Gamma-Ray Imaging of the 2003 October/November Solar Flares

Abstract

We present RHESSI imaging of three flares (2003 October 28 and 29 and November 2) in the 2.223 MeV neutron-capture gamma-ray line with angular resolution as high as 35''. Comparisons of imaged and spatially integrated fluences show that in all cases most, if not all, of the emission was confined to compact sources with size scales of tens of arcseconds or smaller that are located within the flare active region. Thus, the gamma-ray-producing ions appear to be accelerated by the flare process and not by a widespread shock driven by a fast coronal mass ejection. The 28 October event yielded the first such image to show double-footpoint gamma-ray line sources. These footpoint sources straddled the flaring loop arcade but were displaced from the corresponding 0.2-0.3 MeV electron-bremsstrahlung emission footpoints by 14'' and 17'' ± 5''. As with the previously studied 2002 July 23 event, this implies spatial differences in acceleration and/or propagation between the flare-accelerated ions and electrons.