HR: 08:00h
AN: SM41B-01 INVITED     [Abstracts]
TI: Scarf Award Presentation: Magnetosphere-Ionosphere Coupling Studies of Dayside High-Latitude Transients
AU: * Murr, D L
EM: david.murr@dartmouth.edu
AF: Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755 United States
AB: Magnetosphere-ionosphere coupling studies are difficult since they (ideally) require simultaneous observations of the region of the magnetosphere generating field-aligned currents and of the ionospheric closure of those field-aligned currents. The dayside magnetosphere presents some advantages over the nightside magnetosphere with regard to these studies; the fields and plasmas in the dayside magnetosphere tend to be more ordered (dipolar) making, for example, fieldline mapping more tractable and dayside dynamics tend to be directly driven by solar wind forcing. This paper presents recent advances in the study of two classes of high-latitude dayside transients: Traveling Convection Vortices (TCVs) and Sudden Impulse (SI) events. We will show that TCVs are driven by cavities formed in the foreshock region that in turn deform the magnetopause locally. The deformations of the magnetopause drive magnetospheric plasma motions that generate field-aligned currents. TCVs are the ionospheric signature of the closure of these field-aligned currents. A similar sequence of events occurs during SI events, with the exception that they are driven by sharp solar wind pressure discontinuities in the ambient solar wind. Due to the nature of the solar wind driver, SI events are more readily modeled using existing global MHD simulations. We will show that existing MHD codes reproduce the large-scale features of these events rather well. Finally, we will investigate how the transient ionospheric flows associated with these events can cause intense frictional ion heating, a result that may explain the observed correlation between dayside ionospheric outflow and the standard deviation of the solar wind dynamic pressure.
DE: 2407 Auroral ionosphere (2704)
DE: 2409 Current systems (2708)
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2437 Ionospheric dynamics
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting