Regional Features of the Secular Variation of the Geomagnetic Field in China Area

Abstract

On the basis of the magnetic survey data during 1998-2001, the China Geomagnetic Reference Field Secular Variation model for 2000, CGRF-SV2000, is established. The model shows a slow and smooth variation of the magnetic field in China area. The unsigned average annual rates are 12.2nT/a, 8.2nT/a, 43.8nT/a, 11.8nT/a, 0.96'/a, 2.99'/a and 22.4nT/a for seven elements X,Y,Z,H,D,I and F, respectively. These rates are less than the global rates of IGRF by 1/3 to 1/2. The variations of different elements show an unified SV pattern in China: the north geomagnetic pole is moving to China, or China is moving toward high latitude at a rate 3'/a. In addition, the variation of declination D shows that the contrast of D between Eastern and Western China is enhanced. As a comparison and test, the 8-th generation of the International Geomagnetic Reference Field (IGRF) models is analyzed. The global SV estimated by IGRF models shows similar characteristics compared with CGRF-SV2000, although the annual rates of IGRF-SV are greater than those of CGRF-SV, and some regional (or local) anomalies are noted.