“…The indirect dependence of the tail characteristics on the solar wind through the substorm process has been shown by many authors (Heppner et al, 1967, Lazarus et al, 1968, Hones et al, 1968, Hones 1969, Akasofu et al, 1970, Hones et al, 1970, Fairfield and Ness 1970, Brody and Holzer 1970, Meng and Anderson 1970, Camidge Lnd Rostoker 1970. We have shown in this paper that the tail characteristics depend also directly on the interplanetary field and that the tail at 30 Re reacts immediately to the changes in the motion electric field 22 (VxB) associated with changes in the solar wind magnetic field orientation.…”