论文标题

在恒星风环境中倾斜的Alfvén波,带有非弹性碰撞和光电离心的灰尘颗粒

Oblique Alfvén waves in a stellar wind environment with dust particles charged by inelastic collisions and by photoionization

论文作者

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

论文摘要

讨论了在恒星风环境中向环境磁场倾斜向环境磁场传播的Alfvén波的特征。考虑到电子和离子的麦克斯韦分布,采用了磁性灰尘等离子体的动力学配方,以及通过吸收等离子体颗粒和光电离心发电的固定灰尘颗粒。分散关系是在数值上解决的,结果与以前研究的情况进行了比较,在这些情况下,光电离电源未充电,这是相对热星的恒星风中的重要过程。我们表明,灰尘的存在导致剪切alfvén波呈现零频率的波数值区域,并且模式再次变散的最小波长与尘埃晶粒暴露的辐射强度大致成正比。对于所考虑的参数,观察到剪切和压缩alfvén波的阻尼速率随着辐射通量的增加而降低。对于当辐射通量不存在或弱时,这两种模式都呈现为无效的实际频率区域的特定情况,这表明当辐射通量足够强,光电离机制可能会导致该区域变小甚至消失,以使压缩的Alfvén波。在这种情况下,对于所有波数值,压缩的alfvén波呈现非零频率,而剪切alfvén波仍然以一定的波数值间隔显示无效的频率,随着辐射的存在,它会变小。

The characteristics of Alfvén waves propagating in a direction oblique to the ambient magnetic field in a stellar wind environment are discussed. A kinetic formulation for a magnetized dusty plasma is adopted considering Maxwellian distributions of electrons and ions, and immobile dust particles electrically charged by absorption of plasma particles and by photoionization. The dispersion relation is numerically solved and the results are compared with situations previously studied where dust particles were not charged by photoionization, which is an important process in a stellar wind of a relatively hot star. We show that the presence of dust causes the shear Alfvén waves to present a region of wavenumber values with zero frequency and that the minimum wavelength for which the mode becomes dispersive again is roughly proportional to the radiation intensity to which the dust grains are exposed. The damping rates of both shear and compressional Alfvén waves are observed to decrease with increasing radiation flux, for the parameters considered. For the particular case where both modes present a region with null real frequency when the radiation flux is absent or weak, it is shown that when the radiation flux is sufficiently strong, the photoionization mechanism may cause this region to get smaller or even to vanish, for compressional Alfvén waves. In that case, the compressional Alfvén waves present non zero frequency for all wavenumber values, while the shear Alfvén waves still present null frequency in a certain interval of wavenumber values, which gets smaller with the presence of radiation.

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