arXiv subjects

A. S. Motorin

Publications and source records attributed to A. S. Motorin.

3 recordsLinked to original sources

arXiv2026

Post-impulsive millimeter emission of the 2022-05-04 solar flare

The present work aims at analyzing the nature of millimeter (mm) emission observed during the post-impulsive phase of the solar flare SOL2022-05-04T08:45 (M5.7), detected by the RT-7.5 radio telescope of the Bauman Moscow State Technical University at 93 GHz. We investigate the relationship of mm and extreme ultraviolet (EUV) emission with variations in the temperature and coronal plasma emission measure obtained from SDO/AIA and GOES data. The results show that the enhanced mm emission at the post-impulsive phase of the flare coincides with the increase of EUV emission, indicating a connection with moderately hot (~1 MK) plasma. Based on the calculation of the differential emission measure, we determine the parameters of the post-impulsive flare plasma and conclude that the optically thin coronal plasma may contribute of about 20% to the mm emission.

astro-ph.SR↗

arXiv2025

Investigation of possible precursors of solar flares in the active region 12230 On December 9, 2014

The question of the nature of precursors of solar flares, as well as their relationship with subsequent flares, still has no unambiguous answer. This is due, in particular, to the lack of systematic statistical work, the relative incompleteness (in isolation from the context of the development of the entire active region) of studies of individual events and the ambiguity of the term 'precursor' itself. In this paper, we consider the dynamics of the NOAA 12230 active region (AR), in which a series of homologous flares (C5-C9) occurred on December 9, 2014 within 12 hours, with an average frequency of about 2 hours. This AR was characterized by a rapid increase in flare activity followed by a rapid decay, which can be considered as a good example for studying potential precursors of flare series. We investigated the evolution of AR 12230 over a relatively long period (several days) and its transition from the 'no-flare' state to the flare-active regime. For this purpose, we study the magnetic field dynamics using SDO/HMI vector magnetograms, UV-EUV images based on SDO/AIA data, and X-ray observations from GOES/XRS and RHESSI data. We conclude that the significant increase in the chromospheric radiation variations against the background of a small flux of soft X-ray and UV emission from the corona observed on December 8, 2014, together with the magnetic flux emergence, can be considered as a precursor to a series of flares. The results show the importance and prospects of applying new methods of synoptic observations of the Sun in the context of collecting statistics ("history") of the AR energy release in different ranges of the electromagnetic spectrum.

astro-ph.SR↗

arXiv2023

Pre-impulsive and Impulsive Phases of the Sub-Terahertz Flare of March 28, 2022

Properties of the solar radio spectrum, as well as the temporal profiles of flare emission, indicate the thermal nature of the sub-terahertz (sub-THz) component observed as the growth of radio emission in the frequency range of 100-1000 GHz. The sub-THz flare onset can be ahead of the impulsive phase for several minutes. However, the origin of the pre-impulsive and impulsive sub-THz emission remains unclear. The present work is devoted to a detailed analysis of the M4.0 X-class solar flare observed on March 28, 2022 with the Bauman Moscow State Technical University Radio Telescope RT-7.5 at 93 GHz. We supply these data with multiwavelength solar observations in the X-ray (GOES, GBM/Fermi), extreme ultraviolet (AIA/SDO), and microwave ranges. The differential emission measure (DEM) responsible for EUV emission is determined by solving the inverse problem based on the AIA/SDO data. Using the DEM and assuming a thermal free-free emission mechanism in pre-impulsive and impulsive phases, we calculated the millimeter emission flux of coronal plasma of the flare source, which turned out to be much smaller than the observed values. We concluded that electrons accelerated in the corona and heat fluxes from the coronal loop top cannot be responsible for heating the sub-THz emission source located in the transition region and upper chromosphere. A possible origin of chromospheric heating in the pre-impulsive phase of the solar flare is discussed.

astro-ph.SR↗