Hard X-ray Observations of the Coronal Acceleration Region of a Solar Flare

The most discussed coronal hard X-ray source has been the above-the-loop-top source ob-served in the Masuda flare. We present Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations of a similar event with simultaneous microwave observations by the Nobeyama Radioheliograph. These observations clearly show that the above-the-loop-top source is produced by a non-thermal electron population with a power law distribution ex-tending up to the MeV range. To account for this extremely bright hard X-ray source in the low density corona, all electrons in the above-the-loop-top source have to be accelerated. This strongly suggests that the above-the-loop-top source is itself the electron acceleration region.