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.

Generation of Field Aligned Current During Substorm

Abstract: A mechanism for the generation of field aligned currents during magnetospheric substorms is presented. The energy which is injected to the geomagnetic tail is converted into plasma flow energy in solar and anti-solar directions. When the flow meets the inner magnetosphere, a viscous interaction occurs. This interaction creates time-increasing vorticities which produce field aligned currents upward in the pre-midnight sector and downward in the post-midnight sector.

Geodynamo Simulations—How Realistic Are They?

Abstract: ▪ Abstract The past seven years have seen significant advances in computational simulations of convection and magnetic field generation in the Earth's core. Although dynamically self-consistent models of the geodynamo have simulated magnetic fields that appear in some ways quite similar to the geomagnetic field, none are able to run in an Earth-like parameter regime because of the considerable spatial resolution that is required. Here we discuss some of the subtle compromises that have been made in current models and propose a grand challenge for the future, requiring significant improvements in numerical methods and spatial resolution.

Driven Alfven waves and electron acceleration: A FAST case study

Abstract: [1] Observations of electric and magnetic field oscillations and accelerated electron distributions within an inverted-V region suggest the propagation of an Alfven wave from the outer magnetosphere into the auroral acceleration region. This hypothesis is tested for a case study event by simulating the propagation of an Alfven wave driven by an oscillating potential in the outer magnetosphere. At the spacecraft altitude the waveform and the associated electron distributions and spectra formed due to acceleration in the Alfven wave field are similar to those observed. The results show that more than 50% of the downgoing wave Poynting flux is dissipated through electron acceleration parallel to the geomagnetic field.

Reduction to the pole as an inverse problem and its application to low-latitude anomalies

Abstract: Traditionally, reduction to the pole has been accomplished either by space- or wavenumber-domain filtering. In the two-dimensional case, this procedure is stable regardless of the latitude, as long as the source strike is not parallel to the horizontal projection of the geomagnetic field. In the three-dimensional case, however, reduction-to-the-pole filtering is stable only at high magnetic latitudes. At latitudes lower than 15 degrees, it is of no practical use due to a sharply increasing instability toward the magnetic equator.The three-dimensional instability of this filtering technique is demonstrated, and the reduction-to-the-pole problem is formulated in the context of a general linear inverse problem. As a result, stable solutions are found by using well-known stabilizing procedures developed for the inverse linear problem. The distribution of magnetization of an equivalent layer of doublets that reproduces the observed data is computed. The magnetic doublets are parallel to the magnetization direction which is assumed constant throughout the sources. The magnetic field reduced to the pole is then obtained by changing the inclinations of the geomagnetic field and the doublets to 90 degrees and recalculating the total field.The usefulness and limitations of the method at low magnetic latitudes are assessed using theoretical data. The effects of noise and anomaly truncation are also investigated for both high and low latitudes. In all cases, application of the proposed method produced meaningful results regardless of the latitude. The method is applied to field data from two different low-latitude anomalies. The first anomaly is due to a seamount in the Gulf of Guinea with reversed magnetization. The geomagnetic field at this location is about -23 degrees. The second anomaly is an intrabasement anomaly from Parnaiba Basin, Brazil, where the magnetization is assumed to be induced by a geomagnetic field with -1.4 degree inclination. The results obtained confirm that the proposed method produces stable, meaningful, reduced-to-the-pole maps.

Measurements of ground-level muons at two geomagnetic locations

Abstract: We report new measurements of the muon spectra and the muon charge ratio at ground level in the momentum range from 200 MeVc to 120 GeVc for two different geomagnetic locations. Above 0.9 GeVc the absolute spectra measured in the two locations are in good agreement and are about 10% to 15% lower than previous experimental results. At lower momenta the data show latitude dependent geomagnetic effects. These observations are important for the understanding of the observed neutrino anomaly.