The Diurnal Variation of Geo‐Electric Field Along the Longitude and Latitude Chains in China Mainland

AbstractThis paper studied the time and frequency characteristics of the geo‐electric field diurnal variation along two longitude chains and two latitude chains in China mainland, using the data of geo‐electric field observed at 37 stations along the chains. The following significant results are obtained. The diurnal variation at most stations appears as semi‐diurnal waves twice a day, near before and after the noon; in descending order of the FFT amplitude spectrums, the main periods of the diurnal variation are 12.4 h/12 h, 8 h, 24 h, etc., which are in accordance with the periods of the tidal harmonic components; the diurnal variation changes with latitude as the wave crest‐to‐trough amplitude gradually becomes bigger/smaller with reduced/increased latitude of the station, and also varies with longitude as the phase difference agrees with the local‐time difference between the stations along the same latitude. Furthermore, the amplitude of the diurnal variation is related with the Loyd season, which reduces orderly in J‐, E‐ and D‐seasons. The possible reasons which cause the main periodic components of the diurnal variation have been discussed, as a result, it is believed that the variation of the ground eddy current intensity caused by lunisolar tidal forces and the space electromagnetic activity aroused by the solar wind jointly produce the semi‐diurnal period components of the geo‐electric diurnal variation.