Ionospheric effects of the solar eclipse of March 9, 1997, as deduced from GPS data

This paper presents data from first measurements of total electron content (TEC) and its gradient during the solar eclipse of March 9, 1997, obtained with the GPS-radio interferometer at Irkutsk The interferometer consists of three receivers (one Turbo-Rogue SNR-8000, and two Ashtech 2-12) located at the vertices of a triangle and spaced by about 3-5 km. The measured TEC variations are indicative of profound changes in the ion production process in the ionosphere attendant on the solar eclipse, simultaneously in a large volume of space with a radius of at height 300 km at 300 km altitude. The delay of a minimum value of TEC with respect to the maximum phase of eclipse at 300 km altitude was about 10 min, and the depression depth of TEC growth varies from 1 divided by 3x10(16)m(-2). By analyzing the data on TEC gradient variations, one is led to conclude that the depression of TEC growth during the eclipse is essentially independent of the longitude and of the latitude (within the observation ranges 52+/-6 degrees N and 104+/-11 degrees E).