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EP: Fachverband Extraterrestrische Physik

EP 11: Heliosphäre

EP 11.2: Talk

Thursday, March 29, 2007, 10:00–10:15, H46

Slow evolution of 2D magnetic potential fields in barotropic ideal MHD flows — •Dieter Nickeler and Marian Karlicky — Astronomical Institute AV CR Ondrejov, Fricova 298, 25 165 Ondrejov, Czech Republic

2D potential fields for modelling pre-flare magnetic field structures have already often been used in the literature. The equation of motion is often neglected as the plasma beta is assumed to be very small in the regions above the photosphere. In contrast to that we analyse how magnetic potential fields do evolve in the frame of barotropic ideal MHD flows. We show special solutions by solving the set of ideal MHD equations in the case of a quasi-static approach. This implies that the non-linear term in the equation of motion is neglected. Here neither the pressure gradient nor the equation of motion can be neglected, especially if one investigates this system of ideal MHD equation in the vicinity of a magnetic neutral point. We find the occurence of finite time singularities and instabilities, which can be regarded as precursors of reconnection and flare processes on the sun. This finite time singularities and instabilities in the vicinity of a singular point can also mark global instabilities of the counterflow regions of astrospheres, like our heliosphere.