We have analysed 64 flares observed with GOES and RHESSI in the 3.1 ? 24.8 keV band (0.5 ? 4 ?). Flares were randomly chosen to represent different GOES classes, between B1 and M6. RHESSI was used to image the flaring region on the surface of the Sun. We derived the spatial area of the flare on the surface of the Sun from the imaging observations, scaled it dimensionally to volume, and used the spectroscopically derived emission measure to obtain several flare parameters. We experimented with several imaging methods and selected the use of 50% maximum image photon flux contours to define the flare area (F 50%). Most of the flares showed a single spherical loop-top source. The volume measurement for V, temperature T, and electron density N produced power indices that showed no correlation within the boundaries of error. Larger flares by loop-top source volume are thus neither hotter nor denser. The background-subtracted GOES flux ? RHESSI Total Emission Measure (TEM RHESSI) and TEM GOES ? TEM RHESSI dependencies were in agreement with the instrument characteristics and earlier studies. Nonthermal flux was noticed to increase with thermal energy and TEM, which can be said to agree with the ?Big Flare Syndrome,? with nonthermal photon flux being considered as one flare manifestation.
Authors: Mikko Vaananen and Silja Pohjolainen
Publication Status: published electronically
Last Modified: 2007-05-09 12:35