VHF-long-distance-propagation by auroral backscatter

Extended investigations of VHF auroral backscatter communications was carried out in Europe in the years from 1958 to 1969 using the results of the observation of beacon transmitters and of an extended network of amateur stations convering big parts of Europe. The frequency of occurrence of this kind of propagation as a function of geomagnetic activity and location, time of day, season and sunspot cycle is shown by several diagrams. The physical reasons for this backscatter phenomenon and especially for the typical daily variation in the frequency of occurrence are discussed. Proposals are made for special arrangements to suppress this kind of propagation in case of frequency sharing.