Hard X-rays and associated weak decimetric bursts

Results are presented of observations (made with the Hard X-Ray Burst Spectrometer on the SMM and with the Itapetinga antenna) that unambiguously show associations of hard X-ray bursts with RS-type III bursts between 16:46 UT and 16:52 UT on July 9, 1985. The comparison between the hard X-ray and the radio observations shows a clear association, in at least 13 cases, of the hard X-ray and the decimetric RS bursts. On the average, the X-ray peaks were delayed from the peak of the RS bursts at 1.6 Ghz by about 400 msec. It is shown that, if the time comparisons are made between the peak of the radio pulse and the start of the X-ray burst, the delays are consistent with an electron travel time with a velocity of about 0.3 c from the 800 MHz plasma level to the lower corona, assuming that the radio emission is at the second harmonic.