HR: 1340h
AN: NG23A-1182    [Abstracts]
TI: Modelling the multi-scale coupling in solar reconnection
AU: * Buechner, J
EM: buechner@mps.mpg.de
AF: Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Str.2, Katlenburg-Lindau, 37191 Germany
AB: Solar reconnection is a typical example of a nonlinear, multi-scale phenomenon which follows as a direct consequence from the fundamental nonlinearity of plasma physical equations and the variety of complicated initial and boundary conditions in a non-uniform plasma. Reconnection needs dissipation, which has to be treated microscopically but it also needs magnetic energy accumulation at large scale. The inter-scale coupling between the two is the real open question in this strongly nonlinear problem. Any proper treatment of reconnection has to combine both aspects, which appeared to be an non-trivial problem, impossible to be solved directly even using for modern massively parallelized computer simulation techniques. We are considering the follwoing way out of this dilemma: let us start with known boundary and initial conditions as the input to large scale modelling based on truncated equation. This allows to obtain the times and critical regions, where small-scale phenomena have to be taken into account and the truncation is inappropriate. Next we use these results about critical regions as boundary and initial conditions for the analysis of microphysical processes at their naturally shorter temporal and spatial scales. Feeding this information back to the large scale truncated system in terms of an appropriate parametrization we than investigate the further evolution of the large scale system already including the small-scale microphysical results extending the truncated macroscopic evolution equations in an appropriate way. We demonstrate the workability of such approach applying it to model the heating of EUV and X-ray Bright Points in the solar corona. The initial system of MHD equations uses a severely truncated energy equation which does, nevertheless, describe the large corona appropriately. This allows us to identify the potential sites of non-force-free current sheets, where the current carriers will be accelerated until their velocity exceeds the theshold of microinstabilities. The latter are considered kinetically, which in turn provides transport equations and coefficients for the large scale MHD approach. The feedback of microphysical processes to the large scale system is especially strong where the large scale topology and geometry tends to form deformations or even singularities. This allowed us already, for example, to localize the energization of the solar corona better as approaches could do which did not consider the specific feedback of microprocesses. As an example, we identified the locations of coronal Bright Points based on solar photospheric observations.
DE: 7509 Corona
DE: 7835 Magnetic reconnection
DE: 3210 Modeling
DE: 3220 Nonlinear dynamics
DE: 3230 Numerical solutions
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting