HR: 11:15h
AN: SM21C-04    [PDF]
TI: Relationship Between Alfv\'{e}nic Aurora and Large-Scale Convection and Currents
AU: * Lotko, W
EM: wlotko@dartmouth.edu
AF: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 United States
AU: Streltsov, A
EM:
AF: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 United States
AB: While Alfv‚n-wave-induced electron precipitation and fluctuations are prevalent near the polar cap boundary and in the cusp, where the field-aligned currents tend to be irregular, isolated Alfv\'{e}nic arcs also form within slowly varying, large-scale regions of convection and field-aligned current. Is the occurrence of these isolated Alfv\'{e}nic arcs regulated by magnetotail processes or M-I coupling? Observations and theory show that the ionospheric conductivity becomes severely depleted in regions of downward field-aligned current while the associated Pedersen electric field is simultaneously enhanced. This situation creates conditions favorable to feedback instability, which develops on a time scale of a few minutes or less and releases energy into ionospheric Alfv‚n resonator oscillations that would otherwise flow into ionospheric Joule dissipation. Using numerical simulations based on a two-fluid MHD model of magnetospheric Alfv\'{e}n wave dynamics and E-region ionospheric activity, we have investigated the development of such oscillations in large-scale (of order 100-km), field-aligned current channels. The energetics of these processes are described along with diagnostics that illustrate measurements of the effect by a low-altitude, polar-orbiting satellite. Modulation of electron precipitation by IAR oscillations is also discussed.
DE: 2704 Auroral phenomena (2407)
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2752 MHD waves and instabilities
DE: 7827 Kinetic and MHD theory
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting