Fe XIX observations of active region brightenings in the corona
Max-Planck Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany e-mail: firstname.lastname@example.org
Accepted: 15 May 2006
Small flarelike brightenings seen in the hot flare line, , by the spectrometer SUMER on SOHO are analysed. We observe active region coronae about 30 Mm off the limb of the Sun for a period of several days. Brightenings are observed with a frequency per hour and their lifetimes range from min, with an average of about 25 min. The measured size of the events along the spectrometer slit range from Mm, but most are around 7 Mm. Like soft X-ray active region transient brightenings, they range in estimated thermal energy from 1026 to 1029 erg with a power law index of 1.7 to 1.8, beyond 1027 erg. We conclude that they are the coronal parts of loops heated to >6 MK by soft X-ray microflares.
Key words: Sun: activity / Sun: corona / Sun: flares / Sun: UV radiation / Sun: X-rays, gamma rays
© ESO, 2006