show very good agreement with the geomagnetic field intensity directly measured inside and around the kiln, thus reasserting the reliability of the Triaxe protocol and the relevance of the quality criteria used. They further demonstrate the potential of the Saran pottery production for archeomagnetism. The new archeointensity results allow a precise and coherent description of the geomagnetic field intensity variations in Western Europe during the Early Medieval period, which was until now poorly documented. They show a significant increase in intensity during the 6th century AD, high intensity values from the 7th to the 9th century, with a minimum of small amplitude at the transition between the 7th and the 8th centuries and finally an important decrease until the beginning of the 11th century. Together with published intensity results available within a radius of 700 km around Paris, the new data were used to compute a master curve of the Western European geomagnetic intensity variations over the past 1500 years. This curve clearly exhibits five intensity maxima: at the transition between the 6th and 7th century AD, at the middle of the 9th century, during the 12th century, in the second part of the 14th century and at the very beginning of the 17th century AD. Some of these peaks are smoothed, or

  4. Incorporation of geomagnetic data and services into EPOS infrastructure

    Science.gov (United States)

    Hejda, Pavel; Chambodut, Aude; Curto, Juan-Jose; Flower, Simon; Kozlovskaya, Elena; Kubašta, Petr; Matzka, Jürgen; Tanskanen, Eija; Thomson, Alan

    2016-04-01

    Monitoring of the geomagnetic field has a long history across Europe that dates back to 1830', and is currently experiencing an increased interest within Earth observation and space weather monitoring. Our goals within EPOS-IP are to consolidate the community, modernise data archival and distribution formats for existing services and create new services for magnetotelluric data and geomagnetic models. Specific objectives are: • Enhance existing services providing geomagnetic data (INTERMAGNET- INTErnational Real-time MAGnetic observatory NETwork; World Data Centre for Geomagnetism; IMAGE- International Monitor for Auroral Geomagnetic Effects) and existing services providing geomagnetic indices (ISGI - International Service of Geomagnetic Indices). • Develop and enhance the geomagnetic community's metadata systems by creating a metadata database, filling it and putting in place processes to ensure that it is kept up to date in the future. • Develop and build access to magnetotelluric (MT) data including transfer functions and time series data from temporary, portable MT-arrays in Europe, as well as to lithospheric conductivity models derived from TM-data. • Develop common web and database access points to global and regional geomagnetic field and conductivity models. • Establish links from the geomagnetic data services, products and models to the Integrated Core Services. The immediate task in the current period is to identify data models of existing services, modify them and integrate into a common model of Geomagnetic Thematic Core Services.

  5. Improved geomagnetic referencing in the Arctic environment

    Science.gov (United States)

    Poedjono, B.; Beck, N.; Buchanan, A. C.; Borri, L.; Maus, S.; Finn, Carol; Worthington, Bill; White, Tim

    2016-01-01

    Geomagnetic referencing uses the Earth’s magnetic field to determine accurate wellbore positioning essential for success in today's complex drilling programs, either as an alternative or a complement to north-seeking gyroscopic referencing. However, fluctuations in the geomagnetic field, especially at high latitudes, make the application of geomagnetic referencing in those areas more challenging. Precise crustal mapping and the monitoring of real-time variations by nearby magnetic observatories is crucial to achieving the required geomagnetic referencing accuracy. The Deadhorse Magnetic Observatory (DED), located at Prudhoe Bay, Alaska, has already played a vital role in the success of several commercial ventures in the area, providing essential, accurate, real-time data to the oilfield drilling industry. Geomagnetic referencing is enhanced with real-time data from DED and other observatories, and has been successfully used for accurate wellbore positioning. The availability of real-time geomagnetic measurements leads to significant cost and time savings in wellbore surveying, improving accuracy and alleviating the need for more expensive surveying techniques. The correct implementation of geomagnetic referencing is particularly critical as we approach the increased activity associated with the upcoming maximum of the 11-year solar cycle. The DED observatory further provides an important service to scientific communities engaged in studies of ionospheric, magnetospheric and space weather phenomena.

  6. Geomagnetic excursions date early hominid migration to China

    Science.gov (United States)

    Bhattacharya, Atreyee

    2012-09-01

    Global-scale geomagnetic reversals, which are periods when the direction of Earth's magnetic field flips, leave imprints in magnetic minerals present in sediments. But so do smaller-scale, even local, changes in Earth's magnetic field direction. Paleomagnetists believe that the smaller-scale events represent “failed reversals” and refer to them as “geomagnetic excursions.” Scientists use geomagnetic excursions in sedimentary basins as markers to tie together events of Earth's history across the globe.

  7. Virtualization research on IGRF 10(International Geomagnetic Reference Field)model%IGRF国际地磁参考场模型可视化研究

    Institute of Scientific and Technical Information of China (English)

    王丹; 彭丰林; 马麦宁; 袁晓茹; 白春华; 孙立江

    2009-01-01

    IGRF(International Geomagnetic Reference Field)即全球地磁参考模型,是由国际地磁和高空物理学联合会(International Association of Geomagnetism and Aeronomy)发布的一系列关于地球主磁场及其年变率的数学模型.作为科学研究和工程应用的背景场、参考场广泛用于地球深部、地壳、电离层和磁层的研究.本文以最新的一代至第10代IGRF模型为基础,以Google公司开发的虚拟三维地球软件Google Earth为载体,进行了国际地磁参考场可视化研究.生成了一系列地磁要素的KML文件.并发布在世界数据中心中国地球物理学科中心的网站上,用户通过下载并打开这些文件就可以在Google Earth上查看到中国地区地磁场7个分量的可视化结果.本文所使用的方法也同样适用于第一代至第九代IGRF模型以及今后将要建立的IGRF模型.

  8. New constraints on the maximum rate of change of the geomagnetic field intensity in Western Europe during the last two millennia

    Science.gov (United States)

    Gomez-Paccard, Miriam; Osete, Maria Luisa; Chauvin, Annick; Pérez-Asensio, Manuel; Jimenez-Castillo, Pedro

    2014-05-01

    Available European data indicate that during the past 2500 years there have been periods of rapid intensity geomagnetic fluctuations interspersed with periods of little change. The challenge now is to precisely describe these rapid changes. Due to the difficulty to obtain precisely dated heated materials to obtain a high-resolution description of past geomagnetic field intensity changes, new high-quality archeomagnetic data from archeological heated materials founded in well-defined superposed stratigraphic units are particularly valuable. In this work we report the archeomagnetic study of several groups of ceramic fragments from southeastern Spain that belong to 14 superposed stratigraphic levels corresponding to a surface no bigger than 3 m by 7 m. Between four and eight ceramic fragments were selected per stratigraphic unit. The age of the pottery fragments range from the second half of the 7th to the11th centuries. The dates were established by three radiocarbon dates and by archeological/historical constraints including typological comparisons and well-controlled stratigraphic constrains.Between two and four specimens per pottery fragment were studied. The classical Thellier and Thellier method including pTRM checks and TRM anisotropy and cooling rate corrections was used to estimate paleointensities at specimen level. All accepted results correspond to well-defined single components of magnetization going toward the origin and to high-quality paleointensity determinations. From these experiments nine new high-quality mean intensities have been obtained. The new data provide an improved description of the sharp abrupt intensity changes that took place in this region between the 7th and the 11th centuries. The results confirm that several rapid intensity changes (of about ~15-20 µT/century) took place in Western Europe during the recent history of the Earth.

  9. Bayesian inference in geomagnetism

    Science.gov (United States)

    Backus, George E.

    1988-01-01

    The inverse problem in empirical geomagnetic modeling is investigated, with critical examination of recently published studies. Particular attention is given to the use of Bayesian inference (BI) to select the damping parameter lambda in the uniqueness portion of the inverse problem. The mathematical bases of BI and stochastic inversion are explored, with consideration of bound-softening problems and resolution in linear Gaussian BI. The problem of estimating the radial magnetic field B(r) at the earth core-mantle boundary from surface and satellite measurements is then analyzed in detail, with specific attention to the selection of lambda in the studies of Gubbins (1983) and Gubbins and Bloxham (1985). It is argued that the selection method is inappropriate and leads to lambda values much larger than those that would result if a reasonable bound on the heat flow at the CMB were assumed.

  10. On the suitability of refractory bricks from a mediaeval brass melting and working site near Dinant (Belgium) as geomagnetic field recorders

    Science.gov (United States)

    Hus, J.; Geeraerts, R.; Plumier, J.

    2004-11-01

    Directional field archaeomagnetic data from two oval shaped kilns, of which still one was lined with refractory bricks, unearthed in a brass melting and working site in Bouvignes-sur-Meuse in Belgium, confirm the archaeologic dating as 14-15th century A.D. for the main site activities. The archaeomagnetic dates, obtained using reference secular variation curves of the geomagnetic field direction for France and Great Britain, lead to better time constraints for the cessation of kiln operations. Refractory bricks (firebricks) that are used for their chemical and thermal properties, and in particular for their resistance to high temperatures and temperature changes, are not unusual in metal melting and working sites. The firebricks from the examined site are coarse-grained and very porous inside but possess a very stable remanent magnetisation and revealed to be suitable magnetic field recorders. Although the firebricks have a single-component remanent magnetization, non-random deviations in remanence direction in function of the relative azimuth from the centre of the kiln or with the position of the bricks in the kiln wall, were observed. Several hypotheses for the origin of the deviations were considered: anisotropy, refraction, magnetic interaction, magnetic field distortion and the presence of a local disturbing magnetic source.

  11. Three centuries of geomagnetic field intensity changes in Spain (from the 9th to the 12th centuries)

    Science.gov (United States)

    Gomez-Paccard, M.; Osete, M. L.; Chauvin, A.; Jimenez-Castillo, P.; Perez-Asensio, M.

    2013-12-01

    Available European data indicate that during the past 2500 years there have been periods of rapid intensity geomagnetic fluctuations (at least of ~20 μT/century) interspersed with periods of little change. The challenge now is to precisely describe these rapid changes by the acquisition of well-dated high-quality archeomagnetic data. In this study we report the archeomagnetic study of Spanish ceramic fragments. The collected fragments belong to 14 superposed stratigraphic levels corresponding to a surface no bigger than 3 m by 7 m. The pottery fragments dates back to the 9th and 11th centuries. The dating was established by 4 radiocarbon dates and by archeological/historical constraints including typological comparisons and well-controlled stratigraphic constrains between the different stratigraphic units. From classical Thellier experiments including TRM anisotropy and cooling rate corrections upon archeointensity estimates and conducted on 79 fragments, twelve new high-quality mean intensities have been obtained. Together with previously published high-quality data from Western Europe, the new data provide an improved description of the intensity changes that took place in Spain between the 9th and the 12th centuries. The results confirm that rapid intensity changes took place in Western Europe during the recent history of the Earth.

  12. Geomagnetic disturbance effects on power systems

    Energy Technology Data Exchange (ETDEWEB)

    Albertson, V.D.; Bozoki, B.; Feero, W.E.; Kappenman, J.G.; Larsen, E.V.; Nordell, D.E.; Ponder, J.; Prabhakara, F.S.; Thompson, K.; Walling, R.

    1993-07-01

    In the northern hemisphere, the aurora borealis is visual evidence of simultaneous fluctuations in the earth's magnetic field (geomagnetic field). These geomagnetic disturbances (GMD's), or geomagnetic storms, can affect a number of man-made systems, including electric power systems. The GMD's are caused by the electromagnetic interaction of the solar wind plasma of protons and electrons with the geomagnetic field. These dynamic impulses in the solar wind are due to solar flares, coronal holes, and disappearing filaments, and reach the earth from one to six days after being emitted by a solar event. Instances of geomagnetic storms affecting telegraph systems were noted in England in 1846, and power system disturbances linked to GMD's were first reported in the United States in 1940. This Working Group report is a summary of the state of knowledge and research activity to the present time, and covers the GMD/Geomagnetically-induced currents (GIC) phenomena, transformer effects, the impact on generators, protective relay effects, and communication system effects. It also summarizes modeling and predicting GIC, measuring and monitoring GIC, mitigation methods, system operating guidelines during GMD's, and alerting and forecasting procedures and needs for the power industry.

  13. Heart attacks and geomagnetic activity.

    Science.gov (United States)

    Knox, E G; Armstrong, E; Lancashire, R; Wall, M; Haynes, R

    1979-10-18

    Malin and Srivastava reported a remarkable correlation between daily variations in the geomagnetic field strength and daily admissions to the cardio-thoracic wards of hospitals in Hyderabad and Secunderabad, for cardiac emergencies, during 1967--72. We have now carried out a similar enquiry in the West Midlands region of the UK for the years 1969--70, but were unable to confirm the Indian results.

  14. Observed Coupling Between the International Space Station PCU Plasma and a FPMU Langmuir Probe Facilitated by the Geomagnetic Field

    Science.gov (United States)

    Hartman, William; Koontz, Steven L.

    2010-01-01

    Electrical charging of the International Space Station (ISS) is a matter of serious concern resulting from the possibility of vehicle arcing and electrical shock hazard to crew during extravehicular activity (EVA). A Plasma Contactor Unit (PCU) was developed and integrated into ISS in order to control the ISS floating potential, thereby, minimize vehicle charging and associated hazards. One of the principle factors affecting ISS electrical charging is the ionosphere plasma state (i.e., electron temperature and density). To support ISS electrical charging studies a Floating Potential Monitoring Unit (FPMU) is also integrated into ISS in order to measure the ionosphere properties using Langmuir probes (LP). The FPMU was located on the Starboard side of ISS. The PCU is located near the center of ISS with its plasma exhaust pointed to port. From its integration on ISS in 2006 through November of 2009, the FPMU data exhibited nominal characteristics during PCU operation. On November 21, 2009 the FPMU was relocated from the Starboard location to a new Port location. After relocation significant enhanced noise was observed in both the LP current-voltage sweeps and the derived electron temperature data. The enhanced noise only occurred when the PCU was in discharge and at unique and repeatable locations of the ISS orbit. The cause of this enhanced noise was investigated. It was found that there is coupling occurring between the PCU plasma and the FPMU LP. In this paper we shall 1) present the on-orbit data and the presence of enhanced noise, 2) demonstrate that the coupling of the PCU plasma and the FPMU measurements is geomagnetically organized, 3) show that coupling of the PCU plasma and the FPMU is primarily due to and driven by particle-wave interaction and 4) show that the ionosphere conditions are adequate for Alfven waves to be generated by the PCU plasma.

  15. Secular variation of the middle and late Miocene geomagnetic field recorded by the Columbia River Basalt Group in Oregon, Idaho and Washington, USA

    Science.gov (United States)

    Dominguez, Ada R.; Van der Voo, Rob

    2014-06-01

    This study of 118 discrete volcanic flows from the Columbia River Basalt Group is aimed to determine their distribution of geomagnetic field directions and virtual geomagnetic poles (VGPs) and to compare the inherent secular variation parameters with those from other studies. The magnetic signature of these rocks is uniformly carried by primary titanomagnetite, indicating that magnetic changes are due to variations in the magnetic field. Although most flows are flat lying, those that are tilted pass the Tauxe and Watson tilt test. Sequential flows with statistically similar site means were grouped, and directions that were considered outliers were evaluated and removed using the Vandamme cut-off method. Three normal-polarity (N-polarity) and three reversed-polarity (R-polarity) intervals are revealed by the stratigraphically ordered flows and have mean directions of N polarity (dec/inc = 6.6°/+61.2°, k = 29.3, α95 = 4.2°), and R polarity (dec/inc = 178.2°/-59.2°, k = 16, α95 = 5.5°). Regression analysis indicates that the secular variation analysis has not been affected by regional rotation, and that apparent polar wander is negligible. The VGP distribution is almost perfectly circular and supports the preference of VGP positions for the dispersion analysis. Dispersion parameters with corrections for within-site scatter (Sb) show a range of 14.3°-25.5°, including error limits, and were consistently higher for R-polarity results than for those of N polarity. Published dispersion parameters for extrusives <5 Ma show Sb values slightly lower than ours, yielding values of 16°-19°, although the difference is not statistically significant. In contrast, published dispersion parameters from high quality data from the Cretaceous Normal Superchron are lower than those for the Neogene, which suggests that the noisiness of the magnetic field correlates with the frequency of reversals. Our new results allow us to extend the Plio-Pleistocene palaeosecular variation

  16. New Archaeointensity Result from Middle-Eastern China and Its Constraints on the Variation of the Geomagnetic Field during the last 6 kyr

    Science.gov (United States)

    Cai, S.; Jin, G.; Deng, C.; Tauxe, L.; Qin, H.; Pan, Y.; Zhu, R.

    2015-12-01

    Archaeomagnetic study is an effective way to understand the variation of the geomagnetic field over periods of hundreds to thousands of years. We have carried out archaeointensity studies on archaeological artifacts, including pottery fragments, bricks and baked clay, collected from several sites covering the middle to eastern part of China spanning the past ~6 kyr. We designed detailed rock magnetic and archaeointensity experiments in this study. Rock magnetic results indicate that the main magnetic carriers of these samples are stable magnetite or titanomagnetite with mainly fine particles of SD and SP. About 40% of the specimens in the paleointensity experiment pass the strict selection criteria and are considered to record robust intensity values. The virtual axial dipole moments (VADMs) of our sites range from ~2.5×1022 to ~15.8×1022 Am2. We record three low intensity values with VADMs of less than 3×1022 Am2, two of them comparable to the one reported by Cai et al. (2015) at ~3000 BCE while the other one comparable to those reported by Cai et al. (2014) at ~2200 BCE, which supply further evidence for the existence of 'DIPs' (decreases in paleoinetnsity) in China during the period of ~3000-2000 BCE. A high intensity value of ~16×1022 Am2 is recorded by our new data at ~1300 BCE, which may represent a new spike at this time period. The low and high values recorded by our new data update the six-fold variation between ~2200 BCE and ~1300 BCE discussed in Cai et al. (2014) to eight-fold, which may indicate a stronger geodynamic process during this period. Our new data are generally in good agreement with the published data in China, Japan and Korea at similar time periods, except the extreme low and high values discussed above, which will improve the Eastern Asian model greatly. The new data together with the published data suggest severe fluctuation of the geomagnetic field in Eastern Asia during the last 6 kyr. Vast quantities of reliable data are needed to

  17. Properties of Pliocene sedimentary geomagnetic reversal records from the Mediterranean

    NARCIS (Netherlands)

    Linssen, J.H.

    1991-01-01

    In the history of the Earth the dipolar geomagnetic field has frequently reversed polarity. Though this property was already known early this century (Brunhes, 1906), nowadays the characteristics and the origin of polarity transitions are still largely unknown. The geomagnetic field and its

  18. Properties of Pliocene sedimentary geomagnetic reversal records from the Mediterranean

    NARCIS (Netherlands)

    Linssen, J.H.

    1991-01-01

    In the history of the Earth the dipolar geomagnetic field has frequently reversed polarity. Though this property was already known early this century (Brunhes, 1906), nowadays the characteristics and the origin of polarity transitions are still largely unknown. The geomagnetic field and its variatio

  19. Quantifying Power Grid Risk from Geomagnetic Storms

    Science.gov (United States)

    Homeier, N.; Wei, L. H.; Gannon, J. L.

    2012-12-01

    We are creating a statistical model of the geophysical environment that can be used to quantify the geomagnetic storm hazard to power grid infrastructure. Our model is developed using a database of surface electric fields for the continental United States during a set of historical geomagnetic storms. These electric fields are derived from the SUPERMAG compilation of worldwide magnetometer data and surface impedances from the United States Geological Survey. This electric field data can be combined with a power grid model to determine GICs per node and reactive MVARs at each minute during a storm. Using publicly available substation locations, we derive relative risk maps by location by combining magnetic latitude and ground conductivity. We also estimate the surface electric fields during the August 1972 geomagnetic storm that caused a telephone cable outage across the middle of the United States. This event produced the largest surface electric fields in the continental U.S. in at least the past 40 years.

  20. A statistical study of magnetospheric ion composition along the geomagnetic field using the Cluster spacecraft for L values between 5.9 and 9.5

    Science.gov (United States)

    Sandhu, J. K.; Yeoman, T. K.; Fear, R. C.; Dandouras, I.

    2016-03-01

    Using ion density data obtained by the CODIF (ion Composition and Distribution Function analyser) instrument on board the Cluster spacecraft, for the interval spanning 2001-2005, an empirical model describing the average ion mass distribution along closed geomagnetic field lines is determined. The empirical model describes the region spanning 5.9≤L ions in the energy range of 0.025 to 40 keV/charge. The data reduction process involves the identification and rejection of CODIF data contaminated by penetrating energetic radiation belt particles, found to frequently occur for L ion mass along the field lines were modeled using a power law form, which maximizes toward the magnetic equatorial plane, with observed power law index values ranging between approximately -2.0 and 0.0. The resulting model illustrates some key features of the average ion mass spatial distribution, such as an average ion mass enhancement at low L in the evening sector, indicating the transport of high-latitude heavy ion outflows to the closed inner magnetosphere.

  1. [The comparative characteristics of the bone marrow cellular composition in rats after the prolonged continuous or interrupted action of a low geomagnetic field].

    Science.gov (United States)

    Azarenko, V V; Smirnov, R V

    1992-01-01

    Bone marrow cell composition in male Wistar rats exposed to long-term continuous (Run 1) or interrupted (Run 2) hypo-geomagnetic field (HGMF) with an attenuation coefficient of 172.5 generating in a permalloic chamber has been studied. When comparing the rat myelograms of the two test runs, a significant increase of lymphoid cell content, less pronounced during an interrupted exposure to HGMF by 10.1 and 6.5%, respectively, was noted. Analysis of myeloid cell response indicated that on a continuous exposure to HGMF the percentage of neutrophilic promyelocytes and myelocytes is somewhat declined. The levels of mature relating to stab and nuclear-segmental neutrophils in bone marrow during both modes of HGMF exposures practically remained unchanged. A certain decrease in cell fractions of erythroblastic shoot (chiefly at the cost of polychromatophilic normocytes), to a lesser extent manifested during an interrupted exposure to HGMF (by 5.8 and 2.4%, respectively) was noted. Long-term exposure of the animals to a weak terrestrial magnetic field causes a particular eosinophilia of bone marrow due to an increased fraction of mature eosinophils approximately similar on both HGMF profiles (by 2.1 and 2.0% respectively). On an interrupted HGMF exposure there was a significant myelogram elevation of the mast cell counts by 1.4%.

  2. Long-term variations in the flux of cosmogenic isotope 10Be over the last 10000 years: Variations in the geomagnetic field and climate

    Science.gov (United States)

    Vasiliev, S. S.; Dergachev, V. A.; Raspopov, O. M.; Jungner, H.

    2012-02-01

    A spectral analysis of data on the flux of cosmogenic 10Be in ice core samples from the Central Greenland (project GRIP) over the last 10 thousand years have been carried out. It has been shown that the 10Be flux varies cyclically; the most significant cycle is of about 2300 years. Variations in the position of the virtual geomagnetic pole over 8000 years have been analyzed. Significant components, pointing to the cyclic variation in the position of the geomagnetic pole with a period of about 2300 years, have been revealed in a periodogram of the virtual geomagnetic pole longitude. In addition to the nearly 2300-year-long cycle, some lines are observable in the 10Be flux periodogram, which can be considered as a manifestation of the 1000-year-long cycle of the 10Be deposition rate on the ice surface. The relationship between the cyclicity of the geomagnetic pole position and the 10Be flux is discussed.

  3. Relative paleointensity of the geomagnetic field over the last 4,500 years BP from sediment cores of Laguna Chaltel (Patagonia, Argentina)

    Science.gov (United States)

    Gogorza, C. G.; Irurzun, M. A.; Sinito, A. M.; Aldana, M.; Fey, M.; Ohlendorf, C.; Zolitschka, B.

    2013-05-01

    One motivation to investigate the magnetism of rocks is to study the behaviour of Earth's magnetic field of the past. The magnetic field is a vector field, having both direction and intensity. A complete understanding of it requires the study of all vector properties. However, paleointensity determinations are much more difficult than directions alone. This is one reason why the majority of paleomagnetic studies is concerned only with the directional variability of the magnetic field. Four short gravity cores from Laguna Chaltel in Patagonia, Argentina (49° 57'S, 71° 06'W) have been used to estimate the regional geomagnetic paleointensity. Measurements of intensity and directions of Natural Remanent Magnetization (NRM), magnetic susceptibility (k), isothermal remanent magnetization (IRM), saturation isothermal remanent magnetization (SIRM), as well as back field and anhysteretic remanent magnetization at 100 mT (ARM100mT) were performed and associated parameters calculated (ARM100mT/k, SIRM/ ARM100mT). In order to identify the magnetic mineralogy of the samples, IRM curves of a group of pilot samples were decomposed applying a Direct Signal Analysis (DSA) (Aldana et al., 2011). Results indicate the presence of magnetite, with logB1/2=1.8 and a relative proportion of 80%. Two other magnetic phases are observed at lower and higher logB1/2 values, probably greigite and goethite, respectively. DSA also indicates that the relative proportion of these minerals is the same in all samples analyzed. Studies also show that the magnetic grain size varies between 1 and 8 μm and that their concentration is between 0.01 and 0.08%. This range of the studied parameters indicates that our samples are suitable for paleointensity studies. The remanent magnetization at 15 mT (NRM15mT) has been normalized using the anhysteretic remanent magnetization at 15 mT (ARM15 mT), the saturation of isothermal remanent magnetization at 15 mT (SIRM15mT) and low field magnetic susceptibility (k

  4. Development and Application of a Synchronous Control System to Seismo-geomagnetic Field Observations%地震地磁场野外观测同步控制系统研制与应用

    Institute of Scientific and Technical Information of China (English)

    闫计明; 王新胜; 杨世英

    2015-01-01

    The application of geomagnetic measurements is mainly focused in two areas.The first is scientific re-search,national defense,and national economic and social development,such as mineral exploration.The second is to serve earthquake monitoring and prediction.Seismo-geomagnetic field measurements are regularly repeated measure-ments at several points in the field using a high-precision magnetometer.The purpose behind taking such measure-ments is to research the temporal change and spatial distribution of the local geomagnetic field before and after earthquakes.In the field,a survey grid or line is used for obtaining geomagnetic observations,the spatial coverage of which is generally not less than 1 50 km×1 50 km for a survey grid and not less than 200 km for a survey line.In ad-dition,the distance between measuring points is usually 5 ~40 km.For the measurement of total local geomagnetic intensity using mobile observations,two survey pegs (main and vice)were installed at field observation points.These observations were synchronized with a station that records the diurnal geomagnetic variation using a specialized in-strument installed under the same conditions as for high-precision magnetic measurements.The purpose of this was to reduce or eliminate short-period and diurnal variations (Sq )of the geomagnetic field.After the Xingtai Earthquake (1 966),mobile seismo-geomagnetic observations were initiated.Different from global geomagnetic measurements,the observation stations were generally set in earthquake regions or around active faults.Moreover,the repeated period of measurement was relatively short,i.e.,usually four times per year.However,irrespective of the form of measure-ment,a manual method for synchronizing the observations from the measuring stations in the field with the diurnal stations is necessary.Single independent magnetometers in the field cannot transmit data from the diurnal stations to the scene of the field observations in real time

  5. Geomagnetic disturbances imprints in ground and satellite altitude observatories

    Science.gov (United States)

    Yahiat, Yasmina; Lamara, Souad; Zaourar, Naima; Hamoudi, Mohamed

    2016-04-01

    The temporal evolution of the geomagnetic field and its variations have been repeatedly studied from both ground observatories and near-earth orbiting platforms. With the advent of the space ageand the launches of geomagnetic low altitude orbits satellites, a global coverage has been achieved. Since Magsat mission, more satellites were put into orbit and some of them are still collecting data enhancing the spatial and temporal descriptions of the field. Our study uses new data gathered by the latest SWARM satellite mission launched on November, 22nd 2013. It consists of a constellation of three identical satellites carrying on board high resolution and accuracy scientific equipment. Data from this constellation will allow better understanding the multiscale behavior of the geomagnetic field. Our goal is to analyze and interpret the geomagnetic data collected by this Swarm mission, for a given period and try to separate the external disturbances from internal contributions. We consider in the study the variation of the horizontal component H, for different virtual geomagnetic observatories at the satellite altitude. The analysis of data by Swarm orbital segments shows clearly the external disturbances of the magnetic field like that occurring on 27th of August 2014. This perturbation is shown on geomagnetic indexes and is related to a coronal mass ejection (CME). These results from virtual observatories are confirmed, by the equivalent analysis using ground observatories data for the same geographic positions and same epochs. Key words: Geomagnetic field, external field, geomagnetic index, SWARM mission, virtual observatories.

