Verification of the geomagnetic secular variation models based on laboratory experiments and numerical simulations.

基于实验室实验和数值模拟的地磁长期变化模型的验证。

基本信息

批准号：
15204038
负责人：
HAMANO Yozo
金额：
$ 31.28万
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 (A)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

Purpose of the present research is to verify several models for the geomagnetic secular variations based on laboratory experiments and the numerical simulations. This project consists of (1)observation of the variations of the geomagnetic fields in various time scales, (2)laboratory experiments on the turbulent properties of thermal convection in liquid metal, and (3)numerical simulations of generation of the magnetic field in a conducting fluid shell. (1)In the geomagnetic field observations, paleomagnetic studies on the historical lava flows from Izu-Oshima volcano and Mt.Fuji, and the lake sediments from Nakaumi, Japan and Lake Qarun, Egypt, were performed and the geomagnetic secular variations during the past several thousand years were estimated. (2)In the laboratory experiments, a new apparatus was developed for observing fluid motions in liquid metal layer by using the ultrasonic velocimetry technique. Observations of turbulent convective motions in liquid Gallium layer at high Rayleigh numbers have been continued by using the newly developed apparatus. Based of the present experiments, we found the quasi periodic fluctuation of convection patterns at a certain range of the Rayleigh number. The oscillation frequency of the patterns varies as a function of the Rayleigh numbers, where the higher frequency was observed at the higher Rayleigh number. (3)Examination of the results of the high resolution geodynamo simulations using the Earth Simulator revealed that the turbulent state in the fluid shell can be inferred from the temporal variation of geomagnetic fields. observed at the earth's surface. The results of the observations, laboratory experiments, and the numerical simulations can be integrated to infer the origin of the geomagnetic field and its variations.

本研究的目的是基于实验室实验和数值模拟来验证地磁长期变化的几种模型。该项目包括（1）不同时间尺度下地磁场变化的观测，（2）液态金属中热对流湍流特性的实验室实验，以及（3）磁场产生的数值模拟。导电流体壳。 (1)地磁场观测中，对伊豆大岛火山、富士山的历史熔岩流、日本中海、埃及卡伦湖的湖泊沉积物进行了古地磁研究，并对过去地磁长期变化进行了研究。估计有几千年。 (2)在实验室实验中，研制了一种利用超声波测速技术观察液态金属层中流体运动的新型装置。使用新开发的设备继续观测高瑞利数液态镓层中的湍流对流运动。基于目前的实验，我们发现对流模式在瑞利数一定范围内存在准周期性涨落。图案的振荡频率作为瑞利数的函数而变化，其中在较高的瑞利数处观察到较高的频率。 (3)使用地球模拟器对高分辨率地球发电机模拟结果进行检查表明，流体壳中的湍流状态可以从地磁场的时间变化推断出来。在地球表面观测到。观测、实验室实验和数值模拟的结果可以综合起来推断地磁场的起源及其变化。