HR: 08:34h
AN: SM41B-03    [Abstracts]
TI: Direct Measurement of Ionospheric Flows Associated with a Sudden Impulse Event
AU: * Murr, D L
EM: david.murr@dartmouth.edu
AF: Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755 United States
AU: Holliday, M J
EM: Michael.J.Holliday@Dartmouth.EDU
AF: Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755 United States
AU: Shepherd, S G
EM: Simon.G.Shepherd@Dartmouth.EDU
AF: Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755 United States
AB: We present the first direct observations of high-latitude ionospheric flows associated with the passage of a Sudden Impulse (SI) event. The SI event is caused by the passage of a solar wind discontinuity during which the solar wind pressure rapidly decreased from 8 to 2 nPa. This rapid reduction in solar wind pressure deforms the magnetopause, reconfiguring the outer magnetosphere and driving field-aligned currents that close in the high-latitude ionosphere. The new observations, obtained with the SuperDARN network of coherent backscatter radars and the Sondestrom incoherent radar, allow for the direct calculation of the strength and spatial extent of SI field-aligned currents. Ground-based magnetometer observations are also employed for a complete characterization of the transient field-aligned current system. Together, these measurements provide a unique opportunity to observationally and quantitatively relate the magnetospheric generation and the ionospheric closure of a magnetospheric current system. The results are also compared with global MHD simulations of the event and similar events to examine the nature of magnetosphere-ionosphere coupling processes during this class of events.
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