Statistical research into low-power solar flares. Main phase duration

Abstract

Abstract. This paper is a sequel to earlier papers on time parameters of solar flares in the Hα line. Using data from the International Flare Patrol, an electronic database of solar flares for the period 1972-2010 has been created. The statistical analysis of the duration of the main phase has shown that it increases with increasing flare class and brightness. It has been found that the duration of the main phase depends on the type and features of development of solar flares. Flares with one brilliant point have the shortest main phase; flares with several intensity maxima and two-ribbon flares, the longest one. We have identified more than 3000 cases with an ultra-long duration of the main phase (more than 60 minutes). For 90 % of such flares the duration of the main phase is 2-3 hrs, but sometimes it reaches 12 hrs.

The Processes of Energy Release in Low-Power Solar Flares

“…There is no relationship between the time of brightness rise to maximum and the time of its decay (according to our estimates, the correlation coefficient is less than 0.4). Borovik, Zhdanov [2017b, 2018a, 2018b] using a great body of data have obtained distributions of solar flares by the time of brightness rise to maximum, decay time, and total duration in accordance with the international classification of chromospheric flares. According to the optical classification, flares are divided by area into five classes: S, 1, 2, 3, 4.…”

“…All the T rel distributions have a positive asymmetry and an extended decrease and, like time parameters of flares [Borovik, Zhdanov, 2017b, 2018a, 2018b, exhibit a significant mutual overlap of distributions ( Figure 3, a, b). This implies that the high percentage of flares with increasing area class does not show the general tendency.…”

“…In this paper, we analyze the results obtained in [Borovik, Zhdanov, 2017b, 2018a, 2018b, present a number of important, in our opinion, conclusions about dynamics and power of flare processes.…”

Statistical studies of duration of low-power solar flares

“…As in [Borovik, Zhdanov, 2017a], we impose the same restrictions on the database in assessing time parameters of solar flares as in estimating variance in groups (see the previous section). Since for small flares on the edge of the solar disk the data are not as reliable as for flares near its center, class S and 1 flares with a longitude >65° are excluded from the database.…”

“…The duration of solar flares is composed of two characteristic intervals: initial (flash) phase and main phase. The main phase has been examined in detail in [Borovik, Zhdanov, 2017a]. This paper studies the total duration of solar flares.…”