A coronal thick-target interpretation of two hard X-ray loop events

Veronig, A.M. and Brown, J.C. (2004) A coronal thick-target interpretation of two hard X-ray loop events. Astrophysical Journal, 603(2), L117-L120.

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 greater than or similar 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.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Brown, Professor John
• Authors: Veronig, A.M., and Brown, J.C.
• Subjects: Q Science > QB Astronomy; Q Science > QC Physics
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Astrophysical Journal
• ISSN: 0004-637X