AN INTERPRETATION OF GLE71 CONCURRENT CME-DRIVEN SHOCK WAVE

Abstract

Particle accelerations in solar flares and CME-driven shocks can sometimes result in very high-energy particle events (>= 1 GeV) that are known as ground level enhancements (GLEs). Recent studies on the first GLE event (GLE71 2012 May 17 01:50 UT) of solar cycle 24 suggested that CME-driven shock played a leading role in causing the event. To verify this claim, we have made an effort to interpret the GLE71 concurrent shock wave. For this, we have deduced the possible speed and height of the shock wave in terms of the frequency (MHz) of the solar radio type II burst and its drift rate (MHz min(-1)), and studied the temporal evolution of the particle intensity profiles at different heights of the solar corona. For a better perception of the particle acceleration in the shock, we have studied the solar radio type II burst with concurrent solar radio and electron fluxes. When the particle intensity profiles are necessarily shifted in time at similar to 1 AU, it is found that the growth phases of the electron and cosmic ray intensity fluxes are strongly correlated (>0.91; >= 0.87) with the frequency drift rate of the type II burst, which is also consistent with the intensive particle accelerations at upper coronal heights (similar to >= 0.80 R-S < 1.10 R-S). Thus, we conclude that the CME-driven shock was possibly capable of producing the high-energy particle event. However, since the peaks of some flare components are found to be strongly associated with the fundamental phase of the type II burst, the preceding flare is supposed to contribute to the shock acceleration process.