HR: 1340h
AN: SM23B-0424    [Abstracts]
TI: Features of Self-organization in Space Plasma: Generation and Evolution of Extremely Thin Current Sheets
AU: * Kropotkin, A P
EM: apkrop@dec1.sinp.msu.ru
AF: Skobeltsyn Institute of Nuclear Physics , Moscow State University, Moscow, 119992 Russian Federation
AU: Domrin, V I
EM: dmr@dec1.sinp.msu.ru
AF: Skobeltsyn Institute of Nuclear Physics , Moscow State University, Moscow, 119992 Russian Federation
AB: Thin current sheets (TCS) have been earlier shown to be specific structures forming in magnetized plasmas under a variety of conditions. We argue that fast evolution which may follow the slow, quasi-static process of TCS initial formation, can be started by a fast loss of equilibrium in the system produced by localized (e.g. tearing) instability, and MHD disturbance propagating along TCS from instability location. That fast evolution involves formation of extremely thin embedded structures, with scales ranging down to the ion Larmor radius, and it must be analysed based on plasma kinetics. The analysis has been carried out by means of kinetic simulation using the hybrid technique. The process appears to have quite different features, i.e. to follow various dynamical paths, depending on initial conditions. We demonstrate in particular the key role of the magnetic field normal component. The dominating features may be either those of a slow switch-off shock or those of a stationary forced current sheet (FCS), with its extremely anisotropic ion distributions. In both cases, however, at later stages, the process appears to be spontaneously self-sustained, as a finite magnitude MHD disturbance of a rarefaction wave type propagates back over the background plasma outside the CS. Transformation of electromagnetic energy into the energy of plasma flows occurs at the TCS in both cases, providing an effect of magnetic field "annihilation" which is a necessary constituent of fast magnetic reconnection.
DE: 2753 Numerical modeling
DE: 2764 Plasma sheet
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005