Detecting and Inverting Magnetic Waves for the Structure and Dynamics of Earth's Core

众所周知，地球内部磁场的波动发生在广泛的时间范围内。在地质记录中检测到磁反转的时间间隔大约为几十万年，而现代的地面观测显示，磁场在短短几年内发生了突变。最近卫星飞行任务的高保真记录表明，磁场的突然变化比之前认为的更频繁。这些事件影响了我们预测磁场的能力，但这些扰动的来源却鲜为人知。一种可行的解释涉及到地核顶部的波。研究人员发现了几种类型的波，它们解释了磁扰的周期和空间模式。这项研究的目标是在地磁观测中探测到这些波，并恢复对波传播速度的估计。这些信息将增强我们预测磁场的能力，还将提供对地核物理状态的独特见解，这将提高我们对地核对流如何产生磁场的理解。该项目将支持加州大学伯克利分校一名拉美裔研究生的研究。这名学生将被介绍先进的数据分析和计算方法，以及并行计算和科学可视化。研究人员建议利用集群卫星的观测来确定地核赤道地区快速地磁波动的来源。他们假设这些波动是地核顶部波动的结果，并计划采用几种类型的波动模型来解释地磁信号。研究人员打算使用波动模型来提取有关核-地幔边界附近普遍存在的物理条件的信息，包括可能存在稳定的层结。他们还试图确定波源机制的特征，因为它将波幅与地心更深的对流过程联系起来。研究人员还计划使用高保真的地磁场时间变化记录来寻找核-地幔边界上的地形证据。恢复核-地幔边界上的地形信息将对最低地幔的对流类型提供意想不到的限制。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Fluctuations in the Earth's internal magnetic field are known to occur over a broad range of time scales. Magnetic reversals are detected in the geological record at irregular intervals of roughly several hundred thousand years, whereas modern ground-based observations reveal abrupt changes in the magnetic field over just a few years. Higher fidelity records from recent satellite missions now suggest that the abrupt changes in the magnetic field occur more frequently than previously believed. These events affect our ability to forecast the magnetic field, yet the origin of these disturbances is poorly understood. One viable interpretation involves waves at the top of the core. The investigators have found several types of waves that account for the periods and spatial patterns of the magnetic disturbance. The goal of this research is to detect these waves in geomagnetic observations and to recover estimates for the wave propagation speeds. This information will enhance our ability to forecast the magnetic field, and it will also provide unique insights into the physical state of the Earth's core, which will improve our understanding of how the magnetic field is generated by convection in the core. The project will support the research of a Hispanic graduate student at the University of California, Berkeley. This student will be introduced to advanced data analysis and computational methods, as well as parallel computing and scientific visualization.The investigators propose to use observations from the SWARM satellite to identify the origin of rapid geomagnetic fluctuations in the equatorial region of the Earth's core. They hypothesize that these fluctuations are a result of waves at the top of the core, and plan to adopt several types of wave models to interpret the geomagnetic signals. The investigators intend to use the wave models to extract information about the physical conditions that prevail near the core-mantle boundary, including the possible presence of stable stratification. They also seek to characterize the source mechanism for the waves because it connects the wave amplitudes to convective processes deeper in the core. The researchers also plan to search for evidence of topography on the core-mantle boundary using high-fidelity records of time variations in the geomagnetic field. Recovery of information about the topography on the core-mantle boundary would offer unexpected constraints on the style of convection in the lowermost mantle.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.