skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Limits on plasma anisotropy in a tail-like magnetic field

Abstract

Understanding the static balance of forces in a hypothetical stationary, steady-state magnetotail configuration is central to our understanding of planetary magnetotail dynamics, even though the actual planetary magnetotails may rarely if ever attain such a steady state. We are not likely to achieve an understanding of the observed departures from equilibrium if we do not first understand the nature of the equilibrium itself, albeit hypothetical. The condition of magnetohydrostatic equilibrium implies tight constraints on the degree of anisotropy that is supportable in a magnetotail field geometry. If the plasma pressure tensor is assumed to be gyrotropic at the tail midplane (z = 0), then equilibrium requires that it also be nearly isotropic there, with P[sub [perpendicular]0]/P[sub [parallel]0] in the range 1 [plus minus] [delta][sup 2], where [delta] [approximately] 0.1 is the ratio of the normal field component at the symmetry plane to the field strength in the tail lobe. The upper and lower limits are essentially equivalent, respectively, to the marginal mirror and firehose stability conditions evaluated at z = 0, which have been invoked previously to limit the degree of anisotropy in the plasma sheet. 21 refs., 1 fig.

Authors:
;  [1]
  1. Rice Univ., Houston, TX (United States)
Publication Date:
OSTI Identifier:
7061935
Resource Type:
Journal Article
Journal Name:
Geophysical Research Letters (American Geophysical Union); (United States)
Additional Journal Information:
Journal Volume: 19:24; Journal ID: ISSN 0094-8276
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; MAGNETOTAIL; EQUILIBRIUM; PLASMA; PLASMA PRESSURE; ANISOTROPY; CONSTRAINTS; GEOMETRY; HOSE INSTABILITY; MAGNETIC FIELDS; PLASMA INSTABILITY; PLASMA SHEET; SYMMETRY; EARTH ATMOSPHERE; EARTH MAGNETOSPHERE; INSTABILITY; MATHEMATICS; PLASMA MICROINSTABILITIES; 661320* - Auroral, Ionospheric, & Magnetospheric Phenomena- (1992-)

Citation Formats

Hill, T W, and Voigt, G H. Limits on plasma anisotropy in a tail-like magnetic field. United States: N. p., 1992. Web. doi:10.1029/92GL02497.
Hill, T W, & Voigt, G H. Limits on plasma anisotropy in a tail-like magnetic field. United States. https://doi.org/10.1029/92GL02497
Hill, T W, and Voigt, G H. 1992. "Limits on plasma anisotropy in a tail-like magnetic field". United States. https://doi.org/10.1029/92GL02497.
@article{osti_7061935,
title = {Limits on plasma anisotropy in a tail-like magnetic field},
author = {Hill, T W and Voigt, G H},
abstractNote = {Understanding the static balance of forces in a hypothetical stationary, steady-state magnetotail configuration is central to our understanding of planetary magnetotail dynamics, even though the actual planetary magnetotails may rarely if ever attain such a steady state. We are not likely to achieve an understanding of the observed departures from equilibrium if we do not first understand the nature of the equilibrium itself, albeit hypothetical. The condition of magnetohydrostatic equilibrium implies tight constraints on the degree of anisotropy that is supportable in a magnetotail field geometry. If the plasma pressure tensor is assumed to be gyrotropic at the tail midplane (z = 0), then equilibrium requires that it also be nearly isotropic there, with P[sub [perpendicular]0]/P[sub [parallel]0] in the range 1 [plus minus] [delta][sup 2], where [delta] [approximately] 0.1 is the ratio of the normal field component at the symmetry plane to the field strength in the tail lobe. The upper and lower limits are essentially equivalent, respectively, to the marginal mirror and firehose stability conditions evaluated at z = 0, which have been invoked previously to limit the degree of anisotropy in the plasma sheet. 21 refs., 1 fig.},
doi = {10.1029/92GL02497},
url = {https://www.osti.gov/biblio/7061935}, journal = {Geophysical Research Letters (American Geophysical Union); (United States)},
issn = {0094-8276},
number = ,
volume = 19:24,
place = {United States},
year = {Thu Dec 24 00:00:00 EST 1992},
month = {Thu Dec 24 00:00:00 EST 1992}
}