A Coronal Thick-Target Interpretation of Two Hard X-Ray Loop Events
Abstract
We report a new class of solar flare hard X-ray (HXR) sources in which the emission is mainly in a coronal loop so dense as to be collisionally thick at electron energies up to >~50 keV. In most of the events previously reported, most of the emission is at the dense loop footpoints, although sometimes with a faint high-altitude component. HXR RHESSI data on loop dimensions and nonthermal electron parameters and GOES soft X-ray data on hot loop plasma parameters are used to model coronal thick-target physics for two ``discovery'' events (2002 April 14 [23:56 UT] and 2002 April 15 [23:05 UT]). We show that loop column densities N are consistent with (1) a nonthermal coronal thick-target interpretation of the HXR image and spectrum; (2) chromospheric evaporation by thermal conduction from the hot loop rather than by electron beam heating; and (3) the hot loop temperature being due to a balance of thick-target collisional heating and (mainly) conductive cooling.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2004
- DOI:
- 10.1086/383199
- Bibcode:
- 2004ApJ...603L.117V
- Keywords:
-
- Sun: Flares;
- Sun: X-Rays;
- Gamma Rays