HR: 0800h
AN: SM51A-1271    [Abstracts]
TI: Density Structures Produced by Nonlinear ULF Waves in the Auroral Magnetosphere-Ionosphere System
AU: * Streltsov, A V
EM: streltsov@dartmouth.edu
AF: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 United States
AU: Lotko, W
EM: william.lotko@dartmouth.edu
AF: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 United States
AB: Results from a numerical study of the nonlinear interaction between ultralow-frequency shear Alfvén waves, slow MHD waves, and the high-latitude auroral ionosphere are presented. The goal of this study is to investigate the role of magnetic field-aligned currents carried by shear Alfvén waves in the formation and spatiotemporal development of density structures in the low-altitude auroral magnetosphere and the ionosphere. Interest in this problem is motivated by ground-based radar and satellite observations of field-aligned ion flows and density cavities, extended along the ambient magnetic field and localized across it, in conjunction with discrete auroral arcs and intense field-aligned currents. The study is based on a reduced, two-fluid MHD model describing shear Alfvén and slow MHD waves in the cold, low-altitude magnetospheric plasma. Coupling between these two MHD modes occurs due to (a) the finite plasma compressibility, and (b) the nonlinear j×B term in the ion momentum equation. Another important nonlinear effect included in the model is active ionospheric boundary conditions (ionospheric feedback mechanism). Numerical simulations of the model equations have been performed in dipole magnetic field geometry with realistic parameters of the ambient plasma. Simulations show that the ionospheric feedback is one of the major mechanisms responsible for formation of intense electromagnetic and plasma structures in the ionosphere and low-altitude magnetosphere at high latitudes.
DE: 2704 Auroral phenomena (2407)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2753 Numerical modeling
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005