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Studies on the propagation of ULF waves in the magnetosphere-ionosphere coupled system

磁层-电离层耦合系统中超低频波的传播研究

基本信息

批准号：
09640532
负责人：
ITONAGA Masahiro
金额：
$ 1.47万
依托单位：
Yamaguchi University (1998)Kyushu University (1997)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640532/
关键词：
magnetosphere ionosphere ULF wave compressional wave Alfven wave field line oscillation field-aligned current Hall current サブストーム Pi2脈動

项目摘要

The propagation of IJLF waves in the magnetosphere-ionosphere coupled system was investigated and the following main results were obtained : 1. Both in the cases of the ground magnetic field being due to compressional MHD waves directly incident on the ionosphere and to the ionospheric current of polar origin, its phase at the dip equator lags behind those in the off-equatorial region. Such a phase lag arises from an enhancement of the ionospheric conductivity at the dip equator. 2. When the localized Alfv_n mode impulse is incident on the polar ionosphere, there are two types of horizontal transmission of electromagnetic signals in the Earth-ionosphere waveguide. One is the electromagnetic transmission and the other is the electrostatic transmission. The former is associated with the poloidal mode wave induced from the Alfven mode impulse through the ionospheric Hall current. The latter is a horizontal spread of the electric field represented with a scalar potential, where the electric field is directly associated with the Alfv_n mode impulse. The electrostatic transmission occurs. only when the ionosphere is non-uniform. 3. The field-aligned current is closed in the ionosphere via the divergent Hall current driven by the rotational electric field as well as the ordinary Pedersen current. Such a closing brings about an effective control of eigenmodes of the field line oscillation by the height-integrated Pedersen and Hall conductivities.

研究了IJLF波在磁层-电离层耦合系统中的传播，得到了以下主要结果：1。无论是在地面磁场的情况下，由于压缩MHD波直接入射到电离层和电离层电流的极地起源，其相位在倾角赤道落后于那些在离赤道地区。这种相位滞后是由于磁倾角赤道处电离层电导率的增强引起的。2.当局域Alfv_n模脉冲入射到极区电离层时，电磁信号在地-电离层波导中的水平传输有两种类型。一种是电磁传输，另一种是静电传输。前者与阿尔芬模脉冲通过电离层霍尔电流感应的极向模波有关。后者是用标量势表示的电场的水平扩展，其中电场与Alfv_n模脉冲直接相关。发生静电传输。只有当电离层是不均匀的。3.场向电流在电离层中通过旋转电场驱动的发散霍尔电流以及普通彼得森电流闭合。这样的关闭带来了一个有效的控制本征模式的场线振荡的高度集成彼得森和霍尔电导率。