Southern Hemisphere ionosphere and plasmasphere response to the interplanetary 
shock event of 29-31 October 2003

E. Yizengaw, M.B. Moldwin, P.L. Dyson, T.J. Immel


We analyze the effects on the Southern Hemisphere ionosphere and plasmasphere
due to the 29-31 October 2003 geomagnetic storms (the so-called series of
Halloween storms). Solar wind data from ACE and ionospheric data from the GPS
(Global Position System) ground and LEO (Low Earth Orbit) receivers, the
TOPEX/Poseidon altimeter, the IMAGE FUV camera, and the DMSP drift meter are
used to understand the ionospheric dynamics as a function of the storm phase.
The detailed structure of the ionosphere has been obtained using tomographic
reconstruction applied to data from both ground- and space-based GPS receivers.
The tomographic approach using LEO observations of signals received from GPS
satellites above the LEOÕs horizon allows us to investigate the topside
ionospheric and plasmaspheric density distribution in more detail than can be
obtained using ground-based GPS receivers. This is because with groundbased
receivers, the higher topside ionosphere and plasmasphere contribute only a
small fraction to the total electron content (TEC) and so the measurements are
dominated by the ionospheric structure at the F2 peak. In contrast, the
Australian LEO satellite, FedSat, which has been used for this study, orbits at
800 km altitude, well above the F2 peak and hence the TEC measured is primarily
due to the upper topside ionosphere and plasmasphere. This paper presents the
tomographically reconstructed topside ionosphere and plasmasphere electron
density distributions using LEO observations. The temporal and regional maps of
TEC and the IMAGE FUV data show that the storm that commenced on 29 October
dramatically decreased the plasma density in the Southern Hemisphere middle and
high latitudes. The region remained depleted of plasma for more than 24 hours
until 31 October, when the second severe storm began. TOPEX/Poseidon data shows
a daytime localized density enhancement occurred above the middle of the Pacific
Ocean. These results show large interhemispheric and longitudinally narrow
storm-time structure in the ionosphere and topside ionosphere/plasmasphere.

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Journal of Geophysical Research, 110, A09S30, doi:10.1029/2004JA010920.