Evidence for a Common Origin of the Electrons Responsible for the Impulsive X-Ray and Type III Radio Bursts

Observations of impulsive solar flare X-rays ≳ 10 keV made with the OGO-5 satellite are compared with ground based measurements of type III solar radio bursts in 10-580 MHz range. It is shown that the times of maxima of these two emissions, when detectable, agree within ∼ 18 s. This maximum time difference is comparable to that between the maxima of the impulsive X-ray and impulsive microwave bursts. In view of the various observational uncertainties, it is argued that the observations are consistent with the impulsive X-ray, impulsive microwave, and type III radio bursts being essentially simultaneous. The observations are also consistent with 10-100 keV electron streams being responsible for the type III emission. It is estimated that the total number of electrons ≳ 22 keV required to produce a type III burst is ≲ 10³⁴. The observations indicate that the non-thermal electron groups responsible for the impulsive X-ray, impulsive microwave, and type III radio bursts are accelerated simultaneously in essentially the same region of the solar atmosphere.