Study of Time Evolution of Thermal and Non-Thermal Emission from an M-Class Solar Flare

Abstract

We conduct a wide-band X-ray spectral analysis in the energy range of 1.5-100 keV to study the time evolution of the M7.6 class flare of 2016 July 23, with the Miniature X-ray Solar Spectrometer (MinXSS) CubeSat and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft. With the combination of MinXSS for soft X-rays and RHESSI for hard X-rays, a non-thermal component and three-temperature multi-thermal component -- "cool" ($T\approx$ 3 MK), "hot" ($T\approx$ 15 MK), and "super-hot" ($T\approx$ 30 MK) -- were measured simultaneously. In addition, we successfully obtained the spectral evolution of the multi-thermal and non-thermal components with a 10 s cadence, which corresponds to the Alfvén time scale in the solar corona. We find that the emission measures of the cool and hot thermal components are drastically increasing more than hundreds of times and the super-hot thermal component is gradually appearing after the peak of the non-thermal emission. We also study the microwave spectra obtained by the Nobeyama Radio Polarimeters (NoRP), and we find that there is continuous gyro-synchrotron emission from mildly relativistic non-thermal electrons. In addition, we conducted a differential emission measure (DEM) analysis by using Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and determine that the DEM of cool plasma increases within the flaring loop. We find that the cool and hot plasma components are associated with chromospheric evaporation. The super-hot plasma component could be explained by the thermalization of the non-thermal electrons trapped in the flaring loop.

arXiv comment20 pages, 12 figures, 1 tables. Accepted for publication in ApJ

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• Spectral performance of single-channel plastic and GAGG scintillator bars of the CUbesat Solar Polarimeter (CUSP)
• Aditya-L1 and SDO Observations of a Confined X-Class Flare with an EUV Late Phase: Thermal and Nonthermal Emission, Magnetic Topology, and Flux Rope Confinement