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1.
D. M. Pechersky A. A. Lyubushin Z. V. Sharonova 《Izvestiya Physics of the Solid Earth》2012,48(1):42-60
The data on geomagnetic reversals, organic changes, and lower-mantle plume magmatism in the Phanerozoic are collected and
correlated. No direct relationship is revealed between the geomagnetic reversals, plumes, and biozones. However, the frequency
of geomagnetic reversals is found to correlate to the frequency of biozonal alterations. We relate this inconsistency to the
coupling of the two processes, which are mutually independent, with the long-term changes in the Earth’s rotation. The plumes
are formed at the core-mantle boundary and, thus, the reversals should have a different source. We hypothesize that the change
in the geomagnetic polarity is due to the nonuniform rotation of the inner core relative to the mantle in combination with
the changes in the axial tilt of the Earth’s rotation. 相似文献
2.
D. M. Pechersky 《Izvestiya Physics of the Solid Earth》2007,43(10):844-854
The data on the amplitude of variations in the direction and paleointensity of the geomagnetic field and the frequency of reversals throughout the last 50 Myr near the Paleozoic/Mesozoic and Mesozoic/Cenozoic boundaries, characterized by peaks of magmatic activity of Siberian and Deccan traps, and data on the amplitude of variations in the geomagnetic field direction relative to contemporary world magnetic anomalies are generalized. The boundaries of geological eras are not fixed in recorded paleointensity, polarity, reversal frequency, and variations in the geomagnetic field direction. Against the background of the “normal” field, nearly the same tendency of an increase in the amplitude of field direction variations is observed toward epicenters of contemporary lower mantle plumes; Greenland, Deccan, and Siberian superplumes; and world magnetic anomalies. This suggests a common origin of lower mantle plumes of various formation times, world magnetic anomalies, and the rise in the amplitude of geomagnetic field variations; i.e., all these phenomena are due to a local excitation in the upper part of the liquid core. Large plumes arise in intervals of the most significant changes in the paleointensity (drops or rises), while no correlation exists between the plume generation and the reversal frequency: times of plume formation correlate with the very diverse patterns of the frequency of reversals, from their total absence to maximum frequencies, implying that world magnetic anomalies, variations in the magnetic field direction and paleointensity, and plumes, on the one hand, and field reversals, on the other, have different sources. The time interval between magmatic activity of a plume at the Earth’s surface and its origination at the core-mantle boundary (the time of the plume rise toward the surface) amounts to 20–50 Myr in all cases considered. Different rise times are apparently associated with different paths of the plume rise, “delays” in the plume upward movement, and so on. The spread in “delay” times of each plume can be attributed to uncertainties in age determinations of paleomagnetic study objects and/or the natural remanent magnetization, but it is more probable that this is a result of the formation of a series of plumes (superplumes) in approximately the same region at the core-mantle boundary in the aforementioned time interval. Such an interpretation is supported by the existence of compact clusters of higher field direction amplitudes between 300 and 200 Ma that are possible regions of formation of world magnetic anomalies and plumes. 相似文献
3.
The specific features of the spatial structure and time dynamics of the main geomagnetic field during the 20th century, proceeding
from the present-day concepts of geomagnetic jerks have been studied. The variations, caused by global dissipation of the
geomagnetic field dipole part, have been separated from the regional variations, described by nondipole spatial harmonics
of the spherical harmonic expansion series. It has been indicated that the geomagnetic field westward drift manifests itself
in a limited region of the Earth’s surface, forming the known Brazil anomaly. However, the drift component in the variations
in the geomagnetic field morphological structures is globally found out during the considered almost 100-year period along
the narrow belt around the geomagnetic axis. However, this drift is northwestward in the Northern Hemisphere, and the structures
drift southeastward in the Southern Hemisphere. The detected variations of the drift nature are reflected in the variations
in the integral geomagnetic characteristic, when changes in the position of the Earth’s magnetic center are considered. The
direct correlation between the global geomagnetic variations of the drift nature and the trend variations in the orientation
of the vector of the Earth daily rotation velocity has been detected. 相似文献
4.
Based on the WIND and GOES satellite data on the solar wind and IMF parameters and the data on the surface magnetic field,
it has been indicated that the secondary MHD rarefaction wave can affect the geomagnetic field during a storm sudden commencement
(SSC) event. The secondary rarefaction wave originates in the magnetosheath when the shock wave interacts with the Earth’s
magnetosphere. 相似文献
5.
