On the Possible Mechanism of GLE Initiation

Abstract

Abstract\nWith the goal of understanding the initiations of solar energetic particle (SEP) (MeV) and ground-level enhancement (GLE) (GeV) particles, we have studied relative timings at?approximately?the Sun between temporal evolutions of the particles and some electromagnetic radiation components representing flares and shocks. Results show that GLE onsets appear after flare prompt onsets and m-type II onsets, while the GLE-associated SEP onsets appear before the flare prompt onsets and m-type II onsets, thus specifying that the GLE-associated SEPs originate over the flare initial phases and get accelerated intensively over the flare prompt phases associated with coronal shocks. The flare initial phase is found always earlier than the coronal mass ejection (CME) initial phase, further justifying that the MeV particles are initiated particularly by the flare initial phases and are accelerated to GeV energetic by flare prompt phases associated with the coronal shocks. On the contrary, most of the non-GLE-SEP onsets appear well after the flare prompt onsets and m-type II onsets, demonstrating that the non-GLE-SEPs mostly generate over the most intense part of the flare rise phases associated with the coronal shocks. In another development, the relative timings of flare prompt onset and peak times to the m- and DH-type II onsets show that usually the m-type II bursts commence before the flare peaks and DH-type II bursts commence after the flare peaks, signifying that the coronal shocks manifested in m-type II bursts operate over the flare main acceleration phases, while the coronal shocks manifested in DH-type II bursts operate over the flare decay and/or CME propagation phases, thereby suggesting that the evolution of the particles accelerated at the flare main acceleration phases can be prolonged by the shocks associated with the CME propagation phases.