HR: 09:00h
AN: SM11B-05    [PDF]
TI: Transport of Angular Momentum in the Magnetosphere of Jupiter
AU: * Vasyli\=unas, V M
EM: vasyliunas@linmpi.mpg.de
AF: Max-Planck-Institut f\"ur Aeronomie, Max-Planck-Str. 2, Katlenburg-Lindau, 37191 Germany
AB: The subcorotation of plasma in the Jovian magnetosphere is attracting renewed interest. In Hill's classical theory, as plasma injected deep within the magnetosphere is transported outward, corotation can only be maintained as long as Birkeland currents supply sufficient angular momentum from the ionosphere and atmosphere. These Birkeland currents are now widely viewed as primarily responsible for the main auroral emissions at Jupiter. Mathematical models for calculating the radial profiles of mean angular velocity and associated Birkeland currents have been developed by Hill, Cowley and coworkers, and others. In all these models, angular momentum is assumed to be simply convected outward by a (zonally averaged) mean flow. The dependence of angular velocity on radial distance is then determined (given a model of the magnetic field and of the ionospheric conductance) by a first-order differential equation (Hill-Pontius equation), subject to the single boundary condition of corotation at the inner boundary. In the region where the magnetic field lines are closed, however, there can be no mean MHD outflow, and the outward transport must be described as a diffusion process, averaging over inward and outward flows. Here I apply the mathematical description of diffusion, familiar from mass transport, to angular momentum transport. The Hill-Pontius equation generalizes to a differential equation of second order (thus requiring an additional boundary condition), which in the limit of long acceleration time reduces to a diffusion equation for flux tube content of angular momentum, of the same form and with the same diffusion coefficient as the equation for flux tube mass content. Physical implications and simple examples of solutions will be discussed.
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2756 Planetary magnetospheres (5443, 5737, 6030)
DE: 2760 Plasma convection
DE: 5737 Magnetospheres (2756)
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting