A basic study on the main Geoelectric field

主要地电场的基础研究

• 批准号: 11640406
• 负责人: UTADA Hisashi
• 金额: $ 1.79万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640406/
• 关键词: Geomagnetic field; Earth's core; Geoelectric field; Toroidal magnetic field; Geodynamo; Ocean bottom observbatory; Submarine cable; 地球ダイナモ; コアーマントル境界; 永年変化; 観測; 電気伝導度; 不均質構造

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

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，我们要特别注意地电场，这是与地球发电机产生的主磁场有关的地球电场。本研究分为两个部分，其结果将在下文中给出。定量估算地球发电机所期望的地电场的理论研究在以前的工作中，我们阐明了核幔边界（CMB）处的环形磁场强度与在地球表面观测到的相关电场强度之间的可能关系。这项研究亦显示，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，这种评价是简单地作出的，没有考虑其场的性质.在地核内，环向场只能作为地球发电机过程的结果而存在。 ...更多信息 SS.因此，在这项研究中，我们研究了环向磁场和表面电场之间的关系，预计从一个特定的发电机过程的运动发电机模拟。通过几个实例的研究，我们发现可观测强度的地电场可以作为地球发电机的稳定解。仪器设计和实验室实验在这项研究中，我们设计了一个仪器，试图测量电场的第一部分，这个项目在一个任意的海洋区域，退休的海底电缆是不可用的。考虑到理论研究预期的信号与噪声比，指出信号检测所需的电缆长度估计至少为100 km。根据这一估算，我们设计了一种不使用专用电缆安装船而铺设100 km长电缆的方法。然而，在这种方法中，我们必须使用高质量的电极，因为电缆长度比通常的海底电缆电压测量短得多。为此，对用银-铬化合物包绕银丝制成的Ag-AgCl电极进行了试验，并与其它电极进行了比较。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

项目成果

Shimizu H.: "On the magnetic field variation induced during spin-up."106^<th> SGEPSS fall meeting, Nov.9-12, 1999, Sendai..

Shimizu H.：“关于旋转过程中引起的磁场变化。”第 106 次 SGEPSS 秋季会议，1999 年 11 月 9 日至 12 日，仙台。

Evans, L., P. Taris, A.D. Chave, G. Heinson, H. Utada et al.: "Structure in the Mantle Beneath the East Pacific Rise at 17゜ S"Science. 286. 752-756 (1999)

Evans, L.、P. Taris、A.D. Chave、G. Heinson、H. Utada 等人：“南纬 17 度东太平洋海隆下方的地幔结构”《科学》。

Shimizu,H.and H.Utada: "On the electric field in the D"layer"Proc.OHP/ION Joint Syjmposium. 49-52 (2001)

Shimizu,H. 和 H.Utada：“论 D”层中的电场”Proc.OHP/ION Joint Syjmposium. 49-52 (2001)

Shimizu, H.and H.Utada: "On the electric field in the D" layer"Prof.OHP/ION Joint symposium. 49-52 (2001)

Shimizu, H. 和 H.Utada：“论 D”层中的电场”Prof.OHP/ION Joint symposium. 49-52 (2001)

Utada, H., H.Shimizu, M.Ichiki, T.Koyama, N.Seama, H.Toh, and Y.Hamano: "OHP geoelectromagnteic network."OHP/ION Joint symposium, Yamanashi. (2001)

Utada, H.、H.Shimizu、M.Ichiki、T.Koyama、N.Seama、H.Toh 和 Y.Hamano：“OHP 地电磁网络”。OHP/ION 联合研讨会，山梨县。