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.

Geodynamo, Solar Wind, and Magnetopause 3.4 to 3.45 Billion Years Ago

Abstract: Stellar wind standoff by a planetary magnetic field prevents atmospheric erosion and water loss. Although the early Earth retained its water and atmosphere, and thus evolved as a habitable planet, little is known about Earth’s magnetic field strength during that time. We report paleointensity results from single silicate crystals bearing magnetic inclusions that record a geodynamo 3.4 to 3.45 billion years ago. The measured field strength is ~50 to 70% that of the present-day field. When combined with a greater Paleoarchean solar wind pressure, the paleofield strength data suggest steady-state magnetopause standoff distances of ≤5 Earth radii, similar to values observed during recent coronal mass ejection events. The data also suggest lower-latitude aurora and increases in polar cap area, as well as heating, expansion, and volatile loss from the exosphere that would have affected long-term atmospheric composition.

Shape of the geomagnetic field solar wind boundary

Abstract: The shape of the boundary of the geomagnetic field in a solar wind has been calculated by a self-consistent method in which, in first order, approximate magnetic fields are used to calculate a boundary surface. The electric currents in this boundary produce magnetic fields, which can be calculated once the first surface is known. These are added to the dipole field to give more accurate fields, which are then used to compute a new surface. This iterative procedure converges rapidly, and the final surface may be tested by finding how close the total fields outside the boundary are to the required value of zero. The result of this stringent test is that the magnetic fields in the plasma outside the fourth surface and within twice the distance to the boundary on the solar side are everywhere less than 1 per cent of the geomagnetic dipole field in the absence of a solar wind. This surface has been used to calculate the perturbation of the geomagnetic field by the solar wind; the results of these calculations, plus a number of applications, are given in an accompanying paper.

Interplanetary magnetic field control of high-latitude electric fields and currents determined from Greenland Magnetometer Data

Abstract: To determine the effects of the interplanetary magnetic field (IMF) on the electric potential as well as on ionospheric and field-aligned currents, a recently available numerical algorithm is applied to an empirical model of high-latitude magnetic perturbations, parameterized in terms of the By and Bz components of the IMF. The empirical model is derived from 20-min average magnetometer data observed during summer at the chain on the west coast of Greenland and the corresponding IMF information from the HEOS 2 satellite. The calculated results reproduce fairly well overall features of the influence of the IMF on high-latitude electric fields which have been reported on the basis of more direct measurements. This confirms the validity of the numerical method and the conductivity distribution models. In addition, our results indicate that the system of ionospheric and Birkeland currents near the polar cusp, which has been shown to depend strongly on By, exists independently of the system of region 1 and region 2 field-aligned currents, which, on the other hand, depends strongly on Bz. The direction of the field-aligned currents in the dayside polar cap is uniquely controlled by the sign of the By component of the IMF, namely upward currents for By > 0 in the northern polar cap and oppositely directed for By 0 and By small the ionospheric and field-aligned currents are localized near the dayside polar cusp, and the electric field has a dusk-dawn component in a narrow region near magnetic local noon in agreement with reported satellite measurements. The associated distribution of field-aligned currents consists of the region 1 current system and an additional pair of oppositely directed currents located poleward of the region 1 currents.