Topic
Dipole model of the Earth's magnetic field
About: Dipole model of the Earth's magnetic field is a research topic. Over the lifetime, 2756 publications have been published within this topic receiving 83021 citations.
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115 citations
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TL;DR: In this paper, it was shown that if a spherical shell is magnetized in the direction of and proportional to a magnetic field of origin internal to the shell and the magnetizing field later disappears, no magnetic field exists external to a shell.
115 citations
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TL;DR: In this article, a self-consistent equilibria of a collisionless relativistic electron-positron gas in the vicinity of a magnetic X-point was derived.
Abstract: We have calculated self-consistent equilibria of a collisionless relativistic electron-positron gas in the vicinity of a magnetic X-point. For the considered conditions, pertinent to extragalactic jets, we find that leptons are accelerated up to Lorentz factors Γ0 = κeB0L2/mc2 1, where B0 is the typical magnetic field strength, ≡ E0/B0, with E0 the reconnection electric field, L is the length scale of the magnetic field, and κ ≈ 12. The acceleration is due to the dominance of the electric field over the magnetic field in a region around the X-point. The distribution function of the accelerated leptons is found to be approximately dn/dγ ∝ γ-1 for γ Γ0. The apparent distribution function may be steeper than γ-1 due to the distribution of Γ0 values and/or the radiative losses. Self-consistent equilibria are found only for plasma inflow rates to the X-point less than a critical value.
115 citations
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TL;DR: A review of the most common magnetic coordinate systems and how they are defined, where they are used, and how to convert between them can be found in this paper, where the definitions are presented based on the spherical harmonic expansion coefficients of the International Geomagnetic Reference Field (IGRF) and, in some of the coordinate systems, the position of the Sun which we show how to calculate from the time and date.
Abstract: Geospace phenomena such as the aurora, plasma motion, ionospheric currents and associated magnetic field disturbances are highly organized by Earth’s main magnetic field. This is due to the fact that the charged particles that comprise space plasma can move almost freely along magnetic field lines, but not across them. For this reason it is sensible to present such phenomena relative to Earth’s magnetic field. A large variety of magnetic coordinate systems exist, designed for different purposes and regions, ranging from the magnetopause to the ionosphere. In this paper we review the most common magnetic coordinate systems and describe how they are defined, where they are used, and how to convert between them. The definitions are presented based on the spherical harmonic expansion coefficients of the International Geomagnetic Reference Field (IGRF) and, in some of the coordinate systems, the position of the Sun which we show how to calculate from the time and date. The most detailed coordinate systems take the full IGRF into account and define magnetic latitude and longitude such that they are constant along field lines. These coordinate systems, which are useful at ionospheric altitudes, are non-orthogonal. We show how to handle vectors and vector calculus in such coordinates, and discuss how systematic errors may appear if this is not done correctly.
115 citations
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01 Mar 1954TL;DR: In this paper, a class of known electrostatic solutions of the field equations to be adapted to the magnetostatic case was proved, and exact solutions referring to a uniform magnetic field and to a magnetic dipole were given.
Abstract: A theorem is proved which enables a class of known electrostatic solutions of the field equations to be adapted to the magnetostatic case. Exact solutions referring to a uniform magnetic field and to a magnetic dipole are given. The solution for a circular loop of wire carrying a steady current is considered, and it is shown that if the mass of the wire be neglected, both the magnetic and gravitational fields at great distances are equivalent to those of a magnetic dipole. The paper concludes with a short discussion of the significance of the solutions presented here, and in an earlier paper, for relativistic electromagnetic theory.
114 citations