A basic study on the main Geoelectric field

这个为期两年的项目旨在为地核动力学研究开辟一个新的研究方向。在这里，我们特别注意地电场，它是与地球发电机产生的主磁场相关联的地球电场。本研究由两部分组成，其结果将在以下给出。第1部分。地球动力学预测地电场定量评价的理论研究在以往的工作中，我们阐明了地核-地幔边界环向磁场强度与地表观测到的相关电场强度之间的可能关系。这项研究还表明，如果使用长海底电缆进行测量，这种电场变化将具有可观察到的强度。然而，评价是简单的，没有考虑到环面场本身的性质。在地核内部，环面磁场只能作为地球发电机过程的结果而存在。因此，在本研究中，我们通过运动学发电机模拟研究了环面磁场与表面电场之间的关系，这是一个特定发电机过程所期望的。经过几个实例的研究，我们发现对于地球发电机的稳定解，可观测强度的地电场是可以预期的。第2部分。仪器设计和实验室实验在本研究中，我们设计了一种仪器，试图在没有退役海底电缆的任意海洋区域测量本项目第一部分所期望的电场。考虑到理论研究期望的信号与噪声比，估计信号检测所需的电缆长度至少为100 km。根据这一估计，我们设计了一种无需使用专用电缆安装船即可铺设100公里长的电缆的方法。但是在这种方法中，由于电缆长度比通常的海底电缆电压测量短得多，我们必须使用高质量的电极。为此，对一种由氯化银包裹的银丝制成的Ag-AgCl电极进行了测试，并与其他电极进行了比较。结果表明，新设计的电极具有足够的稳定性，可以检测到预期的信号，同时具有易于操作的优点。少

This two-year project aimed to develop a new research direction in study of the dynamics in the Earth's core. Here we pay special attention to the Geoelectric field that is the Earth's electric field associated with the main magnetic field generated by the geodynamo. The study consisted of two parts and their results will be given in the followings.Part 1. Theoretical study for quantitative evaluation of the Geoelectric field expected by geodynamosIn the previous work, we elucidated the possible relation between the intensity of the toroidal magnetic field at the core-mantle boundary (CMB) and that of relating electric field observed at the Earth's surface. This study also showed that such electric field variations will be of observable strength if a long submarine cable is used for measurement. However the evaluation was made simply without considering the nature of the toroidal field itseld. Within the Earth's core, the toroidal field can only exist as a result of the geodynamo proce … More ss. Therefore in this study, we examined the relation between the toroidal magnetic field and the surface electric field that is expected from a particular dynamo process by a kinematic dynamo simulation. After several case studies, we found that the geoelectric field of observable intensity can be expected for a stable solution of geodynamo.Part 2. Instrumental design and laboratory experimentsIn this study, we designed an instrumentation for attempting to measure the electric field expected by Part 1 of this project in an arbitrary ocean area where a retired submarine cable is not available. Considering the signal expected by theoretical study to noise ratio, it was indicated that the cable length necessary for signal detection was estimated as at least 100 km. According to this estimation, we designed a method to lay a 100 km long cable without using special cable installation vessel. However in this method, we must use electrodes of high quality as the cable length is much shorter than usual submarine cable voltage measurements. For the purpose, an Ag-AgCl electrode was tested which is made of a silver wire corted by silver-chrolide, and compared with other electrodes. It was concluded that the newly designed electrode is stable enough to detect the expected signal and, at the same time, has great advantage of easy handling. Less