Characteristics of the Spatial Distribution and Secular Variation of Gradients of the Main Geomagnetic Field

Abstract

AbstractBased on the GUFM1 and IGRF11 models, we calculate the horizontal and vertical gradients of three geomagnetic components during 1590–2010, i.e., the geomagnetic intensity F, the horizontal component H and the declination I. Their spatial distribution and secular variation are also analyzed. The results suggest that the spatial distributions of the vertical gradients of the intensity F and the horizontal component H are similar to that of their main field. However, the horizontal gradients of F and H and the gradients of I in three directions are quite different in their field distributions. The gradients of H in three directions clearly show the position of the South magnetic pole. The secular variation of the gradients indicates that the anomaly foci are drifting slowly in the northern hemisphere, but fast in the southern hemisphere. The vertical gradient of I is a negative anomaly in the middle Pacific, and the positive anomaly in the neighboring region tends to rotate around this negative one. The turning of the gradient anomaly belt near the equator of 60°W is caused by the movement of the Indian anomaly toward the Africa.