Study on kinetic Alfven wave in inertial regime
Study on kinetic Alfven wave in inertial regime
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惯性区运动阿尔文波研究
DOI：
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发表时间：
2009
期刊：
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通讯作者：
M. Tiwari
中科院分区：
文献类型：
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作者：
Nidhi Shukla;P. Varma;M. Tiwari
本文研究了电子惯性对动力学阿尔芬波的影响。FAST航天器在其整个高度范围（350-4180）内报告了在极光电子加速区域传播的惯性阿尔芬波（例如，Chaston等人，Physics Scripta，T84，（2000）64）。采用Vlasov动力学理论计算了不同等离子体密度下色散关系、阻尼率和增长长度与归一化垂直波数（k_（？）c/ω_e）的关系。观察到惯性Alfven波频率（ω）随（k ∈ c/ω pe）和等离子体密度的增大而减小。计算了不同（me/β mi）下的生长速率和生长长度，其中β是电子压与磁场压的比值，mi，e分别是离子和电子的质量，β = me/β mi代表动力学和惯性区域之间的边界。给出了当波向低电离层高密度侧传播时，电子密度对波的频率、增长率和增长长度的影响。虽然，波是高度阻尼的，它需要更长的传播距离，如增长长度所预测的。因此，由于较高的生长长度，单独的朗道阻尼机制是不够的，因此某些其它机制也应该可操作以耗散动力学阿尔芬波能量。结果给出了北方和南半球极光的分布情况（Swift D W，J Geophys Res，112（2007）A12207）。最后指出了研究极光加速区的意义。
The effect of electron inertia on kinetic Alfven wave (KAW) has been studied. The inertial Alfven waves propagating in regions of auroral electron acceleration are reported from the FAST spacecraft over its entire altitude range (350-4180), (e.g., Chaston et al., Physics Scripta, T84, (2000) 64). The Vlasov-kinetic theory has been adopted to evaluate the dispersion relation, damping rate and growth length, with respect to the normalized perpendicular wave number (k ⊥ c/ω pe ) with different plasma density. It is observed that inertial Alfven wave frequency (ω) is decreasing with (k ⊥ c/ω pe ) and plasma density. The growth rate and growth length are evaluated for different (m e /βm i ), where β is the ratio of electron pressure to the magnetic field pressure, m i,e are the mass of ion and electron, respectively as β = m e /βm i represent boundary between the kinetic and inertial regimes. The effects of electron density on the wave frequency, growth rate and growth length are also given as the wave propagates towards higher density side of the lower ionospheric region. Although, the wave is highly damped, it requires longer distance of propagation as predicted by growth length. Thus, some another mechanism should also be operative to dissipate kinetic Alfven wave energy as the Landau damping mechanism alone is not sufficient due to higher growth length. The results show the scenario of auroral pattern in northern and southern hemisphere (Swift D W, J Geophys Res, 112 (2007) A12207). The significance of the investigation for the auroral acceleration region is also presented.