NASA Research Announcement NRA-01-OES-05

该项目将允许美国国家航空航天局(NASA)资助两项利用地磁卫星数据的提案。每个方案的摘要如下：凯瑟琳·康斯特布尔多颗卫星感应研究UCSD 22-8760环电流产生的磁场的变化将用于研究地球内部的电磁感应，最终目标是确定地幔的三维电导结构。归纳研究是对其他地球物理方法的补充，以了解地球深处的热、成分和流变结构。我们的工作将包括数据分析以及理论和算法的发展。我们将研究利用多颗卫星同时测量磁场的建模过程。我们认为这是我们研究的第二部分的关键，即改进了对在地球内部感应磁场的外部源场的表示。这将使我们能够对主要和次要领域使用更好的参数化模型。第三个方面将涉及利用卫星数据研究三维感应的理论和实践工具的发展。根据单颗卫星估计的一维卫星电磁响应函数已经被证明与由地磁观测数据得出的平均响应相一致，并将全球响应函数扩展到104个S周期。目前长周期卫星响应估计的约束条件相当差，我们将在可行的情况下，通过使用更长的时间序列和更好的估计技术，包括多个卫星测量，来改进这些估计。利用现代外部反演技术获得的电导率估计将对上地幔的流变和热状态提供约束，并解决地球地幔过渡带的电导率结构问题。卫星观测得出的横向电导率变化的定性测量表明，海洋和地壳对近地表电性结构的影响占主导地位。目前的算法开发将被用来生成预测这些影响的正演模型：这将允许评估是否可以在地壳以下探测到三维电导率结构。我们计划利用Champ、Orsted和SAC-C(Orsted-2)观测，使用不同的轨道配置和卫星高度来评估关于外部源场结构假设的局限性。使用的数据将是沿着各个卫星通道的正交矢量磁场分量的0.1赫兹样本，如果它们可用的话。当没有足够的姿态控制可用时，对于长期估计，我们希望使用标量数据。这项研究预计将持续三年，但一旦解释技术和算法到位，继续增加数据就有可能不断改进地球电导率模型，并了解大风暴等事件如何调制外部源场的结构。核心动力学的地球发电机建模及其在地表地球动力学观测中的应用(PI：魏家矿)固体地幔、流体外核和固体内核通过不同的机制和不同的时间尺度相互作用。我们建议使用数值地球发电机模型来研究地核动力学和地幔的响应，并研究其在地表地球动力学观测中的应用。这项拟议的工作有三个具体目标：(1)我们打算利用我们的数值地球发电机模型结合在地球表面观测到的地磁场长期变化(SV)来研究岩芯流动和地磁场在十年时间尺度上的变化。特别是，我们将研究核-地幔边界(CMB)的非静水压力，以及驱动核对流的外核密度异常所引起的大规模质量重分布，以及内核相对于地幔旋转引起的大范围质量重分布。(2)基于我们在(1)中的理解，我们打算考察固体地球对这些核心变化的响应。特别是，我们将侧重于核心对时变重力场和可能的地表变形的贡献的大小和时间尺度，以及它们在过去和未来空间飞行任务(包括卫星激光测距、CHAMP、GRACE、GOCE以及可能的COSMIC和GRACE后续任务)的重力场信号中的可探测性。(3)在文(1)研究的基础上，根据前人对地核角动量变化的了解，我们打算继续我们的研究(由国家气象局和美国国家科学基金会支持)，研究核-地幔相互作用及其对地球自转变化的影响，特别是十年一遇的极移(Markowitz Wobble)。拟议的工作涉及《国家地质局》(A.1)中列出的几个主题：核心过程的磁流体力学模拟、其在分析地磁场内部分量的时空变化、核心对时变重力场的贡献、地表变形和地球自转变化方面的应用。这项拟议的工作是多学科研究地球内部的经典例子，它利用美国宇航局的任务观测和建模能力来促进我们对地球系统变化的了解。

This project will allow the National Aeronautics and Space Administration (NASA) to fund two proposals that utilize geomagnetic satellite data. The abstract of each proposal is listed below:Catherine Constable Multiple Satellite Induction Studies UCSD 22-8760Variations in the magnetic field generated by the ring current will be used to study electromagnetic induction in the interior of the Earth, with the ultimate goal of determining three-dimensional electrical conductivity structure in Earth's mantle. Induction studies complement other geophysical approaches to understanding thermal, compositional, and rheological structures in the deep earth.Our work will involve data analysis as well as theoretical and algorithm developments. We will investigate modeling procedures that take advantage of more than one satellite simultaneously measuring the magnetic field. We believe this is key to the second part of our study, namely improved representation of the external source fields that induce magnetic fields in Earth's interior. This will allow us to use better-parameterized models for both primary and secondary fields. The third aspect will concern development of both theoretical and practical tools for studying 3-dimensional induction using satellite data.One-dimensional satellite electromagnetic response function estimates from single satellites have already been shown to be compatible with an average of responses derived from geomagnetic observatory data, and extend the global response function down to 104 s periods. Current long period satellite response estimates are rather poorly constrained and we will improve them through the use of longer time series and better estimation techniques involving multiple satellites measurements where feasible. Electrical conductivity estimates, obtained using modem external inversiontechniques, will provide constraints on the rheological and thermal state of the upper mantle and address the issue of conductivity structure in the transition zone of Earth's