New aspects of plasma sheet dynamics - MHD and kinetic theory

[摘要] Magnetic reconnection is a process offundamental importance for the dynamics of the Earth's plasma sheet. In thiscontext, the development of thin current sheets in the near-Earth plasma sheetis a topic of special interest because they could be a possible cause ofmicroscopic fluctuations acting as collective non-idealness from a macroscopicpoint of view. Simulations of the near-Earth plasma sheet including boundaryperturbations due to localized inflow through the northern (or southern) plasmasheet boundary show developing thin current sheets in the near-Earth plasmasheet about 810 R_E tailwards of the Earth. This location islargely independent from the localization of the perturbation. The second partof the paper deals with the problem of the macroscopic non-ideal consequences ofmicroscopic fluctuations. A new model is presented that allows the quantitativecalculation of macroscopic non-idealness without considering details ofmicroscopic instabilities or turbulence. This model is only based on theassumption of a strongly fluctuating, mixing dynamics on microscopic scales inphase space. The result of this approach is an expression for anomalousnon-idealness formally similar to the Krook resistivity but now describing themacroscopic consequences of collective microscopic fluctuations, not ofcollisions.

Key words. Magnetospheric physics (plasma sheet) ·Space plasma physics (kinetic and MHD theory; magnetic reconnection)

[学科分类] 地球科学(综合)