An Experimental study of the Earth's Electric Field

这项为期三年的研究项目旨在开发一种新的观测系统，使我们能够使用长电缆（10-100公里）记录深海海底地球电场的时间变化。我们的可行性研究的研究结果得出结论，使用这样的系统是必不可少的，以检测外芯的环形磁模式的电场。观测这一物理量的地球物理学重要性是显而易见的，因为预计它将对外核的磁流体动力学产生重大约束。除了来自外核的这一信号外，拟议的观测系统被认为有助于研究海洋通量的长期变化和深部地幔的电导率结构，该系统由主记录单元和一条10公里长的电缆组成。它的设计是通过使用深拖系统进行安装，并通过使用遥控操作车辆进行回收。该系统是由 ...更多信息 假设DT-4000和Kaiko-10 K都是JAMSTEC的深拖和深拖。在第一年，建造了一台仪器，并进行了陆地测试。第二年，我们试图在菲律宾海（南大东岛附近）安装该系统，但由于电缆在开始运行后不久断裂，安装失败。对这一失败的原因进行了广泛的审查和澄清。对系统设计进行了一些修改，并在该项目的第二年年底建立了改进的系统。该系统被命名为EFOS-10，代表地球电场观测系统，具有10公里长的电缆。2004年5月，在“夏岛”号考察船上，使用DT-4000成功地安装了EFOS-10。计划在安装一年后进行回收，即，在2005年5月。这是由于JAMSTEC的卫星（Kaiko-10 K于2003年丢失，其辅助车辆Kaiko-7 K于2005年5月可用）的可用性，成功回收了记录单元，从中获得了长达1年的电力变化时间序列记录。对数据质量进行了检查，并证实符合预期。它的结论是EFOS-10可以用于各种电磁调查在海上。少

This three-year research project aimed to develop a new observation system that enables us to record time variations of the electric field of the Earth at deep ocean bottom by using a long (10-100 km) cable.. The research result of our feasibility study concluded that the use of such a system is essential to detect the electric field of Toroidal magnetic mode in the outer core. The geophysical importance of the observation of this physical quantity is obvious because it is expected to give significant constraints on the magneto-hydrodynamics in the outer core,. Besides this signal from the outer core, the proposed observation system is considered to be useful for studying long-term variabilities of ocean flux and the electrical conductivity structure in the deep mantle.The system consists of the main recording unit and a 10 km long cable. It is designed to be installed by using a deep-tow system and to be recovered by using a ROV (Remotely Operating Vehicle). The system was designed by … More assuming DT-4000 and Kaiko-10K both of JAMSTEC for a deep-tow and ROV. During the first year, an instrument was built and on-land tests were performed. In the second year, we tried to install the system in the Philippine Sea (near Minami-Daito Island), but the installation was failed due to a break of the cable soon after the beginning of run. Causes for this failure were extensively examined and clarified. Several modifications were made to the system design and the improved system was built at the end of the second year of this project. This system was named EFOS-10 that stands for Earth's electric Field Observation System with a 10 km long cable. The EFOS-10 installation was successfully made by using DT-4000 on R/V Natsushima cruise in May, 2004. Its recovery was scheduled one year after the installation, i.e., in May, 2005. It is because of the availability of ROV of JAMSTEC (The vehicle of Kaiko-10K was lost in 2003, and its supplementary vehicle Kaiko-7K became available in May 2005).The recording unit was successfully recovered, form which 1-year-long time series record of electric variations was obtained. The data quality was examined and was confirmed to be satisfactory as it has been expected. It is concluded that the EFOS-10 can be useful for various electromagnetic investigations at sea. Less