Following the eruption of a filament from a flaring active region, sunwardflowing 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 (EUV) and soft X-ray coronal imagers and spectrographs (e.g, TRACE, SOHO/SUMER, Hinode/XRT, SDO/AIA). Observations made prior to the operation of AIA suggested that these plasma voids (which are seen in contrast to bright, hightemperature plasma associated with current sheets) are the cross-sections of evacuated flux tubes retracting from reconnection sites high in the corona. The high temperature imaging afforded by AIA's 131, 94, and 193Å channels coupled with the fast temporal cadence allows for unprecedented scrutiny of the voids. For a flare occurring on 2011 October 22, we provide evidence suggesting that SADs, instead of being the cross-sections of relatively large, evacuated flux tubes, are actually wakes (i.e., trailing regions of low density) created by the retraction of much thinner tubes. This re-interpretation is a significant shift in the fundamental understanding of SADs, as the features once thought to be identifiable as the shrinking loops themselves now appear to be "side effects" of the passage of the loops through the supra-arcade plasma. In light of the fact that previous measurements have attributed to the shrinking loops characteristics that may instead belong to their wakes, we discuss the implications of this new interpretation on previous parameter estimations, and on reconnection theory.

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We determine the thermal radiation generated by a loss-of-equilibrium model for CMEs and eruptive solar flares. The magnetic configuration of the model consists of an outward-moving flux rope with a vertical current sheet below it. Reconnection at the sheet releases magnetic energy, some of which is converted into thermal energy that drives chromospheric evaporation along the newly connected field lines exiting the current sheet. The thermal energy release is calculated by assuming that all of the Poynting flux flowing into the reconnection region is eventually thermalized. We find that the fraction of the released magnetic energy that goes into thermal energy depends on the inflow Alfvén Mach number. The evolution of the temperatures and densities resulting from chromospheric evaporation is calculated using a simple evaporative cooling model. Using these temperatures and densities, we calculate simulated flare light curves for TRACE, the SXT on Yohkoh, and GOES. We find that when the background magnetic field strength is weak, the radiation emitted by the reconnected X-ray loops beneath a CME is faint. Additionally, it is possible to have two CMEs with nearly the same trajectories and speeds that have a significant difference in the peak intensities of their light curves. We also examine the relationship between the thermal energy release rate and the derivative of the soft X-ray light curve and discuss the implications for the Neupert effect.

Axions are a promising dark matter candidate as well as a solution to the strong charge-parity (CP) problem in quantum chromodynamics (QCD). We describe a new mission concept for SmallSat Solar Axion and Activity X-ray Imager (SSAXI) to search for solar axions or axion-like particles (ALPs) and to monitor solar activity of the entire solar disc over a wide dynamic range. SSAXI aims to unambiguously identify X-rays converted from axions in the solar magnetic field along the line of sight to the solar core, effectively imaging the solar core. SSAXI also plans to establish a statistical database of X-ray activities from Active Regions, microflares, and Quiet Sun regions to understand the origin of the solar corona heating processes. SSAXI employs Miniature lightweight Wolter-I focusing X-ray optics (MiXO) and monolithic CMOS X-ray sensors in a compact package. The wide energy range (0.5 -6 keV) of SSAXI can easily distinguish spectra of axion-converted X-rays from typical X-ray spectra of solar activities, while encompassing the prime energy band (3 -4.5 keV) of axion-converted X-rays. The high angular resolution (30 arcsec HPD) and large field of view (40 arcmin) in SSAXI will easily resolve the enhanced X-ray flux over the 3 arcmin wide solar core while fully covering the X-ray activity over the entire solar disc. The fast readout in the inherently radiation tolerant CMOS X-ray sensors enables high resolution spectroscopy with a wide dynamic range in a broad range of operational temperatures. SSAXI will operate in a Sun-synchronous orbit for 1 yr preferably near a solar minimum to accumulate sufficient X-ray photon statistics.