Preflare characteristics of active regions observed in soft X-rays

✍ Scribed by S. W. Kahler

• Publisher: Springer
• Year: 1979
• Tongue: English
• Weight: 699 KB
• Volume: 62
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00155363

✦ Synopsis

X-ray images from the AS&E telescope on Skylab are used to investigate coronal conditions in solar active regions during the 20-min periods preceding the X-ray onsets of small flares. The preflare or precursor phase is defined as a phase with a characteristic length or time scale significantly different from that of the rise phase. We show that there is no observational evidence of a requirement for a coronal preflare heating phase with a time scale longer than 2 min for small flares characterized by one or two loops. In 18 out of 25 cases the flaring X-ray structure was not the brightest feature in the preflare active region. The electron densities are estimated for preflare loops.