Dynamic Processes at the Outer Boundary of the Magnetosphere, Including Coupling to the Ionosphere.

摘要

Three numerical models relevant to the Earth's low-latitude boundary layer (LLBL) and its coupling to the dayside auroral ionosphere have been developed: (1) A self-consistent steady state model of the equatorial portion of the LLBL, located immediately Earthward of the Magnetopause, in which dense plasma of magnetosheath origin flows in the antisolar (tailward) direction across closed geomagnetic field lines; (2) A self-consistent model of the narrow layers that connect the equatorial LLBL to the northern and southern ionispheres. In these layer inertia, pressure, and viscous forces are negligible so that the field configuration must be force free; (3) A three-dimensional time-dependent simulation model of Kelvin-Helmholtz (KH) instability in the LLBL, including the effect of parabolic field lines with different curvature in different parts of the layer. The simulations indicate that the KH instability can be severely suppressed by this curved field geometry. Then the instability does develop, it leads to three-dimensional vortex/current structures that may be related to auroral bright spots. In addition, the properties of the resistive tearing mode instability at the subsolar magnetopause have been investigated theoretically, the principal new element being the presence of stagnation point flow in the unperturbed equilibrium and also viscosity.