Hard and Soft X‐Ray Observations of Occulted and Nonocculted Solar Limb Flares

Using observations from the Y ohkoh Bragg Crystal Spectrometer (BCS), the Soft X-Ray Telescope, and the Hard X-Ray Telescope, we have examined the properties of 45 limb —ares. Twenty-eight of the —ares appear to have most or all of their footpoints occulted by the solar limb, leaving only soft X-ray emission from a looptop source visible. The remaining 17 —ares have exposed footpoints. In most obser- vational characteristics, occulted limb —ares are indistinguishable from nonocculted limb —ares. There does appear to be some evidence that the peak temperature observed in the BCS Ca XIX channel is lower by 2¨3 MK in the occulted —ares. We also see some tendency for the hard X-ray spectra averaged over the entire event to exhibit a softer spectral index in the occulted limb —ares. Most of the —ares for which it is possible to measure a peak in the Ca XIX nonthermal broadening velocity as a function of time show that the peak in the nonthermal broadening velocity occurs after the —rst signi—cant hard X-ray peak. Subject headings: Sun: —aresSun: X-rays, gamma rays