Release Episodes of Electrons and Protons in Solar Energetic Particle Events

We analyzed a sample of 21 solar energetic particle (SEP) events with clear signatures in both near-relativistic electrons and high-energy protons spanning over similar to 2.5 solar cycles from 1997 to 2016. We employed velocity dispersion analysis (VDA) for protons and fractional VDA (FVDA) for electrons, as well as time shifting analysis (TSA) in order to identify the solar release times (SRTs) of the electrons. We found that, for the majority of the events (62%), a simultaneous release was observed, while, for 14% of the events, electrons were released later than protons (i.e., delayed electrons); for 24% of the events, the opposite result was found (i.e., delayed protons). We found that the path length (L) traveled by the protons and electrons was not related to the aforementioned categorization. Moreover, we show that, in the case of simultaneous SEP events, protons and electrons are being released in close connection to type III and type II bursts, while the opposite is the case for delayed events. In addition, we demonstrate that, for the simultaneous events, both the proton and the electron release are established in heights < 5R(S) and that, especially for the well-connected simultaneous events, there is a co-occurrence of the type II burst with the release time of the particles.