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Stabilization of the Kelvin‐Helmholtz instability by the transverse magnetic field in the Magnetosphere‐Ionosphere Coupling System
Author(s) -
Miura Akira
Publication year - 1996
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/96gl00598
Subject(s) - physics , magnetosphere , instability , field line , ionosphere , magnetohydrodynamics , magnetic field , geophysics , joule heating , electric field , coupling (piping) , mechanics , quantum mechanics , mechanical engineering , engineering
A sheared flow equilibrium in the magnetosphere‐ionosphere (M‐I) coupling system and its stability against the Kelvin‐Helmholtz (K‐H) instability are investigated within the ideal MHD by using a box‐shaped magnetospheric model. Without forcing, the unperturbed transverse (convection) electric field responsible for the E × B drift declines exponentially with time due to the ionospheric Joule dissipation and the decay (e‐folding) time is larger than one‐half of the Alfvén bounce period. The restoring force due to the line bending associated with the transverse magnetic field is responsible for the existence of a critical height‐integrated Pedersen conductivity Σ Pc ∼(µ o V A ) −1 , where V A is the average Alfvén velocity along the field line, above which the K‐H instability in the magnetosphere is suppressed completely.