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.

Characteristics of the Secular Variation and Secular Acceleration Distributions of the Main Geomagnetic Field from the CHAMP Satellite

“…This characteristic is also clear in other anomalies. Similar feature has been revealed by studying the relationship of the SV in theẊ,Ẏ andŻ distributions [4] , and this characteristic is more evident for the SA distribution when compared with each other. Nearly all the magnetic anomalies of the SA agree with this relation.…”

“…Compared the distributions of the secular variations from the POMME-4.2S , the IGRF [4] and the WMM models, we find that, although the time scales of these models are different, the intensity and the distribution of the secular variation are also different, the main areas of the strong anomaly distribution for these models agree well with each other. For example, the positive anomaly can be clearly seen in all the models.…”

Chinese Geomagnetic Reference Field 2020 by the Revised Surface Spline Method

“…Seven generations of China geomagnetic charts were published during 1960~2000 (every 10 years). These charts were generated mainly using the Taylor polynomial method [18][19][20]. After that, China geomagnetic charts have been made using the spherical cap harmonic (SCH) method [21][22][23][24][25][26][27][28][29].…”