Kelvin-Helmholtz instability at the magnetospheric boundary: Dependence on the magnetosheath sonic Mach number
- Univ. of Tokyo (Japan)
It has recently been demonstrated, by means of a two-dimensional MHD simulation, that a finite thick velocity shear layer with super-Alfvenic velocity jump at the magnetospheric boundary is unstable to the Kelvin-Helmholtz (K-H) instability no matter how large the magnetosheath sonic Mach number (M{sub s}); a result suggesting that the tail flank boundary of the magnetosphere is unstable to the K-H instability. In order to investigate this consequence further, the dependence of the development of the K-H instability of M{sub s} is studied in detail. For all magnetosheath sonic Mach numbers a velocity boundary layer is formed by the instability inside of the magnetopause, and it becomes wider for a smaller magnetosheath sonic Mach number. A flow vortex is excited at the inner edge of the velocity boundary layer of all sonic Mach numbers, and the magnetopause boundary is more highly nonlinearly corrugated by the instability for a smaller sonic Mach number. The net energy and momentum flux densities into the magnetosphere are calculated just prior to the saturation stage. The anomalous viscosity by the instability decreases in the absolute magnitude with increasing M{sub s}; result suggests that the dayside (except the subsolar region) and the dawn-dusk magnetopauses, where the magnetosheath flow remains subsonic, are the most viscous parts of the boundary, although the tail flanks are also found to be viscous enough for the viscous interaction.
- OSTI ID:
- 7012637
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 97:A7; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
EARTH MAGNETOSPHERE
HELMHOLTZ INSTABILITY
MAGNETOSHEATH
MACH NUMBER
BOUNDARY LAYERS
HYDROMAGNETIC WAVES
INTERACTIONS
SHEAR
SHOCK WAVES
SOLAR WIND
VORTICES
EARTH ATMOSPHERE
INSTABILITY
LAYERS
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
SOLAR ACTIVITY
VELOCITY
661320* - Auroral
Ionospheric
& Magnetospheric Phenomena- (1992-)