Interplanetary Shock Waves from McMath Region 11976 During Its Passage in August 1972

Abstract

(J. Geophys. Res.). The August 1972 events provided an excellent opportunity for synthesizing a variety of observations in a coordinated fashion for the purpose of improving flare-shock associations, and our understanding of interplanetary shock propagation and solar wind interaction with planets and comets. These observations included the usual sudden commencements of magnetic storms at Earth; preliminary shock data from Heos-2, Prognoz-1 and Prognoz-2 (at Earth) and the radially-aligned Pioneers 9 (0.77 AU) and 10 (2.2 AU) located about 45° east of the Sun–Earth axis; solar radio types II and IV (as reported in World Data Center A's UAG Report 28, 1973, and this Symposium); discrete radio source scintillations in the solar wind; and the more speculative ideas regarding the solar wind's interaction with planets and comets. In the last case, Jupiter and Comet P/Schwassmann-Wachmann I exhibited non-Io-associated radio emission and a brightness increase, respectively, as a possible result of shock waves from the flare and/or coronal ejection activity initiated on 1972 June 15. During the August events, Comet P/Giacobini-Zinner exhibited statistically-significant sudden brightness decrease following its perihelion on 1972 August 4 at 1 AU approximately 57° west of the Sun–Earth axis.