Session 7E - Space and Basic.
ORAL session, Thursday morning, November 14
Majestic Ballroom, Adam's Mark
Using theory and numerical simulations, we investigate the nonlinear evolution of vortices generated by the Kelvin-Helmholtz (KH) instability of a sheared ion current in the Earth's magnetosphere. The extent of broadening of the shear flow, and the energy and enstrophe exchange between the shear flow and KH vortices, are characterized in the two-dimensional plane across the magnetic field lines. A new stationary vortex street solution is found, and two distinct phases of the nonlinear dynamics are identified. The first involves a transient phase in which burst like pulsations of the flow lead to a rapid dissipation of enstrophe. After the transient phase, an asymptotic smooth state is reached which corresponds to a periodic chain of dipolar vortices. Some effects of the KH wave form evolution arising due to the radiating field aligned current in three-dimensional geometry will be also described. The consequences of the model for the dynamics of field line resonances in the Earth's magnetosphere will be discussed.