  6. Evaluation of using R-SCHA to simultaneously model main field and secular variation multilevel geomagnetic data for the North Atlantic

    Science.gov (United States)

    Talarn, Àngela; Pavón-Carrasco, F. Javier; Torta, J. Miquel; Catalán, Manuel

    2017-02-01

    One efficient approach to modelling the Earth's core magnetic field involves the inclusion of crossover marine data which cover areas lacking in observatory and repeat station data for epochs when precise three-component satellite magnetic field measurements were not common. In this study, we show how the Revised Spherical Cap Harmonic Analysis (R-SCHA) can appropriately provide a continuous-time field model for the North Atlantic region by using multilevel sets of geomagnetic data such as marine, repeat station, observatory, and satellite data. Taking advantage of the properties of the R-SCHA basis functions we can model the radial and horizontal variations of the main field and its secular variation with the most suitable spatial and temporal wavelengths. To assess the best compromise between the data fit and the model roughness, temporal and spatial regularization matrices were implemented in the modelling approach. Two additional strategies were also used to obtain a satisfactory regional model: the opportunity to fit the anomaly bias at each observatory location, and constraining the regional model to the CHAOS-6 model at the end of its period of validity, i.e. 1999-2000, allowing a smooth transition with the predictions of this recent model. In terms of the root mean square error, the degree of success was limited partly because of the high uncertainties associated with some of the datasets (especially the marine ones), but we have produced a model that performs comparably to the global models for the period 1960-2000, thus showing the benefits of using this regional technique.

  7. A GPS Independent Geomagnetic Field Mapping and Correction Algorithm%不依赖GPS的磁图测绘与校正新方法

    Institute of Scientific and Technical Information of China (English)

    寇义民; 夏红伟; 刘睿; 王常虹

    2011-01-01

    针对水下磁场测绘中因载体难以经常上浮修正导航误差而导致的测绘结果坐标误差较大的问题,结合磁场测量的特殊性,并采用边导航边校正的思想,提出了一种不依赖GPS的全新磁图测绘方法.首先以惯性导航系统为标准进行第一次测绘并获得具有一定坐标误差的初始磁图,然后对初始磁图进行图形处理与信息提取,在此基础上进行第二次测绘.在第二次测绘中用从初始磁图获得的特征信息结合磁场传感器与惯性器件的输出构建卡尔曼滤波器,从而达到同时修正自身运动状态与初始磁图的目的.理论分析与仿真结果都证实了本方法可以通过两次误差较大的低精度测绘获得精度高得多的测绘结果.%A new algorithm for GPS independenl geomagnetic field mapping is developed in this paper. The idea from the SLAM ( simultaneous localization and mapping) method is implementted here, while several tricks are put forward to make the idea applicable. The algorithm is divided into three steps. Firstly, an inaccurate map is created with magnetic measurement data and position output from inertial navigation systems. Secondly, the map is analyzed and processed to extract shape information. Thirdly, another mapping process is carried out along the same route; meanwhile an extended Kalman filter is constructed by using the shape information of the original map, the status of the inertial navigation system, and the new measurement data. The initial mapping errors and the navigation errors will be estimated and adjusted together after the fiher' s convergence. Theoretical analysis and simulation results both prove that a much more accurate geomagnetic map can be built based on two inaccurate GPS independent surveys.

  8. An archaeomagnetic study of Upper Mesopotamia and Central Anatolia between 2500 and 700 BCE. Further evidence for an extremely strong geomagnetic field ca. 3000 years ago

    Science.gov (United States)

    Ertepinar, Pinar; Langereis, Cor; Biggin, Andrew; de Groot, Lennart

    2014-05-01

    The distribution of archaeomagnetic data in eastern Europe and the Near and Middle East shows a remarkable gap in Turkey. This study presents the first archaeomagnetic results from eight different archaeological sites in Central and Southeast Turkey. We sampled furnaces, burnt mud-brick walls, and granite and ignimbrite foundation stones. The rock magnetic experiments indicate that in the majority of the samples the dominant magnetic carrier is magnetite, which is stable to heating to temperatures of 700° C. In general, the demagnetization diagrams are single component and all sets display well-defined characteristic magnetizations and clustered directions. For the period between 2500 and 700 BCE, the declinations are between 350° and 20° while inclinations are in the range of 49-64° . The directional results are compared with the global geomagnetic field models (CALS7k.2, ARCH3k_cst.1 and CALS3k.4) and the data from the archaeomagnetic database GEOMAGIA50v2. The results are coherent with both the data and the models except for two near-contemporaneous sets dating ~2000 BCE, which are offset to the east by more than 20° with respect to CALS7k.2. Archaeointensity measurements were made using the microwave and conventional thermal Thellier methods, as well as the multi-specimen method. These different methods yielded comparable and intriguing results. While intensities from the furnaces are slightly higher than the CALS7k.2 model and in agreement with the GEOMAGIA50v2 and the Middle East data, the results from mud-brick walls suggest a high intensity of 100.8μT (17.7 x 1022 Am2 )at ~1000 BCE. This result is in excellent agreement with recent claims of extremely high intensity measured in other regions of the Middle East for this time period though less consistent with these being associated with extremely short-lived events. Finally, we discuss our new and other recently published archaeointensity results in terms of geomagnetic intensity versus climate.

  9. Archaeomagnetic study of five mounds from Upper Mesopotamia between 2500 and 700 BCE: Further evidence for an extremely strong geomagnetic field ca. 3000 years ago

    Science.gov (United States)

    Ertepinar, P.; Langereis, C. G.; Biggin, A. J.; Frangipane, M.; Matney, T.; Ökse, T.; Engin, A.

    2012-12-01

    The distribution of archaeomagnetic data in eastern Europe and the Near and Middle East shows a remarkable gap in Turkey. This study presents the first archaeomagnetic results from five different mounds in southeast Turkey, the northern part of Mesopotamia. The rock magnetic experiments indicate that in the majority of the samples the dominant magnetic carrier is magnetite, which is stable to heating to temperatures of 700 °C. In general, the demagnetization diagrams are single component and all five sets display well-defined characteristic magnetizations and clustered directions. For the period between 2500 and 700 BCE, the declinations are between 350° and 20° while inclinations are in the range of 49-64°. The directional results are compared with the global geomagnetic field models (CALS7k.2, ARCH3k_cst.1 and CALS3k.4) and the data from the archaeomagnetic database GEOMAGIA50v2. The results are coherent with both the data and the models except for two near-contemporaneous sets dating ˜2000 BCE, which are offset to the east by more than 20° with respect to CALS7k.2. Archaeointensity measurements were made using the microwave and conventional thermal Thellier methods applied to five sets of samples (four furnaces and a mud-brick wall). These yielded comparable and intriguing results. While those from the furnaces are slightly higher than the CALS7k.2 model and in agreement with the GEOMAGIA50v2 and the Middle East data, the results from the mud-brick wall suggest a high intensity of 100.8 μT (17.7×1022 Am2) at ˜1000 BCE. This result is in excellent agreement with recent claims of extremely high intensity measured in other regions of the Middle East for this time period though less consistent with these being associated with extremely short-lived events. Finally, we discuss our new and other recently published archaeointensity results in terms of geomagnetic intensity versus climate.

  10. Moon Shadow by Cosmic Rays under the Influence of Geomagnetic Field and Search for Antiprotons at Multi-TeV Energies

    CERN Document Server

    Amenomori, M; Bi, X J; Chen, D; Cui, S W; Danzengluobu; Ding, L K; Ding, X H; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gao, X Y; Geng, Q X; Guo, H W; He, H H; He, M; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Huang, Q; Jia, H Y; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren; Le, G M; Li, A F; Li, J Y; Lou, Y Q; Lü, H; Lu, S L; Meng, X R; Mizutani, K; Mu, J; Munakata, K; Nagai, A; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ouchi, T; Ozawa, S; Ren, J R; Saitô, T; Saito, T Y; Sakata, M; Sako, T K; Sasaki, T; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, B S; Wang, H; Wang, X; Wang, Y G; Wu, H R; Xue, L; Yamamoto, Y; Yan, C T; Yang, X C; Yasue, S; Ye, Z H; Yu, G C; Yuan, A F; Yuda, T; Zhang, H M; Zhang, J L; Zhang, N J; Zhang, X Y; Zhang, Y; Zhang Zhaxisangzhu, Yi; Zhou, X X

    2007-01-01

    We have observed the shadowing of galactic cosmic ray flux in the direction of the moon, the so-called moon shadow, using the Tibet-III air shower array operating at Yangbajing (4300 m a.s.l.) in Tibet since 1999. Almost all cosmic rays are positively charged; for that reason, they are bent by the geomagnetic field, thereby shifting the moon shadow westward. The cosmic rays will also produce an additional shadow in the eastward direction of the moon if cosmic rays contain negatively charged particles, such as antiprotons, with some fraction. We selected 1.5 x10^{10} air shower events with energy beyond about 3 TeV from the dataset observed by the Tibet-III air shower array and detected the moon shadow at $\\sim 40 \\sigma$ level. The center of the moon was detected in the direction away from the apparent center of the moon by 0.23$^\\circ$ to the west. Based on these data and a full Monte Carlo simulation, we searched for the existence of the shadow produced by antiprotons at the multi-TeV energy region. No evid...

  11. Coronal mass ejections and geomagnetic storms: Seasonal variations

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, J.L.; Gosling, J.T.; McComas, D.J.

    1992-07-01

    The well-established semiannual geomagnetic cycle, with peak activity near the equinoxes, has been attributed to the angle between the solar rotation axis and the geomagnetic dipole, which modulates the GSM Bz component in the interplanetary magnetic field (MF). This effect is predicted to be accentuated in the shocked plasma ahead of fast coronal mass ejections (CMESs); its relevance to the internal fields of the ejecta is unclear. CMEs, particularly fast events driving interplanetary shocks, are the cause of almost all large geomagnetic storms near solar maximum. We use a set of CMEs identified by ISEE-3 observations of bidirectional electron streaming, plus IMF and geomagnetic data, to investigate the semiannual geomagnetic variation and its relation to CMEs. We find that the geomagnetic effectiveness of CMEs and post-shock solar wind is well-ordered by speed and by the southward component of the IMF in GSM coordinates, as well as by preexisting geomagnetic conditions. The post-shock seasonal effect, with geomagnetic effectiveness maximizing near April 5 for negative GSEQ By and near October 5 for positive GSEQ By, is identifiable in shock and shock/CME events, but not for CME events without leading shocks. When used to complement the more fundamental causal parameter of CME speed, the seasonal effect appears to have value for prediction of geomagnetic storms.

  12. Coronal mass ejections and geomagnetic storms: Seasonal variations

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, J.L.; Gosling, J.T.; McComas, D.J.

    1992-01-01

    The well-established semiannual geomagnetic cycle, with peak activity near the equinoxes, has been attributed to the angle between the solar rotation axis and the geomagnetic dipole, which modulates the GSM Bz component in the interplanetary magnetic field (MF). This effect is predicted to be accentuated in the shocked plasma ahead of fast coronal mass ejections (CMESs); its relevance to the internal fields of the ejecta is unclear. CMEs, particularly fast events driving interplanetary shocks, are the cause of almost all large geomagnetic storms near solar maximum. We use a set of CMEs identified by ISEE-3 observations of bidirectional electron streaming, plus IMF and geomagnetic data, to investigate the semiannual geomagnetic variation and its relation to CMEs. We find that the geomagnetic effectiveness of CMEs and post-shock solar wind is well-ordered by speed and by the southward component of the IMF in GSM coordinates, as well as by preexisting geomagnetic conditions. The post-shock seasonal effect, with geomagnetic effectiveness maximizing near April 5 for negative GSEQ By and near October 5 for positive GSEQ By, is identifiable in shock and shock/CME events, but not for CME events without leading shocks. When used to complement the more fundamental causal parameter of CME speed, the seasonal effect appears to have value for prediction of geomagnetic storms.

  13. New Contributions to the Geomagnetic Instability Time Scale: Paleomagnetic study of Tequila and Ceboruco-San Pedro-Amado Nervo Volcanic Fields (Trans Mexican Volcanic Belt)

    Science.gov (United States)

    Rodriguez Ceja, M.; Gogichaishvili, A.; Alva-Valdivia, L.; Rosas Elguera, J.; Calvo, M.; Urrutia-Fucugauchi, J.

    2005-05-01

    The Trans-Mexican Volcanic Belt (TMVB) is one of the largest continental volcanic arcs of the North American plate. It spans about 1000 km from the Pacific to the Gulf of Mexico. Despite the abundance of thick lava sequences with quite high extrusion rates, the TMVB have been relatively little studied from a paleomagnetic point of view. Previous studies were aimed for tectonic evolution of the region rather than documenting fluctuations of Earth's magnetic field in terms of both directions and intensity. We report a detailed paleomagnetic and rock-magnetic study of Tequila and Ceboruco-San Pedro-Amado Nervo volcanic fields. 350 oriented samples belonging to 31 independent cooling units were collected. All these sites were previously dated by means of the state-of-the-art 40Ar-39Ar geochronological method and span from 1.1 Ma to 2 Ky. Rock-magnetic experiments which included continuous susceptibility, isothermal remanence acquisition and hysteresis measurements point to simple magnetic mineralogy. In most of cases, the remanence is carried by Ti-poor titanomagnetite of pseudo-single-domain magnetic structure. The paleodirections of the flow dated as 819±25 ka correspond to a VGP latitude of 18° N. This anomalous field behaviour apparently recorded prior to the Matuyama-Brunhes reversal may coincide with the geomagnetic event, defined as M-B precursor. Two independent lava flows, dated as 623±91 and 614±16 ka respectively, yield reverse paleodirections and one lava flow dated as 690±29 yields transitional paleodirections. It is possible that these lavas erupted during the worldwide observable Big Lost or Delta events.

  14. Geomagnetic Indices Bulletin (GIB)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Geomagnetic Indices Bulletin is a one page sheet containing the magnetic indices Kp, Ap, Cp, An, As, Am and the provisional aa indices. The bulletin is published...

  15. Geomagnetic aa Indices

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The geomagnetic aa indices are the continuation of the series beginning in the year 1868. A full description of these indices is given in the International...

  16. Geomagnetic Storm Sudden Commencements

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Storm Sudden Commencements (ssc) 1868 to present: STORM1 and STORM2 Lists: (Some text here is taken from the International Association of Geomagnetism and Aeronomy...

  17. Magnetic local time dependence of geomagnetic disturbances contributing to the AU and AL indices

    DEFF Research Database (Denmark)

    Tomita, S; Nose´, M; Iyemori, T;

    2010-01-01

    The Auroral Electrojet (AE) indices, which are composed of four indices (AU, AL, AE, and AO), are calculated from the geomagnetic field data obtained at 12 geomagnetic observatories that are located in geomagnetic latitude (GMLAT) of 61.7°-70°. The indices have been widely used to study magnetic...... activity in the auroral zone. In the present study, we examine magnetic local time (MLT) dependence of geomagnetic field variations contributing to the AU and AL indices. We use 1-min geomagnetic field data obtained in 2003. It is found that both AU and AL indices have two ranges of MLT (AU: 15:00-22:00MLT...

  18. Thermospheric mass density variations during geomagnetic storms and a prediction model based on the merging electric field

    NARCIS (Netherlands)

    Liu, R.; Lühr, H.; Doornbos, E.; Ma, S.Y.

    2010-01-01

    With the help of four years (2002–2005) of CHAMP accelerometer data we have investigated the dependence of low and mid latitude thermospheric density on the merging electric field, Em, during major magnetic storms. Altogether 30 intensive storm events (Dstmin <−100 nT) are chosen for a statistical s

  19. Application of PWVD in time-frequency analysis of geomagnetic field%伪魏格纳-维勒分布在地磁时频分析中的应用

    Institute of Scientific and Technical Information of China (English)

    何康; 晏锐; 郑海刚; 李军辉; 方震

    2013-01-01

    Using Pseudo Wigner-Ville Distribution ( PWVD ) in time-frequency analysis of geomagnetic Z-component on magnetically quiet and disturbed days, we discover geomagnetic daily variations with period 6~24 hour in all stations. The part with period 2~6 hour is not only influenced by external field, but also contains regional information, which shows the characteristics of crustal and induction field. Using Smoothed Pseudo Wigner-Ville Distribution (SPWVD) in time-frequency analysis of geomagnetic Z-component before the Wenchuan Ms8. 0 earthquake , we found that the geomagnetic stations near the epicenter recorded an abnormal signal with period 4.4 hour before the major earthquake, and the amplitudes of the signal in different stations decreased with epicentral distance increased.%采用伪魏格纳-维勒分布对静日和扰日的地磁场Z分量数据进行时频分析,结果表明周期为6~ 24h的静日变化在静日和扰日的各个台站都存在;而2~6h部分既受外源场影响,也反映了区域信息,表现出感应磁场和地壳磁场的特征.采用平滑伪魏格纳-维勒分布对汶川8.0级地震前各台的Z分量数据进行时频分析,结果显示震中附近的地磁台站在震前记录到了周期约为4.4h的异常信号,其振幅随震中距增大而减小.

  20. Concerning long-term geomagnetic variations and space climatology

    Directory of Open Access Journals (Sweden)

    K.-H. Glassmeier

    2004-11-01

    Full Text Available During geomagnetic polarity transitions the surface magnetic field of the Earth decays to about 25% and less of its present value. This implies a shrinking of the terrestrial magnetosphere and posses the question of whether magnetospheric magnetic field variations scale in the same manner. Furthermore, the geomagnetic main field also controls the magnetospheric magnetic field and space weather conditions. Long-term geomagnetic variations are thus intimately related to space climate. We critically assess existing scaling relations and derive new ones for various magnetospheric parameters. For example, we find that ring current perturbations do not increase with decreasing dipole moment. And we derive a scaling relation for the polar electrojet contribution, indicating a weak increase with increasing internal field. From this we infer that the ratio between external and internal field contributions may be weakly enhanced during polarity transitions. Our scaling relations also provide more insight on the importance of the internal geomagnetic field contribution for space climate.

  1. Toward a possible next geomagnetic transition?

    Directory of Open Access Journals (Sweden)

    A. De Santis

    2013-09-01

    Full Text Available The geomagnetic field is subject to possible reversals or excursions of polarity during its temporal evolution. Considering that: (a the typical average time between one reversal and the next (the so-called chron is around 300 000 yr, (b the last reversal occurred around 780 000 yr ago, (c more excursions (rapid changes of polarity can occur within the same chron and (d the geomagnetic field dipole is currently decreasing, a possible imminent geomagnetic reversal or excursion would not be completely unexpected. In that case, such a phenomenon would represent one of the very few natural hazards which are really global. The South Atlantic Anomaly (SAA is a great depression of the geomagnetic field at the Earth's surface, caused by a reverse magnetic flux in the terrestrial outer core. In analogy with critical point phenomena characterised by some cumulative quantity, we fit the surface extent of this anomaly over the last 400 yr with power or logarithmic functions in reverse time, also decorated by log-periodic oscillations, whose final singularity (a critical point tc reveals a great change in the near future (2034 ± 3 yr, when the SAA area reaches almost a hemisphere. An interesting aspect that has been recently found is the possible direct connection between the SAA and the global mean sea level (GSL. That the GSL is somehow connected with SAA is also confirmed from the similar result when an analogous critical-like fit is performed over GSL: the corresponding critical point (2033 ± 11 yr agrees, within the estimated errors, with the value found for SAA. From this result, we point out the intriguing conjecture that tc would be the time of no return, after which the geomagnetic field could fall into an irreversible process of a global geomagnetic transition that could be a reversal or excursion of polarity.

  2. Toward a possible next geomagnetic critical transition?

    Science.gov (United States)

    Qamili, Enkelejda; De Santis, Angelo; Wu, Lixin

    2014-05-01

    The geomagnetic field is subject to possible reversals or excursions of polarity during its temporal evolution. Considering the characteristics of the recent geomagnetic field, a possible imminent geomagnetic reversal or excursion would not be completely unexpected. In that case, such a phenomenon would represent one of the very few natural hazards that are really global. The South Atlantic Anomaly (SAA) is a great depression of the geomagnetic field strength at the Earth's surface, caused by a reverse magnetic flux in the terrestrial outer core. In analogy with critical point phenomena characterized by some cumulative quantity, we fit the surface extent of this anomaly over the last 400 yr with power law or logarithmic functions in reverse time, also decorated by log-periodic oscillations, whose final singularity (a critical point tc) reveals a great change in the near future (2034±3 yr), when the SAA area reaches almost a hemisphere. An interesting aspect that has recently been found is the possible direct connection between the SAA and the global mean sea level (GSL). That the GSL is somehow connected with SAA is also confirmed by the similar result when an analogous critical-like fit is performed over GSL: the corresponding critical point (2033±11 yr) agrees, within the estimated errors, with the value found for the SAA. From this result, we point out the intriguing conjecture that tc would be the time of no return, after which the geomagnetic field could fall into an irreversible process of a global geomagnetic transition that could be a reversal or excursion of polarity.

  3. Toward a possible next geomagnetic transition?

    Science.gov (United States)

    De Santis, A.; Qamili, E.; Wu, L.

    2013-12-01

    The geomagnetic field is subject to possible reversals or excursions of polarity during its temporal evolution. Considering that: (a) in the last 83 million yr the typical average time between one reversal and the next (the so-called chron) is around 400 000 yr, (b) the last reversal occurred around 780 000 yr ago, (c) more excursions (rapid changes in polarity) can occur within the same chron and (d) the geomagnetic field dipole is currently decreasing, a possible imminent geomagnetic reversal or excursion would not be completely unexpected. In that case, such a phenomenon would represent one of the very few natural hazards that are really global. The South Atlantic Anomaly (SAA) is a great depression of the geomagnetic field strength at the Earth's surface, caused by a reverse magnetic flux in the terrestrial outer core. In analogy with critical point phenomena characterized by some cumulative quantity, we fit the surface extent of this anomaly over the last 400 yr with power law or logarithmic functions in reverse time, also decorated by log-periodic oscillations, whose final singularity (a critical point tc) reveals a great change in the near future (2034 ± 3 yr), when the SAA area reaches almost a hemisphere. An interesting aspect that has recently been found is the possible direct connection between the SAA and the global mean sea level (GSL). That the GSL is somehow connected with SAA is also confirmed by the similar result when an analogous critical-like fit is performed over GSL: the corresponding critical point (2033 ± 11 yr) agrees, within the estimated errors, with the value found for the SAA. From this result, we point out the intriguing conjecture that tc would be the time of no return, after which the geomagnetic field could fall into an irreversible process of a global geomagnetic transition that could be a reversal or excursion of polarity.

  4. On Geomagnetism and Paleomagnetism

    Science.gov (United States)

    Voorhies, Coerte V.

    1998-01-01

    A statistical description of Earth's broad scale, core-source magnetic field has been developed and tested. The description features an expected, or mean, spatial magnetic power spectrum that is neither "flat" nor "while" at any depth, but is akin to spectra advanced by Stevenson and McLeod. This multipole spectrum describes the magnetic energy range; it is not steep enough for Gubbins' magnetic dissipation range. Natural variations of core multipole powers about their mean values are to be expected over geologic time and are described via trial probability distribution functions that neither require nor prohibit magnetic isotropy. The description is thus applicable to core-source dipole and low degree non-dipole fields despite axial dipole anisotropy. The description is combined with main field models of modem satellite and surface geomagnetic measurements to make testable predictions of: (1) the radius of Earth's core, (2) mean paleomagnetic field intensity, and (3) the mean rates and durations of both dipole power excursions and durable axial dipole reversals. The predicted core radius is 0.7% above the 3480 km seismologic value. The predicted root mean square paleointensity (35.6 mu T) and mean Virtual Axial Dipole Moment (about 6.2 lx 1022 Am(exp 2)) are within the range of various mean paleointensity estimates. The predicted mean rate of dipole power excursions, as defined by an absolute dipole moment <20% of the 1980 value, is 9.04/Myr and 14% less than obtained by analysis of a 4 Myr paleointensity record. The predicted mean rate of durable axial dipole reversals (2.26/Myr) is 2.3% more than established by the polarity time-scale for the past 84 Myr. The predicted mean duration of axial dipole reversals (5533 yr) is indistinguishable from an observational value. The accuracy of these predictions demonstrates the power and utility of the description, which is thought to merit further development and testing. It is suggested that strong stable stratification

  5. Geomagnetic Workshop, Canberra

    Science.gov (United States)

    Barton, C. E.; Lilley, F. E. M.; Milligan, P. R.

