摘要:
运用一维混合模拟方法，研究了垂直于等离子体磁场入射的低能质子环束流与等离子体的相互作用过程。结果显示：由质子环束流激发的等离子体波首先经历指数式快速增长的线性阶段，随后出现饱和、衰减和相对稳定的非线性阶段。在线性阶段，质子束投掷角散射使波模共振作用迅速减弱，波的增长很快出现饱和。随后，持续的投掷角散射，使入射质子在速度空间从环状分布渐变为均匀分布，同时初始阶段的右手共振不稳定性逐渐消失，在最后相对稳定阶段只存在阿尔芬波。研究发现，背景等离子体的有效加热始于非线性阶段，等离子体波的形成有助于将质子束动能转换为背景等离子体的热能。
Abstract:
In this paper, the interaction between the low energy proton ring-beam with an initial velocity perpendicular to the background magnetic field, and the background plasma is studied by one-dimensional (1D) hybrid simulations. In the initial stage, the excited plasma waves experience a fast growth exponentially, which is consistent with the linear theory. After that, three non-linear stages, including the saturation process, the fast damping process and the relatively stable stage, follow in sequence. In the linear stage, the mode-resonance damps with the pitch angle scattering of the injected protons, and the plasma oscillation reaches the peak quickly. The continuing pitch angle scattering makes the velocity distributions of the proton beam and the background ions uniformly distributed. Meanwhile, the initially excited right-handed resonant instability decreased, with only the Alfven waves left in the stable stage. The results also show that the effective heating of the background plasma is achieved after the linear stage, instead from the very beginning of the injection of the protons. This demonstrates that the excited plasma waves lead to the energy transferring from the injected proton beams to the background plasma.
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