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Ann. Geophys., 23, 707-721, 2005
www.ann-geophys.net/23/707/2005/
© European Geosciences Union 2005
Ionosphere dynamics over the Southern Hemisphere during the 31 March 2001 severe magnetic storm using multi-instrument measurement data
E. Yizengaw1, P. L. Dyson2, E. A. Essex2, and M. B. Moldwin1
1Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, California, USA
2CRC for Satellite System, Physics Department, La Trobe University, Bundoora, Vic 3086, Australia
Abstract. The effects of the 31 March 2001 severe magnetic storm on the Southern Hemisphere
ionosphere have been studied using ground-based and satellite
measurements. The prime goal of this comprehensive study is to track the
ionospheric response from high-to-low latitude to obtain a clear understanding
of storm-time ionospheric change. The study uses a combination of ionospheric
Total Electron Content (TEC) obtained from GPS signal group delay and phase
advance measurements, ionosonde data, and data from satellite in-situ
measurements, such as the Defense Metrological Satellite Program (DMSP),
TOPographic EXplorer (TOPEX), and solar wind data from the Advanced
Composition Explorer (ACE). A chain of Global Positioning System (GPS)
stations near the 150° E meridian has been used to give
comprehensive latitude coverage extending from the cusp to the equatorial
region. A tomographic inversion algorithm has been applied to the GPS TEC
measurements to obtain maps of the latitudinal structure of the ionospheric
during this severe magnetic storm period, enabling both the spatial and
temporal response of the ionosphere to be studied. Analysis of data from
several of the instruments indicates that a strong density enhancement
occurred at mid-latitudes at 11:00 UT on 31 March 2001 and was followed by
equatorward propagating large-scale Travelling Ionospheric Disturbances
(TIDs). The tomographic reconstruction revealed important features in
ionospheric structure, such as quasi-wave formations extending finger-like to
higher altitudes. The most pronounced ionospheric effects of the storm
occurred at high- and mid-latitudes, where strong positive disturbances
occurred during the storm main phase, followed by a long lasting negative
storm effect during the recovery phase. Relatively minor storm effects
occurred in the equatorial region.
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