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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 8
Ann. Geophys., 14, 786–793, 1996
https://doi.org/10.1007/s00585-996-0786-z
© European Geosciences Union 1996
Ann. Geophys., 14, 786–793, 1996
https://doi.org/10.1007/s00585-996-0786-z
© European Geosciences Union 1996

  31 Aug 1996

31 Aug 1996

Shear flow instabilities in the Earth's magnetotail

R. V. Reddy and G. S. Lakhina R. V. Reddy and G. S. Lakhina

Abstract. Shear flow instability is studied in the Earth's magnetotail by treating plasma as compressible. A dispersion relation is derived from the linearized MHD equations using the oscillating boundary conditions at the inner central plasma sheet/outer central plasma sheet (OCPS) interface and OCPS/plasma-sheet boundary layer (PSBL) interface, whereas the surface-mode boundary condition is used at the PSBL/lobe interface. The growth rates and the real frequencies are obtained numerically for near-Earth (∣X∣~10–15 RE) and far-Earth (∣X∣~100 RE) magnetotail parameters. The periods and wavelengths of excited modes depend sensitively on the value of plasma-sheet half thickness, L, which is taken as L=5 RE for quiet time and L=1 RE for disturbed time. The plasma-sheet region is found to be stable for constant plasma flows unless MA3>1.25, where MA3 is the Alfvén Mach number in PSBL. For near-Earth magnetotail, the excited oscillations have periods of 2–20 min (quiet time) and 0.5–4 min (disturbed time) with typical transverse wavelengths of 2–30 RE and 0.5–6.5 RE, respectively; whereas for distant magnetotail, the analysis predicts the oscillation periods of ~8–80 min for quiet periods and 2–16 min for disturbed periods.

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