Based on the time series of observational variations of the length of day (LOD) and seismic data in the world, the relations
of the decadal fluctuation and seasonal variation in the Earth’s rotation with global seismic activity are studied in this
paper. The results suggest that there are overall correlations on temporal scale and regional discrepancy on spatial scale
between global seismic activity and the Earth’s variable rotation, especially the seismic activity in the Eurasian seismic
zone (not including southeast Asia) and the Lower California-Eastern Alaska seismic zone correlating well with the Earth’s
variable rotation. According to the relations mentioned above, the observational data of the Earth’s rotation might provide
a referential basis for monitoring global seismic activity.
This project is sponsored by the National Key Basic Research Project and the National Natural Science Foundation of China.
The English version is improved by Prof. Xin-Ling QIN, Institute of Geophysics, SSB, China. 相似文献
6.
O. V. Kozyreva I. N. Myagkova E. E. Antonova N. G. Kleimenova 《Geomagnetism and Aeronomy》2009,49(6):741-749
Precipitation of electrons with energies of 0.3–1.5 MeV has been analyzed based on the CORONAL-F satellite data at polar latitudes
of the Northern Hemisphere on December 13, 2003. The instants of electron precipitation have been compared with the ground-based
observations of geomagnetic disturbances and auroras near the satellite orbit projection. It has been indicated that precipitation
of energetic electrons in the high-latitude nightside sector is accompanied by the simultaneous development of bay-like magnetic
field disturbances on the Earth’s surface and the appearance of riometer absorption bursts and Pi3 geomagnetic pulsations,
and auroras. 相似文献
7.
N. G. Kleimenova O. V. Kozyreva M. Kubicki S. Michnowski 《Geomagnetism and Aeronomy》2010,50(1):48-57
The effects of morning magnetospheric substorms in the variations in near-Earth atmospheric electricity according to the observations
of the electric field vertical component (E
z
), at Hornsund polar observatory (Spitsbergen). The E
z, data, obtained under the conditions of fair weather (i.e., in the absence of a strong wind, precipitation, and fog), are
analyzed. An analysis of the observations indicated that the development of a magnetospheric substorm in the Earth’s morning
sector is as a rule accompanied by positive deviations in E
z, independently of the Hornsund location: in the polar cap or at its boundary. In all considered events, Hornsund was located
near the center of the morning convection vortex. In the evening sector, when Hornsund fell in the region of evening convection
vortex, the development of a geomagnetic substorm was accompanied by negative deviations in E
z., It has been concluded that the variations in the atmospheric electric field E
z), at polar latitudes, observed during the development of magnetospheric substorms, result from the penetration of electric
fields of polar ionospheric convection (which are intensified during a substorm) to the Earth’s surface. 相似文献
8.
Measurements of solar cosmic ray (SCR) protons in the magnetosphere can be used to verify models of the Earth’s magnetic field.
The latitudinal profiles of precipitating SCRs with energies of 1–90 MeV were measured on the CORONAS-F low-orbiting satellite
during a strong magnetic storm on October 29–30, 2003. A flux of precipitating protons can remain equal to the interplanetary
flux only due to a strong pitch angle diffusion that originates when the radius of the field line curvature is close to that
of the particle rotation Larmor radius. The observed boundaries of the strong diffusion region can be compared with the boundaries
anticipated according to the models of the magnetic field of the Earth’s magnetosphere. The adiabaticity parameter values,
calculated for several instants of the CORONAS-F satellite pass based on the TS05 and parabolic models, do not always correspond
to measurements. How possible changes in the model configurations of the magnetic field can allow us to eliminate discrepancies
with the experiment and to explain why solar protons with energies of several megaelectronvolts penetrate deep in the Earth’s
inner magnetosphere is considered here. 相似文献
9.
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 0.20–.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. 相似文献
10.