mantle. Qualitative measures of lateral conductivity variations derived from satellite observations demonstrate the pre-dominant influence of the oceans and crust on near-surface electrical structure. Current algorithm developments will be used to generate forward models that predict these effects: this will allow an assessment of whether 3-dimensional conductivity structures can be detected below the crust.We plan to exploit Champ, Orsted, and SAC-C (Orsted-2) observations, using different orbital configurations and satellite altitudes to assess limitations in assumptions about external source field structures. Data used will be 0.1 Hz samples of orthogonal vector magnetic field components along individual satellite passes where they are available. When adequate attitude control is not available, and for long period estimates we expect to use scalar data. Anticipated duration of this investigation is three years, but once interpretation techniques and algorithms are in place continued addition of,data offers potential for ongoing improvement of Earth conductivity models and understanding of how events such as large storms modulate the structure of the external source field.ABSTRACT Geodynamo Modeling of Core Dynamics and its Applications to Surface Geodynamic Observables (pI: Weijia Kuang) The solid mantle, the fluid outer core, and the solid inner core interact with one another through various mechanisms and on various time scales. We propose to investigate the Earth's core dynamics and the response of the mantle using a numerical geodynamo model, and study its applications to surface geodynamic observables. The proposed work has three specific objectives: (1) We intend to study variation of core flow and geomagnetic field on decadal time scales, using our numerical geodynamo modeling in conjunction with the geomagnetic field secular variation (SV) observed at Earth's surface. In particular, we shall study the non-hydrostatic pressure at the core-mantle boundary (CMB), and large-scale mass redistribution arising from density anomalies in the outer core that drive core convection, as well as that from inner core rotation relative to the mantle.. (2) Based on our understandings from (1), we intend to examine the responses of the solid Earth to these core variations. In particular, we shall focus on the magnitude and time scales of the contributions of core on time-variable gravity field and on possible surface deformation, and their detectability in gravity field signals from past and future space missions (including satellite- laser-ranging, CHAMP, GRACE, GOCE, and possibly COSMIC and GRACE Follow-On). (3) Based on research in (1), and on previous knowledge about the core angular momentum variation that changes the decadallength-of-day, we intend to continue our research (supported by SENH and by NSF) on the core-mantle interactions and their effect on variation of the Earth's rotation, in particular the decadal polar motion (Markowitz wobble). The proposed work cuts across several topics listed in the (A. 1) of the NRA: magnetohydrodynamic modeling of core processes, its applications to analysis of spatial and temporal variations of internal component of the geomagnetic field, of core contributions to time-variable gravity field, surface deformation, and Earth's rotation variation. The proposed work is a classic example of multi-disciplinary studies of Earth's interior that makes use of NASA's mission observations and modeling capabilities in advancing our knowledge about Earth system changes.