High spectral resolution, high sensitivity microwave and associated hard X-ray bursts

We have carried out mm-wavelength (18 – 23) GHz observations of solar bursts in June 1989, in Brazil. Nine of the bursts were observed simultaneously with the Hard X-ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM). The Owens Valley Radio Observatory (OVRO) observed five of these events from 1 to 18 GHz. To date, we have analyzed six of these events and the preliminary results are: (i) The turnover frequency of all of these bursts were in the frequency range of 7 – 11 GHz and the radio spectral index ranged from −0.3 to −5.3; (ii) In three bursts, dominant features of high energy (≥ 200 keV) X-rays coincided in time with mm-wavelength peaks, suggesting that the high energy electrons are responsible for the mm-wavelength emission.