X-ray plasma ejection and magnetic reconnection

Abstract

X-ray plasma ejections are discovered above soft X-ray loops in impulsive flares through Yohkoh observations. An X-ray plasmoid in November 11, 1993 flare formed after its footpoint brightened long before the impulsive phase, and was already heated to about 10 MK before the impulsive phase. Before the impulsive phase the electron density of the X-ray plasmoid was already an order of magnitude larger than the typical density of the active-region corona. From these observational results we propose that the ejected plasma was supplied owing to chromospheric evaporation caused by the preflare heating. The kinetic energy of the plasmoid was smaller than the thermal energy content of the flare loop. This indicates that the plasmoid ejection is not the energy source of the flare. A strong acceleration of the plasmoid occurred around the onset of the hard X-ray emission, and the velocity of the X-ray plasmoid and the hard X-ray emission are increased. This indicates that plasmoid ejection and reconnection are closely coupled.