Relationship between soft X-rays and EUV emissions during solar flares: a case study for October-November 2003

Abstract

Temporal variation in the intensity of X, M, and C class flares in soft X-rays (1-8 Å, from GOES) and in EUV (26-34 nm, from SOHO/SEM) are studied for the solar active period of October- November 2003. Although EUV is known to have impulsive and gradual emission peaks during flare, we found that the impulsive and gradual emission peaks manifest in several ways. Both the impulsive and gradual EUV peaks were found to be shifted in time with respect to the 1-8 Å soft X-ray peak. The relationship of these time delays with the strength of flare (1-8 Å peak X-ray flux) is investigated. It is found that the time delay for the EUV 26-34 nm impulsive and gradual peak shows a linear correlation with the strength of flare; however, the trend need not be similar for the flares within a single class of the flare. The relative enhancement for both impulsive and gradual EUV emission shows a linear trend with the peak X-ray flux. These results have implications on the radiation emission mechanism during the flare and the existing standard solar flare model.