Measurements at GPS ground stations of the International GPS Service (IGS)
have been used to derive the total electron content (TEC) of the ionosphere
over Europe and over three North American stations for the 6-11 January 19
97 storm event. The derived TEC data indicate large deviations from the ave
rage behaviour especially at high latitudes on the night-side:early morning
longitude sector.
The high-latitude perturbation causes a well-pronounced positive phase on t
he day-side sector over Europe.
Both meridional winds as well as transient electric fields are assumed to c
ontribute to the signature of the ionospheric perturbation propagating from
high to low latitudes. The observations indicate a subsequent enhanced pla
sma loss which is probably due to the equatorward expansion of storm induce
d composition changes. (C) 1999 Elsevier Science Ltd. All rights reserved.