Magnetic field structures of hard X-ray flares observed by HINOTORI spacecraft.

The magnetic field structure of five flares observed by HINOTORI spacecraft is studied. The double source structure of impulsive flares indicates hard X-ray emission from the two footpoints of a flaring loop. The potential field computation, however, does not reproduce a loop connecting the two sources, implying that the magnetic field could be in a highly sheared configuration. Gradual flares are characterized by hard X-ray sources located in the corona, 20,000 to 40,000 km above the photosphere. The potential field modeling is found to give a reasonable fitting in this type of flare, and the hard X-ray sources are located at the top of the magnetic loop or arcade, as is expected in the thick-target trap model of hard X-ray bursts.