Study of geomagnetic secular variation in China

Using the data of the geomagnetic diurnal means during 2000 similar to 2004 at 34 observatories in China, we calculated the mean annual change rates on the quiet days and all days, and the fitting annual change rates on the quiet days. The Taylor polynomial model and the spline model of the geomagnetic secular variation in China for epoch 2000.0 similar to 2005.0 were established, based on the above annual change rates. The similarity and difference between the Taylor polynomial model, the spline model and the secular variation model of International Geomagnetic Reference Field (IGRF-SV) were analyzed and discussed. The results show that the shape and the value of the Taylor polynomial model and the spline model for the geomagnetic secular variation in China are quite consistent, and their long-term trends are also consistent with IGRF-SV. However, the geomagnetic secular variation in China has some regional characteristics.