Electromagnetic Radiation from Solar Flares

Abstract

RECENT rocket and satellite observations of 10–100 keV X-ray emission, together with ground-based observations of cm wavelength bursts, have thrown much light on the electromagnetic emission of solar flares. It is widely believed that cm wavelength emission from flares is through synchrotron radiation, while the X-ray emission is from bremsstrahlung. The correlation between the two regions of the electromagnetic spectrum has been studied in detail by Arnoldy et al.¹. It has been shown that the X-ray and the centimetric bursts are best correlated for the first events in a flare; for subsequent events they are not well correlated. This type of correlation between the two phenomena can be understood if both emissions are assumed to come from a common source. This leads to various difficulties. The alternative is that the radio and the X-ray emission come through the same energetic electrons from different layers of the solar atmosphere. But, considering the various mechanisms proposed so far to explain the emissions, the problem of correlating the two remains unresolved. We therefore propose alternative mechanisms to explain this correlation.