    On May 14-15, 1985, 63 discerning geomagnetists flocked to Canberra to attend the Geomagnetic Workshop coorganized by the Australian Bureau of Mineral Resources (BMR) and the Research School of Earth Sciences, Australian National University (ANU). With an aurorally glowing cast that included an International Association of Geomagnetism and Aeronomy (IAGA) president, former president, and division chairman, the Oriental Magneto-Banquet (which was the center of the meeting), was assured of success. As a cunning ploy to mask the true nature of this gastronomic extravagance from the probings of income tax departments, a presentation of scientific papers on Australian geomagnetism in its global setting was arranged.The Australian region, including New Zealand, Papua New Guinea, Indonesia, and a large sector of the Antarctic, covers one eighth of the Earth's surface and historically has played an important role in the study of geomagnetism. The region contains both the south magnetic and geomagnetic poles, and two Australian Antarctic stations (Casey and Davis) are situated in the region of the south polar cusp (see Figure 1).

  6. Tests for orbital influences on the geomagnetic field, and Quarternary magnetic records from North Atlantic and Arctic deep-sea sediments

    Science.gov (United States)

    Xuan, Chuang

    This dissertation investigated the possible connection between orbital variations and the Earth's magnetic field, and the origin of orbital periods in sedimentary relative paleointensity (RPI) records, using previously published data. Circular statistic methods were utilized to test whether there is any consistent relationship between the phase of orbital parameters and the timing of geomagnetic reversals or excursions. The results indicate no discernable tendency, disagreeing with orbital forcing on the geodynamo. Numerical simulations further indicate that precision of the current polarity timescales need to be improved for any firm relationship to be established. Wavelet analyses methods were employed to investigate the origin of orbital periods in the RPI records. In some records, significant coherence at orbital periods occurs between RPI and a particular magnetic grain-size proxy. Therefore, orbital periods in some RPI records are attributed to lithologic 'contamination' resulted from incomplete normalization of the natural remanent magnetization (NRM) record. Comparison of RPI records from different regions of the world in both the time and time-frequency domains imply that the 'contamination' does not debilitate most RPI records as a global signal that is primarily of geomagnetic origin. Calibrated RPI and oxygen isotope stack records (PISO-1500) were developed by simultaneously matching and stacking both RPI and oxygen isotope data for 13 pairs of high-resolution global records. Wavelet analyses on the PISO-1500 RPI stack record failed to show significant orbital periods, and no tendencies were found for RPI minima in the stack to occur at particular phases of orbital variations. The generation of high-resolution paleomagnetic data is often associated with processing large volumes of measurement data. MATLAB(TM) software with graphical user interfaces was developed in this dissertation work to improve the efficiency of processing large volumes of

  7. New archaeomagnetic directions from Portugal and evolution of the geomagnetic field in Iberia from Late Bronze Age to Roman Times

    Science.gov (United States)

    Palencia-Ortas, A.; Osete, M. L.; Campuzano, S. A.; McIntosh, G.; Larrazabal, J.; Sastre, J.; Rodriguez-Aranda, J.

    2017-09-01

    This study presents new archaeomagnetic results from 33 combustion structures (kilns and hearths) from the archaeological sites of Castelinho, Crestelos, Olival Poço da Barca and Fonte do Milho in NE Portugal. The age of the investigated structures ranges from 1210 BC to 200 AD according to calibrated radiocarbon dating, thermoluminescence dating and archaeological constraints. Stepwise thermal and alternating field demagnetization isolate a single, stable, characteristic remanence component with very well defined directions. Rock magnetic analyses suggest low-Ti titanomagnetite/maghemite as the main magnetic carrier of the remanence. Mean directions are well grouped in most structures. The effect of thermoremanent anisotropy on mean directions has been evaluated and was found to be important. Inclination increases of between 2° and 13° after applying the anisotropy correction at specimen level. This highlights the requirement of evaluating this effect on the directions of small and flattened thin kilns and hearths. The 31 new directional data improve both the temporal and spatial distribution of the Iberian archaeomagnetic dataset from Late Bronze Age to Roman Times. Finally, a new directional palaeosecular variation curve for Iberia for the last twelve centuries BC is proposed. The curve has been computed using the bootstrap method and includes data coming from sites within 900 km of Madrid. The new palaeodirectional secular variation curve for Iberia is consistent with the Western European palaeosecular variation curve and with the prediction of regional European models.

  8. Steady induction effects in geomagnetism. Part 1A: Steady motional induction of geomagnetic chaos

    Science.gov (United States)

    Voorhies, Coerte V.

    1992-01-01

    Geomagnetic effects of magnetic induction by hypothetically steady fluid motion and steady magnetic flux diffusion near the top of Earth's core are investigated using electromagnetic theory, simple magnetic earth models, and numerical experiments with geomagnetic field models. The problem of estimating a steady fluid velocity field near the top of Earth's core which induces the secular variation indicated by broad-scale models of the observed geomagnetic field is examined and solved. In Part 1, the steady surficial core flow estimation problem is solved in the context of the source-free mantle/frozen-flux core model. In the first paper (IA), the theory underlying such estimates is reviewed and some consequences of various kinematic and dynamic flow hypotheses are derived. For a frozen-flux core, fluid downwelling is required to change the mean square normal magnetic flux density averaged over the core-mantle boundary. For surficially geostrophic flow, downwelling implies poleward flow. The solution of the forward steady motional induction problem at the surface of a frozen-flux core is derived and found to be a fine, easily visualized example of deterministic chaos. Geomagnetic effects of statistically steady core surface flow may well dominate secular variation over several decades. Indeed, effects of persistent, if not steady, surficially geostrophic core flow are described which may help explain certain features of the present broad-scale geomagnetic field and perhaps paleomagnetic secular variation.

  9. Extreme geomagnetically induced currents

    Science.gov (United States)

    Kataoka, Ryuho; Ngwira, Chigomezyo

    2016-12-01

    We propose an emergency alert framework for geomagnetically induced currents (GICs), based on the empirically extreme values and theoretical upper limits of the solar wind parameters and of d B/d t, the time derivative of magnetic field variations at ground. We expect this framework to be useful for preparing against extreme events. Our analysis is based on a review of various papers, including those presented during Extreme Space Weather Workshops held in Japan in 2011, 2012, 2013, and 2014. Large-amplitude d B/d t values are the major cause of hazards associated with three different types of GICs: (1) slow d B/d t with ring current evolution (RC-type), (2) fast d B/d t associated with auroral electrojet activity (AE-type), and (3) transient d B/d t of sudden commencements (SC-type). We set "caution," "warning," and "emergency" alert levels during the main phase of superstorms with the peak Dst index of less than -300 nT (once per 10 years), -600 nT (once per 60 years), or -900 nT (once per 100 years), respectively. The extreme d B/d t values of the AE-type GICs are 2000, 4000, and 6000 nT/min at caution, warning, and emergency levels, respectively. For the SC-type GICs, a "transient alert" is also proposed for d B/d t values of 40 nT/s at low latitudes and 110 nT/s at high latitudes, especially when the solar energetic particle flux is unusually high.

  10. Research on Stealthy Headphone Detector Based on Geomagnetic Sensor

    Directory of Open Access Journals (Sweden)

    Liu Ya

    2016-01-01

    Full Text Available A kind of stealth headphone detector based on geomagnetic sensor has been developed to deal with the stealth headphones which are small, extremely stealthy and hard to detect. The U.S. PNI geomagnetic sensor is chosen to obtain magnetic field considering the strong magnetic performance of stealth headphones. The earth’s magnetic field at the geomagnetic sensor is eliminated by difference between two geomagnetic sensors, and then weak variations of magnetic field is detected. STM8S103K2 is chosen as the central controlling chip, which is connected to LED, buzzer and LCD 1602. As shown by the experimental results, the probe is not liable to damage by the magnetic field and the developed device has high sensitivity, low False Positive Rate (FAR and satisfactory reliability.

  11. On the Possibilities of Predicting Geomagnetic Secular Variation with Geodynamo Modeling

    Science.gov (United States)

    Kuang, Wei-Jia; Tangborn, Andrew; Sabaka, Terrance

    2004-01-01

    We use our MoSST core dynamics model and geomagnetic field at the core-mantle boundary (CMB) continued downward from surface observations to investigate possibilities of geomagnetic data assimilation, so that model results and current geomagnetic observations can be used to predict geomagnetic secular variation in future. As the first attempt, we apply data insertion technique to examine evolution of the model solution that is modified by geomagnetic input. Our study demonstrate that, with a single data insertion, large-scale poloidal magnetic field obtained from subsequent numerical simulation evolves similarly to the observed geomagnetic variation, regardless of the initial choice of the model solution (so long it is a well developed numerical solution). The model solution diverges on the time scales on the order of 60 years, similar to the time scales of the torsional oscillations in the Earth's core. Our numerical test shows that geomagnetic data assimilation is promising with our MoSST model.

  12. Wavelet analysis of paleomagnetic data: 5. Early Jaramillo reversal and main characteristic times in the interval from 3 to 70 ka in the variations of the elements of geomagnetic field (Western Turkmenia)

    Science.gov (United States)

    Gurarii, G. Z.

    2013-01-01

    The data on the variations in the elements of the geomagnetic field with the characteristic times of 3-70 ka during the 180-ka interval that includes the final stage of the Matuyama chron, the Jaramillo subchron, and the Early Jaramillo reversal are presented. A series of particular features are revealed in the variations. It is shown that such detailed characteristics of the variations, which might be critical for identifying the causes of the reversals, can only be derived by thorough investigation of the sedimentary rocks that were accumulated during very long time intervals (many hundreds of years) and slowly cooling intrusions.

  13. 地磁场中潜艇运动感应静电场建模%Model of the Induced Static Electric Field by Moving Submarine in the Geomagnetic Field

    Institute of Scientific and Technical Information of China (English)

    嵇斗; 王向军; 柳懿; 刘德红

    2014-01-01

    A submarine with metal hull can induces static electric field when it moves across geomagnetic field .A submarine can be treated simply as a metal spheroid hull with long macroaxis and considering sub-marine in two conditions:moving on surface and diving,the induced static electric field model was de-duced.Taking one USN nuke submarine as an example,the distribution of its induced electric field is sim-ulated by computers conveniently to obtain two kinds of underwater electric field distribution.Results show that,the magnitude of induced electric field near the submarine is large with apparent characteristics of range attenuation.%地磁场中的金属壳体潜艇在航行时会产生感应电动势,从而产生感应静电场,将潜艇简化为长椭球壳,分别建立了潜艇处于浮航和潜航两种状态下的运动感应静电场模型,给出了电场三分量表达式;以美海国军洛杉矶级潜艇为例进行了感应电场的仿真计算,获得了两种状态下潜艇水下电场分布,仿真结果表明:感应电场在潜艇附近量值较大,随距离衰减明显。

  14. International Geomagnetic Reference Field—the eighth generation

    Science.gov (United States)

    Mandea, Mioara; Macmillan, Susan

    2000-12-01

    The eighth generation of the International Geomagnetic Reference Field (IGRF) was adopted in 1999 by the International Association of Geomagnetism and Aeronomy (IAGA) Division V, Working Group 8. This differs from the previous generation by the addition of the IGRF 2000 which comprises a main-field model for the epoch 2000.0 and a predictive secular-variation model for 2000.0-2005.0. This paper lists the IGRF coefficients and includes contour maps computed using IGRF 2000.

  15. Geomagnetic disturbance and the orientation of nocturnally migrating birds.

    Science.gov (United States)

    Moore, F R

    1977-05-06

    Free-flying passerine migrants respond to natural fluctuations in the earth's magnetic field. The variability in flight directions of nocturnal migrants is significantly correlated with increasing geomagnetic disturbance as measured by both the K index and various components of the earth's magnetic field. The results indicate that such disturbances influence the orientation of free-flying migrants, but the evidence is not sufficient to show that geomagnetism is a cue in their orientation system.

  16. Comment on Decay of the Dst Field of Geomagnetic Disturbance After Substorm Onset and its Implication to Storm-Substorm Relation

    Science.gov (United States)

    Rostoker, G.; Baumjohann, W.; Gonzalez, W.; Kamide, Y.; Kokubun, S.; McPherron, R. L.; Tsurutani, B. T.

    1996-01-01

    Over the past few years, there has been a considerable revival in the study of geomagnetic storms stimulated by an increasing knowledge of the energetic particles which comprise the ring current. It is only in recent years that the composition of the ring current has been thouroughly explored and the important role of the oxygen component of the near Earth plasma sheet has become recognized.

  17. Geomagnetic Earthquake Precursors Improvement Formulation on the basis of SKO (Skopje) and PAG (Intermagnet) Geomagnetic Data

    CERN Document Server

    Mavrodiev, Strachimir Chterev

    2012-01-01

    In this paper we show that the simple analysis of the local geomagnetic field behaviour can serve as reliable imminent precursor for regional seismic activity increasing. As the first step the problem was investigated using one- component Dubna fluxgate magnetometer. The result of 2001-2004 Sofia monitoring confirmed many old papers for connection between Earth tide (Sun- Moon tides as earthquakes trigger) and jump (Geomagnetic quake) of daily averaged one minute standart deviation of the geomagnetic field. The second step (2004-present), which included analisys of three-component Danish fluxgate magnetometer data, worked in Skopje Seismological observatory, confirmed the first step result. The analysis of INTERMAGNET data stations around which was happened stronger earthquakes also confirmed our result. The distribution of time difference between the times of such earthquakes and local daily averaged tide vector movement for impending tide extreme confirms our estimate that the increasing seismicity is reali...

  18. Minimax confidence intervals in geomagnetism

    Science.gov (United States)

    Stark, Philip B.

    1992-01-01

    The present paper uses theory of Donoho (1989) to find lower bounds on the lengths of optimally short fixed-length confidence intervals (minimax confidence intervals) for Gauss coefficients of the field of degree 1-12 using the heat flow constraint. The bounds on optimal minimax intervals are about 40 percent shorter than Backus' intervals: no procedure for producing fixed-length confidence intervals, linear or nonlinear, can give intervals shorter than about 60 percent the length of Backus' in this problem. While both methods rigorously account for the fact that core field models are infinite-dimensional, the application of the techniques to the geomagnetic problem involves approximations and counterfactual assumptions about the data errors, and so these results are likely to be extremely optimistic estimates of the actual uncertainty in Gauss coefficients.

  19. An Impending geomagnetic transition? Hints from the past.

    Directory of Open Access Journals (Sweden)

    Carlo eLAJ

    2015-10-01

    Full Text Available The rapid decrease of the geomagnetic field intensity in the last centuries has led to speculations that an attempt to a reversal or an excursion might be under way. Here we investigate this hypothesis by examining past records of geomagnetic field intensity obtained from sedimentary cores and from the study of cosmogenic nuclides. The selected records describe geomagnetic changes with an unprecedented temporal resolution between 20 and 75 kyr B.P. We find that some aspects of the present-day geomagnetic field have some similarities with those documented for the Laschamp excursion 41 kyr ago. Under the assumption that the dynamo processes for an eventual future reversal or excursion would be similar to those of the Laschamp excursion, we tentatively suggest that, whilst irreversible processes that will drive the geodynamo into a polarity change may have already started, a reversal or an excursion should not be expected before 500 to 1000 years.

  20. The Study of Two Geomagnetic Jerks in China

    Institute of Scientific and Technical Information of China (English)

    Zhang Suqin; Yang Dongmei; Li Qi; Zhao Yongfen

    2009-01-01

    This paper analyzes the first differences of the annual means (annual rate) for the Y and Z components of the geomagnetic field from nine magnetic observatories in China, measured from 1985 to 2003. The 1991 jerk was obvious in the Y component measured but not clear for the Z component. Rapid changes in the Z components were ubiquitous around 2000 -2001, but not seen for the Y component. External effects were removed from the monthly means by comparing the monthly mean of the geomagnetic field components at the observatories with the monthly time series of the Ap geomagnetic index. However, some examples were analyzed and showed whether external effects were removed or not, there was no marked distinction in determining the jerks in China for the Y component and the Z component of the geomagnetic field. Finally, the isolines of the first differences of the annual means were used to analyze the spatial and temporal distributions of the jerks.

  1. Geographical localisation of the geomagnetic secular variation

    OpenAIRE

    Aubert, Julien; Finlay, Chris; Olsen, Nils

    2013-01-01

    Directly observed changes in Earth’s magnetic field occur most prominently at low latitudes beneath the Atlantic hemisphere, while the Pacific is comparatively quiet. This striking hemispheric asymmetry in geomagnetic secular variation is a consequence of the geographical localisation of intense, westward moving, magnetic flux patches at the core surface. Despite its successes in explaining the main morphological properties of Earth’s magnetic field, self-consistent numerical modelling of the...

  2. The Wavelet Property of the Geomagnetic Anomaly Signal

    Institute of Scientific and Technical Information of China (English)

    JiangfaLIN; GangWANG

    1997-01-01

    In this study,wavelet analysis is utilized to analyze the geomagnetic signals for oil-gas exploration,in order to show the relation between the wavelet property of the geomagnetic signals and the underground treasure.At firest,the global geomagentic anomaly signal in the oil exploration is given.Then.with the wavelet theory the geomagnetic signals of an oil-gas field is analyzed.The preliminary wavelet analysis shows that the underground oil-gas location can be determined with the help of its regional high frequency signal distributions.

  3. Measuring the chemical composition of cosmic rays at about 10 to the 13th - 10 to the 15th eV by utilizing the solar and geomagnetic fields

    Science.gov (United States)

    Heintze, J.; Lennert, P.; Polenz, S.; Schmidt, B.; Spitzer, J.

    1989-01-01

    According to a proposal of Lloyd-Evans (1985), the average charge of particles in the cosmic radiation near 100 TeV can be determined by observing the effect of the solar magnetic field on the sun's shadow in the angular distribution of energetic primary cosmic-ray particles. This suggestion is shown to be realizable with a new type of EAS array proposed for the purpose of high-energy gamma-ray astronomy. The same measurement provides information on the integrated strength of the solar magnetic field. As the array will be sensitive and provide good angular resolution down to a few TeV, more detailed results on the primary composition near 10 TeV can be obtained by investigating the shape of the shadow of the moon as affected by the geomagnetic field.

  4. The geomagnetic cutoff rigidities at high latitudes for different solar wind and geomagnetic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chu, W. [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Space Weather; Univ. of Chinese Academy of Sciences, Beijing (China). College of Earth Sciences; Qin, G. [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Space Weather

    2016-04-01

    Studying the access of the cosmic rays (CRs) into the magnetosphere is important to understand the coupling between the magnetosphere and the solar wind. In this paper we numerically studied CRs' magnetospheric access with vertical geomagnetic cutoff rigidities using the method proposed by Smart and Shea (1999). By the study of CRs' vertical geomagnetic cutoff rigidities at high latitudes we obtain the CRs' window (CRW) whose boundary is determined when the vertical geomagnetic cutoff rigidities drop to a value lower than a threshold value. Furthermore, we studied the area of CRWs and found out they are sensitive to different parameters, such as the z component of interplanetary magnetic field (IMF), the solar wind dynamic pressure, AE index, and Dst index. It was found that both the AE index and Dst index have a strong correlation with the area of CRWs during strong geomagnetic storms. However, during the medium storms, only AE index has a strong correlation with the area of CRWs, while Dst index has a much weaker correlation with the area of CRWs. This result on the CRW can be used for forecasting the variation of the cosmic rays during the geomagnetic storms.

  5. On regional geomagnetic charts

    Science.gov (United States)

    Alldredge, L.R.

    1987-01-01

    When regional geomagnetic charts for areas roughly the size of the US were compiled by hand, some large local anomalies were displayed in the isomagnetic lines. Since the late 1960s, when the compilation of charts using computers and mathematical models was started, most of the details available in the hand drawn regional charts have been lost. One exception to this is the Canadian magnetic declination chart for 1980. This chart was constructed using a 180 degrees spherical harmonic model. -from Author

  6. Geomagnetic storms: historical perspective to modern view

    Science.gov (United States)

    Lakhina, Gurbax S.; Tsurutani, Bruce T.

    2016-12-01

    The history of geomagnetism is more than 400 years old. Geomagnetic storms as we know them were discovered about 210 years ago. There has been keen interest in understanding Sun-Earth connection events, such as solar flares, CMEs, and concomitant magnetic storms in recent times. Magnetic storms are the most important component of space weather effects on Earth. We give an overview of the historical aspects of geomagnetic storms and the progress made during the past two centuries. Super magnetic storms can cause life-threatening power outages and satellite damage, communication failures and navigational problems. The data for such super magnetic storms that occurred in the last 50 years during the space era is sparce. Research on historical geomagnetic storms can help to create a database for intense and super magnetic storms. New knowledge of interplanetary and solar causes of magnetic storms gained from spaceage observations will be used to review the super magnetic storm of September 1-2, 1859. We discuss the occurrence probability of such super magnetic storms, and the maximum possible intensity for the effects of a perfect ICME: extreme super magnetic storm, extreme magnetospheric compression, and extreme magnetospheric electric fields.

  7. High northern geomagnetic field behavior and new constraints on the Gilsá event: Paleomagnetic and 40Ar/39Ar results of ∼0.5–3.1 Ma basalts from Jökuldalur, Iceland

    DEFF Research Database (Denmark)

    Døssing Andreasen, Arne; Muxworthy, Adrian R.; Supakulopas, Radchagrit

    2016-01-01

    Recent paleomagnetic results of extrusive rocks from high southern latitudes (>60°S) and high northern latitudes (>60°N) have been suggested to reflect a hemispheric asymmetry of the geomagnetic field on time-scales of 105 to 106 yrs, with higher and more stable fields in the north. This interpre...

  8. Influence of geomagnetic activity and atmospheric pressure in hypertensive adults.

    Science.gov (United States)

    Azcárate, T; Mendoza, B

    2017-03-30

    We performed a study of the systolic and diastolic arterial blood pressure behavior under natural variables such as the atmospheric pressure and the horizontal geomagnetic field component. We worked with a group of eight adult hypertensive volunteers, four men and four women, with ages between 18 and 27 years in Mexico City during a geomagnetic storm in 2014. The data was divided by gender, age, and day/night cycle. We studied the time series using three methods: correlations, bivariate analysis, and superposed epoch (within a window of 2 days around the day of occurrence of a geomagnetic storm) analysis, between the systolic and diastolic blood pressure and the natural variables. The correlation analysis indicated a correlation between the systolic and diastolic blood pressure and the atmospheric pressure and the horizontal geomagnetic field component, being the largest during the night. Furthermore, the correlation and bivariate analyses showed that the largest correlations are between the systolic and diastolic blood pressure and the horizontal geomagnetic field component. Finally, the superposed epoch analysis showed that the largest number of significant changes in the blood pressure under the influence of geomagnetic field occurred in the systolic blood pressure for men.

  9. Influence of geomagnetic activity and atmospheric pressure in hypertensive adults

    Science.gov (United States)

    Azcárate, T.; Mendoza, B.

    2017-03-01

    We performed a study of the systolic and diastolic arterial blood pressure behavior under natural variables such as the atmospheric pressure and the horizontal geomagnetic field component. We worked with a group of eight adult hypertensive volunteers, four men and four women, with ages between 18 and 27 years in Mexico City during a geomagnetic storm in 2014. The data was divided by gender, age, and day/night cycle. We studied the time series using three methods: correlations, bivariate analysis, and superposed epoch (within a window of 2 days around the day of occurrence of a geomagnetic storm) analysis, between the systolic and diastolic blood pressure and the natural variables. The correlation analysis indicated a correlation between the systolic and diastolic blood pressure and the atmospheric pressure and the horizontal geomagnetic field component, being the largest during the night. Furthermore, the correlation and bivariate analyses showed that the largest correlations are between the systolic and diastolic blood pressure and the horizontal geomagnetic field component. Finally, the superposed epoch analysis showed that the largest number of significant changes in the blood pressure under the influence of geomagnetic field occurred in the systolic blood pressure for men.

  10. Geomagnetic Jerks in the Swarm Era

    Science.gov (United States)

    Brown, William; Beggan, Ciaran; Macmillan, Susan

    2016-08-01

    The timely provision of geomagnetic observations as part of the European Space Agency (ESA) Swarm mission means up-to-date analysis and modelling of the Earth's magnetic field can be conducted rapidly in a manner not possible before. Observations from each of the three Swarm constellation satellites are available within 4 days and a database of close-to-definitive ground observatory measurements is updated every 3 months. This makes it possible to study very recent variations of the core magnetic field. Here we investigate rapid, unpredictable internal field variations known as geomagnetic jerks. Given that jerks represent (currently) unpredictable changes in the core field and have been identified to have happened in 2014 since Swarm was launched, we ask what impact this might have on the future accuracy of the International Geomagnetic Reference Field (IGRF). We assess the performance of each of the IGRF-12 secular variation model candidates in light of recent jerks, given that four of the nine candidates are novel physics-based predictive models.

  11. Ionospheric response to great geomagnetic storms during solar cycle 23

    Science.gov (United States)

    Merline Matamba, Tshimangadzo; Bosco Habarulema, John

    2016-07-01

    The analyses of ionospheric responses due to great geomagnetic storms i.e. Dst index Total Electron Content (TEC) and ionosonde data over Southern and Northern Hemisphere mid-latitudes were used to study the ionospheric responses. A geomagnetic latitude region of ±30° to ±46° within a longitude sector of 15° to 40° was considered. Using a criteria of Dst Physical mechanisms related to (but not limited to) composition changes and electric fields will be discussed.

  12. Geomagnetic Variations of Near-polar Regions and Human Health

    Science.gov (United States)

    Tchistova, Z. B.; Kutinov, Y. G.

