Modeling of CHAMP satellite data according to the 3D surface spline model of geomagnetic fields*
Yan Feng♦1,2,3, Huang Ya 3, Liu Shuang 1, Li Yu-jun 1, and Jiang Yi 2
1. The College of Mathematics and Statistics, Nanjing University of Information Science & Technology, Nanjing 210044,China.
2. State Key Laboratory of Lunar and Planetary Sciences (Macau University of Science and Technology), Macau 999078,China.
3. State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, China.
Abstract：
Surface observations and CHAMP measurement data are employed to develop a three-dimensional surface spline (3DSS) model of mainland China. The magnetic field distribution at the satellite level is then demonstrated using the model obtained. The results of this model are compared and verifi ed by deriving the corresponding two (2DTY) and threedimensional (3DTY) Taylor polynomial models. Issues such as the removal of disruptive geomagnetic fi elds, the data gap between the surface and satellite levels, and boundary eff ects are carefully considered during modeling. We then focus on evaluating the modeling eff ect of the satellite data. Ten satellite points not involved in the modeling procedure are selected, and the residuals, absolute change rates, and RMSEs of these points are calculated. Results show that the distribution of the magnetic fi eld determined by the 3DSS model is highly consistent with that obtained from the IGRF12 model. Expect for component Y, the absolute change rates of other components are less than 0.5%. Specifi cally, the RMSE of Y of 3DSS is nearly 60% lower than those of 3DTY and 2DTY; the RMSE of other components of the former are also over 90% lower than those of the latter. This fi nding implies that the 3DSS model has good performance for modeling satellite data and its results are reliable. Moreover, the modeling eff ect of 3DTY is better than that of 2DTY.
2020, Vol. 17 
