Liu Kangkang
Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
University of Chinese Academy of Science, Beijing, China.
Sci Rep. 2019 Jul 29;9(1):10963. doi: 10.1038/s41598-019-47550-5.
The intuitive physical description of magnetic Rayleigh-Taylor instability in some textbooks is generally considered to be: a small perturbation causes current discontinuity, which produce charge accumulation, the electric field produced by the accumulated charge amplify the initial perturbation. However, in calculating the linear growth rate of magnetic Rayleigh-Taylor instability (MRTI), the displacement current term in the Maxwell's equations is ignored, which means the contribution of charge accumulation to the growth of MRTI is totally ignored. In this article, we calculated the linear growth rate of MRTI with the displacement current term in Maxwell's equations retained. We show that the contribution of charge accumulation to the growth of MRTI is negligible only when the nominal Alfvén speed is much smaller than the light speed. For space plasma whose nominal Alfvén speed is generally much smaller than the light speed, the linear growth rate previous calculated is right but the intuitive physical description of MRTI is wrong. For laboratory plasma whose nominal Alfvén speed maybe comparable to light speed, the intuitive physical description of MRTI is also inaccurate and the linear growth rate of MRTI is undervalued.
一些教科书中对磁瑞利 - 泰勒不稳定性的直观物理描述通常被认为是：一个小扰动导致电流不连续，这会产生电荷积累，积累电荷产生的电场会放大初始扰动。然而，在计算磁瑞利 - 泰勒不稳定性（MRTI）的线性增长率时，麦克斯韦方程组中的位移电流项被忽略了，这意味着电荷积累对MRTI增长的贡献被完全忽略了。在本文中，我们在保留麦克斯韦方程组中位移电流项的情况下计算了MRTI的线性增长率。我们表明，只有当标称阿尔文速度远小于光速时，电荷积累对MRTI增长的贡献才可以忽略不计。对于标称阿尔文速度通常远小于光速的空间等离子体，之前计算的线性增长率是正确的，但对MRTI的直观物理描述是错误的。对于标称阿尔文速度可能与光速相当的实验室等离子体，对MRTI的直观物理描述也是不准确的，并且MRTI的线性增长率被低估了。