    In polar region geomagnetic variations play active role to non-linear tectonic processes. This analysis is based on spatial-time spectral representation of geomagnetic variation and wave migration transformation. Many perturbations in electromagnetic fields may because by external factors (e.g. magnetic storms, ionosphere anomalies and other phenomena related to solar activity) "trigging" tectonic processes but having no direct relation to the processes of their preparation. Geophysical processes are responsible for perturbations in Earth's rotation and orientation on wide range of time-scale, from less than a day of millions of years. The geological structure of some sites of Earth's crust promotes occurrence of wave guides a number of geophysical fields (acoustic, seismic, electromagnetic), usually of transportation of acoustic, seismic, electromagnetic energy in Earth's crust are coincide spatially. During last 250 mln years Arctic Segment has been developing as an autonomous region with circumpolar zonality of geomagnetic fields, and mass - and-energy transfer in its bowlers as well as shitting of lithospheric plates and expansion of ocean are caused by rotation forces under of expanding planet. The dynamic structure of the geomagnetic variations may be characteriz ed by the variations of the order-chaos state. The order manifest itself in the rhythmic change of the medium state. Analysis of amplitude and phase of geomagnetic variations can be information on ecological state of regions. Geomagnetic variations is intrincically a multiscale process in time and space. One of the most important features of geomagnetic variations is multicyclic character, whish predetermined both extent and character of geomagnetic show, and specific features. Recently, there are collected many facts, show dependence between the processes in the Earth's biosphere, the elements of it, gelio- geo- physical and meteorological factors. The recent experimental data gives us opportunity

  13. On Geomagnetism and Paleomagnetism I

    Science.gov (United States)

    Voorhies, Coerte V.

    2000-01-01

    A partial description of Earth's broad scale, core-source magnetic field has been developed and tested three ways. The description features an expected, or mean, spatial magnetic power spectrum that is approximately inversely proportional to horizontal wavenumber atop Earth's core. This multipole spectrum describes a magnetic energy range; it is not steep enough for Gubbins' magnetic dissipation range. Temporal variations of core multipole powers about mean values are to be expected and are described statistically, via trial probability distribution functions, instead of deterministically, via trial solution of closed transport equations. The distributions considered here are closed and neither require nor prohibit magnetic isotropy. The description is therefore applicable to, and tested against, both dipole and low degree non-dipole fields. In Part 1, a physical basis for an expectation spectrum is developed and checked. The description is then combined with main field models of twentieth century satellite and surface geomagnetic field measurements to make testable predictions of the radius of Earth's core. The predicted core radius is 0.7% above the 3480 km seismological value. Partial descriptions of other planetary dipole fields are noted.

  14. MoSST DAS: The First Working Geomagnetic Data Assimilation System

    Science.gov (United States)

    Kuang, Weijia; Wei, Zigang; Tangborn, Andrew

    2011-01-01

    The Earth possesses an internal magnetic field (geomagnetic field) generated by convection in the outer core (geodynamo). Previous efforts have been focused along two distinct paths: (1) numerical geodynamo modeling to understand the origin of the geomagnetic field, and the mechanisms of geomagnetic secular variations (SV); and (2) geomagnetic field modeling to map the spatial/temporal variations of the field from geomagnetic data, and to derive core properties, e.g. inversion of core flow near the core-mantle boundary (CMB). Geomagnetic data assimilation is a new approach emerged over the past 5 years: surface observations are assimilated with geodynamo models for better understanding of the core dynamical state, and accurately prediction of SV. In collaboration with several geomagnetic research groups, we have developed the first working geomagnetic data assimilation system, Modular, Scalable, Self-consistent, and Three-dimensional (MoSST) DAS, that includes the MoSST numerical dynamo model; 7000 years of geomagnetic field maps from several field models utilizing satellite and ground observatory data, historical magnetic records and archeo/paleo magnetic data; and an ensemble based optimal interpolation (01) assimilation algorithm. With this system, we have demonstrated clearly that the assimilated core dynamical state is substantially different from those of pure geodynamo simulations. Ensemble assimilation runs also show the convergence of the assimilated solutions inside the core, suggesting that the simulation state is pulled closer to the truth via data assimilation. The forecasts from this system are also very accurate: the 5-year forecast of the geomagnetic field agrees very well with the observations; and the 5-year secular variation forecast is more accurate than the IGRF SV forecast models in the past. Using geomagnetic records up to 2009, we have made an SV forecast for the period from 2010-2015, and is a candidate SV model for IGRF-11.

  15. Multifractal analysis of low-latitude geomagnetic fluctuations

    Directory of Open Access Journals (Sweden)

    M. J. A. Bolzan

    2009-02-01

    Full Text Available The technique of large deviation multifractal spectrum has shown that the high-latitude (77.5° N, 69.2° W geomagnetic fluctuations can be described from direct dissipation process or loading-unloading regimes of the solar wind-magnetosphere coupling. In this paper, we analyze the H-component of low-latitude (22.4° S, 43.6° W geomagnetic field variability observed during the month of July 2000 at the Geomagnetic Observatory, Vassouras, RJ, Brazil. The variability pattern during this period is a mixture of quiet and disturbed days including the Bastille Day intense geomagnetic storm on 15 July. Due to the complexity of this data, we pursue a detailed analysis of the geomagnetic fluctuations in different time scales including a multifractal approach using the singular power spectrum deviations obtained from the wavelet transform modulus maxima (WTMM. The results suggest, as observed from high-latitude data, the occurrence of low-latitude multifractal processes driving the intermittent coupling between the solar wind-magnetosphere and geomagnetic field variations. On finer scales possible physical mechanisms in the context of nonlinear magnetosphere response are discussed.

  16. Geomagnetic observatories: monitoring the Earth’s magnetic and space weather environment

    OpenAIRE

    Thomson, Alan W.P.

    2014-01-01

    Geomagnetism research provides insight into the Earth’s properties and processes, from the core out to space. For this reason continuous geomagnetic field observations have been carried out in the UK for more than 170 years. Geomagnetism also has diverse applications, in navigation, maps, even smart phone apps, and in the monitoring and prediction of space weather impacts on technology. Modern instruments, together with digital sampling, real-time data processing and product dissemination, su...

  17. High northern geomagnetic field behavior and new constraints on the Gilsá event: Paleomagnetic and 40Ar/39Ar results of ∼0.5-3.1 Ma basalts from Jökuldalur, Iceland

    Science.gov (United States)

    Døssing, Arne; Muxworthy, Adrian R.; Supakulopas, Radchagrit; Riishuus, Morten S.; Mac Niocaill, Conall

    2016-12-01

    Recent paleomagnetic results of extrusive rocks from high southern latitudes (>60°S) and high northern latitudes (>60°N) have been suggested to reflect a hemispheric asymmetry of the geomagnetic field on time-scales of 105 to 106 yrs, with higher and more stable fields in the north. This interpretation, however, is based on only a few modern-standard paleodirectional data sets and on high northern stable field paleointensity data of rocks that are mainly younger than 100 kyr. The sparsity of modern-standard data questions the validity (and age range) of this potential geomagnetic asymmetry. In 2013 and 2014, we sampled basaltic lava flows in Jökuldalur, north-eastern Iceland, to obtain high-standard paleodirectional and paleointensity data at relatively high-northern latitudes (65.2°N). On average, we sampled >15 cores per site at 51 sites of predominantly Matuyama age. Complete demagnetization was carried out on all samples using AF or thermal demagnetization. We present 45 distinct paleomagnetic directions based on overall N > 10 ChRMs per site and α 95 age data. The dispersion SB overall supports the interpretation of a dependence of SB on latitude during the Matuyama, while the negligible ΔI suggests little deviation from a GAD field. Based on relatively strict cut-off criteria we also present six new field strength estimates from the time interval ∼1.2-1.83 Ma, thus filling a large data gap of the high-northern stable field behavior. We obtain a median VADM of 57 ± 3ZAm2 (VDM of 60 ± 5Am2), which is higher than the median VADM of 16 intensity estimates from Antarctica (39 ± 7 ZAm2) from the same period. A higher northern field is also found when using less strict cut-off criteria resulting in 14 field estimates from Jökuldalur, i.e. we find support for higher field strength in the northern hemisphere as compared to the southern hemisphere during the Matuyama. Finally, we deliver a revised magneto-chronostratigraphic model of Jökuldalur and conduct

  18. Enhancement in Surface Atmospheric Pressure Variability Associated with a Major Geomagnetic Storm

    CERN Document Server

    Selvam, A M; Athale, S U; Tinmaker, M I R

    1998-01-01

    Observational studies indicate that there is a close association between geomagnetic storm and meteorological parameters. Geomagnetic field lines follow closely the isobars of surface pressure . A Physical mechanism linking upper atmospheric geomagnetic storm disturbances with tropospheric weather has been proposed by the author and her group where it is postulated that vertical mixing by turbulent eddy fluctuations results in the net transport upward of positive charges originating from lower levels accompanied simultaneously by downward flow of negative charges from higher levels. The present study reports enhancement of high frequency (<15 days period) fluctuations in daily surface pressure during March 1989 in association with major geomagnetic storm (Ap index = 246) on 13 march 1989.

  19. History of the Munich-Maisach-Fürstenfeldbruck Geomagnetic Observatory

    Science.gov (United States)

    Soffel, H. C.

    2015-07-01

    The Munich-Maisach-Fürstenfeldbruck Geomagnetic Observatory is one of the observatories with the longest recordings of the geomagnetic field. It started with hourly measurements on 1 August 1840. The founder of the observatory in Munich was Johann von Lamont (1805-1879), the Director of the Royal Bavarian Astronomical Observatory. He had been stimulated to build his own observatory by the initiative of the Göttingen Magnetic Union founded in 1834 by Alexander von Humboldt (1769-1859) and Carl Friedrich Gauss (1777-1855). Before 1840 fewer than five observatories existed; the most prominent ones were those in London and Paris. At the beginning Lamont used equipment delivered by Gauss in Göttingen, but soon started to build instruments of his own design. Among them was a nonmagnetic theodolite which allowed precise geomagnetic measurements to be made also in the field. During the 1850s Lamont carried out geomagnetic surveys and produced geomagnetic maps for Germany and many other European countries. At the end of the nineteenth century accurate geomagnetic measurements in Munich became more and more disturbed by the magnetic stray fields from electric tramways and industry. During this period the quality of the data suffered and the measurements had to be interrupted several times. After a provisional solution in Maisach, a village 25 km west of Munich, a final solution could be found in the vicinity of the nearby city of Fürstenfeldbruck. Here the measurements started again on 1 January 1939. Since the 1980s the observatory has been part of INTERMAGNET, an organization providing almost real-time geomagnetic data of the highest quality.

  20. Geomagnetic effects on the average surface temperature

    Science.gov (United States)

    Ballatore, P.

    Several results have previously shown as the solar activity can be related to the cloudiness and the surface solar radiation intensity (Svensmark and Friis-Christensen, J. Atmos. Sol. Terr. Phys., 59, 1225, 1997; Veretenenkoand Pudovkin, J. Atmos. Sol. Terr. Phys., 61, 521, 1999). Here, the possible relationships between the averaged surface temperature and the solar wind parameters or geomagnetic activity indices are investigated. The temperature data used are the monthly SST maps (generated at RAL and available from the related ESRIN/ESA database) that represent the averaged surface temperature with a spatial resolution of 0.5°x0.5° and cover the entire globe. The interplanetary data and the geomagnetic data are from the USA National Space Science Data Center. The time interval considered is 1995-2000. Specifically, possible associations and/or correlations of the average temperature with the interplanetary magnetic field Bz component and with the Kp index are considered and differentiated taking into account separate geographic and geomagnetic planetary regions.

  1. Historically Large Geomagnetic Storms and Potential Electric Power Grid Impacts

    Science.gov (United States)

    Kappenman, J. G.

    2004-05-01

    While recent work has been done to examine the possible Dst Intensity of historically large geomagnetic storms, the impacts caused to modern day electric power grids from these storms occurs due to rapid rate-of-change of regional geomagnetic fields which in most cases are driven by large ionospheric electrojet current intensifications. These temporally and spatially dynamic disturbance morphologies are not well-characterized by Dst or other broad geomagnetic storm indices. For estimates of storm intensity that correctly scale the threat potential to electric power grids, it is necessary to describe the rate-of-change of geomagnetic field. The rate-of-change of the geomagnetic field (dB/dt usually measured in nT/min) creates at ground level a geoelectric field that causes the flow of geomagnetically-induced currents (GIC) through ground connection points in electric power grids. Therefore in general, the larger the dB/dt, the larger the resulting geo-electric field and GIC in exposed power grid infrastructures and the greater the operational impact these induced currents will have on the power grid. Both extensive modeling analysis and recent operational experience suggests that power grids are becoming more vulnerable to geomagnetic storms as they grow in size and complexity. Also, large power grid blackouts have occurred at relatively low geomagnetic storm intensities. For example, the regional disturbance intensity that triggered the Hydro Quebec collapse during the March 13, 1989 Superstorm only reached an intensity of 479 nT/min. Large numbers of power system impacts in the United States were also observed for intensities that ranged from 300 to 600 nT/min during this storm. Yet both recent and historical data indicate that storms with disturbance levels that range from 2000 nT/min to as much ~5000 nT/min may be possible over extensive regions at latitudes of concern for large continental power grids across North America and Europe. Large GIC have also been

  2. Intermittency and multifractional Brownian character of geomagnetic time series

    Directory of Open Access Journals (Sweden)

    G. Consolini

    2013-07-01

    Full Text Available The Earth's magnetosphere exhibits a complex behavior in response to the solar wind conditions. This behavior, which is described in terms of mutifractional Brownian motions, could be the consequence of the occurrence of dynamical phase transitions. On the other hand, it has been shown that the dynamics of the geomagnetic signals is also characterized by intermittency at the smallest temporal scales. Here, we focus on the existence of a possible relationship in the geomagnetic time series between the multifractional Brownian motion character and the occurrence of intermittency. In detail, we investigate the multifractional nature of two long time series of the horizontal intensity of the Earth's magnetic field as measured at L'Aquila Geomagnetic Observatory during two years (2001 and 2008, which correspond to different conditions of solar activity. We propose a possible double origin of the intermittent character of the small-scale magnetic field fluctuations, which is related to both the multifractional nature of the geomagnetic field and the intermittent character of the disturbance level. Our results suggest a more complex nature of the geomagnetic response to solar wind changes than previously thought.

  3. Features of the Geomagnetic Variations In the Moscow Region

    Science.gov (United States)

    Riabova, Svetlana; Spivak, Alexander

    2017-04-01

    The results of instrumental observations indicate the presence of significant amplitude variations in Earth's magnetic field. The data obtained in the research of geomagnetic variations allow us to not only establish and classify their sources, but also to form the basis for the improvement and development of new source models of magnetospheric and ionospheric disturbances, new methods of magnetotelluric and magnetovariational sensing and diagnostic methods of geodynamic state of the Earth's crust and the research of meteorological processes in the atmosphere. In this research we used the results of instrumental observations of geomagnetic field, carried out in the period of 2009 - 2015 at Geophysical Observatory "Mikhnevo" of Institute of Geosphere Dynamics of Russian Academy of Sciences. The observatory (54,960N; 37,774E) is located in the Moscow region. The analysis shows that in general the geophysical situation in the Moscow region is disturbed. The tendency to increasing in geomagnetic activity over time is established (the number of days with a perturbed state of the geomagnetic field is increased by 7.6 times during the period of 2009 - 2015). Repeatability of geomagnetic disturbances is characterized by clearly pronounced periodicity with characteristic periods of about 14, 27, 60, 182 and 365 days.

  4. Geomagnetic Observatory Database February 2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA National Centers for Environmental Information (formerly National Geophysical Data Center) maintains an active database of worldwide geomagnetic observatory...

  5. Online calculators for geomagnetic models at the National Geophysical Data Center

    Science.gov (United States)

    Ford, J. P.; Nair, M.; Maus, S.; McLean, S. J.

    2009-12-01

    NOAA’s National Geophysical Data Center at Boulder provides online calculators for geomagnetic field models. These models provide current and past values of the geomagnetic field on regional and global spatial scales. These calculators are popular among scientists, engineers and the general public across the world as a resource to compute geomagnetic field elements. We regularly update both the web interfaces and the underlying geomagnetic models. We have four different calculators to compute geomagnetic fields for different user applications. The declination calculators optionally use our World Magnetic Model (WMM) or the International Geomagnetic Reference Field (IGRF) to provide geomagnetic declination as well as its annual rate of change for the chosen location. All seven magnetic field components for a single day or for a range of years from 1900-present can obtained using our Magnetic Field Calculator IGRFWMM. Users can also compute magnetic field values (current and past) over an area using the IGRFGrid calculator. The USHistoric calculator uses a US declination model to compute the declination for the conterminous US from 1750 - present (data permitting). All calculators allow the user to enter the location either as a Zip Code or by specifying the geographic latitude and longitude.

  6. Geomagnetic observations on Tristan da Cunha, South Atlantic Ocean

    DEFF Research Database (Denmark)

    Matzka, J.; Olsen, Nils; Maule, C. F.

    2009-01-01

    Few geomagnetic ground observations exist of the Earth's strongest core field anomaly, the South Atlantic Anomaly (SAA). The geomagnetic repeat station on the island Tristan da Cunha, located half-way between South Africa and South America at 37 degrees 05' S, 12 degrees 18' W, is therefore...... of crucial importance. We have conducted several sets of repeat station measurements during magnetically quiet conditions (Kp 2o or less) in 2004. The procedures are described and the results are compared to those from earlier campaigns and to the predictions of various global field models. Features...... and operate a magnetometer station on Tristan da Cunha during the Swarm magnetic satellite mission (2011-2014)....

  7. Ionospheric redistribution during geomagnetic storms.

    Science.gov (United States)

    Immel, T J; Mannucci, A J

    2013-12-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dststorm strength that corresponds closely to the TEC variation but follows it by 3-6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow.

  8. Observation and analysis of geomagnetic abnormity associated with the Ms=5.7 Jiujiang-Ruichang earthquake

    Institute of Scientific and Technical Information of China (English)

    GU Zuo-wen; ZHANG Yi; YAO Tong-qi; GAO Jin-tian; LIU Xin; CHEN Bin; ZHAN Zhi-jia; GU Chun-lei

    2006-01-01

    A three-component geomagnetic survey was carried out during the period from 2002 to 2004 in China including Jiujiang-Ruichang region. Comparing the "2005.0 surface spline model of China geomagnetic field" created on the basis of the survey data with the "1970.0 surface spline model of China geomagnetic field", we can see an obvious abnormity in the geomagnetic horizontal component within a range of about 100 km around the epicenter of the Ms=5.7 Jiujiang-Ruichang earthquake occurred on November 26, 2005. After the earthquake, we carried out a repeated geomagnetic survey at 21 stations in the Jiujiang-Ruichang region and created a corresponding "2005.0 partially revised surface spline model of China geomagnetic field". By comparing the above three models, analyzing the geomagnetic horizontal component at the profile in the Jiujiang-Ruichang region and quantitatively studying the geomagnetic data of every stations around the Ms=5.7 earthquake, we have obtained the geomagnetic abnormity associated with this earthquake. Then the geomagnetic abnormity and its relation with seismic activity are discussed in this paper.

  9. Geomagnetically Induced Currents in the Irish Power Network during Geomagnetic Storms

    CERN Document Server

    Blake, Seán P; Jones, Alan G; Hogg, Colin; Campanyà, Joan; Beggan, Ciarán; Thomson, Alan W P; Kelly, Gemma S; Bell, David

    2016-01-01

    Geomagnetically induced currents (GICs) are a well-known terrestrial space weather hazard. They occur in power transmission networks and are known to have adverse effects in both high and mid-latitude countries. Here, we study GICs in the Irish power transmission network (geomagnetic latitude 54.7--58.5$^{\\circ}$ N) during five geomagnetic storms (06-07 March 2016, 20-21 December 2015, 17-18 March 2015, 29-31 October 2003 and 13-14 March 1989). We simulate electric fields using a plane wave method together with two ground resistivity models, one of which is derived from magnetotelluric measurements (MT model). We then calculate GICs in the 220, 275 and 400~kV transmission network. During the largest of the storm periods studied, the peak electric field was calculated to be as large as 3.8~V~km\\textsuperscript{-1}, with associated GICs of up to 23~A using our MT model. Using our homogenous resistivity model, those peak values were 1.46~V~km\\textsuperscript{-1} and 25.8~A. We find that three 400 and 275~kV subs...

  10. Geomagnetically induced currents in the Irish power network during geomagnetic storms

    Science.gov (United States)

    Blake, Seán. P.; Gallagher, Peter T.; McCauley, Joe; Jones, Alan G.; Hogg, Colin; Campanyà, Joan; Beggan, Ciarán. D.; Thomson, Alan W. P.; Kelly, Gemma S.; Bell, David

    2016-12-01

    Geomagnetically induced currents (GICs) are a well-known terrestrial space weather hazard. They occur in power transmission networks and are known to have adverse effects in both high-latitude and midlatitude countries. Here we study GICs in the Irish power transmission network (geomagnetic latitude 54.7-58.5°N) during five geomagnetic storms (6-7 March 2016, 20-21 December 2015, 17-18 March 2015, 29-31 October 2003, and 13-14 March 1989). We simulate electric fields using a plane wave method together with two ground resistivity models, one of which is derived from magnetotelluric measurements (magnetotelluric (MT) model). We then calculate GICs in the 220, 275, and 400 kV transmission network. During the largest of the storm periods studied, the peak electric field was calculated to be as large as 3.8 V km-1, with associated GICs of up to 23 A using our MT model. Using our homogenous resistivity model, those peak values were 1.46 V km-1 and 25.8 A. We find that three 400 and 275 kV substations are the most likely locations for the Irish transformers to experience large GICs.

  11. Methodology for simulation of geomagnetically induced currents in power systems

    Directory of Open Access Journals (Sweden)

    Boteler David

    2014-07-01

    Full Text Available To assess the geomagnetic hazard to power systems it is useful to be able to simulate the geomagnetically induced currents (GIC that are produced during major geomagnetic disturbances. This paper examines the methodology used in power system analysis and shows how it can be applied to modelling GIC. Electric fields in the area of the power network are used to determine the voltage sources or equivalent current sources in the transmission lines. The power network can be described by a mesh impedance matrix which is combined with the voltage sources to calculate the GIC in each loop. Alternatively the power network can be described by a nodal admittance matrix which is combined with the sum of current sources into each node to calculate the nodal voltages which are then used to calculate the GIC in the transmission lines and GIC flowing to ground at each substation. Practical calculations can be made by superposition of results calculated separately for northward and eastward electric fields. This can be done using magnetic data from a single observatory to calculate an electric field that is a uniform approximation of the field over the area of the power system. It is also shown how the superposition of results can be extended to use data from two observatories: approximating the electric field by a linear variation between the two observatory locations. These calculations provide an efficient method for simulating the GIC that would be produced by historically significant geomagnetic storm events.

  12. Improving geomagnetic observatory data in the South Atlantic Anomaly

    Science.gov (United States)

    Matzka, Jürgen; Morschhauser, Achim; Brando Soares, Gabriel; Pinheiro, Katia

    2016-04-01

    The Swarm mission clearly proofs the benefit of coordinated geomagnetic measurements from a well-tailored constellation in order to recover as good as possible the contributions of the various geomagnetic field sources. A similar truth applies to geomagnetic observatories. Their scientific value can be maximised by properly arranging the position of individual observatories with respect to the geometry of the external current systems in the ionosphere and magnetosphere, with respect to regions of particular interest for secular variation, and with respect to regions of anomalous electric conductivity in the ground. Here, we report on our plans and recent efforts to upgrade geomagnetic observatories and to recover unpublished data from geomagnetic observatories at low latitudes in the South Atlantic Anomaly. In particular, we target the magnetic equator with the equatorial electrojet and low latitudes to characterise the Sq- and ring current. The observatory network that we present allows also to study the longitudinal structure of these external current systems. The South Atlantic Anomaly region is very interesting due to its secular variation. We will show newly recovered data and comparisons with existing data sets. On the technical side, we introduce low-power data loggers. In addition, we use mobile phone data transfer, which is rapidly evolving in the region and allows timely data access and quality control at remote sites that previously were not connected to the internet.

  13. Investigation of Characteristics of Large dB/dt for Geomagnetically Induced Currents

    Science.gov (United States)

    Munoz, D.; Ngwira, C.; Damas, M. C.

    2016-12-01

    When geomagnetically induced currents (GICs) flow through electrical networks, they become a potential threat for electrical power systems. Changes in the geomagnetic field (dB/dt) during severe geomagnetic disturbances are the main sources of GICs. These dB/dt phenomena were studied by selecting 24 strong geomagnetic storms with Dst ≤ - 150 nT. ACE spacecraft solar wind data: flow speed, proton density, By and Bz IMF components of the solar wind were correlated with measurements of the magnetic field detected on ground stations at different latitudes. This article reports characteristics of the solar wind during time intervals of large changes in the horizontal geomagnetic field with a threshold of dB/dt ≥ ± 20 nT/min for the 24 geomagnetic storms. The results of this investigation can help scientists to understand the mechanisms responsible for causing large magnetic field variations in order to predict and mitigate possible large events in the future, which is critical for our society that relies constantly on electricity for livelihood and security. In addition, this ongoing project will continue to investigate electron flux response before, during, and after large changes in geomagnetic field.

  14. Gravitational and geomagnetic tidal source of earthquake triggering

    Science.gov (United States)

    Palumbo, A.

    1989-12-01

    A relationship is presently established between large earthquakes and the earth's tides and external geomagnetic fields, in conjunction with a triggering mechanism having its bases in the large solar and lunar variations observed during a number of the shocks examined. A majority of these shocks are noted to be located within a latitude-belt which coincides with the intensity maximum of ionospheric currents. A local magnetostriction process in the rocks appears to be the triggering mechanism. The large number of earthquakes occurring during maximum solar activity may be related to the enhanced geomagnetic triggering effect of higher sunspot numbers.

  15. Wavelet Analysis on Solar Wind Parameters and Geomagnetic Indices

    CERN Document Server

    Katsavrias, Ch; Moussas, X

    2012-01-01

    The sun as an oscillator produces frequencies which propagate in the heliosphere, via solar wind, to the terrestrial magnetosphere. We searched for those frequencies in the parameters of the near Earth solar plasma and the geomagnetic indices for the past four solar cycles. The solar wind parameters used in this work are the interplanetary magnetic field, plasma beta, Alfven Mach number, solar wind speed, plasma temperature, plasma pressure, plasma density and the geomagnetic indices DST, AE, Ap and Kp. We found out that each parameter of the solar wind exhibit certain periodicities which di?erentiate in each cycle. Our results indicate intermittent periodicities in our data, some of them shared between the solar wind parameters and geomagnetic indices.

