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

Abstract

Aims: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.
Methods: 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.
Results: It is found that the magnetic reconnection in this event consists of two parts, and the induced electric field E_rec is temporally correlated with the evolution of hard X-ray and γ-ray emission. In particular, the first hard X-ray and γ-ray emission peak occurred at 10:22 UT, corresponding to the magnetic reconnection in the western part of the flare ribbons and the maximum E_rec of ~9.5 V/cm; the second emission peak at 10:27 UT, corresponding to the eastern part and the maximum E_rec 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.
Conclusions: .A reasonable conclusion is that reconnection electric field makes a crucial contribution to the acceleration of relativistic particles and the impulsive component of the large gradual SEP event, while CME-driven shocks play a dominant role in the gradual component.