Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 16, 518-527, 1998
© European Geosciences Union 1998
31 May 1998
MHD model of magnetosheath flow: comparison with AMPTE/IRM observations on 24 October, 1985
C. J. Farrugia1, H. K. Biernat2, N. V. Erkaev3, L. M. Kistler1, G. Le4, and T. Russell4 1Institute for the Study of Earth, Oceans and Space, University New Hampshire, Durham, NH 03824
2Space Research Institute, Austrian Academy of Sciences, A-8042, Graz, Austria
3Institute of Computational Modelling of the Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, 660036, Russia
4Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90032
Abstract. We compare numerical results obtained from a steady-state MHD model of solar wind flow past the terrestrial magnetosphere with documented observations made by the AMPTE/IRM spacecraft on 24 October, 1985, during an inbound crossing of the magnetosheath. Observations indicate that steady conditions prevailed during this about 4 hour-long crossing. The magnetic shear at spacecraft entry into the magnetosphere was 15°. A steady density decrease and a concomitant magnetic field pile-up were observed during the 40 min interval just preceding the magnetopause crossing. In this plasma depletion layer (1) the plasma beta dropped to values below unity; (2) the flow speed tangential to the magnetopause was enhanced; and (3) the local magnetic field and velocity vectors became increasingly more orthogonal to each other as the magnetopause was approached (Phan et al., 1994). We model parameter variations along a spacecraft orbit approximating that of AMPTE/IRM, which was at slightly southern GSE latitudes and about 1.5 h post-noon Local Time. We model the magnetopause as a tangential discontinuity, as suggested by the observations, and take as input solar wind parameters those measured by AMPTE/IRM just prior to its bow shock crossing. We find that computed field and plasma profiles across the magnetosheath and plasma depletion layer match all observations closely. Theoretical predictions on stagnation line flow near this low-shear magnetopause are confirmed by the experimental findings. Our theory does not give, and the data on this pass do not show, any localized density enhancements in the inner magnetosheath region just outside the plasma depletion layer.

Key words. Steady-state magnetosheath · Plasma depletion layer · Stagnation line flow

Citation: Farrugia, C. J., Biernat, H. K., Erkaev, N. V., Kistler, L. M., Le, G., and Russell, T.: MHD model of magnetosheath flow: comparison with AMPTE/IRM observations on 24 October, 1985, Ann. Geophys., 16, 518-527,, 1998.
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