Further Study of the Origin of Impulsive Solar Energetic Particle Events in Solar Cycle 24

Nariaki Nitta, Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA, United States, Glenn M Mason, JHU / APL, Laurel, MD, United States, Christina Cohen, Caltech, Pasadena, CA, United States and Mark E Wiedenbeck, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
Abstract:
Impulsive solar energetic particle (SEP) events are characterized by enhancement of 3He and heavy ions (such as Fe), typically in energies below a few MeV per nucleon. These ions will lose energy into “suprathermal” ranges as they escape from the solar atmosphere. It is possible that they provide seed particles for acceleration at the shock wave driven by a subsequent coronal mass ejection (CME) that results in a gradual SEP event. Nitta et al. (2015) searched for the solar sources of 3He-rich SEP events in solar cycle 24 and found a few types of transient activities in the corona, including jets. They limited to 26 relatively stronger events with a clear discrete injection, but there are a larger number of weaker impulsive SEP events. Some of them lack a clear injection and last longer. In this study, using remote-sensing data from SDO and STEREO, we try to trace the origins of these 3He or Fe-rich periods as found in ACE and STEREO data, and to examine the properties of the regions that produced the activities likely responsible for compositional anomalies.
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