Average height of the hard X-ray footpoint sources in solar flares

Hard X-ray footpoint sources in solar flares are produced by electrons precipitating along a magnetic loop. Using the Yohkoh Flare Catalogue covering the whole Yohkoh mission period, we determined an accurate position of hard X-ray sources in many flares and then selected events containing footpoint source to derive the source height. We revealed that accelerated electrons emitting hard X-rays (13-93 keV) lose their energies within about 1000 km and the emitting region becomes dense with the increasing electron energy. We briefly show analysis and results of the height of hard X-ray emitting region.