正则化对地球主磁场建模的影响  

The influence of regularization on the geomagnetic core field modeling

作　　者：许钜源 林玉峰 张可可 Xu Juyuan;Lin Yufeng;Zhang Keke(Department of Earth and Space Sciences,Southern University of Science and Technology,Shenzhen 518000,China;Macao Institute of Space Technology and Application,Macao University of Science and Technology,Macao 999078,China)

机构地区：[1]南方科技大学地球与空间科学系,深圳518000 [2]澳门科技大学澳门空间技术与应用研究院,中国澳门999078

出　　处：《地球与行星物理论评（中英文）》2024年第6期719-732,共14页Reviews of Geophysics and Planetary Physics

基　　金：国家自然科学基金资助项目(12250012,42250101);广东省“珠江人才计划”(2019QN01X189)。

摘　　要：地球主磁场是在液态外核中通过发电机作用产生的.通过地磁卫星和地磁台站的观测数据约束,能够构建地球主磁场随时空变化的磁场模型.由于观测数据的时间和空间分辨率有限以及模型参数化的不完备,地磁场建模的反演问题存在多解性.因此,需要在建模过程中加入基于先验信息的正则化约束来缓解反演的非唯一性问题.对于主磁场而言,建模反演的非唯一性主要体现在主磁场随时间的变化上.研究正则化对主磁场建模的影响,可以帮助我们构建更加真实可靠的主磁场模型,特别是如何通过正则化对主磁场长期变化中的虚假时间变化进行压制.本研究基于CHAOS建模理论的框架,构建了一系列不同正则化参数约束的地球主磁场模型,探究正则化对于主磁场建模结果的影响.本文研究结果表明,在完全基于卫星数据的主磁场建模中,加入主磁场正则化约束是必要的.比较主磁场对时间三阶导数的正则化强度不同的模型结果表明,适当强度的三阶导数正则化可以有效压制由于模型对观测数据的过拟合产生的虚假信号,但过强则会降低小尺度长期变化的时间分辨率.Earth's magnetic field is generated through the dynamo action in the liquid outer core.Using observational data from geomagnetic satellites and observatories,we can construct geomagnetic models that describe spatial and temporal variations of the core field.Due to the limited temporal and spatial resolution of observations and incomplete parameterization of the model,the inversion problem of geomagnetic field modeling is non-unique.Therefore,we need to incorporate regularization constraints based on prior information to alleviate the non-uniqueness of the inversion problem for geomagnetic modeling.For the core field,the non-uniqueness of modeling inversion manifests in the temporal variations of the field.Studies on the influence of regularization can help us build more reliable core field models,especially on how to suppress artificial secular variations through regularizations.In this study,we construct a series of models based on different regularization parameters within the framework of CHAOS modeling to explore the impact of regularization on the core field modeling.Our results indicate that it is necessary to use regularization constraints for the core field modeling based solely on satellite data.By comparing models with different regularization intensities of the third time derivative of the core field,we show that regularization of the third time derivative with appropriate intensity can effectively suppress artificial signals caused by overfitting of the model to observational data.However,too strong regularizations will reduce the temporal resolu-tion of small-scale secular variations.

关 键 词：地磁场建模 长期变化 正则化 

分 类 号：P318[天文地球—固体地球物理学]