The photospheric motion, powered by the sub-photospheric plasma convection is a major source of energy for solar plasma acceleration. In order to understand, where and how reconnection can accelerate solar plasma, we developed a fully three-dimensional dissipative MHD simulation approach based on observed photospheric magnetic fields and plasma motion.
Our model starts with an appropriate for MHD boundary conditions force-free extrapolation of observed longitudinal components of the photospheric magnetic field and with a VAL-type stratified chromospheric-coronal plasma equilibrium.
Heat conduction, radiation cooling and gravity are neglected in this early version of the model. By our choice of the photospheric boundary condition we consider the horizontal photospheric plasma motion which drives the chromospheric and coronal plasma dynamics.
The plasma motion perturbs the equilibrium and results in current flows both parallel and perpendicular to the magnetic field. In order to allow reconnection anomalous resistivity is switched on as soon as the local current density exceeds a critical value.
We obtained reconnection and plasma acceleration mainly in the transition region between chromosphere and corona, where
the plasma density decreases and plasma collisions become less efficient. We demonstrate the acceleration for a SOHO-MDI observation on October 17, 1996.
Authors: J. Buechner, B. Nikutowski, A. Otto
Publication Status: AGU monograph 156 ''Astrophysical Particle Acceleration in Geospacae and Beyond'' in press
Last Modified: 2005-09-05 01:51