Solar wind interaction with the earth's magnetic field : I) Magnetopause and Magnetosheath

Properties of plasma and magnetic field within the magnetosheath, in the period December 1968-December 1969, are presented, as observed by the European satellite HEOS-1. Periodic motions of the magnetopause, with characteristic time of ~6 min. and ~60 min. have been detected. Three states of the magnetosheath plasma have been distinguished on the basis of different upstream conditions, characterized by: (1) low magnetosonic Mach number (M1 <3) and low B; (2) high values of MI and B and absence of upstream waves; (3) presence of upstream waves. The distribution function of proton velocities and the magnetic turbulence in the magnetosheath have been studied in connection with these three upstream situations.