Anomalous transport effects on the parallel E field in downward auroral current regions of the Earth's magnetosphere

作者:Jasperse John R*; Basu Bamandas; Lund Eric J; Gros**ard Neil
来源:JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2011, 116: A00K11.
DOI:10.1029/2010JA016314

摘要

The physical processes that determine the fluid quantities and the self-consistent electric field (E-parallel to) parallel to the magnetic field have been an unresolved problem in magnetospheric physics for over 40 years. We review a recently developed kinetic and multimoment fluid theory for inhomogeneous, nonuniformly magnetized plasma with temperature anisotropy in the guiding-center and gyrotropic approximation and apply the theory to solve for the quasi steady state in the long-range potential region of a downward Birkeland current sheet when electrostatic ion cyclotron turbulence is dominant. We find that an electron, bump-on-tail-driven ion cyclotron instability produces the turbulence and that a large enhancement in vertical bar E-parallel to vertical bar by nearly a factor of 40 occurs when the turbulence is present compared to the case when it is absent. Anomalous momentum transfer (anomalous resistivity) by itself has a very small effect on E-parallel to; however, the presence of the turbulence and the anomalous energy transfers (anomalous heating and cooling) that result have a very large effect on the entire solution. In the electron and ion momentum balance equations for E-parallel to, the turbulence enhances the magnitude of E-parallel to by reducing the effect of the generalized parallel pressure gradients and thereby enhancing the effect of the mirror forces. A new, nonlinear formula for the current-voltage relationship in downward Birkeland current regions is also given.

  • 出版日期2011-8-20