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), Skylab^2–4, Solar Maximum Mission⁵ and currently Solwind^6,7 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.