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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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Journal ArticleDOI
TL;DR: In this paper, the instantaneous free magnetic energy and relative magnetic helicity of an unknown three-dimensional nonlinear force-free (NLFF) magnetic structure extending above a single known lower-boundary magnetic field vector are derived.
Abstract: Expanding on an earlier work that relied on linear force-free (LFF) magnetic fields, we self-consistently derive the instantaneous free magnetic energy and relative magnetic helicity budgets of an unknown three-dimensional nonlinear force-free (NLFF) magnetic structure extending above a single known lower-boundary magnetic field vector. The proposed method does not rely on the detailed knowledge of the three-dimensional field configuration but is general enough to employ only a magnetic connectivity matrix on the lower boundary. The calculation yields a minimum free magnetic energy and a relative magnetic helicity consistent with this free magnetic energy. The method is directly applicable to photospheric or chromospheric vector magnetograms of solar active regions. Upon validation, it basically reproduces magnetic energies and helicities obtained by well known, but computationally more intensive and non-unique, methods relying on the extrapolated three-dimensional magnetic field vector. We apply the method to three active regions, calculating the photospheric connectivity matrices by means of simulated annealing, rather than a model-dependent NLFF extrapolation. For two of these regions we correct for the inherent LFF overestimation in free energy and relative helicity that is larger for larger, more eruptive, active regions. In the third region studied, our calculation can lead to a physical interpretation of observed eruptive manifestations. We conclude that the proposed method, including the proposed inference of the magnetic connectivity matrix, is practical enough to contribute to a physical interpretation of the dynamical evolution of solar active regions.

72 citations

Journal Article
TL;DR: In this paper, a simple analytic model for the magnetic field in the solar corona and interplanetary space was proposed, which is appropriate to solar minimum conditions. But the model is not suitable for the case of solar minimum.
Abstract: We describe a simple analytic model for the mag- netic field in the solar corona and interplanetary space which is appropriate to solar minimum conditions. The model com- bines an azimuthal current sheet in the equatorial plane with an axisymmetric multipole field representing the internal mag- netic field of the Sun. The radial component of the field filling interplanetary space is approximately monopolar at large helio- centric distances as observed. These open field lines connect to the polar regions of the Sun and define the polar coronal holes which are prevalent at solar minimum and which are the source of the fast solar wind. By including both dipole and a quadrupole terms at the origin it is possible to construct a good representa- tion of the coronal magnetic field in such conditions. We also note that the Parker spiral will be underwound relative to the case of the monopole because the open field lines emanate from solar latitudes in excess of 60.

72 citations

Journal ArticleDOI
TL;DR: In this paper, the magnetic field within the magnetosphere has been obtained as a solution of the magnetostatics problem, summarised with the field of magnetopause currents induced by the internal sources.

71 citations

Journal ArticleDOI
TL;DR: McPhase as discussed by the authors is a program package developed to calculate static and dynamic magnetic properties of rare earth compounds, where the two ion interaction may be chosen anisotropic and also terms of higher order (e.g. quadrupolar interactions) can be taken into account.

71 citations

Journal ArticleDOI
TL;DR: In this article, the Tsyganenko 89 magnetic field model for the night, dawn, prenoon, and postnoon magnetic local time (MLT) sectors for different levels of geomagnetic activity and distances is presented.
Abstract: The outer radiation belt electrons in the inner magnetosphere show high variability during the geomagnetically disturbed conditions. Quasi-linear diffusion theory provides both a framework for global prediction of particle loss at different energies and an understanding of the dynamics of different particle populations. It has been recently shown that the pitch angle scattering of electrons due to wave-particle interaction with chorus waves modeled in a realistic magnetic field may be significantly different from those estimated in a dipole model. In this work, we present the lifetimes of 1 keV–2 MeV electrons computed in the Tsyganenko 89 magnetic field model for the night, dawn, prenoon, and postnoon magnetic local time (MLT) sectors for different levels of geomagnetic activity and distances. The lifetimes in the realistic field are also compared to those computed in the dipole model. We develop a realistic chorus lower band and upper band wave models for each MLT sector using the recent statistical studies of wave amplitude, wave normal angle, and wave spectral density distributions as functions of magnetic latitude, distance, and Kp index. The increase of plasma trough density with increasing latitude is also included. The obtained in the Tsyganenko 89 field electron lifetimes are parameterized and can be used in 2-D/3-D/4-D convection and particle tracing codes.

71 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202312
202220
20181
201751
201656
201546