On the kinetic dispersion relation for shear Alfvén waves
On the kinetic dispersion relation for shear Alfvén waves
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DOI：
10.1029/95ja03712
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发表时间：
1996-03
影响因子：
--
通讯作者：
R. Lysak;W. Lotko
中科院分区：
文献类型：
--
作者：
R. Lysak;W. Lotko
自长谷川的开创性工作以来，动能阿尔文波一直被认为与极光流和粒子加速有关。然而，迄今为止，还没有研究考虑色散关系，包括电子和离子的完整动力学效应。给出了这种计算的结果，重点是兰杜亚阻尼在消散阿尔文波中的作用，阿尔文波从外磁层的热等离子体传播到电离层中的冷等离子体。研究发现，当垂直波长大于离子声陀螺半径和电子惯性长度时，Landua阻尼并不重要。此外，离子陀螺半径效应通过将波的平行相速度提高到短垂直波长范围内的电子热速度之上，导致兰杜阿阻尼减小。这些结果表明，当映射到电离层时，垂直波长大于 10 km 量级的低频阿尔文波不会受到朗道阻尼的显着影响。虽然这些基于局部色散关系的结果仅对于短平行波长阿尔文波严格有效，但它们确实表明了兰杜阿阻尼对于较长平行波长波（例如场线谐振）的重要性。 26 个参考文献，5 个图 « 更少
Kinetic Alfven waves have been invoked is association with auroral currents and particle acceleration since the pioneering work of Hasegawa. However, to date, no work has considered the dispersion relation including the full kinetic effects for both electrons and ions. Results from such a calculation are presented, with emphasis on the role of Landua damping in dissipating Alfven waves which propogate from the warm plasma of the outer magnetosphere to the cold plasma present in the ionosphere. It is found that the Landua damping is not important when the perpendicular wavelength is larger than the ion acoustic gyroradius and the electron inertial length. In addition, ion gyroradius effects lead to a reduction in the Landua damping by raising the parallel phase velocity of the wave above the electron thermal speed in the short perpendicular wavelength regime. These results indicate that low-frequency Alfven waves with perpendicular wavelengths greater than the order of 10 km when mapped to the ionosphere will not be significantly affected by Landau damping. While these results based on the local dispersion relation, are strictly valid only for short parallel wavelength Alfven waves, they do give an indication of the importance of Landua damping for longer parallel wavelengthmore » waves such as field line resonances. 26 refs., 5 fig.« less