Instantaneous response of the ionosphere to a sudden commencement of the   strong magnetic storm of April 6, 2000
  We developed a new technology for global detection of atmospheric disturbances, on the basis of phase measurements of the total electron content (TEC) using an international GPS networks. Temporal dependencies of TEC are obtained for a set of spaced receivers of the GPS network simultaneously for the entire set of visible satellites. These series are subjected to filtering in the selected range of oscillation periods using known algorithms for spatio-temporal analysis of signals. An "instantaneous" ionospheric response to the sudden commencement of a strong magnetic storm of April 6, 2000 was detected. On the dayside of the Earth the largest value of the net response amplitude was found to be of order 0.8*10^16 m^-2 (1--2 % of the background TEC value), and the delay with respect to the SC in mid-latitudes was about 200 s. In higher latitudes the delay goes as long as 15 min. On the nightside these values are 0.2*10^16 m^-2 and 30 min, respectively. The velocity of the traveling disturbance from the middle to high latitudes on the dayside as well as from the dayside to the nightside was about 10-20 km/s. 
E. L. Afraimovich, E. A. Kosogorov, L. A. Leonovich, O. S. Lesyuta, I.   I. Ushakov (Institute of Solar-Terrestrial Physics,...