Simultaneous Inversion For Mantle Conductivity And Source Field: Towards A 3-D Global Reference Model

一项研究计划将进行重建的三维变化的电导率的地幔。首先，一组最近发布的全球分布的“响应函数”将被转换成一个比以前更详细的全球尺度地幔模型。在此之后，地磁观测站时间序列数据将被分析，目的是设计新的方法来提取更高分辨率的地幔电导率视图，特别是在地球外部磁场由日（和谐波）Sq（太阳安静）磁层和电离层电流系统主导的频率下。这有望为未来的上地幔研究提供一个提高空间分辨率的框架，并改善我们对与板块构造最密切相关的地区的地球动力学的看法。科学技术优点。地幔的电导率取决于温度、成分（如铁含量）、状态（如部分熔融分数）和挥发物的存在。地幔电导率主要随深度呈放射状增加，但越来越多的证据表明，上地幔和中地幔存在显著的横向非均质性。提出了一项研究计划，该计划将显著改善这些三维变化的成像，并解释和理解全球范围横向电导率变化的地球动力学意义。地球电离层和磁层的外部电流系统（“源电流”）由太阳风活动的变化产生，反过来又诱导电流在地球内部流动。这是一种可以以电磁“响应函数”的形式提取的信号源，而电磁“响应函数”又包含有关地球内部导电分布的信息。地磁观测数据的经验正交函数分析简化了源电流配置的解释任务，提高了响应函数的质量，反演得到的响应函数可获得更高分辨率的地幔电性模型。更广泛的影响。对地球深部三维结构和物理状态的新限制对致力于了解地球动力学和进化的广大研究人员具有重要意义。共同注册的电和地震模型可以用来分离三维层析成像中的温度和成分效应，并建立与地球深部物质相关的状态方程。全球三维电导率参考模型可用于提供边界条件，以及大尺度背景，用于区域电磁研究数据的建模和反演，例如由NSF大陆动力学计划、边缘计划和Earthscope （http://www.earthscope.org/links_pubs/index.html）支持的研究。学术、政府和工业团体可以使用全球三维参考模型来解决在内部磁感应变化是噪声源的情况下数据的污染和偏差解释问题，例如，在利用卫星数据或长基线航磁数据研究地壳磁化的情况下。从地球固定参照系来看，磁层和电离层源场的改进特征将对使用卫星数据的研究人员非常有用，例如，为主场或地壳场的建模以及电离层和磁层物理学的研究提供改进的外部场校正。改进源场特性对卫星感应研究的进展至关重要。

A research program will be carried out to reconstruct the three dimensional variability of the electrical conductivity of the mantle. First, a set of recently published globally-distributed 'response functions' will be transformed into a global-scale mantle model with greater detail than previously possible. Following this, geomagnetic observatory time series data will be analyzed with the goal of devising new methods to extract an even higher resolution view of mantle conductivity, particularly at frequencies where the Earth's external magnetic field is dominated by the diurnal (and harmonic) Sq (solar-quiet) magnetospheric and ionospheric electrical current systems. This promises to provide a framework to improve the spatial resolving power for future upper mantle investigations, and to improve our view of the geodynamics of the region most closely associated with plate tectonics.Scientific and technical merit. The electrical conductivity of the mantle depends on temperature, composition (e.g. Fe content), state (e.g. partial melt fraction), and the presence of volatiles. Mantle conductivity primarily increases radially with depth, but a growing body of evidence indicates there is significant lateral heterogeneity in the upper and mid-mantle. A research program is proposed that will lead to significant improvements in imaging these 3-d variations, and in interpreting and understanding the geodynamic significance of global scale lateral conductivity variations. External electrical current systems in the Earth's ionosphere and magnetosphere ("source currents"), generated by variations in solar wind activity, in turn induce electrical current to flow in the Earth's interior. This is a source of signal that may be extracted in the form of electromagnetic 'response functions', which in turn contain information about the distribution of electrical conduction within the Earth's interior. Empirical orthogonal function analysis of geomagnetic observatory data simplifies the task of interpreting the configuration of the source currents, and improves the quality of the resulting response functions, which are inverted to obtain a higher resolution model of the mantle's electrical properties.Broader impacts. New constraints on the 3-d structure and physical state of the Earth's deep interior are of great importance to the broad community of researchers working to understand the dynamics and evolution of the Earth. Co-registered electrical and seismic models can be used to separate temperature and compositional effects in 3-d tomographic images, and to develop equations of state relevant to deep Earth materials. A global 3-d conductivity reference model can be used to provide boundary conditions, as well as large scale context, for modeling and inversion of data from regional electromagnetic studies, such as those supported by the NSF Continental Dynamics Program, the Margins Program, and Earthscope (http://www.earthscope.org/links_pubs/index.html). A global 3-d reference model can be used by academic, government and industry groups to address the problem of contamination and biased interpretation of data in situations where the induced internal magnetic variations are a source of noise, e.g., in studies of crustal magnetization with satellite data, or long-baseline aeromagnetic data. The improved characterization of magnetospheric and ionospheric source fields, as viewed from an Earth fixed reference frame will be very useful to researchers working with satellite data, e.g., to provide improved external field corrections for modeling of the main or crustal fields, and for studies of ionospheric and magnetospheric physics. Improved characterization of source fields is essential to progress in satellite-based induction studies.