在准静态近似下对超相对论性流动等离子体不稳定性进行建模
Modeling ultrarelativistic streaming plasma instabilities under the quasistatic approximation
AI总结：
研究相对论性带电粒子束激发的等离子体流动不稳定性，利用准静态近似开发理论框架，能捕捉不稳定谱，发现电流丝化不稳定性时空演化及与斜双流不稳定性相互作用，经多种模拟验证，还展示其在稀薄束中捕捉非线性动力学的独特能力。
AI中文摘要：
相对论性带电粒子束激发的等离子体流动不稳定性在天体物理和实验室环境中起着关键作用。然而，其数值研究受到背景等离子体和束粒子之间时空尺度差异的挑战，对于稀薄的超相对论性束，这种差异可能相差几个数量级。在此，我们利用准静态近似（QSA）开发了一个新的理论框架，能够在与前沿不断遇到未受扰动等离子体的束相关的时空区域中捕捉完整的不稳定谱。在这个线性的、完全电磁模型中，我们发现了电流丝化不稳定性以前未报道的时空演化，并阐明了它与斜双流不稳定性的相互作用，预测了丝化在束前沿附近的主导地位。理论、动力学粒子模拟（PIC）和基于QSA的PIC模拟之间的良好一致性验证了该方法的稳健性。通过将基于QSA的PIC模拟推到极其稀薄的电子 - 正电子束，如在耀变体喷流中发现的那些，我们展示了它们在捕捉以前动力学模拟无法达到的参数区域中流动不稳定性丰富非线性动力学方面的独特能力。
英文摘要：
Plasma streaming instabilities excited by relativistic charged particle beams play a pivotal role in astrophysical and laboratory environments. Their numerical study, however, is challenged by the disparity in spatiotemporal scales between the background plasma and beam particles, which can differ by several orders of magnitude for tenuous, ultrarelativistic beams. Here, we exploit the quasistatic approximation (QSA) to develop a new theoretical framework capable of capturing the full unstable spectrum in the spatiotemporal regime relevant for beams that continuously encounter unperturbed plasma at their leading edge. Within this linear, fully electromagnetic model, we uncover a previously unreported spatiotemporal evolution of the current filamentation instability and elucidate its interplay with the oblique two-stream instability, predicting the dominance of filamentation in the vicinity of the beam front. The good agreement between theory, kinetic particle-in-cell (PIC) simulations, and QSA-based PIC simulations validates the robustness of the approach. By pushing QSA-based PIC simulations to extremely dilute electron-positron beams, such as those found in blazar jets, we demonstrate their unique ability to capture the rich nonlinear dynamics of streaming instabilities in parameter regimes previously inaccessible to kinetic simulations.
