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

Abstract

This 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.