Dr. Sabrina Savage
Re-interpretation of Supra-Arcade Downflows in Solar Flares
Following the eruption of a filament from a flaring active region, sunward-flowing voids are often seen above developing post-eruption arcades. First discovered using the soft X-ray telescope aboard Yohkoh, these supra-arcade downflows (SADs) are now an expected observation of extreme ultra-violet and soft X-ray coronal imagers and spectrographs. Observations made prior to the operation of the latest solar flagship mission, SDO/AIA, suggested that these plasma voids (which are seen in contrast to bright, high-temperature plasma associated with current sheets) are the cross-sections of evacuated flux tubes retracting from reconnection sites high in the corona. By applying this interpretation to void measurements, we derived values such as flux tube cross-sectional areas, magnetic fluxes, and shrinkage energies of reconnection outflows. The high temperature imaging now afforded by AIA coupled with its fast temporal cadence allows for unprecedented scrutiny of the voids. Using AIA, I will present evidence suggesting that SADs should no longer be considered cross-sections of relatively large, evacuated flux tubes after all, and I will discuss how a significant shift in the fundamental understanding of SADs affects previous parameter estimations and reconnection theory.