Bayesian inversion for a global apparent magnetic susceptibility model based on quiet-time satellite magnetic field measurements

基于静时卫星磁场测量的全局视磁化率模型贝叶斯反演

• 批准号: 403246894
• 负责人: Dr. Monika Korte, since 10/2021
• 金额: --
• 依托单位: Sektion 2.3: Geomagnetismus
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/403246894?language=en
• 关键词: Bayesian; inversion; global; apparent; magnetic

The study of the lithospheric magnetic field is one of the main goals of the Swarm mission. Its configuration has been designed to be especially beneficial for detecting the small wavelengths of the lithospheric magnetic signal. In particular, satellites Alpha and Charlie fly side by side at a longitudinal distance of 1.4 degrees, which allows for the approximation of the East-West gradient of the magnetic field. This gradient is mainly devoid of the large scale and rapidly varying magnetic field generated by the magnetospheric ring current. Effectively removing the ring current signature from the measurements is currently one of the biggest challenges in achieving high-resolution lithospheric field models and that is why Swarm magnetic field measurements are so valuable. However, gradients cannot effectively remove the unwanted signature of magnetic fields generated by currents flowing over the polar regions, including the Disturbance Polar 2 current system, the polar electrojet and Field-Aligned Currents. In the first part of this proposal, we suggest an innovative way to deal with the polar contamination of lithospheric field models. We suggest that the combined use of SuperMAG indices and data delivered by the AMPERE satellite mission can significantly improve the data selection scheme currently employed over the polar regions, therefore allowing the construction of a magnetically quiet polar data set. This new data selection scheme will be applied on the latest Swarm and CHAMP Level-3 magnetic field data. The additional step of a principal components analysis will help to model and remove any remaining external field noise over the poles. In the second part of the project, the generated data set will be inverted for a global visible magnetization model, along the lines of the project “Structure of the magnetic lithosphere from global analysis of satellite data” from the first phase of SPP1788. Methodological innovations for this part include employing a stochastic inversion approach that delivers posterior estimation of the model uncertainties. In the third part of the project, the magnetization model will be converted to an apparent magnetic susceptibility model. One of the main challenges towards this step is the inherent non-uniqueness of inverting magnetic field data for the apparent susceptibility. However, recently derived equations allow for the first time, under the assumption of induced magnetization, the estimation of the null space of the magnetization and therefore of the apparent magnetic susceptibility. Magnetic susceptibility is a physical quantity of the rocks that reflects properties like age, mineral composition, temperature and pressure. In this respect, it is of direct interest to a variety of disciplines, dealing, e.g., with geology, petrology, seismology, gravity, and tectonic reconstruction studies.

研究岩石圈磁场是Swarm使命的主要目标之一。它的结构设计特别有利于探测岩石圈磁信号的小波长。特别是，卫星Alpha和Charlie以1.4度的纵向距离并排飞行，这使得磁场的东西梯度近似。这种梯度主要是缺乏大规模和快速变化的磁场所产生的磁层环电流。从测量中有效地去除环电流特征是目前实现高分辨率岩石圈场模型的最大挑战之一，这就是为什么Swarm磁场测量如此有价值。然而，梯度不能有效地去除由流过极性区域的电流产生的不需要的磁场特征，包括扰动极性2电流系统、极性电射流和场对准电流。在这个建议的第一部分，我们提出了一个创新的方法来处理岩石圈场模型的极地污染。我们建议，SuperMAG指数和数据的AMPERE卫星使命提供的组合使用可以显着改善目前采用的数据选择方案在极地地区，因此允许建设一个磁安静的极地数据集。这种新的数据选择方案将应用于最新的Swarm和CHAMP Level-3磁场数据。主成分分析的附加步骤将有助于建模和去除极点上任何剩余的外部场噪声。在该项目的第二部分，将按照SPP 1788第一阶段“从全球卫星数据分析看磁性岩石圈结构”项目的思路，沿着全球可见磁化模型反演生成的数据集。这一部分的方法创新包括采用随机反演方法，提供模型不确定性的后验估计。在项目的第三部分，磁化模型将转换为视磁化率模型。这一步骤的主要挑战之一是视磁化率反演磁场数据固有的非唯一性。然而，最近推导出的方程允许第一次，在假设的感应磁化，估计的零空间的磁化，因此的表观磁化率。 磁化率是岩石的物理量，反映了年龄，矿物成分，温度和压力等属性。在这方面，它与各种学科直接相关，例如，地质学、岩石学、地震学、重力学和构造重建研究。