Study of white-light flares observed by Hinode

作     者：Hai-Min Wang 

作者机构：Space Weather Research Lab Center for Solar Terrestrial Research New Jersey Institute of Technology Newark NJ 07102 USA 

出 版 物：《Chinese Journal of Astronomy and Astrophysics》 (中国天文和天体物理学报（英文版）)

年 卷 期：2009年第9卷第2期

页      面：127-132页

核心收录：

学科分类：07[理学] 08[工学] 070401[理学-天体物理] 081304[工学-建筑技术科学] 0813[工学-建筑学] 0704[理学-天文学] 

基　　金：The work is sup-ported by NSF under grant ATM 07-45744 NASA under grants NNX07AH78G, NNX08AJ23Gand NNX08AQ90G 

主　　题：Sun activity - Sun flares - Sun magnetic fields 

摘      要：White-light flares are considered to be the most energetic flaring events that are observable in the optical broad-band continuum of the solar spectrum. They have not been commonly observed. Observations of white-light flares with sub-arcsecond resolution have been very rare. The continuous high resolution observations of Hinode provide a unique opportunity to systematically study the white-light flares with a spatial resolution around 0.2 arcsec. We surveyed all the flares above GOES magnitude C5.0 since the launch of Hinode in 2006 October. 13 of these kinds of flares were covered by the Hinode G-band observations. We analyzed the peak contrasts and equivalent areas （calculated via integrated excess emission contrast） of these flares as a function of the GOES X-ray flux, and found that the cut-off visibility is likely around M1 flares under the observing limit of Hinode. Many other observational and physical factors should affect the visibility of white-light flares; as the observing conditions are improved, smaller flares are likely to have detectable white-light emissions. We are cautious that this limiting visibility is an overestimate, because G-band observations contain emissions from the upper atmosphere. Among the 13 events analyzed, only the M8.7 flare of 2007 June 4 had near-simultaneous observations in both the G-band and the blue continuum. The blue continuum had a peak contrast of 94% vs. 175% in G-band for this event. The equivalent area in the blue continuum is an order of magnitude lower than that in the G-band. Very recently, Jess et al. studied a C2.0 flare with a peak contrast of 300% in the blue continuum. Compared to the events presented in this letter, that event is probably an unusual white-light flare： a very small kernel with a large contrast that can be detected in high resolution observations.