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Kelvin-Helmholtz(K-H) instabilities are often observed at the
dawn-dusk flanks of the magnetopause during northward IMF
(Interplanetary magnetic field). In this thesis study, we first
derive the linear growth rate of surface wave of K-H
instablities on a tangential discontinuity(TD) under simple and
ideal conditions.We then use numerical simulation model to
study the linear growth of the K-H instabilities under more
general conditions. The K-H waves are low frequency surface
waves. They can grow and become unstable under certain
conditions. From the theoretical derivation and numerical
results, we conclude that the K-H instablity is easier to occur
at the dawn-dusk flank of the magnetopause when a surface wave
perturbation propagates nearly perpendicular to the local Earth
magnetic field. Simulation results of nonlinear developments of
K-H instabilities at dayside magnetopauseshow a large amplitude
zigzag structure of surface ave without vortex formations.The
absence of thick layer of vortex structure is due to the large
gradient of plasma density,plasma pressure, plasma beta, and
magnitude of magnetic across the dayside magnetopause.
Simulation results also indicate that field-aligned propagating
magnetic micro plusations can be generated by K-H waves at
dayside magnetopause, if surface waves produced by K-H
instablities propagate not exactly perpendicular to the local
earth's magnetic field.
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