In situ recordings by the solar Wind spacecraft reveal the ubiquitousness of alpha particles, whose drift velocities to the background proton $v_{\alpha }$ are generally less than or equal to the local Alfvén velocity $v_A$. The alpha beam instability plays a significant role in the alpha beam deceleration in the solar wind; nonetheless, the detailed mechanism of deceleration remains unclear. By using the linear Vlasov equation of the PDRK/B0 solver, the present work investigates the kinetic instability caused by both the alpha beam and the electron temperature anisotropy in the solar wind and assesses the effects of the electron temperature anisotropy on such instability. The results show that both anisotropic electrons and alpha beams lead to the excitation of several plasma waves, and the wave frequency, growth rate, and polarization properties are sensitive to the electron temperature anisotropy ($T_{e\perp }/T_{e\Vert }$), the parallel electron beta (${\beta }_{e\Vert }$), and the alpha beam drift velocity ($v_{\alpha }/v_A$). With an excess parallel temperature $T_{e\perp }/T_{e\Vert }<1$, the parallel magnetosonic/whistler (PM/W), parallel Alfvén wave (PAW), and oblique Alfvén/ion cyclotron (OA/IC) instabilities could be generated, while for an excess perpendicular temperature $T_{e\perp }/T_{e\Vert }>1$, the PM/W, OA/IC, parallel whistler (PW), and kinetic Alfvén wave (KAW) instabilities could grow. In the region of $T_{e\perp }/T_{e\Vert }<1$, the thresholds of the PM/W, PAW, and OA/IC instabilities extend to lower drift velocity $v_{\alpha }/v_A$. In the region of $T_{e\perp }/T_{e\Vert }>1$, the thresholds of the PM/W and OA/IC instabilities increase, while those of the PW and KAW instabilities are shifted to lower $v_{\alpha }/v_A$. The current study presents a comprehensive overview for alpha beam instabilities that limit the alpha beam drift velocity in the solar wind.

中文翻译：

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电子温度各向异性对太阳风中 α/质子不稳定性的影响

太阳风航天器的原位记录揭示了无处不在的阿尔法粒子，其漂移速度到背景质子$v_{\alpha }$通常小于或等于局部 Alfvén 速度$v_{\mathrm{一个}}$. α束不稳定性在太阳风中α束减速中起重要作用；然而，减速的详细机制仍不清楚。通过使用 PDRK/B0 求解器的线性 Vlasov 方程，本工作研究了太阳风中 α 束和电子温度各向异性引起的动力学不稳定性，并评估了电子温度各向异性对这种不稳定性的影响。结果表明，各向异性电子和α束均导致多个等离子体波的激发，且波频率、生长速率和极化特性对电子温度各向异性敏感（${吨}_{e\perp }/{吨}_{e\Vert }$），平行电子β（${\beta }_{e\Vert }$) 和 α 光束漂移速度 ($v_{\alpha }/v_{\mathrm{一个}}$）。平行温度过高${吨}_{e\perp }/{吨}_{e\Vert }<1$，可能会产生平行磁声/哨声 (PM/W)、平行 Alfvén 波 (PAW) 和倾斜 Alfvén/离子回旋加速器 (OA/IC) 不稳定性，而对于过高的垂直温度${吨}_{e\perp }/{吨}_{e\Vert }>1$，PM/W、OA/IC、平行哨声 (PW) 和动力学 Alfvén 波 (KAW) 不稳定性可能会增加。在该地区${吨}_{e\perp }/{吨}_{e\Vert }<1$，PM/W、PAW 和 OA/IC 不稳定性的阈值扩展到更低的漂移速度$v_{\alpha }/v_{\mathrm{一个}}$. 在该地区${吨}_{e\perp }/{吨}_{e\Vert }>1$，PM / W和OA / IC不稳定性的阈值增加，而PW和KAW不稳定性的阈值移至更低$v_{\alpha }/v_{\mathrm{一个}}$. 目前的研究全面概述了限制太阳风中阿尔法光束漂移速度的阿尔法光束不稳定性。