论文标题

在磁性灰尘等离子体中倾斜地传播Alfvén波的群体速度

Group velocity of obliquely propagating Alfvén waves in a magnetized dusty plasma

论文作者

De Toni, L. B., Gaelzer, R., Ziebell, L. F.

论文摘要

在这项工作中,我们研究了在典型的恒星风中典型的灰尘等离子体中倾斜地传播alfvén波的群速度的特征。分散关系是借助动力学理论得出的,用于由电子和离子组成的磁性灰尘等离子体,并通过麦克斯韦功能描述的力量分布。灰尘颗粒被认为是不动的,并且具有相同的大小。通过非弹性碰撞和光电离来吸收等离子体颗粒的电荷。我们以数值求解分散性关系,并计算正常模式的组速度(沿横向和横向至磁场)的成分,即压缩和剪切alfvén波(CAW和SAW)。结果表明,CAWS的组速度的方向通过波动向量方向进行了大大修饰。另一方面,锯会沿磁场实际上呈现速度。灰尘参数的变化(例如数量密度和平衡电荷)可能会显着改变波浪的特征。可以看出,对于足够高的灰尘与离子数密度比,锯可能会呈现垂直的速度,其速度与垂直相位速度相反的方向传播,并以较小的波数值间隔为止。我们还注意到,当辐射的通量发生变化时,此间隔可能会改变甚至消失,从而改变谷物的平衡电荷。

In this work we investigate the characteristics of the group velocity of obliquely propagating Alfvén waves in a dusty plasma typical of a stellar wind. The dispersion relation is derived with the aid of the kinetic theory for a magnetized dusty plasma consisting of electrons and ions, with distribution of momenta described by a Maxwellian function. The dust particles are considered to be immobile and have all the same size; they are electrically charged by absorption of plasma particles via inelastic collisions and by photoionization. We numerically solve the dispersion relation and calculate the components of group velocity (along and transverse to the magnetic field) for the normal modes, namely the compressional and shear Alfvén waves (CAW and SAW). The results show that the direction of the group velocity of CAWs is greatly modified with the wave-vector direction. On the other hand, SAWs will present group velocity propagating practically along the magnetic field. The changes in dust parameters, such as number density and equilibrium electrical charge, may significantly change the waves' characteristics. It is seen that for sufficiently high dust to ion number density ratio, the SAWs may present perpendicular group velocity propagating in opposite direction to the perpendicular phase velocity, in a small interval of wavenumber values; we also notice that this interval may change, or even vanish, when the flux of radiation incident on the dust is altered, changing the equilibrium electrical charge of the grains.

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