Quantifying Chromospheric Condensation Characteristics through IRIS Observations in Si IV

Abstract:

Chromospheric condensation is downflow that occurs, in some solar flares, as a back reaction from chromospheric evaporation. Both effects are the results of magnetic energy release initiated by magnetic reconnection high in the corona. Chromospheric ribbons consist of all the footpoints of the reconnect field lines, and therefore provide a projection onto the chromosphere of the reconnection occurring in the corona. Spectroscopic observations of these flare ribbons provide information about the response of the transition region and chromosphere, and thus provide indirect information about the localized magnetic reconnection process initiating the flare. We use sit-and-stare observations of the Si IV spectral line made by the Interface Region Imaging Spectrograph (IRIS) to characterize the dynamics of chromospheric condensation. Looking at ribbons from approximately thirty different flares showing chromospheric condensation, we fit the Si IV lines with single or multiple Gaussian components. We study the time evolutions of the Doppler velocity, line width, and intensity to infer the energy flux and duration of the release process. We use the spatial correlation of the condensation flows to extrapolate the size of the coronal reconnection sites. These characteristics bring us closer to understanding coronal reconnection energy release occurring in flares.