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arXiv 2201.03937physics.plasm-phastro-ph.SR
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弱磁化等离子体中电子束引起的等离子体发射

Plasma Emission Induced By Electron Beam in Weakly Magnetized Plasmas

Yao Chen, Zilong Zhang, Sulan Ni, Chuanyang Li, Hao Ning, Xiangliang Kong

摘要:

以往对束流驱动等离子体发射过程的研究主要针对非磁化等离子体。在这里,我们提出了全动力学电磁粒子模拟研究在弱磁化等离子体的太阳日冕条件下的过程。通过经典的尾部凸点不稳定性激发的主模是束朗缪尔(BL)模。其他模式包括由电子回旋共振不稳定性激发的哨声(W)模式、包括具有较小波数$k$的超光速Z模式分量和具有较大$k$的热朗缪尔分量的广义朗缪尔(GL)波、以及等离子体发射的基波(F)和谐波(H)分支。对不同质量和温度比的电子和质子的进一步模拟表明,GL模和两个逃逸模(F和H)与BL模的强度呈正相关,支持它们是通过BL模参与的非线性波-波耦合过程激发的。我们认为,占主导地位的过程是初级BL模式的衰减。这与等离子体发射的标准理论是一致的。然而,不能完全排除F发射的Z+W $\rightarrow$ O-F聚结过程的其他可能性。

英文摘要:

Previous studies on the beam-driven plasma emission process were done mainly for unmagnetized plasmas. Here we present fully-kinetic electromagnetic particle-in-cell simulations to investigate such process in weakly-magnetized plasmas of the solar corona conditions. The primary mode excited is the beam-Langmuir (BL) mode via the classical bump-on-tail instability. Other modes include the whistler (W) mode excited by the electron cyclotron resonance instability, the generalized Langmuir (GL) waves that include a superluminal Z-mode component with smaller wave number $k$ and a thermal Langmuir component with larger $k$, and the fundamental (F) and harmonic (H) branches of plasma emission. Further simulations of different mass and temperature ratios of electrons and protons indicate that the GL mode and the two escaping modes (F and H) correlate positively with the BL mode in intensity, supporting that they are excited through nonlinear wave-wave coupling processes involving the BL mode. We suggest that the dominant process is the decay of the primary BL mode. This is consistent with the standard theory of plasma emission. Yet, the other possibility of the Z+W$\rightarrow$O--F coalescing process for the F emission cannot be ruled out completely.

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