Effects of the August 11, 1999 total solar eclipse as deduced from total electron content measurements at the GPS network

We present the results derived from measuring fundamental parameters of the ionospheric response to the August 11, 1999 total solar eclipse. Our study is based on using the data from about 70 GPS stations located in the neighbourhood of the eclipse totality phase in Europe. The eclipse period was characterized by a low level of geomagnetic disturbance (Dst - variation from -10 to -20 nT), which alleviated significantly the problem of detecting the ionospheric response to the eclipse. Our analysis revealed a well-defined effect of a decrease (depression) of the total electron content (TEC) for all GPS stations. The delay between minimum TEC values with respect to the totality phase near the eclipse path increased gradually from 4 min in Greenwich longitude (10:40 UT, LT) to 8 min at the longitude 16 degrees (12:09 LT). The depth and duration of the TEC depression were found to be 0.2-0.3 TECU and 60 min, respectively. The results obtained in this study are in good agreement with earlier measurements and theoretical estimates.