  16. Geomagnetic imprint of the Persani volcanism

    Science.gov (United States)

    Besutiu, Lucian; Seghedi, Ioan; Zlagnean, Luminita; Atanasiu, Ligia; Popa, Razvan-Gabriel; Pomeran, Mihai; Visan, Madalina

    2016-04-01

    The Persani small volume volcanism is located in the SE corner of the Transylvanian Depression, at the north-western edge of the intra-mountainous Brasov basin. It represents the south-easternmost segment of the Neogene-Quaternary volcanic chain of the East Carpathians. The alkaline basalt monogenetic volcanic field is partly coeval with the high-K calc-alkaline magmatism south of Harghita Mountains (1-1.6 Ma). Its eruptions post-dated the calc-alkaline volcanism in the Harghita Mountains (5.3-1.6 Ma), but pre-dated the high-K calc-alkaline emissions of Ciomadul volcano (1.0-0.03 Ma). The major volcanic forms have been mapped in previous geological surveys. Still, due to the small size of the volcanoes and large extent of tephra deposits and recent sediments, the location of some vents or other volcanic structures has been incompletely revealed. To overcome this problem, the area was subject to several near-surface geophysical investigations, including paleomagnetic research. However, due to their large-scale features, the previous geophysical surveys proved to be an inappropriate approach to the volcanological issues. Therefore, during the summers of 2014 and 2015, based on the high magnetic contrast between the volcanic rocks and the hosting sedimentary formations, a detailed ground geomagnetic survey has been designed and conducted, within central Persani volcanism area, in order to outline the presence of volcanic structures hidden beneath the overlying deposits. Additionally, information on the rock magnetic properties was also targeted by sampling and analysing several outcrops in the area. Based on the acquired data, a detailed total intensity scalar geomagnetic anomaly map was constructed by using the recent IGRF12 model. The revealed pattern of the geomagnetic field proved to be fully consistent with the direction of magnetisation previously determined on rock samples. In order to enhance the signal/noise ratio, the results were further processed by

  17. 3-D FDTD Maxwell's-Equations Modeling of Sub-30 kHz Electromagnetic Wave Propagation in the Earth-Ionosphere Waveguide including Ionospheric Plasma Phenomena as Influenced by the Geomagnetic Field

    Science.gov (United States)

    Simpson, J. J.; Taflove, A.

    2006-12-01

    We report a finite-difference time-domain (FDTD) computational solution of Maxwell's equations for sub-30 kHz electromagnetic (EM) propagation in the Earth-ionosphere waveguide. The FDTD technique used in this study enables a direct, full-vector, three-dimensional (3-D) time-domain calculation of EM propagation accounting for arbitrary horizontal as well as vertical geometrical and electrical inhomogeneities and anisotropies of the excitation, ionosphere, lithosphere, and oceans. This is unlike previous FDTD models which assumed azimuthal symmetry about a vertical current source excitation representing a lightning channel. Our model is therefore unique in that it includes fully 3-D anisotropic plasma phenomena in the ionosphere as influenced by the full-vector geomagnetic field. In this study, we show results for EM propagation from lightning strikes using a spherical-coordinate (latitude- longitude) grid having a 1 x 1 x 1 km resolution. Our new model provides additional capabilities to simulate EM wave phenomena arising from whistlers and other lightning-related events, as well as for better understanding anomalous ionospheric phenomena reported to have occurred prior to and during major earthquakes.

  18. Effects of substorm electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone

    Science.gov (United States)

    Edvardsen, Inge; Johnsen, Magnar G.; Løvhaug, Unni P.

    2016-10-01

    The geomagnetic field often experiences large fluctuations, especially at high latitudes in the auroral zones. We have found, using simulations, that there are significant differences in the substorm signature, in certain coordinate systems, as a function of longitude. This is confirmed by the analysis of real, measured data from comparable locations. Large geomagnetic fluctuations pose challenges for companies involved in resource exploitation since the Earth's magnetic field is used as the reference when navigating drilling equipment. It is widely known that geomagnetic activity increases with increasing latitude and that the largest fluctuations are caused by substorms. In the auroral zones, substorms are common phenomena, occurring almost every night. In principle, the magnitude of geomagnetic disturbances from two identical substorms along concurrent geomagnetic latitudes around the globe, at different local times, will be the same. However, the signature of a substorm will change as a function of geomagnetic longitude due to varying declination, dipole declination, and horizontal magnetic field along constant geomagnetic latitudes. To investigate and quantify this, we applied a simple substorm current wedge model in combination with a dipole representation of the Earth's magnetic field to simulate magnetic substorms of different morphologies and local times. The results of these simulations were compared to statistical data from observatories and are discussed in the context of resource exploitation in the Arctic. We also attempt to determine and quantify areas in the auroral zone where there is a potential for increased space weather challenges compared to other areas.

  19. Resolving issues concerning Eskdalemuir geomagnetic hourly values

    Directory of Open Access Journals (Sweden)

    S. Macmillan

    2011-02-01

    Full Text Available The hourly values of the geomagnetic field from 1911 to 1931 derived from measurements made at Eskdalemuir observatory in the UK, and available online from the World Data Centre for Geomagnetism at http://www.wdc.bgs.ac.uk/, have now been corrected. Previously they were 2-point averaged and transformed from the original north, east and vertical down values in the tables in the observatory yearbooks. This paper documents the course of events from discovering the post-processing done to the data to the final resolution of the problem. As it was through the development of a new index, the Inter-Hour Variability index, that this post-processing came to light, we provide a revised series of this index for Eskdalemuir and compare it with that from another European observatory. Conclusions of studies concerning long-term magnetic field variability and inferred solar variability, whilst not necessarily consistent with one another, are not obviously invalidated by the incorrect hourly values from Eskdalemuir. This series of events illustrates the challenges that lie ahead in removing any remaining errors and inconsistencies in the data holdings of different World Data Centres.

  20. Synthetic and sedimentary records of geomagnetic excursions

    Science.gov (United States)

    Vlag, P.; Thouveny, N.; Rochette, P.

    The geomagnetic excursion recorded in the sediments of Lac St.Front (Massif Central, France) is characterized by shallow and negative inclinations followed by a younger steep inclination interval (Vlag et al., 1996). In the corresponding interval of the nearby Lac du Bouchet only steep inclinations are found. Sedimentary records of the Mono Lake excursion show similar inclination patterns; ‘complete’ records of this excursion show a succession of a shallow by a steep inclination interval, while ‘incomplete’ records only show only steep inclinations (Coe and Liddicoat, 1994). Due to a non-instantaneous acquisition of the remanence, sedimentary records reflect only a smoothed geomagnetic signal. It will be shown that smoothing of a small low-intensity ‘reversed’ interval embedded in a non-antipodal normal field interval may result in records of a shallow inclination interval followed by a steep inclination interval, while further smoothing results in only steep inclinations. Realignment of magnetic grains by the stronger normal field can also produce such records and may explain why such an unusual large lock-in depth is required by the conventional smoothing model. Whatever the mechanism, the similarities between these synthetic records and the excursional records of Lac St. Front-Lac du Bouchet and Mono Lake suggest that the latter are more or less affected by vector addition of two non-antipodal directions.

  1. First results from the first Croatian geomagnetic observatory

    Science.gov (United States)

    Mandic, Igor; Herak, Davorka; Heilig, Balazs

    2013-04-01

    The first Croatian geomagnetic observatory was established in the area of the Nature Park Lonjsko Polje, after a century of sporadic efforts originating from the proposals of Andrija Mohorovicic. The location was chosen after exhaustive surveys of possible sites. It is located far enough from sources of civilization noise, and was found to be an area without magnetic anomalies and with a low field gradient. The construction of the observatory buildings was completed in the autumn of 2011. The furnishing and installation of instruments and test measurements were completed by the beginning of summer 2012, ever since we have continuous recordings of the geomagnetic elements. In the beginning of December 2012 the fluxgate magnetometer LEMI-035 (H,D,Z orientation) has been installed under the framework of the PLASMON project in cooperation with the Tihany Observatory (Hungary). Permanent data of high quality from our observatory will contribute to the monitoring of the Earth's magnetic field on the regional and global levels, thus enabling further development of geomagnetism in Croatia through collaboration with scientists from the other countries, participation in the international projects, eventual membership in the International Real-time Magnetic Observatory Network (INTERMAGNET), etc. The field elements for the epoch 2012,75 and the baselines are presented together with highlights of some recorded geomagnetic events so far. Furthermore, the comparison between the variation data recorded by the dIdD and the fluxgate LEMI-035 magnetometer is presented.

  2. Derivation of characteristics of the relation between geomagnetic and geoelectric variation fields from the surface impedance for a two-layer earth

    National Research Council Canada - National Science Library

    Pirjola, Risto

    2010-01-01

    ... at the earth’s surface in the frequency domain. Studying the properties of the surface impedance enables conclusions about the corresponding relation between the surface electric and magnetic variation fields in the time domain...

  3. High definition geomagnetic models: A new perspective for improved wellbore positioning

    DEFF Research Database (Denmark)

    Maus, Stefan; Nair, Manoj C.; Poedjono, Benny;

    2012-01-01

    Earth's gravity and magnetic fields are used as natural reference frames in directional drilling. The azimuth of the bottomhole assembly is inferred by comparing the magnetic field measured-while-drilling (MWD) with a geomagnetic reference model. To provide a reference of sufficient quality...... for accurate well placement, the US National Geophysical Data Center (NGDC), in partnership with industry, has developed high-definition geomagnetic models (HDGM), updated regularly using the latest satellite, airborne and marine measurements of the Earth's magnetic field. Standard geomagnetic reference models....... These are compiled into a global magnetic anomaly grid and expanded into ellipsoidal harmonics. The harmonic expansion coefficients are then included in the high-definition models to accurately represent the direction and strength of the local geomagnetic field. The latest global model to degree and order 720...

  4. GEOMAGNETIC STORMS AND CARRINGTON EVENT = TEMPESTADES GEOMAGNETICAS E O EVENTO CARRINGTON

    National Research Council Canada - National Science Library

    Gerson Antonio Santarine; Roberto Naves Domingos

    2014-01-01

    .... If Earth is directly in line sight of a coronal blast, a shock wave of energetic charged particles from the star will cause a geomagnetic storm due to its abrupt interaction with terrestrial magnetic field...

  5. International Geomagnetic Reference Field—the tenth generation

    Science.gov (United States)

    Macmillan, Susan; Maus, Stefan

    2005-12-01

    The International Geomagnetic Reference Field (IGRF) 10th Generation was adopted in 2004 by the International Association of Geomagnetism and Aeronomy (IAGA) Working Group V-MOD. It is the latest version of a standard mathematical description of the Earth's main magnetic field and is used widely in studies of the Earth's deep interior, its crust and its ionosphere and magnetosphere. This generation differs from the previous generation with the replacement of the secular-variation model for 2000.0-2005.0 with a main-field model at 2005.0 and a secular-variation model for 2005.0-2010.0. The IGRF is the product of a huge collaborative effort between magnetic field modellers and the institutes involved in collecting and disseminating magnetic field data from satellites and from observatories and surveys around the world. This paper lists the new coefficients and includes contour maps and pole positions.

  6. Mantle superplumes induce geomagnetic superchrons

    Directory of Open Access Journals (Sweden)

    Peter eOlson

    2015-07-01

    Full Text Available We use polarity reversal systematics from numerical dynamos to quantify the hypothesis that the modulation of geomagnetic reversal frequency, including geomagnetic superchrons, results from changes in core heat flux related to growth and collapse of lower mantle superplumes. We parameterize the reversal frequency sensitivity from numerical dynamos in terms of average core heat flux normalized by the difference between the present-day core heat flux and the core heat flux at geomagnetic superchron onset. A low-order polynomial fit to the 0-300 Ma Geomagnetic Polarity Time Scale (GPTS reveals that a decrease in core heat flux relative to present-day of approximately 30% can account for the Cretaceous Normal Polarity and Kiaman Reverse Polarity Superchrons, whereas the hyper-reversing periods in the Jurassic require a core heat flux equal to or higher than present-day. Possible links between GPTS transitions, large igneous provinces (LIPs, and the two lower mantle superplumes are explored. Lower mantle superplume growth and collapse induce GPTS transitions by increasing and decreasing core heat flux, respectively. Age clusters of major LIPs postdate transitions from hyper-reversing to superchron geodynamo states by 30-60 Myr, suggesting that superchron onset may be contemporaneous with LIP-forming instabilities produced during collapses of lower mantle superplumes.

  7. A New Theory of Geomagnetism

    OpenAIRE

    Sidharth, B. G.

    1999-01-01

    It is pointed out, that in the light of recent results on the semionic or anomalous behaviour of electrons below the Fermi temperature, the solid core of the earth which has been ignored so far, would contribute significantly to Geomagnetism and help explain the puzzling magnetic reversals.

  8. CM5, a Pre-Swarm Comprehensive Geomagnetic Field Model Derived from Over 12 Yr of CHAMP, Orsted, SAC-C and Observatory Data

    Science.gov (United States)

    Sabaka, Terence J.; Olsen, Nils; Tyler, Robert H.; Kuvshinov, Alexey

    2014-01-01

    A comprehensive magnetic field model named CM5 has been derived from CHAMP, Ørsted and SAC-C satellite and observatory hourly-means data from 2000 August to 2013 January using the Swarm Level-2 Comprehensive Inversion (CI) algorithm. Swarm is a recently launched constellation of three satellites to map the Earth's magnetic field. The CI technique includes several interesting features such as the bias mitigation scheme known as Selective Infinite Variance Weighting (SIVW), a new treatment for attitude error in satellite vector measurements, and the inclusion of 3-D conductivity for ionospheric induction. SIVW has allowed for a much improved lithospheric field recovery over CM4 by exploiting CHAMP along-track difference data yielding resolution levels up to spherical harmonic degree 107, and has allowed for the successful extraction of the oceanic M2 tidal magnetic field from quiet, nightside data. The 3-D induction now captures anomalous Solar-quiet features in coastal observatory daily records. CM5 provides a satisfactory, continuous description of the major magnetic fields in the near-Earth region over this time span, and its lithospheric, ionospheric and oceanic M2 tidal constituents may be used as validation tools for future Swarm Level-2 products coming from the CI algorithm and other dedicated product algorithms.

  9. Spherical harmonic representation of the main geomagnetic field for world charting and investigations of some fundamental problems of physics and geophysics

    Science.gov (United States)

    Barraclough, D. R.; Hide, R.; Leaton, B. R.; Lowes, F. J.; Malin, S. R. C.; Wilson, R. L. (Principal Investigator)

    1982-01-01

    Progress in the harmonic analysis of MAGSAT data is reported. Single-day data sets were subdivided into information on the sunrise side of the Earth and information on the sunset side of the Earth. Data for the main and external fields each demonstrate a clear and consistent systematic difference between the sets of data which was determined to be, due to ionospheric currents which differ from the sunset to the sunrise terminator. A toroidal field was analyzed for and determined to be an apparent toroidal field resulting from electric currents concentrated in the two terminators. Progressive elimination of auroral zone data demonstrates that the information presented does not arise from complications due to Birkeland currents.

  10. [The characteristics of tissue lipid peroxidation in the internal organs and the lipid metabolic indices of the blood plasma in a low geomagnetic field].

    Science.gov (United States)

    Babych, V I

    1995-01-01

    It was found in experiments on guinea-pigs and white rats that 100-time weakened magnetic field of the earth considerably increased the activity of peroxide oxidation of lipids (POL) in tissues of inner organs. In the lungs, liver, kidneys, small intestine under the influence of hypogeomagnetic field (HGMF) we have observed reduction of ferment antioxidizing activity and of non-ferment mechanisms in the heart. The process is accompanied by reduction of cholesterol, phospholipids and triglycerides in guinea-pigs and increase of this indices in white rats after 5-day-long stay of animals in the hypogeomagnetic chamber. The data of experiments on white rats underlie a conclusion that the 5-day-long influence of HGMF promotes the change of the carbohydrate metabolism for lipid metabolism. The reaction of guinea-pigs on the stay under the weakened magnetic field of the earth displays in reduction of the level of lipid metabolism indices in the blood serum.

  11. Study of the Forbush Decreases, Geomagnetic Storms, and Ground-Level Enhancements in Selected Intervals and Their Space Weather Implications

    Science.gov (United States)

    Badruddin; Kumar, Anand

    2015-04-01

    We analysed geomagnetic storms, ground-level enhancements (GLEs), and Forbush decreases in cosmic-ray intensity that occurred in selected intervals. We used data of ground-based neutron monitors for the cosmic-ray intensity. We used the geomagnetic index Dst as a measure of the geomagnetic storm intensity. Solar observations and interplanetary plasma/field parameters were used to identify the solar cause(s), interplanetary structure(s), and physical mechanism(s) responsible for the geomagnetic storms, the Forbush decreases, and the GLEs of different amplitudes and time profiles; all of them occurring within four selected periods of one month each. The observed differences in cosmic-ray and geomagnetic-activity responses to the same solar sources were used to distinguish the structures and mechanisms responsible for transient cosmic-ray modulation and geomagnetic storms.

  12. CM5, a pre-Swarm comprehensive geomagnetic field model derived from over 12 yr of CHAMP, Ørsted, SAC-C and observatory data

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Olsen, Nils; Tyler, Robert H.

    2015-01-01

    A comprehensive magnetic field model named CM5 has been derived from CHAMP, Orsted and SAC-C satellite and observatory hourly-means data from 2000 August to 2013 January using the Swarm Level-2 Comprehensive Inversion (CI) algorithm. Swarm is a recently launched constellation of three satellites ...

  13. The science of geomagnetically induced currents

    Science.gov (United States)

    Pulkkinen, A.

    2012-12-01

    Geomagnetically induced currents (GIC) phenomenon impacting long conductor systems on the ground can be considered as the end link of chain of complex physical processes comprising the Sun-Earth system. In this paper I briefly review the current status of our understanding of the physics of GIC and novel applications enabled by the new understanding. More specifically, I will demonstrate how we can follow the chain of physical processes from the solar corona down to the upper mantle of the Earth and to GIC. Further, I will show how state-of-the-art models enable predictive modeling of the entire chain of complex processes. The potential for severe societal consequences has been driving recent increasing interest in extreme GIC events. I will show how we have addressed the issue by generating 100-year GIC event scenarios. These scenarios are of substantial power grid industry interest and have been fed directly into further engineering analyses. I will review the results of our of 100-year geomagnetically induced current scenarios work and discuss some of the future directions in the field.

  14. Geomagnetic storm effects on GPS based navigation

    Directory of Open Access Journals (Sweden)

    P. V. S. Rama Rao

    2009-05-01

    Full Text Available The energetic events on the sun, solar wind and subsequent effects on the Earth's geomagnetic field and upper atmosphere (ionosphere comprise space weather. Modern navigation systems that use radio-wave signals, reflecting from or propagating through the ionosphere as a means of determining range or distance, are vulnerable to a variety of effects that can degrade the performance of the navigational systems. In particular, the Global Positioning System (GPS that uses a constellation of earth orbiting satellites are affected due to the space weather phenomena.

    Studies made during two successive geomagnetic storms that occurred during the period from 8 to 12 November 2004, have clearly revealed the adverse affects on the GPS range delay as inferred from the Total Electron Content (TEC measurements made from a chain of seven dual frequency GPS receivers installed in the Indian sector. Significant increases in TEC at the Equatorial Ionization anomaly crest region are observed, resulting in increased range delay during the periods of the storm activity. Further, the storm time rapid changes occurring in TEC resulted in a number of phase slips in the GPS signal compared to those on quiet days. These phase slips often result in the loss of lock of the GPS receivers, similar to those that occur during strong(>10 dB L-band scintillation events, adversely affecting the GPS based navigation.

  15. Letter to the Editor: Geomagnetic storm effects at low latitudes

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available The geomagnetic horizontal (H field from the chain of nine observatories in India are used to study the storm-time and disturbance daily variations. The peak decrease in storm-time variation in H showed significant enhancements at the equatorial electrojet stations over and above the normally expected decrease due to the ring current effects corrected for geomagnetic latitudes. The disturbance daily variation of H at equatorial stations showed a large decrease around midday hours over and above the usual dawn-maximum and dusk-minimum seen at any mid-latitude stations around the world. These slow and persistent additional decreases of H of disturbance daily variation at equatorial latitudes could be the effect of a westward electric field due to the Disturbance Ionospheric dynamo coupled with abnormally large electrical conductivities in the E region over the equator.Key words. Ionosphere (electric fields and currents · Magnetospheric physics (electric fields; storms and substorms

  16. [The modification of the effect of microwave radiation on the biochemical processes in anaphylactic shock by using exposure to a weak and perturbed geomagnetic field].

    Science.gov (United States)

    Podkovkin, V G

    1993-01-01

    Repeated exposure of guinea pigs to microwave radiation (1 mW/cm2) caused in some animals inhibition of anaphylactic response accompanied by increasing the content of histamine, epinephrine and norepinephrine in the blood. This increase was more pronounced in irradiated guinea pigs died from anaphylactic shock than in nonirradiated animals. The long-term stay in the perturbed and weak geometric field reduced the effect induced by microwave radiation.

  17. Geomagnetic activity influences the melatonin secretion at latitude 70 degrees N.

    Science.gov (United States)

    Weydahl, A; Sothern, R B; Cornélissen, G; Wetterberg, L

    2001-01-01

    Factors other than light may affect variations in melatonin, including disturbances in the geomagnetic field. Such a possibility was tested in Alta, Norway, located at latitude 70 degrees N, where the aurora borealis is a result of large changes in the horizontal component (H) of the geomagnetic field. Geomagnetic disturbances are felt more strongly closer to the pole than at lower latitudes. Also noteworthy in Alta is the fact that the sun does not rise above the horizon for several weeks during the winter. To examine whether changes in geomagnetic activity influence the secretion of melatonin, saliva was collected from 25 healthy subjects in Alta several times during the day-night and at different times of the year. Single cosinor analyses yielded individual estimates of.the circadian amplitude and MESOR of melatonin. A 3-hour mean value for the local geomagnetic activity index, K, was used for approximately the same 24-hour span. A circadian rhythm was found to characterize both melatonin and K, the peak in K (23:24) preceding that of melatonin (06:08). During the span of investigation, a circannual variation also characterized both variables. Correlation analyses suggest that changes in geomagnetic activity had to be of a certain magnitude to affect the circadian amplitude of melatonin. If large enough (> 80 nT/3 h), changes in geomagnetic activity also significantly decreased salivary melatonin concentration.

  18. Geomagnetism of earth's core

    Science.gov (United States)

    Benton, E. R.

    1983-01-01

    Instrumentation, analytical methods, and research goals for understanding the behavior and source of geophysical magnetism are reviewed. Magsat, launched in 1979, collected global magnetometer data and identified the main terrestrial magnetic fields. The data has been treated by representing the curl-free field in terms of a scalar potential which is decomposed into a truncated series of spherical harmonics. Solutions to the Laplace equation then extend the field upward or downward from the measurement level through intervening spaces with no source. Further research is necessary on the interaction between harmonics of various spatial scales. Attempts are also being made to analytically model the main field and its secular variation at the core-mantle boundary. Work is also being done on characterizing the core structure, composition, thermodynamics, energetics, and formation, as well as designing a new Magsat or a tethered satellite to be flown on the Shuttle.

  19. Geomagnetism of earth's core

    Science.gov (United States)

    Benton, E. R.

    1983-01-01

    Instrumentation, analytical methods, and research goals for understanding the behavior and source of geophysical magnetism are reviewed. Magsat, launched in 1979, collected global magnetometer data and identified the main terrestrial magnetic fields. The data has been treated by representing the curl-free field in terms of a scalar potential which is decomposed into a truncated series of spherical harmonics. Solutions to the Laplace equation then extend the field upward or downward from the measurement level through intervening spaces with no source. Further research is necessary on the interaction between harmonics of various spatial scales. Attempts are also being made to analytically model the main field and its secular variation at the core-mantle boundary. Work is also being done on characterizing the core structure, composition, thermodynamics, energetics, and formation, as well as designing a new Magsat or a tethered satellite to be flown on the Shuttle.

  20. Extreme Geomagnetic Storms - 1868 - 2010

    Science.gov (United States)

    Vennerstrom, S.; Lefevre, L.; Dumbović, M.; Crosby, N.; Malandraki, O.; Patsou, I.; Clette, F.; Veronig, A.; Vršnak, B.; Leer, K.; Moretto, T.

    2016-05-01

    We present the first large statistical study of extreme geomagnetic storms based on historical data from the time period 1868 - 2010. This article is the first of two companion papers. Here we describe how the storms were selected and focus on their near-Earth characteristics. The second article presents our investigation of the corresponding solar events and their characteristics. The storms were selected based on their intensity in the aa index, which constitutes the longest existing continuous series of geomagnetic activity. They are analyzed statistically in the context of more well-known geomagnetic indices, such as the Kp and Dcx/Dst index. This reveals that neither Kp nor Dcx/Dst provide a comprehensive geomagnetic measure of the extreme storms. We rank the storms by including long series of single magnetic observatory data. The top storms on the rank list are the New York Railroad storm occurring in May 1921 and the Quebec storm from March 1989. We identify key characteristics of the storms by combining several different available data sources, lists of storm sudden commencements (SSCs) signifying occurrence of interplanetary shocks, solar wind in-situ measurements, neutron monitor data, and associated identifications of Forbush decreases as well as satellite measurements of energetic proton fluxes in the near-Earth space environment. From this we find, among other results, that the extreme storms are very strongly correlated with the occurrence of interplanetary shocks (91 - 100 %), Forbush decreases (100 %), and energetic solar proton events (70 %). A quantitative comparison of these associations relative to less intense storms is also presented. Most notably, we find that most often the extreme storms are characterized by a complexity that is associated with multiple, often interacting, solar wind disturbances and that they frequently occur when the geomagnetic activity is already elevated. We also investigate the semiannual variation in storm occurrence

  1. Revised ages for tuffs of the Yellowstone Plateau volcanic field: Assignment of the Huckleberry Ridge Tuff to a new geomagnetic polarity event

    Science.gov (United States)

    Lanphere, M.A.; Champion, D.E.; Christiansen, R.L.; Izett, G.A.; Obradovich, J.D.

    2002-01-01

    40Ar/39Ar ages were determined on the three major ash-flow tuffs of the Yellowstone Plateau volcanic field in the region of Yellowstone National Park in order to improve the precision of previously determined ages. Total-fusion and incremental-heating ages of sanidine yielded the following mean ages: Huckleberry Ridge Tuff-2.059 ?? 0.004 Ma; Mesa Falls Tuff-1.285 ?? 0.004 Ma; and Lava Creek Tuff-0.639 ?? 0.002 Ma. The Huckleberry Ridge Tuff has a transitional magnetic direction and has previously been related to the Reunion Normal-Polarity Subchron. Dating of the Reunion event has been reviewed and its ages have been normalized to a common value for mineral standards. The age of the Huckleberry Ridge Tuff is significantly younger than lava flows of the Reunion event on Re??union Island, supporting other evidence for a normal-polarity event younger than the Reunion event.

