Can an isotropic plasma pressure distribution be in force balance with the T96 model field?

Sorin Zaharia, C. Z. Cheng

研究成果: Article

19 引文 斯高帕斯(Scopus)

摘要

In this paper we investigate how close the gradient force of an isotropic pressure distribution P can be in force balance with the magnetic (Lorentz) force in the T96 empirical model. The study leads to the conclusion that no isotropic pressure can be found in exact force balance with the magnetic field of the quiet time T96 model. The conclusion is derived from several analyses: (1) computing the loop integral of J × B from the model along a closed contour in the equatorial plane (the integral should vanish if J × B = ▼P); (2) obtaining one-dimensional profiles for P on the Sun-Earth axis by integrating ▼P = J × B and comparing them with observations; and (3) decomposing J × B into gradient-free and curl-free terms (the former term would be zero in an exact equilibrium) and subsequently computing the two terms by solving a Poisson-like equation with constraints. Possible physical reasons for our finding that no P exists such that J times B = ▼P include small mass flows as well as nonisotropic (and possibly even nongyrotropic) terms in the magnetospheric pressure tensor. While the lack of exact force balance with isotropic P will probably be not too serious for many situations, for some physical applications, such as the computation of Birkeland currents using the Vasyliunas relation, care must be exercised if one uses the model field in conjunction with isotropic pressure. Finally, we discuss possible ways of computing magnetospheric configurations in exact force balance with isotropic P by using empirical model fields as a starting point.

原文English
期刊Journal of Geophysical Research: Space Physics
108
發行號A11
DOIs
出版狀態Published - 2003 一月 1

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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