| Abstract : | The First-Ionization-Potential (FIP) effect is a phenomenon where elements with FIP less than 10 eV are seen to be two to four times more abundant in the closed-loop corona compared to the solar photosphere. The origin of this FIP effect is yet to be understood well. Using MESSENGER SAX, we have performed a time-integrated and time-resolved analysis of C, M and X class flares to derive the abundances of Ar, Fe, Ca, and S and also understand their evolution. We compare the results of this study with the abundances (Mg, Al, Si and S) derived from Chandrayaan-2 XSM for A and B-class flares. We find that understanding the quick recovery of the abundances as the flare decays is challenging to explain using current models of the FIP effect. Magnetic reconnection during flares also reconfigures the magnetic field to a lower-energy state. The free energy liberated causes the heating of the plasma and also accelerates particles to non-thermal energies, resulting in the emission of thermal and non-thermal X-rays in a broad energy band. However, there is limited knowledge of the total magnetic energy released and the proportion of distribution of energy to plasma heating and to accelerate particles. To understand this complex process of energy conversion and distribution, we model the combined multi-thermal soft X-ray spectrum simultaneously from MESSENGER-SAX and the hard X-ray spectrum from RHESSI during strong solar flares that were observed by both satellites and present the evolution of the flare parameters (temperature, emission measure and abundances). Following the temporal evolution of the multi-temperature structure of the spectra using Messenger SAX and RHESSI has provided new insights into the potential origins of the thermal and non-thermal emissions and their relationship. Such studies also provide a framework for understanding the multi-thermal structure of chromospheric evaporation. |
