太平洋地区地球主磁场长期变化特征的研究

研究太平洋地区主磁场的长期变化特征，对揭示该地区的“偶极子窗”的时间演变和长期变化规律有重要意义.作者使用最新的国际地磁参考场IGRF13模型资料，分析1900—2020年期间太平洋地区主磁场的长期变化特征.结果表明1900—2020年太平洋地区主磁场的空间展布符合“太平洋偶极子窗”的分布特征.该地区主磁场的长期变化在赤道以北为缓慢变化，以南则是较快变化.偶极子场成分变化缓慢，非偶极子场成分变化较快.非偶极子场的长期变化以西向漂移为主，但各分量的西漂速率有显著的差异.垂直分量（Z）和北向分量（X）的西漂速率分别为0.23°/a和0.21°/a，均接近于0.2°/a的全球非偶极子西漂速率；东向分量（Y）的西漂速率为0.17°/a，低于全球非偶极子西漂速率. Y分量的长期变化在34°N附近发生扭曲并且在北太平洋表现为缓慢东漂，这一长期变化特征可能与太平洋北部的30°N和45°N之间在核幔边界处存在的古板块的俯冲过程有关.

Secular variation characteristics of the earth's main magnetic field in the Pacific region

Studying the secular variation characteristics of the main magnetic field in the Pacific region is significance to reveal the time evolution and secular variation of the dipole window in the region. This paper uses the latest international geomagnetic reference field IGRF13 model data to analyze the secular variation characteristics of the main magnetic field in the Pacific region from 1900 to 2020. The results show that the spatial distribution of the main magnetic field in the Pacific region from 1900 to 2020 conforms to the distribution characteristics of the ‘Pacific dipole window’. The secular variation of the main magnetic field in the region is slow, north of the equator, and rapid, south of it. Dipole field components change slowly, while non-dipole field components change faster. The secular variation of non-dipole field is dominated by westward drift, but the westward drift rates of each component are significantly different. The westward drift rates of vertical component (Z) and north component (X) are 0.23°/a and 0.21°/a, respectively, which are close to the global non-dipole westward drift rate of 0.2°/a; the westward drift rate of the eastward component (Y) is 0.17°/a, which is lower than the global non-dipole westward drift rate. The secular variation of Y component is distorted near 34°N and shows a slow eastward drift in the North Pacific, which may be related to the subduction of the paleoplate at the core-mantle boundary between 30°N and 45°N in the northern Pacific.