Differential emission measure of solar nanoflares measured with the SITES algorithm

Abstract

The paper presents the results of a study of capabilities of the SITES algorithm for reconstructing the differential emission measure (DEM) of a source from its radiation in several parts of the electromagnetic spectrum in the context of observing solar nanoflares with the AIA/SDO instrument. The SITES method was implemented in the Python programming language and was first used to construct the DEM of nanoflares. For this purpose, we tested the efficiency of the algorithm on model single- and double-peak DEM at characteristic temperatures of solar nanoflares. The test results indicate that the SITES algorithm can be of limited applicability for studying the DEM of nanoflares in the single-peak approximation. The algorithm has a combination of high accuracy and high counting rate in the studied temperature range from 1 to 3 MK. The features of DEM nanoflares reconstructed by the SITES method were examined using our previously found sample of 58855 events observed in 2019 with the AIA/SDO instrument. The results confirm that the characteristic plasma temperature in nanoflares is 1–2 MK. The reconstructed DEM of nanoflares generally have one maximum within this range, but the temperature distribution we obtained for all flares forms two clusters with maxima at 1.2 and 1.7 MK. We interpret this as possible evidence for the existence of two types of solar nanoflares, but this result requires further confirmation.