HR: 0800h
AN: SM51A-0266    [Abstracts]
TI: Numerical Modeling of Alfven Waves and Quasistatic Structures in the Plasmasheet Boundary Layer
AU: * Watts, J
EM: jcwatts@dartmouth.edu
AF: Dartmouth College, Thayer School of Engineering, Hanover, NH 03755, United States
AU: Lotko, W
EM: wlotko@dartmouth.edu
AF: Dartmouth College, Thayer School of Engineering, Hanover, NH 03755, United States
AU: Streltsov, A
EM: streltsov@dartmouth.edu
AF: Dartmouth College, Thayer School of Engineering, Hanover, NH 03755, United States
AB: Significant power is transmitted via Alfven waves and quasistatic current structures from the solar wind/magnetosphere dynamo to the auroral region. This study investigates the nature of the developing turbulence within downward field-aligned current in the nightside plasma sheet boundary layer, as observed by the FAST, Polar and Cluster missions. A non-linear, two-fluid, reduced MHD model for cold, collisionless plasma in dipole geometry with a reactive ionosphere is used to simulate the interaction of a large-scale, slowly-evolving field-aligned current with the ionosphere. As the field-aligned current modifies the ionospheric Pederson conductivity, medium scale (~10km) and small scale (~1 km) structures develop in regions of low conductivity. The multi-scale nature of the developing structures is explained by the presence of multiple resonators within the system. The small-scale structures, which are associated with the classical ionospheric Alfven resonator, are confined to low-altitude and experience a high growth rate. The medium-scale structures, associated with a larger resonator bounded from above by high-altitude gradients in the wave conductivity, experience a lower growth rate, but develop at a higher Pederson conductivity. In addition to the numerical results, dispersion analysis for the multi-resonator system is performed. The numerical solution of the resulting dispersion relation, when comparing growth rates and conductivity thresholds of the multiple resonators, agrees with the results of the numerical model.
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2740 Magnetospheric configuration and dynamics
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2753 Numerical modeling
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting