Investigating Intermittent Energy Release during Solar Eruptive Events

Hard X-rays (HXRs) provide a key diagnostic for energy release during a solar flare, as HXRs are emitted from flare-accelerated electrons and strongly heated flare plasma. In the case of a solar eruptive event, a flare is associated with the eruption of a coronal mass ejection (CME); though it is largely understood that reconnection is important for the eventual release of the CME, the triggering mechanism for the eruption and its relationship to flare energy release remains under debate. In this study, we leverage the optimal viewing geometry of the Solar TErrestrial RElations Observatory (STEREO) relative to the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) during 2010-2013 to provide simultaneous measurements of CME evolution, magnetic reconnection, and flare energy release for 12 solar eruptive events. We analyze the relative timing of these phenomena, focusing on event onset and fast-varying features, or “bursts,” in the time profiles to improve our understanding of particle acceleration mechanisms and the connections between flare and CME energization. The studied events fall into two categories: events with a single dominant HXR burst and events with a train of multiple HXR bursts. Through this work, we find that events with multiple HXR bursts, indicative of intermittent reconnection and/or particle acceleration, correspond with faster CMEs. We additionally note that this study has identified two events with rarely-studied RHESSI HXR flares occurring outside of active regions, which can provide further insight on how the magnetic configuration affects the evolution of eruptive events.