Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM -- Sub-A Class Microflares Outside Active Regions

TL;DR

This study presents the first comprehensive analysis of quiet Sun microflares observed in soft X-rays during the 2019-20 solar minimum, revealing their energies and potential role in coronal heating.

Contribution

It provides new insights into microflares outside active regions using Chandrayaan-2 XSM data, expanding understanding of small-scale magnetic reconnection events.

Findings

98 microflares observed with energies 3e26 to 6e27 erg

Microflares occur outside active regions during solar minimum

Implications for coronal heating mechanisms

Abstract

Solar flares, with energies ranging over several orders of magnitude, result from impulsive release of energy due to magnetic reconnection in the corona. Barring a handful, almost all microflares observed in X-rays are associated with the solar active regions. Here we present, for the first time, a comprehensive analysis of a large sample of quiet Sun microflares observed in soft X-rays by the Solar X-ray Monitor (XSM) on board the Chandrayaan-2 mission during the 2019-20 solar minimum. A total of 98 microflares having peak flux below GOES A-level were observed by the XSM during observations spanning 76 days. By using the derived plasma temperature and emission measure of these events obtained by fitting the XSM spectra along with volume estimates from concurrent imaging observations in EUV with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), we estimated their thermal energies to be ranging from 3e26 to 6e27 erg. We present the frequency distribution of the quiet Sun microflares with energy and discuss the implications of these observations of small-scale magnetic reconnection events outside active regions on coronal heating.