D. G. Sibeck, R. P. Lepping, A. J. Lazarus

The Johns Hopkins University, Applied Physics Laboratory, Laurel, Maryland

Magnetosheath magnetic field lines drape about the magnetosphere. Even when the interplanetary magnetic field lies parallel to the ecliptic plane, the magnetosheath magnetic field just outside the dawn and dusk flanks of the magnetosphere is deflected far out of the ecliptic plane. We present simultaneous IMP 8 solar wind and ISEE 1/2 observations for a northern dawn ISEE 1/2 magnetopause crossing on November 6, 1977. During this crossing, ISEE 1/2 observed quasi-periodic pulses of magnetosheath-like plasma on northward magnetic field lines. The ISEE 1/2 observations were originally interpreted as evidence for strong diffusion of magnetosheath plasma across the magnetopause and the Kelvin-Helmholtz instability at the inner edge of the low-latitude boundary layer. An alternate explanation, in terms of magnetic field merging and flux transfer events, has also been advocated. We provide a third interpretation in terms of quasi-periodic magnetopause motion which causes the satellites to repeatedly exit the magnetosphere and observe draped northward magnetosheath magnetic field lines in the plasma depletion layer.

J. Geophys. Res., 95, No. A3, 2433-2440, Mar. 1990