HR: 1340h
AN: SA43A-1063    [Abstracts]
TI: Stormtime Measurements of Topside Ionospheric Upflow from DMSP
AU: * Coley, W R
EM: coley@utdallas.edu
AF: W. B. Hanson Center for Space Sciences University of Texas at Dallas, P.O. Box 830688, MS Fo22, Richardson, TX 75083-0688 United States
AU: Heelis, R A
EM: heelis@utdallas.edu
AF: W. B. Hanson Center for Space Sciences University of Texas at Dallas, P.O. Box 830688, MS Fo22, Richardson, TX 75083-0688 United States
AB: We have examined characteristics of the vertical ion flux of thermal O$^+$ in the topside high-latitude ionosphere before and during a number of geomagnetic storms, including the October and November, 2003 events, using measurements of the vertical ion drift and ion number density made by the DMSP F13 and F15 spacecraft. Prior to storm onset typical upward fluxes of approximately 10$^8$-10$^9$ cm$^{-2}$s$^{-1}$ are observed in the auroral zones with somewhat smaller downward fluxes in the polar caps. Immediately following storm onset upward fluxes reach and sometimes exceed 10$^{10}$ cm$^{-2}$s$^{-1}$ and are observed with vertical velocities of 500--1500 m s$^{-1}$. At the same time downward fluxes at the higher latitudes reach unusually high values of 10$^9$ cm$^{-2}$s$^{-1}$. Separately integrating the upwards and downwards fluxes over the high-latitude region (auroral zone and polar cap) for each spacecraft pass allows the observation of total upflow/downflow during the progression of a geomagnetic storm. A superposed epoch analysis of events from 1998 to 2004 reveals a pattern of sudden onset of upwards flux (averaging approximately 14 hours) with a gradually increasing and more extended period of downward flux (lasting about 24 hours). The upwards fluxes are stronger when the coincident fluctuations in the z-component of the IMF are larger.
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2435 Ionospheric disturbances
DE: 2481 Topside ionosphere
DE: 2736 Magnetosphere/ionosphere interactions
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting