Simultaneous radio scattering and white light observations of a coronal transient

Abstract

Comprehensive observations of coronal transients have been made using the OSO 7 (ref. 1), Skylab2–4, Solar Maximum Mission5 and currently Solwind6,7 coronographs. An important question in regard to understanding these transients and their relationship to solar radio burst observations8 and in situ solar wind measurements9 is whether the shock front produced by the disturbances corresponds to the white light front. It has recently been demonstrated10 that spectral broadening measurements of monochromatic spacecraft radio signals represent a useful tool for detecting and studying shocks near the Sun. We now report that a coronal transient observed by the Solwind coronograph off the west limb of the Sun on 24 October 1979 was also seen in the spectral broadening observations of the Helios-2 2.3-GHz radio signal. A comparison of these simultaneous data suggests that in this case the shock front does not coincide with the white-light front but in fact precedes it.