Cui T.-F.,State Geophysics Observatory in Lanzhou |
Du X.-B.,State Geophysics Observatory in Lanzhou |
Du X.-B.,China Earthquake Administration |
Ye Q.,China Earthquake Networks Center |
And 10 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica)
This paper has studied the time and frequency characteristics of the geo-electric field diurnal variation along the two longitude chains and the two latitude chains, using the data of the geo-electric field observed at the 37 stations along the chains. Accordingly, the following significant results are obtained: the variation appears mainly as semi-diurnal waves twice a day at most of the stations, approximately before and after the noon; according to the big to small 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 latitude effect on diurnal variation is manifested by the amplitude changing with latitude along a longitude chain, and the longitude effect is shown as phase difference consistent with the local-time difference between the stations at 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 for 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. Source