S. V. Starchenko 《Geomagnetism and Aeronomy》2011,51(3):409-414
The large-scale harmonic magnetic-convective sources of the main geomagnetic field in the Earth’s core have been determined
for the first time. The determination is based on a complete system of eigenfunctions of the magnetic diffusion equation in
a homogeneously conducting sphere, which is surrounded by an insulator. The sources of the main geomagnetic field observed,
which is responsible for the distribution of the electric currents generating this field in the core, are expressed in terms
of large-scale eigenfunctions. In this case, the dipole sources are directly related to the observed geomagnetic dipole, whereas
the quadrupole sources are related to the quadrupole, etc. The time variations in the obtained sources are responsible for
individual spatiotemporal features in the generation or suppression of each Gaussian component of the observed geomagnetic
field. When the commonly accepted observational international geomagnetic reference field (IGRF) models were used to partially
reveal these time variations, it became possible to specify the estimate of the Earth’s core conductivity and determine the
minimum period that can separate us from the commencement of further inversion or excursion. 相似文献
11.
K. Ramaswamy M. Dheenathayalu S. Bharathan 《Physics of the Earth and Planetary Interiors》1985,40(1):61-64
A detailed study of the ancient intensity of the Earth's magnetic field in Tamilnadu, India is presented using pottery, bricks, tiles etc., obtained from the excavations that have been carried out at some of the important places of historical and archaeological interest. An attempt is made to reconstruct the secular variation of the geomagnetic field intensity. The results reported here reveal considerable changes in the Earth's magnetic field in this region during the past 2400 y. It is observed that the intensity of the geomagnetic field has been previously 57% greater than at present. 相似文献
12.
The possibility that conditions on the Sun and in the Earth’s magnetosphere can affect human health at the Earth’s surface has been debated for many decades. This work reviews the research undertaken in the field of heliobiology, focusing on the effect of variations of geomagnetic activity on human cardiovascular health. Data from previous research are analysed for their statistical significance, resulting in support for some studies and the undermining of others. Three conclusions are that geomagnetic effects are more pronounced at higher magnetic latitudes, that extremely high as well as extremely low values of geomagnetic activity seem to have adverse health effects and that a subset of the population (10–15%) is predisposed to adverse health due to geomagnetic variations. The reported health effects of anthropogenic sources of electric and magnetic fields are also briefly discussed, as research performed in this area could help to explain the results from studies into natural electric and magnetic field interactions with the human body.Possible mechanisms by which variations in solar and geophysical parameters could affect human health are discussed and the most likely candidates investigated further. Direct effects of natural ELF electric and magnetic fields appear implausible; a mechanism involving some form of resonant absorption is more likely. The idea that the Schumann resonance signals could be the global environmental signal absorbed by the human body, thereby linking geomagnetic activity and human health is investigated. Suppression of melatonin secreted by the pineal gland, possibly via desynchronised biological rhythms, appears to be a promising contender linking geomagnetic activity and human health. There are indications that calcium ions in cells could play a role in one or more mechanisms. It is found to be unlikely that a single mechanism can explain all of the reported phenomena. 相似文献
13.
M. Yu. Reshetnyak 《Izvestiya Physics of the Solid Earth》2012,48(4):326-334
The eigenvalue problem for Parker’s dynamo model is considered. We study how the intensity of convection in the liquid core
of the Earth affects the generation of the geomagnetic field with different directions of latitudinal field propagation. The
scenarios of transition of the geomagnetic field from frequent to rare reversals are suggested. 相似文献
14.
V. V. Kopeikin 《Geomagnetism and Aeronomy》2011,51(5):676-680
It has been indicated that the electric field that exists above the Earth’s surface contains information about the structure
of underground inhomogeneities. Equations have been obtained and are used to illustrate the numerical calculations of the
electric field strength along the Earth’s surface and some types of underground objects. 相似文献
15.
A mathematical modeling method and the global numerical model of the Earth’s upper atmosphere were used to study nighttime enhanced electron density regions (EEDRs) in the ionospheric F2 layer and their possible manifestations at altitudes of the Earth’s plasmasphere. It has been established that EEDRs are formed owing to latitudinally nonuniform longitudinal (along the magnetic field) plasma flows from the plasmasphere into the nighttime ionosphere and the wind transport of ions along geomagnetic field lines. The specific features of the effect of ionospheric-plasmaspheric plasma transport processes, related to their three-dimensional character, on EEDRs have been revealed. 相似文献
16.
Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth’s mass thereby causing the Earth’s rotation and gravitational field to change. The size of this change depends upon the magnitude, focal mechanism, and location of the earthquake. The Sumatran earthquake of December 26, 2004 is the largest earthquake to have occurred since the 1960 Chilean earthquake. Using a spherical, layered Earth model, the coseismic effect of the Sumatran earthquake upon the Earth’s length-of-day, polar motion, and low-degree harmonic coefficients of the gravitational field are computed. Using a model of the earthquake source that is composed of five subevents having a total moment-magnitude M
w
of 9.3, it is found that this earthquake should have caused the length-of-day to decrease by 6.8 microseconds, the position of the Earth’s generalized figure axis to shift 2.32 milliarcseconds towards 127° E longitude, the Earth’s oblateness J
2 to decrease by 2.37 × 10−11 and the Earth’s pear-shapedness J
3 to decrease by 0.63 × 10−11. The predicted change in the length-of-day, position of the generalized figure axis, and J
3 are probably not detectable by current measurement systems. But the predicted change in oblateness is perhaps detectable if other effects, such as those of the atmosphere, oceans, and continental water storage, can be adequately removed from the observations. 相似文献
17.
The results of comparative analysis of the behavior of paleointensity and polarity (intervals between reversals) of the geomagnetic field for the last 167 Ma are presented. Similarities and differences in the behavior of these characteristics of the geomagnetic field are discussed. It is shown that bursts of paleointensity and long intervals between reversals occurred at high mean values of paleointensity in the Cretaceous and Paleogene. However, there are differences between the paleointensity behavior and the reversal regime: (1) the characteristic times of paleointensity variations are less than the characteristic times of the frequency of geomagnetic reversals, (2) the achievement of maximum values of paleointensity at the Cretaceous–Paleogene boundary and the termination of paleointensity bursts after the boundary of 45–40 Ma are not marked by explicit features in the geomagnetic polarity behavior. 相似文献
18.
N. A. Zolotukhina 《Geomagnetism and Aeronomy》2010,50(8):963-969
A comparative analysis of extremely low frequency waves registered by Cluster satellites after a sudden impulse (SI) and the
following substorm onset (SO) at distances L ∼ 4 from the Earth’s center was performed. It was shown that both phenomena in the equatorial morning magnetosphere activated
magnetic field oscillations of periods from 40 to 200 s. Oscillations accompanying SI and SO were found to be of similar spectral
composition but different polarizations. The differences in polarization became well-pronounced near the main spectral maximum
(100–130 s), where the transition from SI to SO was accompanied by reverse of rotation of the magnetic field disturbance vector
and by reorientation of the oscillation polarization ellipse. 相似文献
19.
V. A. Dergachev S. S. Vasiliev O. M. Raspopov H. Jungner 《Geomagnetism and Aeronomy》2012,52(8):959-976
Recent studies have shown that, in addition to the role of solar variability, past climate changes may have been connected with variations in the Earth??s magnetic field elements at various timescales. An analysis of variations in geomagnetic field elements, such as field intensity, reversals, and excursions, allowed us to establish a link between climate changes at various timescales over the last millennia. Of particular interest are sharp changes in the geomagnetic field intensity and short reversals of the magnetic poles (excursions). The beginning and termination of the examined geomagnetic excursions can be attributed to periods of climate change. In this study, we analyzed the possible link between short-term geomagnetic variability (jerks) and climate change, as well as the accelerated drift of the north magnetic pole and surface temperature variations. The results do not rule out the possibility that geomagnetic field variations which modulate the cosmic ray flux could have played a major role in climate change in addition to previously induced by solar radiation. 相似文献
20.
Disturbances in the magnetic field and magnetospheric and ionospheric plasma registered on December 14–16, 2006, during a
strong magnetic storm caused by a solar flare of 4B/X3.4 class are studied. It is shown that in the north of Yakutia, interactions between the Earth’s magnetosphere and the region
of high dynamic pressure of the solar wind led to the formation of sporadic layers in the ionospheric E and F regions, depletion of the critical frequency of the F2 layer, and total absorption. At the end of the magnetic storm’s main phase, anomalously high values of foF2 exceeding the quiet level by a factor of 1.5–1.7 were detected. It was found that the disturbances detected by ground-based
observatories had developed on the background of changes in the temperature, density, and the pitch-angle distribution of
particles at the geostationary orbit manifesting radial shifts of magnetospheric structures (magnetopause, cusp/cleft, and
plasma sheet) relative to the observation points. A conclusion is drawn that in this case, changes in the near-Earth plasma
and magnetic field manifest the dynamics of the physical conditions at the magnetospheric boundary and diurnal rotation of
the Earth. 相似文献