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Ann. Geophys., 20, 655-660, 2002
www.ann-geophys.net/20/655/2002/
© European Geosciences Union 2002
The structure of mid- and high-latitude ionosphere during September 1999 storm event obtained from GPS observations
I. I. Shagimuratov1, L. Baran2, P. Wielgosz2, and G. A. Yakimova1
1WD IZMIRAN, Kaliningrad, Russia
2Institute of Geodesy, University of Warmia and Mazury in Olsztyn, Poland
Correspondence to: L. W. Baran (baran@uwm.edu.pl)
Abstract. TEC data, obtained from
over 60 GPS stations, were used to study the ionospheric effects of the 12–16
September 1999 magnetic storm over Europe. The spatial and temporal changes of
the ionosphere were analysed as a time series of TEC maps, which present 15 min
averages of TEC. The data set consisting of GPS observations, collected by a
dense network of European stations, with sampling rate of 30 s, enable the
creation of TEC maps with high spatial and temporal resolution. The storm
included the positive as well as the negative phase. The positive phase took
place during the first storm day of 12 September 1999. The short-lived daytime
TEC enhancement was observed at all latitudes. The maximal enhancement reached
a factor of 1.3–1.5. On the second and third days, the negative phase of the
storm developed. The TEC decrease was registered regardless of time of the day.
The TEC depression exceeded 70% relative to quiet days. On the following days
(15 and 16 September), a significant daytime enhancement of TEC was observed
once again. The complex occurrence of the ionospheric storm was probably
related to the features of development of the magnetic storm. We found out that
during the storm the large and medium-scale irregularities developed in the
high-latitude ionosphere. The multi-stations technique, employed to create TEC
maps, was particularly successful while studying the mid-latitude ionospheric
trough. We found out that the essential changes of TEC during the storm, which
were registered at the auroral and sub-auroral ionosphere, were connected with
the effect of the trough and its dynamics, which depends on geomagnetic
activity.
Key words. Ionosphere (ionospheric
disturbances; auroral ionosphere; mid-latitude ionosphere)
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