Statistical studies of duration of low-power solar flares

Abstract

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 60 t > 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.

Solar activity research at the Baikal Astrophysical Observatory of ISTP SB RAS

“…Within 10-20 min before the flare, small-scale formations are activated mainly near flare nodes and at 10-60 thousand km from the flare. A cause of this may be changes in large-scale magnetic fields, accompanied by emergence of magnetic fields in an active region [Borovik, 1985;Sattarov et al, 1985;Borovik et al, 1986]. As a rule, the place of occurrence and development of small flares is the boundaries of the chromospheric network, where the magnetic field is strengthened.…”

“…The most comprehensive and reliable data on time parameters of solar flares of different types, classes of area, and importance has been obtained for the first time. This allowed us to reconsider some ideas about solar flares [Borovik, Zhdanov, 2017.…”