This volume contains the review papers presented at the International Symposium on Solar-Terrestrial Physics held at the Tavrichesky Palace, Leningrad, U.S.S.R., 11-19 May 1970. The Symposium may be regarded as the most recent member of a series of inter- national symposia - for instance, the Symposium on Solar-Terrestrial Physics, Belgrade (1966), the Joint IQSY-COSPAR Symposium on Solar-Terrestrial Physics, London (1967), and the Symposium on the Physics of the Magnetosphere, Washington (1968). Like those earlier symposia, the Leningrad Symposium was sponsored by the International...