An Investigation into the Variability of Heating in a Solar Active Region
Abstract
Previous studies have indicated that both steady and impulsive heating mechanisms play a role in active region heating. In this paper, we present a study of 20 hours of soft X-ray and EUV observations of solar active region NOAA AR 8731. We examine the evolution of six representative loop structures that brighten and fade first from X-ray images and subsequently from the EUV images. We determine their lifetime and the delay between their appearance in the different filters. We find that the lifetime in the EUV filters is much longer than expected for a single cooling loop. We also notice that the delay in the loops' appearance in the X-ray and EUV filters is proportional to the loop length. We model one of the loops using a hydrodynamic model with both impulsive and quasi-steady heating functions and find that neither of these simple heating functions can well reproduce the observed loop characteristics in both the X-ray and EUV images. Hence, although this active region is dominated by variable emission and the characteristics of the observed loops are qualitatively consistent with a cooling loop, the timescale of the heating in this active region remains unknown.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2006
- DOI:
- 10.1086/503196
- Bibcode:
- 2006ApJ...643.1245U
- Keywords:
-
- Sun: Corona