基于张衡一号卫星数据的中国区域岩石圈磁场球冠谐分析

张衡一号卫星于2018年2月成功发射升空, 卫星上搭载有测量地磁场的高精度磁强计, 包括标量和矢量磁力仪.本文基于张衡一号卫星2018年3月—2022年5月的标量磁测数据, 利用球冠谐分析进行中国区域的岩石圈磁场建模工作.首先选取地磁活动平静时期(Kp≤2o)的夜侧数据, 来减少外源场的影响; 然后, 利用CHAOS-7模型计算值去除主磁场和外源场, 得到岩石圈磁异常值, 再利用球冠谐分析进行中国区域的地磁场建模, 得到最大阶数为53.17(对应地表波长为752 km)的球冠谐模型.该模型可以明显揭示出中国及邻区的主要岩石圈磁异常, 包括位于我国塔里木盆地、四川盆地、松辽盆地和境外的贝加尔湖、孟加拉盆地附近的高值磁异常, 以及位于青藏高原南部的东西向低值磁异常.为了对模型结果进行进一步分析, 将其与Swarm-A卫星数据球冠谐建模结果和CHAOS-7球谐模型结果在不同高度上进行了对比, 主要磁异常的分布基本一致, 而且在向下延拓到100 km高度时, 本文的模型也能够提供比较稳定的结果, 但是在幅值和磁异常形态细节上存在一定差异.

The spherical cap harmonic model of lithospheric magnetic anomaly in Chinese region derived from CSES satellite data

The China Seismo-Electromagnetic Satellite (CSES) was launched successfully in February 2018. It is China's first satellite to measure geophysical fields with scientific goals in both space and solid earth physics. In this work, we used the CSES scalar magnetic data to derive a regional lithospheric magnetic field model in Chinese region by spherical cap harmonic analysis. The night-side data from March 2018 to May 2022 under quiet space weather condition (Kp≤2o) were selected. Then the core and external field were removed by CHAOS-7 model. The obtained lithospheric magnetic anomaly was used to produce the spherical cap harmonic model in Chinese region with a maximum degree to 53.17, corresponding to wavelength at the Earth's surface of 752 km. This model can clearly reveal the long-wavelength magnetic anomalies in China and surrounding regions: the magnetic high anomalies over Tarim basin, Sichuan basin, Songliao basin, Baikal Lake and Bengal basin, and the magnetic low anomaly in southern Himalayan-Tibetan plateau. It is compared to the spherical cap harmonic model using Swarm-A satellite data and the CHAOS-7 spherical harmonic model, which indicates that they are generally consistent with small differences in details of amplitude and spatial distribution, and the CSES model is still reliable by downward continuation to 100 km altitude.