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Static magnetic field models consistent with nearly isotropic plasma pressure
Author(s) -
Spence Harlan E.,
Kivelson Margaret G.,
Walker Raymond J.
Publication year - 1987
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl014i008p00872
Subject(s) - physics , magnetosphere , earth's magnetic field , magnetic field , isotropy , l shell , dipole model of the earth's magnetic field , plasma , magnetic pressure , flux tube , magnetohydrodynamics , geophysics , computational physics , pressure gradient , magnetic flux , mechanics , solar wind , interplanetary magnetic field , optics , magnetization , quantum mechanics
Using the empirical magnetospheric magnetic field models of Tsyganenko and Usmanov (TU), we have determined the self‐consistent plasma pressure gradients and anisotropies along the midnight meridian in the near‐Earth magnetosphere. By “inverting” the magnetic field, we determine what distributions of an anisotropic plasma, confined within the specified magnetic field configuration, are consistent with the magnetohydrostatic equilibrium condition, J × B = ∇ · P . The TU model, parameterized for different levels of geomagnetic activity by the K p index, provided the magnetic field values from which J × B was numerically evaluated. A best fit solution was found that minimized the average difference between J × B and ∇ · P along an entire flux tube. Unlike previous semi‐empirical models, the TU models contain magnetic stresses that can be balanced by a nearly isotropic plasma pressure with a reasonable radial gradient at the equator.