Investigating Intermittent Energy Release during Solar Eruptive Events with Faint Hard X-ray Sources

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 a previous study, we leveraged multi-viewpoint observations from STEREO, SDO, and RHESSI to provide simultaneous measurements of CME evolution, magnetic reconnection, and flare energy release for 12 solar eruptive events, examining fast-varying features, or “bursts,” in the time profiles to improve our understanding of the connections between flare and CME energization. These bursts represent episodes of energy release which can provide insight on reconnection and acceleration mechanisms during the eruptive event. Here we expand upon this investigation, focusing our attention on the evolution of fainter HXR sources during solar eruptive events, including rarely-studied RHESSI HXR flares occurring outside of active regions, which can provide insight on how the magnetic configuration affects the evolution of eruptive events. We additionally leverage RHESSI observations of partially-occulted flares associated with CMEs to examine faint coronal HXR sources, which have been infrequently observed by previous HXR instruments due to the relative brightness of the footpoint emission. These coronal sources provide the most direct signature of flare particle acceleration, as measurements of the flare footpoint emission include possible transport effects. We investigate the relationship between these faint energy release sites and the evolution of the associated CMEs.