Modelling Of The Regional Geomagnetic Field At Satellite Altitudes Based On Swarm Satellite Data

In order to establish a main magnetic field model with high precision at the satellite's level(400-520km)in China and adjacent regions,sum up to 62 208 000 Swarm satellite data are adopted,the global geomagnetic field model,CHAOS-6 model,is used to remove the crustal and external fields.Finally,2788 main field grid data,which is used to derive the 3D Surface Spline(3DSS)model at satellite's altitude over China,are obtained.Several other regional models(3D,2D Taylor(2DTY,3DTY)model,2D Surface Spline(2DSS)model)and CHAOS-6 model have been adopted to investigate over the same region.The related results are as follows:(1)Comparing the geomagnetic field distributions of the four regional models,the results show that the 3DSS,3DTY and 2DTY models have better simulation results to reflect the geomagnetic field distribution in this region except that there are small differences for the northward component X,the eastward component Y,the vertical component Z,and the total intensity F.(2)To compare with the other regional models,the 3DSS model reduces the average residuals of X,Y,Z and F of the absent points by 69%,71%,88% and 94% respectively.The rootmean-square error(RMSE)values are decreased around 65%,69%,87%,93% respectively.3DSS model reduces the average residuals of X,Y,Z and F of the absent points by 11%,76%,4% and 86% compare with CHAOS-6 model respectively.The RMSE values of Y,Z and F are around 72%,7%,83% lower respectively.In 2018.0,the RMSE value of X was about 1% higher than that of CHAOS-6 model.In 2019.0,the RMSE value of X decreased by about 69.08%.The 3DSS model has smaller errors and more stable,mainly because of its modeling principle of point interpolation and high-density and high-precision data.This model is suitable for regional space modeling,geomagnetic data calculation and small area magnetic anomaly research.(3)The average annual change rates of X,Z and F in this region from 2018.0 to 2019.0 are obtained by using the established regional model,the rates are 0.029%,0.150% and 0.100%.Using these rates,Swarm data from 2017.0 are reduced to 2018.0 and 2019.0.The average residuals and the RMSE value of the 3DSS model values are not more than 0.5%and 1%.The small error is mainly due to the high accuracy of 3DSS model and the simple distribution of X,Z,and F components in this region.The data and method can be used for the time reduction of geomagnetic data in this region in recent years,the calculation of geomagnetic data in a small area and the test of whether the data is true or false.This study does not rely on the ground station data to derive a more accurate 3DSS main field model,and the average annual change rate from 2018.0 to 2019.0 in this region was obtained and verified.Results also imply that less data height difference and high-density data distribution greatly improve the accuracy of the 3DSS model.This study is of reference value for improving the accuracy of geomagnetic field model,analyzing the spatial and temporal distribution characteristics of geomagnetic field at satellite altitudes in China and its adjacent regions,and studying regional magnetic anomalies.