ON NONSINUSOIDAL WAVES AT THE EARTHS MAGNETOPAUSE

We have examined ISEE 1 and 2 data during an interval of multiple magnetopause crossings along the flanks of the tail on January 22, 1978. During the event the interplanetary magnetic field was mainly northward. We found that the surface waves on the magnetopause were nonsinusoidal with steepened sunward facing surfaces. This result is consistent with observations reported for an analogous event by Chen et al. [1993]. The dawn-dusk electric field E in the low-latitude boundary layer was approximately 10 kV/R(E) which is much greater than the approximately 1 kV/R(E) dawn-dusk E field typical of the sunward convecting plasma sheet plasma. The ratio of the dawn-dusk E field in the LLBL to the dusk-dawn E in the magnetosheath was approximately 1/3. We propose that the magnetic field in the magnetosheath modulates the wave form in a way that may result in an anomalous transport of momentum across the magnetopause.