Geomagnetic Gradient Study Of China And Neighboring Areas Based On SWARM Satellite Magnetic Measurement

Based on the Swarm satellites data during 2013-2017,we have calculated the north-south(NS)gradients,east-west(EW)gradients and vertical gradients of four geomagnetic components,such as the north magnetic element X,east component Y,vertical element Z and geomagnetic intensity F.This paper analyze the distribution of geomagnetic gradients in the global and Chinese regions.According to the SIFM model and the CHAOS-6 model,the geomagnetic model gradient maps of the global and China and neighboring regions are calculated and plotted,and the model gradients are compared with the Swarm satellite measured gradients.The similarities and differences between the two kinds of gradients are analyzed.The main results are as follows:The distribution characteristics of the Swarm satellite magnetic gradient.On a global scale,the features of the NS gradient are as follows:?FNs is positive in the northern hemisphere and negative in the southern hemisphere;?Xns is negative in most parts of the northern hemisphere;and A Yns has four anomalous centers;?Zns has 4 abnormal regions.The vertical gradient distribution is characterized by a distinct center of anomaly in the distribution of F?F?and ?AZ?.In China and its adjacent areas,?Xns has a negative anomaly center,? Yns is roughly north-south trend,?Zns turns east-west trend,and ?FNS has positive anomaly.The zero-value line of ?ZEW passes through Xinjiang and shows a trend of increasing along the southeast.?Z?and ?F?appear east-west and there values all positive,and the closer to the equator,the larger the value:?X_present the east-west distributionComparison of Swarm satellite magnetic gradient and global magnetic field model SIFM.CHAOS-6 model gradient.On a global scale,the satellite magnetic survey is consistent with the model calculated NS gradient spatial distribution,but the numerical difference is large;the vertical component has a similar distribution of the east-west gradient ZEw,and ? ZEwm(subscript M is the model gradient).The numerical difference is large;in the vertical gradient.the satellite measurements of the three elements X,Z and F are similar to the spatial distribution characteristics of the model gradient.In China and its adjacent regions,the spatial distribution of NS gradients of the four geomagnetic elements studied is basically the same;both ?Xns and model ?Xnsm have negative anomaly regions;the zero-value line of ?Yns is near 115° E,and? Ynsm is close to 97° E;the distribution of the vertical gradients ?X,?Z and ?F obtained by the satellite and the models are similar.