Direct measurements of impulsive extreme ultraviolet and hard X-ray solar flare emission

Direct, simultaneous measurements of the 100--1030 A EUV and 15--150 keV X-ray emission during solar flares having impulse phases are reported. Time histories of the energy fluxes and flux ratios for three flares were obtained from Solrad 11 satellite data. Separation of the impulsive phase from the gradual phase of the flares provides a test of the partial precipitation model for the EUV and hard X-ray emission, with which the data are generally found to be consistent. A possible conflict with the model could be resolved by assuming that the inpulsive EUV source moves deeper into the chromosphere during the early phases of the burst