Oscillations of magnetospheric boundaries driven by IMF rotations

H. Laakso, D. H. Fairfield, M. R. Collier, H. Opgenoorth, T. -D. Phan, D. G. Sibeck, B. L. Giles, H. J. Singer, R. P. Lepping, R. P. Lin, F. S. Mozer, R. F. Pfaff, K. Tsuruda, and J. R. Wygant

Finnish Meteorological Institute, Helsinki, Finland


The arrival of the magnetic cloud on January 10, 1997, 01:05 UT, was preceded by a 12-hour interval of increased fluctuations in the IMF orientation, which drove boundary oscillations in the magnetosphere. The GEOTAIL spacecraft, initially located near the dawnside magnetopause, experienced multiple crossings of the magnetopause; at the geosynchronous distance, GOES 9 observed weak perturbations associated with these oscillations. During this time, the POLAR spacecraft encountered the dense high-latitude boundary layer, followed by several rapid encounters with the tenuous lobe. The boundary between the mantle and the lobe was observed to be thin as the crossings lasted only 30 seconds. The source of these boundary oscillations is magnetosheath pressure variations produced by rapid IMF directional changes.

Geophys. Res. Lett., 25, 3007-3010, 1998