Electromagnetic Response Function for the Period of 27 Day in the Chinese Region

Abstract

Using the “Sompi” spectral analysis method, the daily mean values for 14 geomagnetic observatories in the Chinese region have been analysed for determining the magnitudes and phases of the P₁⁰ response corresponding to the period of 27d. The contour maps for the apparent depth h and the conductivity σ of the perfect substitude conductor were then plotted for this period. The results indicate that the lateral changes of σ and h are not very large in the central and northern Chinese region, where the average value of h is around 950km and the average value of σ is around 1.0S/m. These values are basically in agreement with those obtained by SCHULTZ and LARSEN (1987) for the neighbouring observatories of China—Irkutsk, Memambetsu, Kakioka and Kanoya. In the southern Chinese observatories we have found lower values of σ and larger values of h. It is not clear whether this characteristic feature in the southern Chinese region is due to the influence of the highly conducting ocean or the equatorial electrojet current or the poor signal to noise ratio in the data of Z magnetic component.