A COMPARISON OF TYPE-II SHOCK SPEEDS

Type II radio bursts are produced by material moving outwards in the s olar atmosphere. Their drift in frequency allows the calculation of th e radial speed with which the shock is moving - very basic information in assessing the likelihood that the shock will reach the Earth and i ts time of arrival. This paper compares the shock speeds derived from radio bursts observed by the Swept Frequency Interferometric Radiomete r (SFIR) equipment at the US Air Force Radio Solar Telescope Network ( RSTN) of observatories with those measured with the Culgoora radiospec trograph operated by IFS Radio and Space Services. The SFIR shock spee ds are found to be 1.5-3.0 times larger than the Culgoora values which are consistent with earlier results. This difference appears to origi nate from the incorrect interpretation of events as a result of the sm aller frequency range of the SFIR equipment.