Soft X-ray emission from active regions shortly before solar flares

Abstract

Detailed examination of the variations in the intensity of soft X-ray emission prior to many solar flares are presented. In addition, these preflare intensity variations are contrasted with the variations typically observed for the same active regions in the absence of a flare. It is shown that a 5-20 min preflare brightening phase is not typically observed. These observations are discussed in context with other complimentary investigations and theoretical models.