Electron temperature anisotropies and electron beams are nonthermal features of the observed nonequilibrium electron velocity distributions in the solar wind. In collision-poor plasmas these nonequilibrium distributions are expected to be regulated by kinetic instabilities through wave-particle interactions. This study considers electron instabilities driven by the interplay of core electron temperature anisotropies and the electron beam, and firstly gives a comprehensive analysis of instabilities in arbitrary directions to the background magnetic field. It clarifies the dominant parameter regime (e.g., parallel core electron plasma beta $\beta_{\mathrm{ec\parallel}}$, core electron temperature anisotropy $A_{\mathrm{ec}}\equiv T_{\mathrm{ec\perp}}/T_{\mathrm{ec\parallel}}$, and electron beam velocity $V_{\mathrm{eb}}$) for each kind of electron instability (e.g., the electron beam-driven electron acoustic/magnetoacoustic instability, the electron beam-driven whistler instability, the electromagnetic electron cyclotron instability, the electron mirror instability, the electron firehose instability, and the ordinary-mode instability). It finds that the electron beam can destabilize electron acoustic/magnetoacoustic waves in the low-$\beta_{\mathrm{ec\parallel}}$ regime, and whistler waves in the medium- and large-$\beta_{\mathrm{ec\parallel}}$ regime. It also finds that a new oblique fast-magnetosonic/whistler instability is driven by the electron beam with $V_{\mathrm{eb}}\gtrsim7V_{\mathrm{A}}$ in a regime where $\beta_{\mathrm{ec\parallel}}\sim0.1-2$ and $A_{\mathrm{ec}}<1$. Moreover, this study presents electromagnetic responses of each kind of electron instability. These results provide a comprehensive overview for electron instability constraints on core electron temperature anisotropies and electron beams in the solar wind.

中文翻译：

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来自太阳风中电子动力学不稳定性的电子温度各向异性和电子束约束

电子温度各向异性和电子束是在太阳风中观察到的非平衡电子速度分布的非热特征。在缺乏碰撞的等离子体中，这些非平衡分布预计会受到波粒相互作用的动力学不稳定性的调节。本研究考虑了由核心电子温度各向异性和电子束相互作用驱动的电子不稳定性，首先对背景磁场任意方向的不稳定性进行了综合分析。它阐明了主要参数机制（例如，平行核心电子等离子体 beta $\beta_{\mathrm{ec\parallel}}$、核心电子温度各向异性 $A_{\mathrm{ec}}\equiv T_{\mathrm{ec\ perp}}/T_{\mathrm{ec\parallel}}$, 和电子束速度 $V_{\mathrm{eb}}$) 对于每种电子不稳定性（例如，电子束驱动的电子声学/磁声不稳定性、电子束驱动的惠斯勒不稳定性、电磁电子回旋不稳定性、电子镜不稳定性、电子管不稳定性和常模不稳定性）。它发现电子束可以在低 $\beta_{\mathrm{ec\parallel}}$ 状态下破坏电子声/磁声波，而在中和大 $\beta_{\mathrm{ec \parallel}}$ 制度。它还发现，在 $\beta_{\mathrm{ 的状态下，具有 $V_{\mathrm{eb}}\gtrsim7V_{\mathrm{A}}$ 的电子束驱动了一种新的斜快磁声/惠斯勒不稳定性ec\parallel}}\sim0.1-2$ 和 $A_{\mathrm{ec}}<1$。而且，这项研究展示了每种电子不稳定性的电磁响应。这些结果提供了对核心电子温度各向异性和太阳风中电子束的电子不稳定性约束的全面概述。