The daily variations of Doppler frequency shift of ionospheric signal on middle-latitude radio lines

Doppler frequency shift (DFS) analyses of middle-latitude radio line signals during different seasons and for different geomagnetic conditions are presented in this work. It is shown; that during quiet geomagnetic conditions the range of DFS variations is the order of 0.1 Hz in the day time and 1-2 Hz during sunset and sunrise. The range of DFS variations during autumn and winter seasons is larger than during summer. The results of simultaneous measurements on two radio lines have been analyzed. One of them is N-S oriented, the other is E-W oriented. The range of DFS variations increases for N-S oriented radio line. The periods of variations with the maximal amplitude has been estimated. These periods are 10-80 min. Such periods are typical for internal gravity waves at ionospheric heights. The DFS variations during geomagnetic storm have been analyzed. Increase of variation range, especially on N-S oriented radio line is observed. The correlation analysis of DFS and indices of geomagnetic activity has been carried out. The correlation coefficient for average values of DFS and Kp indices is −0.55, the correlation coefficient for DFS variations and Kp indices is 0.65. Features of DFS variations during solar eclipse on March, 29th 2006 have been analyzed. On a radio line which crosses a track of total solar eclipse the increase of DFS variations range during an eclipse has been observed.