The acceleration characteristics of solar energetic particles in the 2000 July 14 event

Abstract

In large gradual solar energetic particle (SEP) events, especially the ground-level enhancement (GLE) events, where and how energetic particles are accelerated is still a problem. By using imaging data from TRACE, Yohkoh/HXT, SOHO/MDI and SOHO/EIT, along with the data from the GOES, Apatity NM, and SOHO/LASCO CME catalog, the evolution of the X5.7 two-ribbon flare and the associated SEP event on 14 July 2000 are studied. It is found that the magnetic reconnection in this event consists of two parts, and the induced electric field Erec is temporally correlated with the evolution of hard X-ray and gamma-ray emission. In particular, the first hard X-ray and gamma-ray emission peak occurred at 10:22 UT, corresponding to the magnetic reconnection in the western part of the flare ribbons and the maximum Erec of 9.5 V/cm; the second emission peak at 10:27 UT, corresponding to the eastern part and the maximum Erec of 13.0 V/cm. We also analyze the SEP injection profiles as functions of time and CME-height, and find two-component injection which may result from different acceleration mechanisms. A reasonable conclusion is that reconnection electric field makes a crucial contribution to the acceleration of relativistic particles and to the impulsive component of the large gradual SEP event, while CME-driven shocks play a dominant role in the gradual component.