  2. A new regard about Surlari National Geomagnetic Observatory

    Science.gov (United States)

    Asimopolos, Laurentiu; Asimopolos, Natalia-Silvia; Pestina, Agata-Monica

    2010-05-01

    Geomagnetic field study in Romanian stations has started with irregular measurements in late XIXth century. In 1943, the foundation of Surlari National Geomagnetic Observatory (SNGO) marks the beginning of a new era in the systematic study of geomagnetic field by a continuous registration of its variations and by carrying out standard absolute measurements in a fundamental station. The location of the observatory meets the highest exigencies, being situated in physical-geological conditions of a uniform local field, at a reasonably long distance from human activities. Its laboratories observe strict conditions of non-magnetism, ensuring the possibility of absolute standard measurements (national magnetic standards) for all the units in the country, civil or military, which are endowed with equipment based on geomagnetic metrology. These basic conditions have allowed the observatory to become by developing its initial preoccupations a centre of complex geomagnetic research, constantly involved in national and international issues, promoting new themes in our country and bringing significant contributions. During the last two decades, infrastructure and equipment used in monitoring geomagnetic field at European and planetary level have experienced a remarkable development. New registering techniques have allowed a complete to automate of data acquisition, and sampling step and their precision increased by two classes of size. Systems of transmitting these data in real time to world collecting centres have resulted in the possibility of approaching globalize studies, suitable for following some phenomena at planetary scale. At the same time, a significant development in the procedures of processing primary data has been registered, based on standardized programmes. The new stage of this fundamental research, largely applicable in various fields, is also marked by the simultaneous observation of space-time distribution of terrestrial electromagnetic field by means of

  3. New insights on geomagnetic storms from observations and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Jordanova, Vania K [Los Alamos National Laboratory

    2009-01-01

    Understanding the response at Earth of the Sun's varying energy output and forecasting geomagnetic activity is of central interest to space science, since intense geomagnetic storms may cause severe damages on technological systems and affect communications. Episodes of southward (Bzfield (IMF) which lead to disturbed geomagnetic conditions are associated either with coronal mass ejections (CMEs) and possess long and continuous negative IMF Bz excursions, or with high speed solar wind streams (HSS) whose geoeffectiveness is due to IMF Bz profiles fluctuating about zero with various amplitudes and duration. We show examples of ring current simulations during two geomagnetic storms representative of each interplanetary condition with our kinetic ring current atmosphere interactions model (RAM), and investigate the mechanisms responsible for trapping particles and for causing their loss. We find that periods of increased magnetospheric convection coinciding with enhancements of plasma sheet density are needed for strong ring current buildup. During the HSS-driven storm the convection potential is highly variable and causes small sporadic injections into the ring current. The long period of enhanced convection during the CME-driven storm causes a continuous ring current injection penetrating to lower L shells and stronger ring current buildup.

  4. On the shape of the Geomagnetic Tail at Lunar distances: Preliminary Resuts from Artemis Observations

    Science.gov (United States)

    Gencturk Akay, Iklim; Kaymaz, Zerefsan; Sibeck, David G.

    2013-04-01

    Geomagnetic tail is one of the least investigated regions of the magnetosphere behind the Earth owing to the limited number of spacecraft and observations. It is the region where the geomagnetic dipole field lines of the Earth are organized by the solar wind stretching. The characteristics of the geomagnetic tail and its response to IMF were studied by the missions, ISEE-3, IMP-8, Wind, Geotail, visited geomagnetic tail at different distances. The structure of the geomagnetic tail is controlled by the IMF orientation and its own internal dynamics. Geomagnetic tail has different regions where the plasma and magnetic field characteristics are largely depend on the IMF orientation. These characteristics show differences at different tail distances. For example it is determined that the tail twists as result of the reconnection with IMF By and this twist is higher as one move away from the Earth toward the distant tail. Like a windsock, it is expected that the IMF control will increase toward the distant tail. Twisting also displaces the north and south lobes on the dawn and dusk sides. Tail length and the shape are also different for different IMF orientations. Flattening of the geomagnetic tail cross-section occurs during the strong IMF Bys. It becomes an ellipse in the yz plane as the IMF By stress causes the tail to be flattened on the top and bottom. Models estimate that the geomagnetic tail length can be 165 Re while Pioneer spacecraft detected geomagnetic tail as long as 100 Re. These findings are based on the very limited data from brief geomagnetic tail encounters of the spacecraft. Since August 2011, with the repositioning of the two of THEMIS spacecraft pair, ARTEMIS is giving a new opportunity to study the geomagnetic tail at the lunar distances, 60 Re. Using these observations, we will investigate the geomagnetic field shape and its IMF dependence at 60 Re. Based on the magnetopause locations at 60 Re, we will study the shape of the tail on the xy

  5. Effect of Cross-Correlation on Geomagnetic Forecast Accuracies

    Science.gov (United States)

    Kuang, Weijia; Wei, Zigang; Tangborn, Andrew

    2011-01-01

    Surface geomagnetic observation can determine up to degree L = 14 time-varying spherical harmonic coefficients of the poloidal magnetic field. Assimilation of these coefficients to numerical dynamo simulation could help us understand better the dynamical processes in the Earth's outer core, and to provide more accurate forecast of geomagnetic secular variations (SV). In our previous assimilation studies, only the poloidal magnetic field in the core is corrected by the observations in the analysis. Unobservable core state variables (the toroidal magnetic field and the core velocity field) are corrected via the dynamical equations of the geodynamo. Our assimilation experiments show that the assimilated core state converges near the CMB, implying that the dynamo state is strongly constrained by surface geomagnetic observations, and is pulled closer to the truth by the data. We are now carrying out an ensemble of assimilation runs with 1000 years of geomagnetic and archeo/paleo magnetic record. In these runs the cross correlation between the toroidal and the poloidal magnetic fields is incorporated into the analysis. This correlation is derived from the physical boundary conditions of the toroidal field at the core-mantle boundary (CMB). The assimilation results are then compared with those of the ensemble runs without the cross-correlation, aiming at understanding two fundamental issues: the effect of the crosscorrelation on (1) the convergence of the core state, and (2) the SV prediction accuracies. The constrained dynamo solutions will provide valuable insights on interpreting the observed SV, e.g. the near-equator magnetic flux patches, the core-mantle interactions, and possibly other geodynamic observables.

  6. Magnetospheric effects of cosmic rays. 1. Long-term changes in the geomagnetic cutoff rigidities for the stations of the global network of neutron monitors

    Science.gov (United States)

    Gvozdevskii, B. B.; Abunin, A. A.; Kobelev, P. G.; Gushchina, R. T.; Belov, A. V.; Eroshenko, E. A.; Yanke, V. G.

    2016-07-01

    Vertical geomagnetic cutoff rigidities are obtained for the stations of the global network of neutron monitors via trajectory calculations for each year of the period from 1950 to 2020. Geomagnetic cutoff rigidities are found from the model of the Earth's main field International Geomagnetic Reference Field (IGRF) for 1950-2015, and the forecast until 2020 is provided. In addition, the geomagnetic cutoff rigidities for the same period are obtained by Tsyganenko model T89 (Tsyganenko, 1989) with the average annual values of the Kp-index. In each case, the penumbra is taken into account in the approximation of the flat and power spectra of variations of cosmic rays. The calculation results show an overall decrease in geomagnetic cutoff rigidities, which is associated with the overall decrease and restructuring of the geomagnetic field during the reporting period, at almost all points.

  7. The Causes of Geomagnetic Storms During Solar Maximum

    Science.gov (United States)

    Tsurutani, B. T.; Gonzalez, W. D.

    1998-01-01

    One of the oldest mysteries in geomagnetism is the linkage between solar and geomagnetic activity. The 11-year cycles of both the numbers of sunspots and Earth geomagnetic storms were first noted by Sabine (1852).

  8. High-latitude geomagnetic studies (22-23 millihertz)

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, A. (AT T Bell Laboratories, Murray Hill, NJ (USA) City Univ. of New York, Brooklyn (USA)); Lanzerotti, L.J.; Maclennan, C.C.; Medford, L.V. (AT T Bell Laboratories, Murray Hill, NJ (USA))

    1988-01-01

    Geomagnetic field measurements were initiated at Iqaluit (formerly Frobisher Bay) in the Northwest Territories of Canada during July 1985 (Wolfe et al. 1986). This site was selected because it was calculated to be in the conjugate area to the Amundsen-Scott South Pole Station where extensive geomagnetic research has been conducted. The principal scientific objectives are to study the conjugacy of high-latitude magnetic fluctuations observed at Iqaluit and South Pole (L{approximately}13). In this report, the authors extend the previous report of Wolfe et al. (1987) and comment upon the conjugacy of the stations for magnetic field fluctuations in the Pc3 (22-33 millihertz) hydromagnetic regime and upon the penetration of hydromagnetic energy deeper into the magnetosphere on the local dayside.

  9. Geomagnetic response to solar and interplanetary disturbances

    Directory of Open Access Journals (Sweden)

    Maris Georgeta

    2013-07-01

    Full Text Available The space weather discipline involves different physical scenarios, which are characterised by very different physical conditions, ranging from the Sun to the terrestrial magnetosphere and ionosphere. Thanks to the great modelling effort made during the last years, a few Sun-to-ionosphere/thermosphere physics-based numerical codes have been developed. However, the success of the prediction is still far from achieving the desirable results and much more progress is needed. Some aspects involved in this progress concern both the technical progress (developing and validating tools to forecast, selecting the optimal parameters as inputs for the tools, improving accuracy in prediction with short lead time, etc. and the scientific development, i.e., deeper understanding of the energy transfer process from the solar wind to the coupled magnetosphere-ionosphere-thermosphere system. The purpose of this paper is to collect the most relevant results related to these topics obtained during the COST Action ES0803. In an end-to-end forecasting scheme that uses an artificial neural network, we show that the forecasting results improve when gathering certain parameters, such as X-ray solar flares, Type II and/or Type IV radio emission and solar energetic particles enhancements as inputs for the algorithm. Regarding the solar wind-magnetosphere-ionosphere interaction topic, the geomagnetic responses at high and low latitudes are considered separately. At low latitudes, we present new insights into temporal evolution of the ring current, as seen by Burton’s equation, in both main and recovery phases of the storm. At high latitudes, the PCC index appears as an achievement in modelling the coupling between the upper atmosphere and the solar wind, with a great potential for forecasting purposes. We also address the important role of small-scale field-aligned currents in Joule heating of the ionosphere even under non-disturbed conditions. Our scientific results in

  10. PAMELA's measurements of geomagnetic cutoff variations during the 14 December 2006 storm

    CERN Document Server

    Adriani, O; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bruno, A; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mikhailov, M Mergé V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N

    2016-01-01

    Data from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) satellite experiment were used to measure the geomagnetic cutoff for high-energy (>80 MeV) protons during the 14 December 2006 geomagnetic storm. The variations of the cutoff latitude as a function of rigidity were studied on relatively short timescales, corresponding to spacecraft orbital periods (94 min). Estimated cutoff values were compared with those obtained by means of a trajectory tracing approach based on a dynamical empirical modeling of the Earth's magnetosphere. We found significant variations in the cutoff latitude, with a maximum suppression of about 7 deg at lowest rigidities during the main phase of the storm. The observed reduction in the geomagnetic shielding and its temporal evolution were related to the changes in the magnetospheric configuration, investigating the role of interplanetary magnetic field, solar wind and geomagnetic parameters. PAMELA's results represent the first direct measurement...

  11. Electric Utility Industry Experience with Geomagnetic Disturbances

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, P.R.

    1991-01-01

    A geomagnetic disturbance (GMD) by its nature occurs globally and almost simultaneously. Severe geomagnetic storms cause problems for electric power systems. The vulnerability of electric power systems to such events has apparently increased during the last 10 to 20 years because power system transmission lines have become more interconnected and have increased in length and because power systems are now operated closer to their limits than in the past. In this report, the experience of electric utilities during geomagnetic storms is examined and analyzed. Measured data, effects on power system components, and power system impacts are considered. It has been found that electric power systems are susceptible to geomagnetically induced earth-surface potential gradients as small as a few (2 to 3) volts per kilometer, corresponding to a storm of K-6 intensity over an area of high earth resistivity. The causes and effects are reasonably well understood, but additional research is needed to develop a better understanding of solar-induced geomagnetic storms and the responses of power systems to these types of storms. A better understanding of geomagnetic storms and the power systems' responses to GMDs is needed so that mitigation measures can be implemented that will make power systems less susceptible to severe geomagnetic disturbances. A GMD caused by a large high-altitude nuclear detonation is similar in many ways to that of solar-induced geomagnetic storms except that a nuclear-caused disturbance would be much more intense with a far shorter duration.

  12. Electric utility industry experience with geomagnetic disturbances

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, P.R.; Rizy, D.T.; McConnell, B.W. [Oak Ridge National Lab., TN (United States); Taylor, E.R. Jr. [ABB Power Systems, Inc., Pittsburgh, PA (United States); Tesche, F.M.

    1991-09-01

    A geomagnetic disturbance (GMD) by its nature occurs globally and almost simultaneously. Severe geomagnetic storms cause problems for electric power systems. The vulnerability of electric power systems to such events has apparently increased during the last 10 to 20 years because power system transmission lines have become more interconnected and have increased in length and because power systems are now operated closer to their limits than in the past. In this report, the experience of electric utilities during geomagnetic storms is examined and analyzed. Measured data, effects on power system components, and power system impacts are considered. It has been found that electric power systems are susceptible to geomagnetically induced earth-surface potential gradients as small as few (2 to 3) volts per kilometer, corresponding to a storm of K-6 intensity over an area of high earth resistivity. The causes and effects are reasonably well understood, but additional research is needed to develop a better understanding of solar-induced geomagnetic storms and the responses of power systems to these types of storms. A better understanding of geomagnetic storms and the power systems` responses to GMDs is needed so that mitigation measures can be implemented that will make power systems less susceptible to severe geomagnetic disturbances. A GMD caused by a large high-altitude nuclear detonation is similar in many ways to that of solar-induced geomagnetic storms except that a nuclear-caused disturbance would be much more intense with a far shorter duration. 49 refs.

  13. Electric utility industry experience with geomagnetic disturbances

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, P.R.; Rizy, D.T.; McConnell, B.W. (Oak Ridge National Lab., TN (United States)); Taylor, E.R. Jr. (ABB Power Systems, Inc., Pittsburgh, PA (United States)); Tesche, F.M.

    1991-09-01

    A geomagnetic disturbance (GMD) by its nature occurs globally and almost simultaneously. Severe geomagnetic storms cause problems for electric power systems. The vulnerability of electric power systems to such events has apparently increased during the last 10 to 20 years because power system transmission lines have become more interconnected and have increased in length and because power systems are now operated closer to their limits than in the past. In this report, the experience of electric utilities during geomagnetic storms is examined and analyzed. Measured data, effects on power system components, and power system impacts are considered. It has been found that electric power systems are susceptible to geomagnetically induced earth-surface potential gradients as small as few (2 to 3) volts per kilometer, corresponding to a storm of K-6 intensity over an area of high earth resistivity. The causes and effects are reasonably well understood, but additional research is needed to develop a better understanding of solar-induced geomagnetic storms and the responses of power systems to these types of storms. A better understanding of geomagnetic storms and the power systems' responses to GMDs is needed so that mitigation measures can be implemented that will make power systems less susceptible to severe geomagnetic disturbances. A GMD caused by a large high-altitude nuclear detonation is similar in many ways to that of solar-induced geomagnetic storms except that a nuclear-caused disturbance would be much more intense with a far shorter duration. 49 refs.

  14. Electric utility industry experience with geomagnetic disturbances

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, P.R.; Rizy, D.T.; McConnell, B.W. (Oak Ridge National Lab., TN (United States)); Taylor, E.R. Jr. (ABB Power Systems, Inc., Pittsburgh, PA (United States)); Tesche, F.M.

    1991-09-01

    A geomagnetic disturbance (GMD) by its nature occurs globally and almost simultaneously. Severe geomagnetic storms cause problems for electric power systems. The vulnerability of electric power systems to such events has apparently increased during the last 10 to 20 years because power system transmission lines have become more interconnected and have increased in length and because power systems are now operated closer to their limits than in the past. In this report, the experience of electric utilities during geomagnetic storms is examined and analyzed. Measured data, effects on power system components, and power system impacts are considered. It has been found that electric power systems are susceptible to geomagnetically induced earth-surface potential gradients as small as few (2 to 3) volts per kilometer, corresponding to a storm of K-6 intensity over an area of high earth resistivity. The causes and effects are reasonably well understood, but additional research is needed to develop a better understanding of solar-induced geomagnetic storms and the responses of power systems to these types of storms. A better understanding of geomagnetic storms and the power systems' responses to GMDs is needed so that mitigation measures can be implemented that will make power systems less susceptible to severe geomagnetic disturbances. A GMD caused by a large high-altitude nuclear detonation is similar in many ways to that of solar-induced geomagnetic storms except that a nuclear-caused disturbance would be much more intense with a far shorter duration. 49 refs.

  15. Electric utility industry experience with geomagnetic disturbances

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, P.R.; Rizy, D.T.; McConnell, B.W. [Oak Ridge National Lab., TN (United States); Taylor, E.R. Jr. [ABB Power Systems, Inc., Pittsburgh, PA (United States); Tesche, F.M.

    1991-09-01

    A geomagnetic disturbance (GMD) by its nature occurs globally and almost simultaneously. Severe geomagnetic storms cause problems for electric power systems. The vulnerability of electric power systems to such events has apparently increased during the last 10 to 20 years because power system transmission lines have become more interconnected and have increased in length and because power systems are now operated closer to their limits than in the past. In this report, the experience of electric utilities during geomagnetic storms is examined and analyzed. Measured data, effects on power system components, and power system impacts are considered. It has been found that electric power systems are susceptible to geomagnetically induced earth-surface potential gradients as small as few (2 to 3) volts per kilometer, corresponding to a storm of K-6 intensity over an area of high earth resistivity. The causes and effects are reasonably well understood, but additional research is needed to develop a better understanding of solar-induced geomagnetic storms and the responses of power systems to these types of storms. A better understanding of geomagnetic storms and the power systems` responses to GMDs is needed so that mitigation measures can be implemented that will make power systems less susceptible to severe geomagnetic disturbances. A GMD caused by a large high-altitude nuclear detonation is similar in many ways to that of solar-induced geomagnetic storms except that a nuclear-caused disturbance would be much more intense with a far shorter duration. 49 refs.

  16. Geomagnetic Information Model for the Year 2013

    Directory of Open Access Journals (Sweden)

    Mario Brkić

    2012-12-01

    Full Text Available The finalization of the survey of the Basic Geomagnetic Network of the Republic of Croatia (BGNRC and completion of geomagnetic information models for the Institute for Research and Development of Defence Systems of the Ministry of Defence and the State Geodetic Administration (e.g. Brkić M., E. Jungwirth, D. Matika and Ž. Bačić, 2012, Geomagnetic Information and Safety, 3rd Conference of Croatian National Platform for Disaster Risk Reduction, National Protection and Rescue Directorate, Zagreb was followed in 2012 with validity confirmation of the GI2012 predictive model by geomagnetic observations in quiet conditions. The differences between the measured and modelled declination were found to be within the expected errors of the model. It needs to be pointed out that this was the first successful implementation of night surveying (especially suitable for geomagnetic surveys of airports in the Republic of Croatia.

  17. Geomagnetic Observatory Data for Real-Time Applications

    Science.gov (United States)

    Love, J. J.; Finn, C. A.; Rigler, E. J.; Kelbert, A.; Bedrosian, P.

    2015-12-01

    The global network of magnetic observatories represents a unique collective asset for the scientific community. Historically, magnetic observatories have supported global magnetic-field mapping projects and fundamental research of the Earth's interior and surrounding space environment. More recently, real-time data streams from magnetic observatories have become an important contributor to multi-sensor, operational monitoring of evolving space weather conditions, especially during magnetic storms. In this context, the U.S. Geological Survey (1) provides real-time observatory data to allied space weather monitoring projects, including those of NOAA, the U.S. Air Force, NASA, several international agencies, and private industry, (2) collaborates with Schlumberger to provide real-time geomagnetic data needed for directional drilling for oil and gas in Alaska, (3) develops products for real-time evaluation of hazards for the electric-power grid industry that are associated with the storm-time induction of geoelectric fields in the Earth's conducting lithosphere. In order to implement strategic priorities established by the USGS Natural Hazards Mission Area and the National Science and Technology Council, and with a focus on developing new real-time products, the USGS is (1) leveraging data management protocols already developed by the USGS Earthquake Program, (2) developing algorithms for mapping geomagnetic activity, a collaboration with NASA and NOAA, (3) supporting magnetotelluric surveys and developing Earth conductivity models, a collaboration with Oregon State University and the NSF's EarthScope Program, (4) studying the use of geomagnetic activity maps and Earth conductivity models for real-time estimation of geoelectric fields, (5) initiating geoelectric monitoring at several observatories, (6) validating real-time estimation algorithms against historical geomagnetic and geoelectric data. The success of these long-term projects is subject to funding constraints

  18. The Effect of the Geomagnetic Field on the Secondary Charged Particles Trajectories of Extensive Air Shower%地磁场对广延大气簇射产生的次级带电粒子的偏转效应

    Institute of Scientific and Technical Information of China (English)

    孙宝光

    2011-01-01

    用蒙特卡罗模拟的方法研究了在地磁场作用下,广延大气簇射产生的大量次级带电粒子所发生的偏转.研究发现,地磁场对从北方来的次级带电粒子的横向分布的影响比对从南方来的大,导致宇宙线观测阵列的触发效率南高于北,且随天顶角越大这种效应越明显.此外,用一次谐波和二次谐波对大量的模拟数据进行了拟合,给出了此种偏转效应对触发效率的影响程度.%In the geomagnetic field, the secondary charged particle trajectories of EAS (extensive air shower) will be distorted because of geomagnetism. In this study, the author uses Monte-Carlo simulation to investigate the effect of this distortion and concludes that the geomagnetic field leads to a stretched lateral distribution of the secondaries. This distorting effect is larger for the secondary particles of cosmic-ray coming from the north than that from the south. As a result, the trigger efficiency of the array for the former is lower than that for the latter and it becomes more evident with larger zenith angles. The simulated data is fitted by overlapping the first-harmonic and the second-harmonic to evaluate the extent of the influence of this distorting effect.

  19. Study of cosmic ray intensity and geomagnetic storms with solar wind parameters during the period 1998-2005

    Science.gov (United States)

    Kharayat, Hema; Prasad, Lalan

    2017-01-01

    The aim of this paper is to study the effect of solar wind parameters (solar wind speed V, plasma flow pressure, and plasma density) on cosmic ray intensity and on geomagnetic storms for the period 1998-2005 (solar cycle 23). A Chree analysis by the superposed epoch method has been done for the study. From the present study we have found that the solar wind speed is a highly effective parameter in producing cosmic ray intensity decreases and geomagnetic storms. No time lag is found between cosmic ray intensity decreases, geomagnetic storms, and peak value of solar wind speed. Further, we have found that the plasma flow pressure is effectively correlated with geomagnetic storms but it is weakly correlated with cosmic ray intensity. The cosmic ray intensity and geomagnetic storms are found to be weakly correlated with plasma density. The decrease in cosmic ray intensity and geomagnetic storms takes place one day after the peak values of plasma flow pressure and plasma density. There is a time lag of one day between solar wind parameters (plasma flow pressure and plasma density) and cosmic ray intensity decrease, geomagnetic storms. Also, we have found a high correlation of cosmic ray intensity and geomagnetic storms with the product of interplanetary magnetic field B and solar wind speed V i.e. B\\cdot V. This study may be useful in predicting the space-weather phenomena.

  20. Geomagnetic activity effects on plasma sheet energy conversion

    Directory of Open Access Journals (Sweden)

    M. Hamrin

    2010-10-01

    Full Text Available In this article we use three years (2001, 2002, and 2004 of Cluster plasma sheet data to investigate what happens to localized energy conversion regions (ECRs in the plasma sheet during times of high magnetospheric activity. By examining variations in the power density, E·J, where E is the electric field and J is the current density obtained by Cluster, we have studied the influence on Concentrated Load Regions (CLRs and Concentrated Generator Regions (CGRs from variations in the geomagnetic disturbance level as expressed by the Kp, the AE, and the Dst indices. We find that the ECR occurrence frequency increases during higher magnetospheric activities, and that the ECRs become stronger. This is true both for CLRs and for CGRs, and the localized energy conversion therefore concerns energy conversion in both directions between the particles and the fields in the plasma sheet. A higher geomagnetic activity hence increases the general level of energy conversion in the plasma sheet. Moreover, we have shown that CLRs live longer during magnetically disturbed times, hence converting more electromagnetic energy. The CGR lifetime, on the other hand, seems to be unaffected by the geomagnetic activity level. The evidence for increased energy conversion during geomagnetically disturbed times is most clear for Kp and for AE, but there are also some indications that energy conversion increases during large negative Dst. This is consistent with the plasma sheet magnetically mapping to the auroral zone, and therefore being more tightly coupled to auroral activities and variations in the AE and Kp indices, than to variations in the ring current region as described by the Dst index.

  1. Effect of a huge crustal conductivity anomaly on the H-component of geomagnetic variations recorded in central South America

    Science.gov (United States)

    Padilha, Antonio L.; Alves, Livia R.; Silva, Graziela B. D.; Espinosa, Karen V.

    2017-04-01

    We describe here an analysis of the H-component of the geomagnetic field recorded in several temporary stations operating simultaneously in the central-eastern region of Brazil during nighttime pulsation events in 1994 and the sudden commencement of the St. Patrick's Day magnetic storm in 2015. A significant amplification in the amplitude of the geomagnetic variations is consistently observed in one of these stations. Magnetovariational analysis indicates that the amplification factor is period dependent with maximum amplitude around 100 s. Integrated magnetotelluric (MT) and geomagnetic depth soundings (GDS) have shown that this station is positioned just over a huge 1200-km-long crustal conductor (estimated bulk conductivity greater than 1 S/m). We propose that the anomalous signature of the geomagnetic field at this station is due to the high reflection coefficient of the incident electromagnetic wave at the interface with the very good conductor and by skin effects damping the electromagnetic wave in the conducting layers overlying the conductor. There are some indication from the GDS data that the conductor extends southward beneath the sediments of the Pantanal Basin. In this region is being planned the installation of a new geomagnetic observatory, but its preliminary data suggest anomalous geomagnetic variations. We understand that a detailed MT survey must be carried out around the chosen observatory site to evaluate the possible influence of induced currents on the local geomagnetic field.[Figure not available: see fulltext.

