Statistical studies of duration of low-power solar flares

Abstract

This paper is a sequel to papers dealing with time parameters of solar flares in the Hα line. Using data from the international flare patrol for 1972–2010, we have determined the mean duration of flares of different importance and classes of area. We have established that 94.6 % of flares last more than 60 min. The duration of 90 % of flares with min is 2.1–3.3 hrs. In rare cases, flares can last about 12 hrs. The duration of powerful solar flares does not exceed 8.3 hrs. We have found that the duration of solar flares depends on features of their development. Flares with one brilliant point in the flare region have the shortest duration; two-ribbon flares and flares exhibiting several intensity maxima have the longest duration. We have confirmed that the duration of flares increases with increasing classes of area and brightness.

Latitudinal distribution of solar microflares and high-temperature plasma at solar minimum

“…A small number of HXPs have been detected near the equator. Borovik and Zhdanov in [2018, 2019, 2020 have studied the flare events that can be considered as extremely powerful microflares, using data in the Hα line. It was found that during four solar cycles after cycle 21 there was a significant decrease in the number of flare events recorded in the optical range.…”