X‐Ray Plasma Ejection Associated with an Impulsive Flare on 1992 October 5: Physical Conditions of X‐Ray Plasma Ejection

Abstract

The 1992 October 5 Ñare was associated with an X-ray plasma ejection. Although the ejected plasma looks like a blob (or plasmoid) in short-exposure images, in long-exposure images it appears to be pen- etrated by or connected to the top of a large-scale loop. The ejecta had started to rise with a speed of D250 km s~1 before the main peak of the hard X-ray emission and was accelerated during the impulsive phase (to D500 km s~1). We derived the physical parameters of the ejected plasma and obtained the following results: (1) The temperature of the ejected plasma was 10.6^3.6 MK. (2) Its density was (8È 16)]109 cm~3 and was an order of magnitude larger than that of the typical active-region corona. (3) The mass of the ejected plasma was (2È4)]1013 g. (4) The kinetic energy of the ejecta was smaller than the thermal energy content of the Ñare loop. The overall features and evolution of the hot plasma ejec- tion and Ñare are in rough agreement with those expected from the reconnection model, and the recon- nection rate reconnection region, and is the Alfve n speed. Result 4, however, is not consistent with the assump- VA (MA\Vin/VA) is estimated to be D0.02, where is the speed of the inÑow into the Vin tion in some reconnection models that an ejected plasma stretches the overlying magnetic Ðelds to form a current sheet and hence leads to magnetic reconnection. Instead, our results suggest that both X-ray plasma ejection and reconnection are a consequence of a common dynamical process such as the global MHD instability.