Inverting Observations of Hydromagnetic Vibrations of the Earth's Core for the Structure and Dynamics of the Core and Boundary Region

地球磁场的起源被广泛认为是液态铁核对流的结果，但对于其中涉及的过程几乎没有达成共识。数值地球发电机模型在重现地表地磁场特征方面取得了显著的成功。然而，不同型号的内部工作原理可能大相径庭。由于缺乏关于地核动力状态的信息，区分这些可能性的努力受到了阻碍。研究人员建议使用核心中的流体磁波(扭转振荡)来恢复关于核心和边界区域动力学的信息。这些振动对地核表面的流体流动、日长的变化和重力场的变化具有明显的影响。历史和基于卫星的观测将使用一种新的理论框架进行分析，该框架依赖于正常模式地震学中常用的方法。基本的数学模型描述了流体磁波，以及伴随的地幔和内核的运动。该模型将用于联合反演观测到的地心表面的流动、日长的变化、磁场内部结构的重力变化以及激发波的对流过程(类似于地震学中的地球结构和震源机制的参数)。我们对地核结构和动力学的了解的进展将为地球发电机的运行和电力消耗提供新的见解。这些问题对于理解我们所在星球的热演化和化学演化至关重要，或许也有助于理解为什么金星和火星的演化方式如此不同。

EAR-0309531Bruce BuffettThe origin of Earth's magnetic field is broadly understood to be a consequence of convection in the liquid iron core, yet there is little consensus on the processes involved. Numerical geodynamo models have been remarkably successful in reproducing features of Earth's field at the surface. However, the internal workings of different models can be vastly different. Efforts to distinguish between these possibilities are hampered by a lack of information about the dynamical state of Earth's core. The investigator proposes to use hydromagnetic waves (torsional oscillations) in the core to recover information about the dynamics of the core and boundary regions. The vibrations have observable consequences for fluid flow at the surface of the core, variations in the length of day and changes in the gravity field. Historical and satellite-based observations will be analyzed using a new theoretical framework that relies on methods commonly employed in normal-mode seismlogy. The underlying mathematical model describes the hydromagnetic waves, as well as the accompanying motion of the mantle and inner core. This model will be used to jointly invert observations of flow at the core surface, variations in length of day, and changes in gravity for the internal structure of the magnetic field and convective processes that excite the waves (parameters analogous to earth structure and source mechanism in seismology). Progress in our understanding of the structure and dynamics of Earth's core will provide new insights into the operation and power consumption of the geodynamo. These issues are crucial for understanding the thermal and chemical evolution of our own planet, and perhaps why Venus and Mars evolved so differently.