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Earth's magnetic field

About: Earth's magnetic field is a research topic. Over the lifetime, 20360 publications have been published within this topic receiving 446747 citations. The topic is also known as: magnetic field of Earth & geomagnetic field.


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TL;DR: In this paper, the authors present a synthesis of 0-5 Ma paleomagnetic directional data collected from 17 different locations under the collaborative Time Averaged geomagnetic Field Initiative (TAFI) when combined with regional compilations from the northwest United States, the southwest United States and Japan, New Zealand, Hawaii, Mexico, South Pacific, and the Indian Ocean, a data set of over 2000 sites with high quality, stable polarity, and declination and inclination measurements.
Abstract: We present a synthesis of 0–5 Ma paleomagnetic directional data collected from 17 different locations under the collaborative Time Averaged geomagnetic Field Initiative (TAFI) When combined with regional compilations from the northwest United States, the southwest United States, Japan, New Zealand, Hawaii, Mexico, South Pacific, and the Indian Ocean, a data set of over 2000 sites with high quality, stable polarity, and declination and inclination measurements is obtained This is a more than sevenfold increase over similar quality data in the existing Paleosecular Variation of Recent Lavas (PSVRL) data set, and has greatly improved spatial sampling The new data set spans 78°S to 53°N, and has sufficient temporal and spatial sampling to allow characterization of latitudinal variations in the time-averaged field (TAF) and paleosecular variation (PSV) for the Brunhes and Matuyama chrons, and for the 0–5 Ma interval combined The Brunhes and Matuyama chrons exhibit different TAF geometries, notably smaller departures from a geocentric axial dipole field during the Brunhes, consistent with higher dipole strength observed from paleointensity data Geographical variations in PSV are also different for the Brunhes and Matuyama Given the high quality of our data set, polarity asymmetries in PSV and the TAF cannot be attributed to viscous overprints, but suggest different underlying field behavior, perhaps related to the influence of long-lived core-mantle boundary conditions on core flow PSV, as measured by dispersion of virtual geomagnetic poles, shows less latitudinal variation than predicted by current statistical PSV models, or by previous data sets In particular, the Brunhes data reported here are compatible with a wide range of models, from those that predict constant dispersion as a function of latitude to those that predict an increase in dispersion with latitude Discriminating among such models could be helped by increased numbers of low-latitude data and new high northern latitude sites Tests with other data sets, and with simulations, indicate that some of the latitudinal signature previously observed in VGP dispersion can be attributed to the inclusion of low-quality, insufficiently cleaned data with too few samples per site Our Matuyama data show a stronger dependence of dispersion on latitude than the Brunhes data The TAF is examined using the variation of inclination anomaly with latitude Best fit two-parameter models have axial quadrupole contributions of 2–4% of the axial dipole term, and axial octupole contributions of 1–5% Approximately 2% of the octupole signature is likely the result of bias incurred by averaging unit vectors

222 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss the properties of the plasmoid in the computer simulations, in particular its topology, spatial extent and speed, the current system associated with it and its local appearance at a fixed location in space.
Abstract: Two- and three-dimensional computer models of the dynamics of the magnetosphere and in particular the magnetotail have shown, that the basic features of the idealized linear or steady state reconnection theory are still found in time dependent and spatially more complicated configurations such as the magnetotail, which basically resembles a plane sheet pinch but in addition has small magnetic field components perpendicular to the sheet, field line flaring and variations along both directions parallel to the current sheet. These basic features are the formation of a magnetic neutral x-line or separator, where two surfaces separating magnetic fluxes of different topology intersect, with the generation of an electric field along the separator and the production of strong plasma flows parallel to the current sheet away from the separator in opposite directions. In addition, the computer models of magnetotail dynamics have produced many large scale features that are directly observed or deduced from observation in relation with magnetospheric substorms. Among those features are: the thinning of the plasma sheet, the formation of a plasmoid, a region of closed magnetic loops detached from Earth, which moves tailward at a speed of several hundreds of km/sec, and the generation of field-aligned currents. In viewmore » of the recent discovery of plasmoid signatures in the distant magnetotail at about 200 R/sub E/ from ISEE-3 satellite measurements, we discuss the properties of the plasmoid in the computer simulations, in particular its topology, spatial extent and speed, the current system associated with it and its local appearance at a fixed location in space. Furthermore, we discuss the conversion of the energy flux around the separator, current deviations and the occurrence of field-aligned currents and their generation by shear flows. 10 references, 21 figures, 2 tables.« less

221 citations

Journal ArticleDOI
TL;DR: In this paper, the authors considered three possible sources of energy: radioactive heating in the core itself, loss of internal energy due to cooling and freezing of the outer core, and cooling of the whole core with consequent differentiation to form the inner core with release of gravitational energy.
Abstract: Summary. The persistence of the magnetic field of the Earth demands a constant energy source for the last three thousand million years, and this provides a constraint on the thermal evolution of the core. The equations of global energy and entropy balance are used to estimate the power source required for a specific magnetic field. The amount of power required depends on the exact nature of the source. Three possibilities are considered here: radioactive heating in the core itself, loss of internal energy due to cooling and freezing of the outer core to form the inner core, and cooling of the whole core with consequent differentiation to form the inner core with release of gravitational energy. The last of these includes all the sources except for radioactive heating, but the introduction of some radioactivity into this calculation would be a simple matter. For radioactive heating alone, 1013W is required for the dynamo. This is just within the limits set by the observed surface heat flux (4 x lOI3 W) and what some geochemists believe to be the heating due to K40. Cooling itself cannot release enough heat to power the dynamo because the required cooling rate is so high that the inner core would be a very recent feature of the Earth. The release of gravitational energy can produce a magnetic field of 100-200 gauss, with the inner core growing slowly to its present size over 4Ga, and a heat release of 2.5 x lO'*W. A lower heat flux is required because of the greater efficiency of conversion of gravitational energy into magnetic fields than heat. When pursuing the calculations backwards in time, the rate of energy release is found to be proportional to the mass of the inner core. A surprising feature of this model, which assumes a constant rate of cooling at the top of the core, is that the useful power available for the dynamo increases with time, so that the field should be stronger now than it was in the past, although only by about 30 per cent.

220 citations

Journal ArticleDOI
TL;DR: This paper presented a global stacked record of (230Thex-normalized)10Be deposition in marine sediments representing relative variations in 10Be production rate which are translated into field intensity variations.

220 citations

Journal ArticleDOI
TL;DR: Magnetosphere mathematical model with electric field representing plasma flow superimposed on geomagnetic field is presented in this article, where the electric field represents plasma flow and the magnetic field represents electric field.
Abstract: Magnetosphere mathematical model with electric field representing plasma flow superimposed on geomagnetic field

220 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023657
20221,202
2021477
2020553
2019604
2018581