Ishizaki Wataru, Ioka Kunihito
Astronomical Institute, Graduate School of Science, <a href="https://ror.org/01dq60k83">Tohoku University</a>, Sendai 980-8578, Japan.
Frontier Research Institute for Interdisciplinary Sciences, <a href="https://ror.org/01dq60k83">Tohoku University</a>, Sendai 980-8578, Japan.
Phys Rev E. 2024 Jul;110(1-2):015205. doi: 10.1103/PhysRevE.110.015205.
We investigate parametric decay instability (PDI) of circularly polarized Alfvén wave into daughter acoustic wave and backward Alfvén wave in magnetically dominated plasma, in which the magnetization parameter σ (energy density ratio of background magnetic field to matter) exceeds unity. We analyze relativistic magnetohydrodynamics (MHD), focusing on wave frequencies sufficiently lower than the plasma and cyclotron frequencies. We derive analytical formulas for the dispersion relation and growth rate of the instability as a function of the magnetization σ, wave amplitude η, and plasma temperature θ. We find that PDI persists even in high magnetization σ, albeit with a decreased growth rate up to σ→∞. Our formulas are useful for estimating the decay of Alfvén wave into acoustic wave and heat in high magnetization σ plasma, which is a ubiquitous phenomenon such as in pulsars, magnetars, and fast radio bursts.
我们研究了在磁化主导等离子体中，圆偏振阿尔文波衰变为子声波和反向阿尔文波的参量衰变不稳定性（PDI），其中磁化参数σ（背景磁场与物质的能量密度比）超过1。我们分析了相对论磁流体动力学（MHD），重点关注远低于等离子体频率和回旋频率的波频率。我们推导了作为磁化σ、波幅η和等离子体温度θ的函数的不稳定性色散关系和增长率的解析公式。我们发现，即使在高磁化σ情况下，PDI仍然存在，尽管增长率会降低，直至σ→∞。我们的公式有助于估计在高磁化σ等离子体中阿尔文波衰变为声波和热量的情况，这是一种普遍存在的现象，比如在脉冲星、磁星和快速射电暴中。
