Regional spatiotemporal variations of a nondipole magnetic field over the Chinese mainland and neighboring regions in millennial scale
Feng Yan1,2 and Jiang Yong1
1. The College of Mathematics and Statistics, Nanjing University of Information Science & Technology, Nanjing 210044, China.
2. State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100080, China.
Abstract：
Spatiotemporal variations of the nondipole (ND) magnetic field over the Chinese mainland and neighboring regions from 10000 BC to 1990 AD were analyzed using the latest global geomagnetic models CALS10K.1b, CALS3K.4, and IGRF11. Moreover, for field sources, we investigated 2n (n = 2–10) pole ND fields and their energies. The results suggest that the study period can be divided into three. The intensity of the ND field has been mainly positive since 10000 BC and lasted almost 7500 years, then gradually decreased to negative in 2500 BC to 1500 AD, and finally sharply increased to positive. The anomaly areas of the ND field in East Asia took shape for n = 3, when the anomaly areas in East Asia were shaped into closed circles in the mainland. This suggests that the first three harmonic degrees account for most of the ND field. The energy of the ND field rapidly attenuates at the core–mantle boundary and is stable at the surface.
. Regional spatiotemporal variations of a nondipole magnetic field over the Chinese mainland and neighboring regions in millennial scale[J]. APPLIED GEOPHYSICS, 2017, 14(2): 314-321.
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2017, Vol. 14 
