Authors: I M Chertok A V Belov V V Grechnev
Publish Date: 2015/07/18
Volume: 290, Issue: 7, Pages: 1947-1961
Abstract
Around the peaks of substantial flares bright spurious nearly horizontal saturation streaks Bstreaks corresponding to the brightest parts of the flare sources appear in the STEREO/EUVI 195 Å images We show that the length of these Bstreaks can be used to solve the problem of evaluating the soft Xray flux and class of farside flares that are registered with the twin STEREO spacecraft but are invisible from Earth For this purpose from data on about 350 flares that were observed from January 2007 to July 2014 mainly exceeding the GOES M10 level both with GOES and STEREO we established an empirical relation that correlates the GOES 1 – 8 Å peak flux and the Bstreak length This allowed us to estimate the soft Xray classes for approximately 65 strong farside flares observed by STEREO for the same years The results of this simple and prompt method are consistent with the estimations of Nitta et al Solar Phys 288 241 2013a that were based on the calculations of the EUVI fulldisk digital number output In addition we studied some features of the Bstreaks in impulsive and longduration flares and demonstrate that Bstreaks in several consecutive EUVI images can be used to reconstruct a probable time history of strong farside flaresWe are grateful to the anonymous referee for constructive comments that helped us to improve the manuscript The authors thank the GOES and STEREO teams for their open data used in our study This research was supported by the Russian Foundation of Basic Research under grant 140200367 and the Ministry of Education and Science of Russian Federation under projects 8407 and 14518117047
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