  2. Different Responses of Solar Wind and Geomagnetism to Solar Activity during Quiet and Active Periods

    Science.gov (United States)

    Kim, Roksoon; Park, J.-Y.; Baek, J.-H.; Kim, B.-G.

    2017-08-01

    It is well known that there are good relations of coronal hole (CH) parameters such as the size, location, and magnetic field strength to the solar wind conditions and the geomagnetic storms. Especially in the minimum phase of solar cycle, CHs in mid- or low-latitude are one of major drivers for geomagnetic storms, since they form corotating interaction regions (CIRs). By adopting the method of Vrsnak et al. (2007), the Space Weather Research Center (SWRC) in Korea Astronomy and Space Science Institute (KASI) has done daily forecast of solar wind speed and Dst index from 2010. Through years of experience, we realize that the geomagnetic storms caused by CHs have different characteristics from those by CMEs. Thus, we statistically analyze the characteristics and causality of the geomagnetic storms by the CHs rather than the CMEs with dataset obtained during the solar activity was very low. For this, we examine the CH properties, solar wind parameters as well as geomagnetic storm indices. As the first result, we show the different trends of the solar wind parameters and geomagnetic indices depending on the degree of solar activity represented by CH (quiet) or sunspot number (SSN) in the active region (active) and then we evaluate our forecasts using CH information and suggest several ideas to improve forecasting capability.

  3. Geomagnetic Navigation of Autonomous Underwater Vehicle Based on Multi-objective Evolutionary Algorithm

    Directory of Open Access Journals (Sweden)

    Hong Li

    2017-07-01

    Full Text Available This paper presents a multi-objective evolutionary algorithm of bio-inspired geomagnetic navigation for Autonomous Underwater Vehicle (AUV. Inspired by the biological navigation behavior, the solution was proposed without using a priori information, simply by magnetotaxis searching. However, the existence of the geomagnetic anomalies has significant influence on the geomagnetic navigation system, which often disrupts the distribution of the geomagnetic field. An extreme value region may easily appear in abnormal regions, which makes AUV lost in the navigation phase. This paper proposes an improved bio-inspired algorithm with behavior constraints, for sake of making AUV escape from the abnormal region. First, the navigation problem is considered as the optimization problem. Second, the environmental monitoring operator is introduced, to determine whether the algorithm falls into the geomagnetic anomaly region. Then, the behavior constraint operator is employed to get out of the abnormal region. Finally, the termination condition is triggered. Compared to the state-of- the-art, the proposed approach effectively overcomes the disturbance of the geomagnetic abnormal. The simulation result demonstrates the reliability and feasibility of the proposed approach in complex environments.

  4. An Ensemble Algorithm Based Component for Geomagnetic Data Assimilation

    Directory of Open Access Journals (Sweden)

    Zhibin Sun and Weijia Kuang

    2015-01-01

    Full Text Available Geomagnetic data assimilation is one of the most recent developments in geomagnetic studies. It combines geodynamo model outputs and surface geomagnetic observations to provide more accurate estimates of the core dynamic state and provide accurate geomagnetic secular variation forecasting. To facilitate geomagnetic data assimilation studies, we develop a stand-alone data assimilation component for the geomagnetic community. This component is used to calculate the forecast error covariance matrices and the gain matrix from a given geodynamo solution, which can then be used for sequential geomagnetic data assimilation. This component is very flexible and can be executed independently. It can also be easily integrated with arbitrary dynamo models.

  5. A Quaternary Geomagnetic Instability Time Scale

    Science.gov (United States)

    Singer, B. S.

    2013-12-01

    Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought

  6. The Study of the Geomagnetic Variation for Sq current System

    Science.gov (United States)

    Zhao, X.; Du, A.

    2012-04-01

    The solar quiet variation (Sq) with a period of 24 hrs is a typical one of the quiet variations. Sq is generally caused by atmospheric tide-dynamo in ionosphere and it is controlled by the electric field, electric conductivity in ionosphere and neutral wind in middle-high altitude atmosphere. In our work, the geomagnetic field data observed by 90 ground-based observatories is used to analyze the local time variation of Sq. Sq is derived from five quiet-day geomagnetic data in every month by the FFT method. According to the pattern of geomagnetic X component in Sq, there is a prenoon-postnoon (before noon and after noon) asymmetry. This asymmetry is obvious in spring, summer and winter. The X component at 12:00-13:00 LT is about 5 nT larger than it at 11:00-12:00 LT. The ratio between the X component of daily variable amplitude and Y component of daily variable amplitude in middle and low (high) latitude regions in summer is greater (smaller) than that in winter. Used the sphere harmonic analysis method, the Sq equivalent current system is obtained. From the pattern of Sq current system, the prenoon-postnoon asymmetry may be caused by the electric field in the high latitude region. This electric field has two effects: the one is that the electric field from high latitude maps to the low latitude region; the other is this electric field penetrate to the middle latitude region directly. The combined action of these two effects makes the prenoon-postnoon asymmetry of Sq. The asymmetry also has an obvious seasonal effect. It may relate to the polar Sq and DP2 in the high latitude region.

  7. Solar wind and geomagnetism. Toward a standard classification of geomagnetic activity from 1868 to 2009

    Energy Technology Data Exchange (ETDEWEB)

    Zerbo, J.L. [Univ. Polytechnique de Bobo Dioulasso (Burkina Faso); UPMC/Polytechique/CNRS, UMR 7648, Saint-Maur-des-Fosses (France). LPP-Lab. de Physique des Plasmas; Mazaudier, C. Amory [UPMC/Polytechique/CNRS, UMR 7648, Saint-Maur-des-Fosses (France). LPP-Lab. de Physique des Plasmas; Ouattara, F. [Koudougou Univ. (Burkina Faso). Ecole Normale Superieure; Richardson, J.D. [M.I.T., Cambridge, MA (United States). Center for Space Research

    2012-07-01

    We examined solar activity with a large series of geomagnetic data from 1868 to 2009. We have revisited the geomagnetic activity classification scheme of Legrand and Simon (1989) and improve their scheme by lowering the minimum Aa index value for shock and recurrent activity from 40 to 20 nT. This improved scheme allows us to clearly classify about 80% of the geomagnetic activity in this time period instead of only 60% for the previous Legrand and Simon classification. (orig.)

  8. Comparison and Aanalysis of the 11th international geomagnetic reference field (IGRF11)%第11代国际地磁参考场(IGRF11)的比较分析

    Institute of Scientific and Technical Information of China (English)

    冯彦; 安振昌; 孙涵; 毛飞

    2011-01-01

    利用最新的第11代国际地磁场考场(IGRF11)在中国地区进行了一系列的对比分析.将IGRF11与IGRF10计算的2005年1°×1°网格值相减,分析两者的区别;将两模型在2005~2010年间的年变率相比较,进行了差异分析;最后计算了IGRF11的2010~2015年和2005~2010年的年变率,并进行比较.结果显示:IGRF11和IGRF10的差异很小,2005年中国地区的X、Y、Z和F分量的差异强度都小于30nT,D和Ⅰ分量的差异强度小于0.05°.两模型的年变率存在一定的差异,尤其是Z和F分量在国内的东部区域,Y分量在国内的中部区域,但是分布趋势基本一致.造成两种模型差异主要原因是实测数据的不同.经比较,发现中国地区在2005年到2015年的地磁场6分量呈线性变化.%A series analyses over China region are taken by using the newest 11th International Geomagnetic Reference Field(IGRFll). The differences of two models are researched by subtracting IGRFlO's grids values from IGRF11 in 2005; After comparing annual rate of change between two models during 2005~2010, the differences are also researched; Finally, a comparison of annual rate of change based on IGRF11 is taken between 2010~2015 and 2005~ 2010. Results show that the difference between two models is relatively slight, the absolute values of component X, Y, Z, F and D, I are less than 30nT and 0. 05°, respectively. The annual rate of change of two models have something different, especially the eastern areas of component Z and F, the middle areas of component Y, but the main distribution are prettily consistent. The reason is mainly the different survey data. According to charts, we found that the annual rate of change of IGRFll's 6 elements is linear variation during 2005~2015.

  9. Geomagnetic Secular Variation Prediction with Thermal Heterogeneous Boundary Conditions

    Science.gov (United States)

    Kuang, Weijia; Tangborn, Andrew; Jiang, Weiyuan

    2011-01-01

    It has long been conjectured that thermal heterogeneity at the core-mantle boundary (CMB) affects the geodynamo substantially. The observed two pairs of steady and strong magnetic flux lobes near the Polar Regions and the low secular variation in the Pacific over the past 400 years (and perhaps longer) are likely the consequences of this CMB thermal heterogeneity. There are several studies on the impact of the thermal heterogeneity with numerical geodynamo simulations. However, direct correlation between the numerical results and the observations is found very difficult, except qualitative comparisons of certain features in the radial component of the magnetic field at the CMB. This makes it difficult to assess accurately the impact of thermal heterogeneity on the geodynamo and the geomagnetic secular variation. We revisit this problem with our MoSST_DAS system in which geomagnetic data are assimilated with our geodynamo model to predict geomagnetic secular variations. In this study, we implement a heterogeneous heat flux across the CMB that is chosen based on the seismic tomography of the lowermost mantle. The amplitude of the heat flux (relative to the mean heat flux across the CMB) varies in the simulation. With these assimilation studies, we will examine the influences of the heterogeneity on the forecast accuracies, e.g. the accuracies as functions of the heterogeneity amplitude. With these, we could be able to assess the model errors to the true core state, and thus the thermal heterogeneity in geodynamo modeling.

  10. Remagnetization of lava flows spanning the last geomagnetic reversal

    Science.gov (United States)

    Vella, Jérôme; Carlut, Julie; Valet, Jean-Pierre; Goff, Maxime Le; Soler, Vicente; Lopes, Fernando

    2017-08-01

    Large directional changes of remanent magnetization within lava flows that cooled during geomagnetic reversals have been reported in several studies. A geomagnetic scenario implies extremely rapid geomagnetic changes of several degrees per day, thus difficult to reconcile with the rate of the earth's core liquid motions. So far, no complete rock magnetic model provides a clear explanation. We revisited lava flows sandwiched between an underlying reverse and an overlying normal polarity flow marking the last reversal in three distinct volcanic sequences of the La Palma Island (Canary archipelago, Spain) that are characterized by a gradual evolution of the direction of their remanent magnetization from bottom to top. Cleaning efficiency of thermal demagnetization was not improved by very rapid heating and cooling rates as well as by continuous demagnetization using a Triaxe magnetometer. We did not observe partial self-reversals and minor changes in magnetic grain sizes are not related to the within-flow directional changes. Microscopic observations indicate poor exsolution, which suggests post-cooling thermochemical remagnetization processes. This scenario is strongly reinforced by laboratory experiments that show large resistance to thermal demagnetization when thermoremanence was acquired over a long time period. We speculate that in the present situation exsolution was reactivated during in field reheating and yielded formation of new magnetite, yet magnetic domain state rearrangements could also play a role. Initial reheating when the overlying flow took place, albeit moderate (less than 200-300 °C), was enough to produce overlying components with significantly higher unblocking temperatures.

  11. Correlation of geomagnetic anomalies recorded at Muntele Rosu Seismic Observatory (Romania with earthquake occurrence and solar magnetic storms

    Directory of Open Access Journals (Sweden)

    Adrian Septimiu Moldovan

    2012-04-01

    Full Text Available

    The study presents a statistical cross-correlation between geomagnetic anomalies, earthquake occurrence and solar magnetic storms. The working data are from: (i geomagnetic field records from Muntele Rosu (MLR Observatory, and from Surlari (SUA and/or Tihany (THY INTERMAGNET Observatories; (ii seismic data for the Vrancea source zone; and (iii daily geomagnetic indices from the NOAA/Space Weather Prediction Center. All of the geomagnetic datasets were recorded from 1996 to the present, at MLR, SUA or THY, and they were automatically corrected using a LabVIEW program developed especially for this purpose, highlighting the missing or bad data. Missing data blocks were completed with the last good measured value. After correction of the data, there were a number of issues seen regarding previous interpretations of the geomagnetic anomalies. Some geomagnetic anomalies identified as precursory signals were found to be induced either by increased solar activity or by malfunction of the data acquisition system, which produced inconsistent data, with numerous gaps. The MLR geomagnetic data are compared with the data recorded at SUA/THY and correlated with seismicity and solar activity. These 15 years of investigations cover more than a complete solar cycle, during which time the solar-terrestrial perturbations have fluctuated from very low to very high values, providing the ideal medium to investigate the correlations between the geomagnetic field perturbations, the earthquakes and the solar activity. The largest intermediate depth earthquake produced in this interval had a moment magnitude Mw 6.0 (2004 and provided the opportunity to investigate possible connections between local geomagnetic field behavior and local intermediate seismicity.

     

  12. Space Weather Monitoring for ISS Geomagnetic Storm Studies

    Science.gov (United States)

    Minow, Joseph I.; Parker, Linda Neergaard

    2013-01-01

    The International Space Station (ISS) space environments community utilizes near real time space weather data to support a variety of ISS engineering and science activities. The team has operated the Floating Potential Measurement Unit (FPMU) suite of plasma instruments (two Langmuir probes, a floating potential probe, and a plasma impedance probe) on ISS since 2006 to obtain in-situ measurements of plasma density and temperature along the ISS orbit and variations in ISS frame potential due to electrostatic current collection from the plasma environment (spacecraft charging) and inductive (vxB) effects from the vehicle motion across the Earth s magnetic field. An ongoing effort is to use FPMU for measuring the ionospheric response to geomagnetic storms at ISS altitudes and investigate auroral charging of the vehicle as it passes through regions of precipitating auroral electrons. This work is challenged by restrictions on FPMU operations that limit observation time to less than about a third of a year. As a result, FPMU campaigns ranging in length from a few days to a few weeks are typically scheduled weeks in advance for ISS engineering and payload science activities. In order to capture geomagnetic storm data under these terms, we monitor near real time space weather data from NASA, NOAA, and ESA sources to determine solar wind disturbance arrival times at Earth likely to be geoeffective (including coronal mass ejections and high speed streams associated with coronal holes) and activate the FPMU ahead of the storm onset. Using this technique we have successfully captured FPMU data during a number of geomagnetic storm periods including periods with ISS auroral charging. This presentation will describe the strategies and challenges in capturing FPMU data during geomagnetic storms, the near real time space weather resources utilized for monitoring the space weather environment, and provide examples of auroral charging data obtained during storm operations.

  13. Variations of terrestrial geomagnetic activity correlated to M6+ global seismic activity

    Science.gov (United States)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2013-04-01

    From the surface of the Sun, as a result of a solar flare, are expelled a coronal mass (CME or Coronal Mass Ejection) that can be observed from the Earth through a coronagraph in white light. This ejected material can be compared to an electrically charged cloud (plasma) mainly composed of electrons, protons and other small quantities of heavier elements such as helium, oxygen and iron that run radially from the Sun along the lines of the solar magnetic field and pushing into interplanetary space. Sometimes the CME able to reach the Earth causing major disruptions of its magnetosphere: mashed in the region illuminated by the Sun and expanding in the region not illuminated. This interaction creates extensive disruption of the Earth's geomagnetic field that can be detected by a radio receiver tuned to the ELF band (Extreme Low Frequency 0-30 Hz). The Radio Emissions Project (scientific research project founded in February 2009 by Gabriele Cataldi and Daniele Cataldi), analyzing the change in the Earth's geomagnetic field through an induction magnetometer tuned between 0.001 and 5 Hz (bandwidth in which possible to observe the geomagnetic pulsations) was able to detect the existence of a close relationship between this geomagnetic perturbations and the global seismic activity M6+. During the arrival of the CME on Earth, in the Earth's geomagnetic field are generated sudden and intensive emissions that have a bandwidth including between 0 and 15 Hz, an average duration of 2-8 hours, that preceding of 0-12 hours M6+ earthquakes. Between 1 January 2012 and 31 December 2012, all M6+ earthquakes recorded on a global scale were preceded by this type of signals which, due to their characteristics, have been called "Seismic Geomagnetic Precursors" (S.G.P.). The main feature of Seismic Geomagnetic Precursors is represented by the close relationship that they have with the solar activity. In fact, because the S.G.P. are geomagnetic emissions, their temporal modulation depends

  14. A study of solar and interplanetary parameters of CMEs causing major geomagnetic storms during SC 23

    Directory of Open Access Journals (Sweden)

    C. Oprea

    2013-08-01

    Full Text Available In this paper we analyse 25 Earth-directed and strongly geoeffective interplanetary coronal mass ejections (ICMEs which occurred during solar cycle 23, using data provided by instruments on SOHO (Solar and Heliospheric Observatory, ACE (Advanced Composition Explorer and geomagnetic stations. We also examine the in situ parameters, the energy transfer into magnetosphere, and the geomagnetic indexes. We compare observed travel times with those calculated by observed speeds projected into the plane of the sky and de-projected by a simple model. The best fit was found with the projected speeds. No correlation was found between the importance of a flare and the geomagnetic Dst (disturbance storm time index. By comparing the in situ parameters with the Dst index we find a strong connection between some of these parameters (such as Bz, Bs · V and the energy transfer into the magnetosphere with the strength of the geomagnetic storm. No correlation was found with proton density and plasma temperature. A superposed epoch analysis revealed a strong dependence of the Dst index on the southward component of interplanetary magnetic field, Bz, and to the Akasofu coupling function, which evaluates the energy transfer between the ICME and the magnetosphere. The analysis also showed that the geomagnetic field at higher latitudes is disturbed before the field around the Earth's equator.

  15. The role of 3-D geomagnetic induction in the determination of the ionospheric currents from the ground geomagnetic data

    Directory of Open Access Journals (Sweden)

    A. Pulkkinen

    2005-03-01

    Full Text Available The geomagnetic field variations measured at the surface of the Earth are composed of both internal and external parts. The external field arises from the sources in the magnetosphere and ionosphere, whereas the internal field is generated by the currents induced within the Earth. The internal part may in some situations comprise a notable part of the measured total field and thus a blind usage of geomagnetic field recordings potentially produces significant errors to estimated ionospheric currents. In this paper the role of geomagnetic induction in auroral ionospheric studies is investigated by modeling the induction using simultaneously the realistic ionospheric source and a realistic three-dimensional Earth conductivity structure.

    The modeling results imply that the effects of the lateral ground conductivity anomalies on ionospheric equivalent current patterns are, though clearly detected, less severe than anticipated for fields varying with periods from 5 to 120min. However, the amplification of the determined currents caused by induction is significant, leading to an overestimation of up to 30% of the main current flow intensities, with the overestimation increasing sharply when moving away from the region of the main flow.

    In addition to the 3-D modeling, a simple method is introduced to help estimate the internal contribution to the measured variations of the IL index (local variant of the AL index. A test with the 26 June 1998 substorm event indicates that the method can help to extract the internal contribution from the IL index.

  16. Digitized Historical Geomagnetic Publications in PDF format

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A catalog of 732 historical geomagnetic publications that were at risk of loss have been digitized and converted in pdf documents.

  17. Geomagnetism solid Earth and upper atmosphere perspectives

    CERN Document Server

    Basavaiah, Nathani

    2011-01-01

    This volume elaborates several important aspects of solid Earth geomagnetism. It covers all the basics of the subject, including biomagnetism and instrumentation, and offers a number of practical applications with carefully selected examples and illustrations.

  18. High definition geomagnetic models: A new perspective for improved wellbore positioning

    DEFF Research Database (Denmark)

    Maus, Stefan; Nair, Manoj C.; Poedjono, Benny

    2012-01-01

    Earth's gravity and magnetic fields are used as natural reference frames in directional drilling. The azimuth of the bottomhole assembly is inferred by comparing the magnetic field measured-while-drilling (MWD) with a geomagnetic reference model. To provide a reference of sufficient quality for a...

  19. Gravitational dynamos and the low-frequency geomagnetic secular variation

    Science.gov (United States)

    Olson, P.

    2007-01-01

    Self-sustaining numerical dynamos are used to infer the sources of low-frequency secular variation of the geomagnetic field. Gravitational dynamo models powered by compositional convection in an electrically conducting, rotating fluid shell exhibit several regimes of magnetic field behavior with an increasing Rayleigh number of the convection, including nearly steady dipoles, chaotic nonreversing dipoles, and chaotic reversing dipoles. The time average dipole strength and dipolarity of the magnetic field decrease, whereas the dipole variability, average dipole tilt angle, and frequency of polarity reversals increase with Rayleigh number. Chaotic gravitational dynamos have large-amplitude dipole secular variation with maximum power at frequencies corresponding to a few cycles per million years on Earth. Their external magnetic field structure, dipole statistics, low-frequency power spectra, and polarity reversal frequency are comparable to the geomagnetic field. The magnetic variability is driven by the Lorentz force and is characterized by an inverse correlation between dynamo magnetic and kinetic energy fluctuations. A constant energy dissipation theory accounts for this inverse energy correlation, which is shown to produce conditions favorable for dipole drift, polarity reversals, and excursions. PMID:18048345

  20. Geomagnetism during solar cycle 23: Characteristics

    Directory of Open Access Journals (Sweden)

    Jean-Louis Zerbo

    2013-05-01

    Full Text Available On the basis of more than 48 years of morphological analysis of yearly and monthly values of the sunspot number, the aa index, the solar wind speed and interplanetary magnetic field, we point out the particularities of geomagnetic activity during the period 1996–2009. We especially investigate the last cycle 23 and the long minimum which followed it. During this period, the lowest values of the yearly averaged IMF (3 nT and yearly averaged solar wind speed (364 km/s are recorded in 1996, and 2009 respectively. The year 2003 shows itself particular by recording the highest value of the averaged solar wind (568 km/s, associated to the highest value of the yearly averaged aa index (37 nT. We also find that observations during the year 2003 seem to be related to several coronal holes which are known to generate high-speed wind stream. From the long time (more than one century study of solar variability, the present period is similar to the beginning of twentieth century. We especially present the morphological features of solar cycle 23 which is followed by a deep solar minimum.

  1. Geomagnetism during solar cycle 23: Characteristics.

    Science.gov (United States)

    Zerbo, Jean-Louis; Amory-Mazaudier, Christine; Ouattara, Frédéric

    2013-05-01

    On the basis of more than 48 years of morphological analysis of yearly and monthly values of the sunspot number, the aa index, the solar wind speed and interplanetary magnetic field, we point out the particularities of geomagnetic activity during the period 1996-2009. We especially investigate the last cycle 23 and the long minimum which followed it. During this period, the lowest values of the yearly averaged IMF (3 nT) and yearly averaged solar wind speed (364 km/s) are recorded in 1996, and 2009 respectively. The year 2003 shows itself particular by recording the highest value of the averaged solar wind (568 km/s), associated to the highest value of the yearly averaged aa index (37 nT). We also find that observations during the year 2003 seem to be related to several coronal holes which are known to generate high-speed wind stream. From the long time (more than one century) study of solar variability, the present period is similar to the beginning of twentieth century. We especially present the morphological features of solar cycle 23 which is followed by a deep solar minimum.

  2. Revisiting the Jurassic Geomagnetic Reversal recorded in the Lesotho Basalt (Southern Africa)

    CERN Document Server

    Prévot, M; Thompson, J; Faynot, L; Perrin, M; Camps, P; Prevot, Michel; Roberts, Neil; Thompson, John; Faynot, Liliane; Perrin, Mireille; Camps, Pierre

    2003-01-01

    We carried out a detailed and continuous paleomagnetic sampling of the reversed to normal geomagnetic transition recorded by some 60 consecutive flow units near the base of the Lesotho Basalt (183  1 Ma). After alternating field or thermal cleaning the directions of remanence are generally well clustered within flow units. In contrast, the thermal instability of the samples did not allow to obtain reliable paleointensity determinations. The geomagnetic transition is incompletely recorded due to a gap in volcanic activity attested both by eolian deposits and a large angular distance between the field directions of the flows underlying or overlying these deposits. The transition path is noticeably different from that reported in the pioneer work of van Zijl et al. (1962). The most transitional Virtual Geomagnetic Poles are observed after the volcanic hiatus. Once continents are replaced in their relative position 180 Ma ago, the post-hiatus VGP cluster over Russia. However, two successive rebounds f...

  3. Kristian Birkeland's pioneering investigations of geomagnetic disturbances

    Science.gov (United States)

    Egeland, A.; Burke, W. J.

    2010-04-01

    More than 100 years ago Kristian Birkeland (1967-1917) addressed questions that had vexed scientists for centuries. Why do auroras appear overhead while the Earth's magnetic field is disturbed? Are magnetic storms on Earth related to disturbances on the Sun? To answer these questions Birkeland devised terrella simulations, led coordinated campaigns in the Arctic wilderness, and then interpreted his results in the light of Maxwell's synthesis of laws governing electricity and magnetism. After analyzing thousands of magnetograms, he divided disturbances into 3 categories: 1. Polar elementary storms are auroral-latitude disturbances now called substorms. 2. Equatorial perturbations correspond to initial and main phases of magnetic storms. 3. Cyclo-median perturbations reflect enhanced solar-quiet currents on the dayside. He published the first two-cell pattern of electric currents in Earth's upper atmosphere, nearly 30 years before the ionosphere was identified as a separate entity. Birkeland's most enduring contribution toward understanding geomagnetic disturbances flowed from his recognition that field-aligned currents must connect the upper atmosphere with generators in distant space. The existence of field-aligned currents was vigorously debated among scientists for more than 50 years. Birkeland's conjecture profoundly affects present-day understanding of auroral phenomena and global electrodynamics. In 1896, four years after Lord Kelvin rejected suggestions that matter passes between the Sun and Earth, and two years before the electron was discovered, Birkeland proposed current carriers are "electric corpuscles from the Sun" and "the auroras are formed by corpuscular rays drawn in from space, and coming from the Sun". It can be reasonably argued that the year 1896 marks the founding of space plasma physics. Many of Birkeland's insights were rooted in observations made during his terrella experiments, the first attempts to simulate cosmic phenomena within a

  4. Determination of geomagnetic archaeomagnitudes from clay pipes

    Science.gov (United States)

    Games, K. P.; Baker, M. E.

