Data fitting and modeling of regional geomagnetic field
Feng Yan1,2, Sun Han3, and Jiang Yong1
1. The College of Mathematics and Statistics, Nanjing University of Information Science & Technology, Nanjing 210044, China.
2. Sate Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100080, China.
3. Remote Sensing Application and Experiment Station of National Satellite Meteorological Center/Guangxi Meteorological Disaster Mitigation Institute, Nanning 530022, China.
Abstract：
The selection of the truncation level (TL) and the control of boundary effect (BE) are critical in regional geomagnetic field models that are based on data fitting. We combine Taylor and Legendre polynomials to model geomagnetic data over mainland China for years 1960, 1970, 1990, and 2000. To tackle the TL and BE problems, we first determine the range of TL by calculating the root-mean-square error (RMSE) of the models. Next, we determine the optimum TL using the Akaike information criterion (AIC) and the normalized root-mean-square error (NRMSE). We use the regional anomaly addition (RAA) and the uniform addition (UA) method to add supplementary point outside the national boundary, and find that the intensities of extreme points gradually decrease and stabilize. The UA method better controls BEs over China, whereas the RAA method does a better job at smaller scales. In summary, we rely on a three-step method to determine the optimum TL and propose criteria to determine the optimum number of supplementary points.
Feng Yan,Sun Han,Jiang Yong. Data fitting and modeling of regional geomagnetic field[J]. APPLIED GEOPHYSICS, 2015, 12(3): 303-316.
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2015, Vol. 12 
