Stability of Supra Arcade Downflows (SADs) and Bursty Bulk Flows (BBFs); Differences, Similarities, and Effects on the Surrounding Regions

We examine the stability conditions for two post eruptive phenomena in two different regions of the solar -- terrestrial environment, namely Supra Arcade Downflows (SADs) in the solar corona and Bursty Bulk Flows (BBFs) in the Earth's magnetotail. We specifically investigate the possibility of Kelvin-Helmholtz Instability (KHI) and magnetohydrodynamic (MHD) wave emission along these two shear flow regions that have remarkably similar velocity profiles and length scales of ~ 1000 km. Our results suggest that the KHI and emission of propagating MHD waves due to KHI are possible along both SADs and BBFs, depending on the background values of the magnetic fields, densities, and shear flow speeds. These propagating MHD waves may be a means of energy transport out of SADs and may contribute to the transport of energy into the surrounding corona, perhaps contributing to solar coronal heating. Emission of MHD waves along BBF boundaries may have profound effects on the response in the near-Earth magnetotail, since the emission of magnetosound may transfer energy away from the BBF into the surrounding tail. This may influence the response of substorm-related phenomena in the near-Earth region, including particle injections and through magnetosphere-ionosphere coupling, introduce a possible relationship to the structure of auroral brightenings, and field aligned currents. Moreover, the reduction of the kinetic energy of the flows arising from the emission of MHD waves may contribute to the braking of the flows in SADs and BBFs.