Dynamics of the earth's fluid and solid cores

地球流体和固体核心的动力学

• 批准号: 355636-2008
• 负责人: Dumberry, Mathieu
• 金额: $ 1.75万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2008
• 资助国家: 加拿大
• 起止时间: 2008-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=402635
• 关键词: Dynamics; earth; fluid; solid; cores

The goal of this research is to improve our knowledge of the dynamics in the Earth's fluid core and its interaction with the inner core and mantle. Though the physics describing these systems is complex, progress can be made by focusing on specific aspects of the dynamics. The general approach in this research is to test simple models of the dynamics by investigating whether the predicted variations in the Earth's magnetic field, rotation and gravity field are compatible with actual observations of these quantities. Specific dynamical aspects of the Earth's core that are studied include torsional oscillations, a core flow with a cylindrical geometry detected in the magnetic data and the Earth's rotation variations. Questions remain as to whether these oscillations are free modes, like a mass suspended by a spring, or forced motions by the underlying dynamics. I will study the nature of this flow by numerical modelling. Another project is to investigate the cause of the so-called "geomagnetic jerks", which are magnetic variations occurring on a timescale of approximately 1 year. I propose to study the action between flows and magnetic field near the surface of the core and to test which scenario is most compatible with observations. Using the same framework, I will also study the cause of the so-called "archaeomagnetic jerks", which are observed over a much longer timescale of millennia. Over the same timescale, archaeomagnetic observations will be surveyed to determine whether the motions of magnetic field features near the equator of the CMB observed over the past few centuries have been a feature of the geodynamo for much longer in the past. Finally, two projects involve the role of the inner core in the rotational dynamics of the Earth. First, observed variations in the Earth's rotation rate with a period of 6 years are interpreted to represent axial oscillations between the inner core and mantle. Gravity field and magnetic field data will be surveyed to find further evidences of this oscillation. In the second project, I will study the dynamics of the flow and magnetic field near the inner core, through their ability to imprint a torque on the latter which leads to a tilt of its figure and causes a change in the direction of Earth's rotation.

这项研究的目的是提高我们对地球流体核动力学及其与内核和地幔相互作用的认识。 虽然描述这些系统的物理学是复杂的，但可以通过专注于动力学的特定方面来取得进展。 在这项研究中的一般方法是测试简单的动力学模型，通过调查预测的变化，在地球的磁场，旋转和重力场是否与这些量的实际观测兼容。所研究的地核的具体动力学方面包括扭转振荡、在磁性数据中检测到的具有圆柱形几何形状的地核流和地球自转变化。 问题仍然是，这些振荡是否是自由模式，如弹簧悬挂的质量，或受基础动力学的强迫运动。 我将通过数值模拟来研究这种流动的性质。另一个项目是调查所谓的“地磁急动”的原因，这是在大约一年的时间尺度上发生的磁场变化。 我建议研究流动和磁场之间的作用在核心的表面附近，并测试哪种情况是最符合观测。 使用相同的框架，我也将研究所谓的“古地磁急动”的原因，这是在一个更长的时间尺度上观察到的数千年。 在同一时间尺度内，将对古地磁观测进行调查，以确定在过去几个世纪中观测到的CMB赤道附近的磁场特征的运动是否在过去更长的时间内一直是地球发电机的特征。 最后，有两个项目涉及内核在地球旋转动力学中的作用。 首先，在地球的自转速率与6年的周期观察到的变化被解释为代表内核和地幔之间的轴向振荡。 重力场和磁场数据将被调查，以寻找这种振荡的进一步证据。 在第二个项目中，我将研究内核附近的流动和磁场的动力学，通过它们在后者上施加扭矩的能力，导致其形状倾斜，并导致地球旋转方向的变化。