Effects of azimuthal asymmetry on ULF waves in the dipole magnetosphere
Effects of azimuthal asymmetry on ULF waves in the dipole magnetosphere
复制标题
方位不对称对偶极子磁层中 ULF 波的影响
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
R. Lysak
中科院分区：
文献类型：
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作者：
Dong‐Hun Lee;R. Lysak
纵波和横波的耦合特性强烈地依赖于方位波数m。作者研究这些影响的数值模型中的ULF波传播的偶极磁层。随着方位波数m的增大，磁层整体压缩模的频率增加，耦合位置向等离子体层顶方向移动，磁层整体压缩模的能量被限制在磁层顶附近较小的区域内。这些结论与以前的分析和数值模型定性一致。有人建议，在偶极几何方位角波长的径向依赖性是重要的压缩波的传播。这种效应在盒形或圆柱形模型中都不存在，其中方位波长不依赖于径向距离，并且可以与阿尔芬速度的不均匀性引起的效应区分开来。另一方面，阿尔芬剪切模式被发现有独立于m的周期。
The properties of the coupling of compressional and transverse ULF waves strongly depend on the azimuthal wavenumber m. The authors investigate these effects in a numerical model of ULF wave propagation in a dipolar magnetosphere. As the azimuthal wave number m becomes larger, the frequencies of the global modes are increased, each coupling location is shifted toward the plasmapause, and the wave energy of global compressional modes in the magnetosphere is confined to a smaller region near the magnetopause. These conclusions are qualitatively consistent with previous analytical and numerical models. It is suggested that the radial dependence of the azimuthal wavelength in the dipole geometry is important to the propagation of compressional waves. This effect is not present in either box or cylindrical models, in which the azimuthal wavelength does not depend on the radial distance, and can be distinguished from effects arising from the inhomogeneity of the Alfven speed. On the other hand, the Alfven shear modes are found to have periods independent of m.