AI 中文总结
研究相对论性粒子束在等离子体中的不稳定性，提出统一全电磁准静态模型，不采用SVEA，发现新的时空CFI在前沿占主导，能捕捉多种不稳定性增长，经与粒子模拟比较，证实该模型对相关不稳定性建模的有效性。
AI 中文摘要
相对论性粒子束在致密环境等离子体中传播时易受流不稳定性影响，这在多种天体物理和实验室环境中决定系统动力学。对于未磁化、无碰撞且被稀薄冷相对论性束流渗透的等离子体，主要不稳定性为准静电、斜双流（OTSI）和基本磁电流丝不稳定性（CFI）。虽对其线性和非线性特性研究数十年，但多数处理假设无界、均匀系统，预测纯时间不稳定性增长。现实中束流有界且不断遇到新等离子体，不稳定性时空增长。早在20世纪60年代就有流不稳定性的时空微扰处理，但仅近期才从理论上解决OTSI和CFI的时空区域问题，且这些模型限于特定不稳定性类别，无法描述时空OTSI和CFI间竞争。本文提出统一、全电磁准静态模型，不采用缓变包络近似（SVEA），发现此前未报道的时空CFI在前沿附近占主导，SVEA失效处正是如此，在束流更靠后的位置才被OTSI取代。还证明模型能捕捉长窄束激发的自调制和软管不稳定性增长。与粒子模拟比较证实准静态方法对建模相对论性稀薄束流引发的流等离子体不稳定性的有效性。
英文摘要
Relativistic particle beams propagating through dense ambient plasmas are susceptible to streaming instabilities that can govern the system dynamics in various astrophysical and laboratory settings. For an unmagnetized, collisionless plasma pervaded by a dilute, cold relativistic beam, the dominant instabilities are the quasielectrostatic, oblique two-stream (OTSI) and the essentially magnetic, current filamentation instability (CFI). While their linear and nonlinear properties have been researched for decades, most treatments assume unbounded, uniform systems and thus predict purely temporal instability growth. This assumption, however, is questionable for realistic configurations where a bounded beam continuously encounters fresh plasma. This feature causes instabilities to grow in a spatiotemporal manner. Whereas spatiotemporal perturbative treatments of streaming instabilities were derived as early as the 1960s, only recently have the spatiotemporal regimes of OTSI and CFI been addressed theoretically. Yet these models are restricted to a specific instability class, and hence cannot describe the competition between spatiotemporal OTSI and CFI. In this work, we present a unified, fully electromagnetic quasi-static model of all unstable modes arising throughout the beam. By not adopting the slowly varying envelope approximation (SVEA), we find that a previously unreported spatiotemporal CFI actually prevails near the front, precisely where the SVEA fails, and is only superseded by OTSI further back in the beam. Furthermore, we demonstrate that our model also captures the growth of the self-modulation and hosing instabilities excited by long, narrow beams. Comparisons with particle-in-cell simulations confirm the validity of the quasistatic approach for modeling streaming plasma instabilities triggered by relativistic dilute beams.