    1981-02-01

    Archaeomagnitude determinations of a selection of clay pipes dateable to AD 1645+/-10 as well as studies of pottery samples from the same site and of the same age have been made. Values of the magnitude of the ancient magnetic field (Banc), were obtained from two pottery sherds, two pipe bowls and three pipe stems. The values from the sherds and bowls agree within 2% and compare well with the average value of the magnitude of the magnetic field for the seventeenth century as determined by other archaeomagnetic studies. However, the pipe stems give values of Banc which are significantly less than those from the bowls and pottery. We have not yet been able to explain this and thus we suggest that reliable archaeomagnitude determinations can be made from the bowls of clay pipes but not from the stems. Nevertheless, this result provides a new source of material for investigating variations in the geomagnetic field strength over the past 400 yr. Clay pipes have been manufactured in England since the end of the sixteenth century. In the firing process some pipes were broken and disposed of without ever having been smoked. One such collection, discovered at Rainford, Lancashire, in 1978, consisted of a series of discrete dumps including pipes, kiln debris and a small collection of contemporary used earthenware sherds. The internal consideration of the dumps suggested a very short period of activity and archaeologists (P. Davey, personal communication) ascribe all the material to the period 1645+/-10 yr. With such well-dated material, we set out to check whether or not reliable archaeomagnitudes could be obtained from the pipes.

  5. Analysis of the monitoring data of geomagnetic storm interference in the electrification system of a high-speed railway

    Science.gov (United States)

    Liu, Lianguang; Ge, Xiaoning; Zong, Wei; Zhou, You; Liu, Mingguang

    2016-10-01

    To study the impact of geomagnetic storm on the equipment of traction electrification system in the high-speed railway, geomagnetically induced current (GIC) monitoring devices were installed in the Hebi East traction power supply substation of the Beijing-Hong Kong Dedicated Passenger Line in January 2015, and GICs were captured during the two geomagnetic storms on 17 March and 23 June 2015. In order to investigate the GIC flow path, both in the track circuit and in the traction network adopting the autotransformer feeding system, a GIC monitor plan was proposed for the electrical system in the Hebi East traction power supply substation. This paper analyzes the correlation between the GIC captured on 17 March and the geomagnetic data obtained from the Malingshan Geomagnetic Observatory and presents a regression analysis between the measured GIC and the calculated geoelectric fields on 23 June in the high-speed railway. The maximum GICs measured in the track circuit are 1.08 A and 1.74 A during the two geomagnetic storms. We find that it is necessary to pay attention on the throttle transformers and track circuits, as the most sensitive elements responding to the extreme geomagnetic storms in the high-speed railway.

  6. Influence of high-latitude geomagnetic pulsations on recordings of broadband force-balanced seismic sensors

    Directory of Open Access Journals (Sweden)

    E. Kozlovskaya

    2012-08-01

    Full Text Available Seismic broadband sensors with electromagnetic feedback are sensitive to variations of surrounding magnetic field, including variations of geomagnetic field. Usually, the influence of the geomagnetic field on recordings of such seismometers is ignored. It might be justified for seismic observations at middle and low latitudes. The problem is of high importance, however, for observations in Polar Regions (above 60° geomagnetic latitude, where magnitudes of natural magnetic disturbances may be two or even three orders larger. In our study we investigate the effect of ultra-low frequency (ULF magnetic disturbances, known as geomagnetic pulsations, on the STS-2 seismic broadband sensors. The pulsations have their sources and, respectively, maximal amplitudes in the region of the auroral ovals, which surround the magnetic poles in both hemispheres at geomagnetic latitude (GMLAT between 60° and 80°. To investigate sensitivity of the STS-2 seismometer to geomagnetic pulsations, we compared the recordings of permanent seismic stations in northern Finland to the data of the magnetometers of the IMAGE network located in the same area. Our results show that temporary variations of magnetic field with periods of 40–150 s corresponding to regular Pc4 and irregular Pi2 pulsations are seen very well in recordings of the STS-2 seismometers. Therefore, these pulsations may create a serious problem for interpretation of seismic observations in the vicinity of the auroral oval. Moreover, the shape of Pi2 magnetic disturbances and their periods resemble the waveforms of glacial seismic events reported originally by Ekström (2003. The problem may be treated, however, if combined analysis of recordings of co-located seismic and magnetic instruments is used.

  7. On multifractality of high-latitude geomagnetic fluctuations

    Directory of Open Access Journals (Sweden)

    Z. Vörös

    Full Text Available In order to contribute to the understanding of solar wind-magnetosphere interactions the multifractal scaling properties of high-latitude geomagnetic fluctuations observed at the Thule observatory have been studied. Using the local observatory data and the present experimental knowledge only it seems hard to characterize directly the, presumably intermittent, mesoscale energy accumulation and dissipation processes taking place at the magnetotail, auroral region, etc. Instead a positive probability measure, describing the accumulated local geomagnetic signal energy content at the given time scales has been introduced and its scaling properties have been studied. There is evidence for the multifractal nature of the so defined intermittent field ε, a result obtained by using the recently introduced technique of large deviation multifractal spectra. This technique allows us to describe the geomagnetic fluctuations locally in time by means of singularity exponents α, which represent a generalization of the local degree of differentiability and characterize the power-law scaling dependence of the introduced measure on resolution. A global description of the geomagnetic fluctuations is insured by the spectrum of exponents f(α which represents a rate function quantifying the deviations of the observed singularities α from the expected value. The results show that there exists a multifractal counterpart of the previously reported spectral break and different types of f(α spectra describe the fluctuations in direct dissipation or loading-unloading regimes of the solar wind-magnetosphere interaction. On the time scale of substorms and storms the multi-fractal structure of the loading-unloading mode fluctuations seems to be analogous to the simple multiplicative P-model, while the f(α spectra in direct dissipation regime are close but not equal to the features of a uniform distribution. Larger deviations from the multiplicative

  8. Automatic prediction of solar flares and super geomagnetic storms

    Science.gov (United States)

    Song, Hui

    in solar physics to predict flare occurrences; (4) The magnetic orientation angle [straight theta], determined from a potential field model, is proved to be able to predict the probability of super geomagnetic storms (D= st <=-200nT). The results show that those active regions associated with | [straight theta]| < 90° are more likely to cause a super geomagnetic storm.

  9. Forbush decreases geomagnetic and atmospheric effects cosmogenic nuclides

    Science.gov (United States)

    Flueckiger, E. O.

    1986-01-01

    An overview and synthesis is given of recent developments that have occurred in the areas of Forbush decreases, geomagnetic and atmospheric effects, and cosmogenic nuclides. Experimental evidence has been found for substantial differences in the effects of the various types of interplanetary perturbations on cosmic rays, and for a dependence of these effects on the three-dimensional configuration of the interplanetary medium. In order to fully understand and to be able to simulate the solar cosmic ray particle access to the polar regions of the earth we need accurate models of the magnetospheric magnetic field. These models must include all major magnetospheric current systems (in particular the field aligned currents), and they should represent magnetically quiet time periods as well as different levels of geomagnetic activity. In the evolution of magnetospheric magnetic field models, cosmic ray and magnetospheric physicists should work closely together since cosmic ray measurements are a powerful additional tool in the study of the perturbed magnetosphere. In the field of cosmogenic nuclides, finally, exciting new results and developments follow in rapid succession. Thanks to new techniques and new isotopes the analysis of cosmic ray history has entered into a new dimension.

  10. Geomagnetic spikes on the core-mantle boundary

    Science.gov (United States)

    Davies, Christopher; Constable, Catherine

    2017-05-01

    Extreme variations of Earth's magnetic field occurred in the Levant region around 1000 BC, when the field intensity rapidly rose and fell by a factor of 2. No coherent link currently exists between this intensity spike and the global field produced by the core geodynamo. Here we show that the Levantine spike must span >60° longitude at Earth's surface if it originates from the core-mantle boundary (CMB). Several low intensity data are incompatible with this geometric bound, though age uncertainties suggest these data could have sampled the field before the spike emerged. Models that best satisfy energetic and geometric constraints produce CMB spikes 8-22° wide, peaking at O(100) mT. We suggest that the Levantine spike reflects an intense CMB flux patch that grew in place before migrating northwest, contributing to growth of the dipole field. Estimates of Ohmic heating suggest that diffusive processes likely govern the ultimate decay of geomagnetic spikes.

  11. Geomagnetic transmission disturbances and heavy-ion fluences observed in low Earth orbit during the solar energetic particle events of October 1989.

    Science.gov (United States)

    Boberg, P R; Tylka, A J; Adams, J H; Beahm, L P; Fluckiger, E O; Kleis, T; Kobel, E

    1996-01-01

    The large solar energetic particle (SEP) events and simultaneous large geomagnetic disturbances observed during October 1989 posed a significant, rapidly evolving space radiation hazard. Using data from the GOES-7, NOAA-10, IMP-8 and LDEF satellites, we determined the geomagnetic transmission, heavy ion fluences, mean Fe ionic charge state, and effective radiation hazard observed in low Earth orbit (LEO) for these SEPs. We modeled the geomagnetic transmission by tracing particles through the combination of the internal International Geomagnetic Reference Field (IGRF) and the Tsyganenko (1989) magnetospheric field models, extending the modeling to large geomagnetic disturbances. We used our results to assess the radiation hazard such very large SEP events would pose in the anticipated 52 degrees inclination space station orbit.

  12. Airport geomagnetic surveys in the United States

    Science.gov (United States)

    Berarducci, A.

    2006-01-01

    The Federal Aviation Administration (FAA) and the United States military have requirements for design, location, and construction of compass calibration pads (compass roses), these having been developed through collaboration with US Geological Survey (USGS) personnel. These requirements are detailed in the FAA Advisory Circular AC 150/5300-13, Appendix 4, and in various military documents, such as Handbook 1021/1, but the major requirement is that the range of declination measured within 75 meters of the center of a compass rose be less than or equal to 30 minutes of arc. The USGS Geomagnetism Group has developed specific methods for conducting a magnetic survey so that existing compass roses can be judged in terms of the needed standards and also that new sites can be evaluated for their suitability as potentially new compass roses. First, a preliminary survey is performed with a total-field magnetometer, with differences over the site area of less than 75nT being sufficient to warrant additional, more detailed surveying. Next, a number of survey points are established over the compass rose area and nearby, where declination is to be measured with an instrument capable of measuring declination to within 1 minute of arc, such as a Gurley transit magnetometer, DI Flux theodolite magnetometer, or Wild T-0. The data are corrected for diurnal and irregular effects of the magnetic field and declination is determined for each survey point, as well as declination range and average of the entire compass rose site. Altogether, a typical survey takes about four days to complete. ?? 2006 Springer.

  13. A case for variational geomagnetic data assimilation: insights from a one-dimensional, nonlinear, and sparsely observed MHD system

    CERN Document Server

    Fournier, Alexandre; Alboussière, Thierry

    2007-01-01

    Secular variations of the geomagnetic field have been measured with a continuously improving accuracy during the last few hundred years, culminating nowadays with satellite data. It is however well known that the dynamics of the magnetic field is linked to that of the velocity field in the core and any attempt to model secular variations will involve a coupled dynamical system for magnetic field and core velocity. Unfortunately, there is no direct observation of the velocity. Independently of the exact nature of the above-mentioned coupled system -- some version being currently under construction -- the question is debated in this paper whether good knowledge of the magnetic field can be translated into good knowledge of core dynamics. Furthermore, what will be the impact of the most recent and precise geomagnetic data on our knowledge of the geomagnetic field of the past and future? These questions are cast into the language of variational data assimilation, while the dynamical system considered in this pape...

  14. Principles of major geomagnetic storms forecasting

    Science.gov (United States)

    Zagnetko, Alexander; Applbaum, David; Dorman, Lev; Pustil'Nik, Lev; Sternlieb, Abraham; Zukerman, Igor

    According to NOAA Space Weather Scales, geomagnetic storms of scales G5 (3-hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) are dangerous for people technology and health (influence on power systems, on spacecraft operations, on HF radio-communications and others). To prevent these serious damages will be very important to forecast dangerous geomagnetic storms. In many papers it was shown that in principle for this forecasting can be used data on CR intensity and CR anisotropy changing before SC of major geomagnetic storms accompanied by sufficient Forbush-decreases (e.g., Dorman et al., 1995, 1999). In this paper we consider all types of observed precursor effects in CR what can be used for forecasting of great geomagnetic storms and possible mechanisms of these precursor effects origin. REFERENCES: Dorman L.I., et al. "Cosmic-ray forecasting features for big Forbush-decreases". Nuclear Physics B, 49A, 136-144 (1995). L.I.Dorman, et al, "Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their pre-diction", Proc. of 26-th Intern. Cosmic Ray Conference, Salt Lake City, 6, 476-479 (1999).

  15. Positive and negative ionospheric responses to the March 2015 geomagnetic storm from BDS observations

    Science.gov (United States)

    Jin, Shuanggen; Jin, Rui; Kutoglu, H.

    2017-06-01

    The most intense geomagnetic storm in solar cycle 24 occurred on March 17, 2015, and the detailed ionospheric storm morphologies are difficultly obtained from traditional observations. In this paper, the Geostationary Earth Orbit (GEO) observations of BeiDou Navigation Satellite System (BDS) are for the first time used to investigate the ionospheric responses to the geomagnetic storm. Using BDS GEO and GIMs TEC series, negative and positive responses to the March 2015 storm are found at local and global scales. During the main phase, positive ionospheric storm is the main response to the geomagnetic storm, while in the recovery phase, negative phases are pronounced at all latitudes. Maximum amplitudes of negative and positive phases appear in the afternoon and post-dusk sectors during both main and recovery phases. Furthermore, dual-peak positive phases in main phase and repeated negative phase during the recovery are found from BDS GEO observations. The geomagnetic latitudes corresponding to the maximum disturbances during the main and recovery phases show large differences, but they are quasi-symmetrical between southern and northern hemispheres. No clear zonal propagation of traveling ionospheric disturbances is detected in the GNSS TEC disturbances at high and low latitudes. The thermospheric composition variations could be the dominant source of the observed ionospheric storm effect from GUVI [O]/[N2] ratio data as well as storm-time electric fields. Our study demonstrates that the BDS (especially the GEO) observations are an important data source to observe ionospheric responses to the geomagnetic storm.

  16. Nonlinear Dynamic Study on Geomagnetic Polarity Reversal and Cretaceous Normal Superchron

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    It is generally acknowledged that geomagnetic polarity has reversed many times in geological history and an abnormal geologic phenomenon is the Cretaceous normal superchron. However, the causes have been unknown up to now. The nonlinear theory has been applied to analyze the phenomenon in geomagnetic polarity reversal and the Cretaceous normal superchron. The Cretaceous normal superchron implies that interaction of the Earth's core-mantle and liquid movement in the outer core may be the lowest energy state and the system of Earth magnetic field maintains a sort of temporal or spatial order structure by exchanging substance and energy in the outside continuously.During 121-83 Ma, there was no impact of a celestial body that would result in a geomagnetic polarity reversal, which may be a cause for occurrence of the Cretaceous normal superchron. The randomness of geomagnetic polarity reversal has the self-reversion characteristic of chaos and the chaos theory gives a simple and clear explanation for the dynamic cause of the geomagnetic polarity reversal.

  17. Positive and negative ionospheric responses to the March 2015 geomagnetic storm from BDS observations

    Science.gov (United States)

    Jin, Shuanggen; Jin, Rui; Kutoglu, H.

    2017-01-01

    The most intense geomagnetic storm in solar cycle 24 occurred on March 17, 2015, and the detailed ionospheric storm morphologies are difficultly obtained from traditional observations. In this paper, the Geostationary Earth Orbit (GEO) observations of BeiDou Navigation Satellite System (BDS) are for the first time used to investigate the ionospheric responses to the geomagnetic storm. Using BDS GEO and GIMs TEC series, negative and positive responses to the March 2015 storm are found at local and global scales. During the main phase, positive ionospheric storm is the main response to the geomagnetic storm, while in the recovery phase, negative phases are pronounced at all latitudes. Maximum amplitudes of negative and positive phases appear in the afternoon and post-dusk sectors during both main and recovery phases. Furthermore, dual-peak positive phases in main phase and repeated negative phase during the recovery are found from BDS GEO observations. The geomagnetic latitudes corresponding to the maximum disturbances during the main and recovery phases show large differences, but they are quasi-symmetrical between southern and northern hemispheres. No clear zonal propagation of traveling ionospheric disturbances is detected in the GNSS TEC disturbances at high and low latitudes. The thermospheric composition variations could be the dominant source of the observed ionospheric storm effect from GUVI [O]/[N2] ratio data as well as storm-time electric fields. Our study demonstrates that the BDS (especially the GEO) observations are an important data source to observe ionospheric responses to the geomagnetic storm.

  18. Phase fluctuations of GPS signals and irregularities in the high latitude ionosphere during geomagnetic storm

    Science.gov (United States)

    Shagimuratov, I.; Chernouss, S.; Cherniak, Iu.; Efishov, I.; Filatov, M.; Tepenitsyna, N.

    2016-05-01

    In this report we analysed latitudinal occurrence of TEC fluctuations over Europe during October 2, 2013 geomagnetic storm. The data of GPS stations spaced in latitudinal range 68°-54° N over longitude of 20°E were involved in this investigation. The magnetograms of the IMAGE network and geomagnetic pulsations at Lovozero (68°02'N 35°00'W) and Sodankyla (67°22'N 26°38'W) observatories were used as indicator of auroral activity. During October 2, 2013 the strong geomagnetic field variations took place near 05 UT at auroral IMAGE network. We found good similarities between time development of substorm and fluctuations of GPS signals. The bay-like geomagnetic variations were followed by intensive phase fluctuations at auroral and subauroral stations. The strong short-term phase fluctuations were also found at mid-latitude Kaliningrad station near 05 UT that correspond to the maximal intense geomagnetic bay variations. This date confirms the equatorward expansion of the auroral oval. It brings in evidence also the storm time behavior of the irregularities oval obtained from multi-site GPS observations.

  19. Attitude dynamics and control of spacecraft using geomagnetic Lorentz force

    CERN Document Server

    Abdel-Aziz, Yehia A

    2014-01-01

    The attitude stabilization of a charged rigid spacecraft in Low Earth Orbit (LEO) using torques due to Lorentz force in pitch and roll directions is considered. A spacecraft that generates an electrostatic charge on its surface in the Earth magnetic field will be subject to perturbations from Lorentz force. The Lorentz force acting on an electrostatically charged spacecraft may provide a useful thrust for controlling a spacecraft's orientation. We assume that the spacecraft is moving in the Earth's magnetic field in an elliptical orbit under the effects of the gravitational, geomagnetic and Lorentz torques. The magnetic field of the Earth is modeled as a non-tilted dipole. A model incorporating all Lorentz torques as a function of orbital elements has been developed on the basis of electric and magnetic fields. The stability of the spacecraft orientation is investigated both analytically and numerically. The existence and stability of equilibrium positions is investigated for different values of the charge to...

  20. Ground based observations of Pc3-Pc5 geomagnetic pulsation power at Antarctic McMurdo station

    Directory of Open Access Journals (Sweden)

    C. G. Maclennan

    1998-06-01

    Full Text Available The two horizontal geomagnetic components and, measured by a fluxgate magnetometer at Antarctic McMurdo station (corrected geomagnetic coordinates 80.0° S, 327.5° E, are analyzed for the period May-June 1994; the spectral powers are calculated and integrated over three frequency intervals corresponding to the nominal ranges. The time dependence of those integrated powers and their correlations with northern auroral indices and solar wind speed are considered. The observations are compared with previous results reported from Terra Nova Bay station (located near McMurdo at the same corrected geomagnetic latitude during Antarctic summer intervals. The differences found between the two stations are discussed in terms of the seasonal dependence of geomagnetic field line configurations in the near cusp region.

  1. A time-compressed simulated geomagnetic storm influences the nest-exiting flight angles of the stingless bee Tetragonisca angustula.

    Science.gov (United States)

    Esquivel, D M S; Corrêa, A A C; Vaillant, O S; de Melo, V Bandeira; Gouvêa, G S; Ferreira, C G; Ferreira, T A; Wajnberg, E

    2014-03-01

    Insects have been used as models for understanding animal orientation. It is well accepted that social insects such as honeybees and ants use different natural cues in their orientation mechanism. A magnetic sensitivity was suggested for the stingless bee Schwarziana quadripunctata, based on the observation of a surprising effect of a geomagnetic storm on the nest-exiting flight angles. Stimulated by this result, in this paper, the effects of a time-compressed simulated geomagnetic storm (TC-SGS) on the nest-exiting flight angles of another stingless bee, Tetragonisca angustula, are presented. Under an applied SGS, either on the horizontal or vertical component of the geomagnetic field, both nest-exiting flight angles, dip and azimuth, are statistically different from those under geomagnetic conditions. The angular dependence of ferromagnetic resonance (FMR) spectra of whole stingless bees shows the presence of organized magnetic nanoparticles in their bodies, which indicates this material as a possible magnetic detector.

  2. Time-causal decomposition of geomagnetic time series into secular variation, solar quiet, and disturbance signals

    Science.gov (United States)

    Rigler, E. Joshua

    2017-04-26

    A theoretical basis and prototype numerical algorithm are provided that decompose regular time series of geomagnetic observations into three components: secular variation; solar quiet, and disturbance. Respectively, these three components correspond roughly to slow changes in the Earth’s internal magnetic field, periodic daily variations caused by quasi-stationary (with respect to the sun) electrical current systems in the Earth’s magnetosphere, and episodic perturbations to the geomagnetic baseline that are typically driven by fluctuations in a solar wind that interacts electromagnetically with the Earth’s magnetosphere. In contrast to similar algorithms applied to geomagnetic data in the past, this one addresses the issue of real time data acquisition directly by applying a time-causal, exponential smoother with “seasonal corrections” to the data as soon as they become available.

  3. Geomagnetically trapped, albedo and solar energetic particles: trajectory analysis and flux reconstruction with PAMELA

    CERN Document Server

    Bruno, A; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; Christian, E C; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Ryan, J M; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N

    2016-01-01

    The PAMELA satellite experiment is providing comprehensive observations of the interplanetary and magnetospheric radiation in the near-Earth environment. Thanks to its identification capabilities and the semi-polar orbit, PAMELA is able to precisely measure the energetic spectra and the angular distributions of the different cosmic-ray populations over a wide latitude region, including geomagnetically trapped and albedo particles. Its observations comprise the solar energetic particle events between solar cycles 23 and 24, and the geomagnetic cutoff variations during magnetospheric storms. PAMELA's measurements are supported by an accurate analysis of particle trajectories in the Earth's magnetosphere based on a realistic geomagnetic field modeling, which allows the classification of particle populations of different origin and the investigation of the asymptotic directions of arrival.

  4. Geomagnetic effects on cosmic ray propagation under different conditions for Buenos Aires and Marambio, Argentina

    CERN Document Server

    Masías-Meza, Jimmy J

    2014-01-01

    The geomagnetic field (Bgeo) sets a lower cutoff rigidity (Rc) to the entry of cosmic particles to Earth which depends on the geomagnetic activity. From numerical simulations of the trajectory of a proton using different models for Bgeo (performed with the MAGCOS code), we use backtracking to analyze particles arriving at the location of two nodes of the net LAGO (Large Aperture Gamma ray burst Observatory) that will be built in the near future: Buenos Aires and Marambio (Antarctica), Argentina. We determine the asymptotic trajectories and the values of Rc for different incidence directions, for each node. Simulations were done using several models for Bgeo that emulate different geomagnetic conditions. The presented results will help to make analysis of future observations of the flux of cosmic rays done at these two LAGO nodes.

  5. The responses of the thermosphere due to a geomagnetic storm: A MHD model

    Science.gov (United States)

    Wu, S. T.; Chang, S.

    1972-01-01

    A magnetohydrodynamics theory was used to study the dynamic response of the neutral atmosphere to a geomagnetic storm. A full set of magnetohydrodynamic equations appropriate for the present problem is derived and their various orders of approximation are discussed in some detail. In order to demonstrate the usefulness of this theoretical model, the May 1967 geomagnetic storm data were used in the resulting set of nonlinear, time dependent, partial differential magnetohydrodynamic equations to calculate variations of the thermosphere due to the storm. The numerical results are presented for wind speeds, electric field strength, and amount of joule heating at a constant altitude for the data recorded. Data show that the strongest thermospheric responses are at the polar region becoming weaker in the equatorial region. This may lead to the speculation that a thermospheric wave is generated in the polar region due to the geomagnetic storm which propagates towards the equator.

  6. Improvements in geomagnetic observatory data quality

    DEFF Research Database (Denmark)

    Reda, Jan; Fouassier, Danielle; Isac, Anca

    2011-01-01

    between observatories and the establishment of observatory networks has harmonized standards and practices across the world; improving the quality of the data product available to the user. Nonetheless, operating a highquality geomagnetic observatory is non-trivial. This article gives a record...... of the current state of observatory instrumentation and methods, citing some of the general problems in the complex operation of geomagnetic observatories. It further gives an overview of recent improvements of observatory data quality based on presentation during 11th IAGA Assembly at Sopron and INTERMAGNET......Geomagnetic observatory practice and instrumentation has evolved significantly over the past 150 years. Evolution continues to be driven by advances in technology and by the need of the data user community for higher-resolution, lower noise data in near-real time. Additionally, collaboration...

  7. A realistic treatment of geomagnetic Cherenkov radiation from cosmic ray air showers

    NARCIS (Netherlands)

    Werner, Klaus; de Vries, Krijn D.; Scholten, Olaf

    2012-01-01

    We present a macroscopic calculation of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays, based on currents obtained from three-dimensional Monte Carlo simulations of air showers in a realistic geo-magnetic field. We discuss the importance of a correct

  8. Cosmogenic isotopes and geomagnetic signals in a Mediterranean sea sediment at 35 000 y BP

    Energy Technology Data Exchange (ETDEWEB)

    Cini Castagnoli, G.; Bonino, G.; Taricco, C. [Turin Univ. (Italy). Dipt. di Fisica Generale]|[CNR, Turin (Italy). Ist. di Cosmogeofisica; Lehman, B. [Istituto Nazionale di Geofisica, Rome (Italy)

    1998-03-01

    In this paper the authors present the results on the relative changes of the geomagnetic field intensity measured in the Tyrrenian sea core CT85-5 between 23 and 51 ky BP in order to investigate the origin of the enhancement of the cosmogenic isotope {sup 10}Be concentration, recently reported in the same core at 35 ky BP.

  9. Geomagnetic excursi