High Resolution Observations of the Low Atmospheric Response to Small Heating Events in Active Regions

Abstract:

We investigate the low atmospheric response to small heating events (nano/micro-flares) by analyzing coordinated active region observations with IRIS and SST, and also using the simultaneous SDO/AIA observations to study the coronal emission. The events we observe as intense brightenings in the chromosphere and transition region are clearly associated with heating of the overlying loops to high temperatures (5-10MK), as is clear from the strong Fe XVIII emission observed in the 94A SDO/AIA passband. Some of the chromospheric brightenings have been observed with the SST with the CRISP instrument in Ca II 8542 and H-alpha, as well as with the new CHROMIS instrument in Ca II K, which provides unprecedented resolution. We will present the rich spectral diagnostics offered by IRIS and SST for these events, including insights we obtained by applying a k-means clustering analysis to the SST and IRIS spectra during the heating events. Our observations will help provide more stringent constraints on the properties of non-thermal particles in nanoflares and microflares.