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C. Z. Cheng, G. S. Choe (Princeton Plasma Physics Laboratory, Princeton University), J. Qiu (NJIT/BBSO), Y. Ren (Princeton Plasma Physics Laboratory, Princeton University), Y. J. Moon (Korea Astronomy Observatory)
Recent solar observations have shown that the flare emission, the flux rope motion and the magnetic reconnection rate are closely related. Filament eruptions in the lower corona and CMEs in the higher corona are considered as the motion of a flux rope. From the flare-CME-filament observations it was observed that the most intense peak in the flare nonthermal emissions (hard X-ray, microwaves) and the maximum rate of increase in the total soft X-ray emission during the flare rise phase occur at the time of maximum acceleration of the flux rope's rising motion. Moreover, the magnetic reconnection rate obtained from the magnetogram data and horizontally expanding two-ribbon emissions is found to temporally correlate with the flux rope acceleration. We have performed resistive MHD simulations of the temporal evolution of flux rope motion and magnetic reconnection rate, which depends critically on the nonuniform anomalous resistivity which is a function of current density. The simulation results show that the flux rope's accelerated rising motion is associated with an enhanced magnetic reconnection rate and thus an enhanced reconnection electric field in the current sheet during the flare rise phase. The results are in good quantitative agreement with observations of the acceleration of flux ropes (CMEs) for several CME-flare events. For the X-class flare events the peak reconnection electric field is ~ O(103 V/m) or larger, enough to accelerate electrons to over 100 keV in a field-aligned distance of 0.1 km and produce an impulsive hard X-ray emission observed during the flare rise phase, consistent with the estimated reconnection rate based on observations. Comparisons of the flux rope height, velocity and acceleration between our simulation results and observed CME-flare events will be presented. Moreover, possible scenarios of particle acceleration and particle distributions responsible for flare emissions will be discussed.
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Bulletin of the American Astronomical Society, 36 #2
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