Low-power solar flares in the Hα line: research results

Abstract

The paper summarizes the results of long-term studies of low-power flares in the Hα line (optical class S) obtained using data from the international flare patrol, observational materials in the 6563 Å line of the Baikal Astrophysical Observatory of the ISTP SB RAS and GONG telescopes, observations from the SDO, SOHO, and Kitt Peak Observatory. As a result of the performed studies, the refined, statistically reliable and most complete to date data on the spatiotemporal parameters of solar flares have been obtained, and their total energy in the optical wavelength range has been estimated. Low-power flares were found to form dense clusters on the Sun, which are centers of flare activity (CFA) associated with regions of emerging magnetic fluxes. It was also found that such flares occur near the local small-scale short-lived polarity inversion lines (LPIL) of the longitudinal magnetic field. One of the identified regularities of their occurrence is the increase in the magnetic field gradient in certain sections of the LPIL in the flare region. The duration of growth is from 40 minutes to 1.5 hours. The magnetic field reaches its maximum gradient (1.3-1.5 G/km) at the time of flare occurrence. The results of the study show that low-power flares have development scenarios similar to large flares: they are accompanied by activation and eruption of filaments, have an explosive phase, are accompanied by radiation of different power in the X-ray and radio ranges as well as by proton fluxes. Among them there are flares that cover the sunspot umbrae, two-ribbon and white-light flares. The results obtained can be used to construct physical models, diagnose nonstationary processes on the Sun, and predict solar activity and geoeffective solar events.