Multiwavelength Observations by XSM, Hinode, and SDO of an Active Region. Chemical Abundances and Temperatures

Abstract

We have reviewed the first year of observations of the Solar X-ray Monitor (XSM) on board Chandrayaan-2 and the available multiwavelength observations to complement the XSM data, focusing on the Solar Dynamics Observatory AIA and Hinode XRT and EIS observations. XSM has provided disk-integrated solar spectra in the 1–15 keV energy range, observing a large number of microflares. We present an analysis of multiwavelength observations of AR 12759 during its disk crossing. We use a new radiometric calibration of EIS to find that the quiescent active region (AR) core emission during its disk crossing has a distribution of temperatures and chemical abundances that does not change significantly over time. An analysis of the XSM spectra confirms the EIS results and shows that the low first ionization potential (FIP) elements are enhanced compared to their photospheric values. The frequent microflares produced by the AR did not affect the abundances of the quiescent AR core. We also present an analysis of one of the flares it produced, SOL2020-04-09T09:32. The XSM analysis indicates isothermal temperatures reaching 6 MK. The lack of very high-T emission is confirmed by AIA. We find excellent agreement between the observed XSM spectrum and the one predicted using an AIA DEM analysis. In contrast, the XRT Al-poly/Be-thin filter ratio gives lower temperatures for the quiescent and flaring phases. We show that this is due to the sensitivity of this ratio to low temperatures, as the XRT filter ratios predicted with a DEM analysis based on EIS and AIA give values in good agreement with the observed ones.