From Filamentation to Stratification: Instability Dynamics in Scissors-Shaped Relativistic Beam-Plasma System

Abstract: Counter-streaming systems are a canonical model for beam-plasma instabilities, such as the filamentation instability, which is critical in high energy density physics. However, scenarios involving intersecting fast electron beams break the cylindrical symmetry inherent to such systems. Here, we introduce the scissors-shaped configuration, a fundamental multi-velocity-component system that captures this broken symmetry. Through theoretical analysis and particle-in-cell simulations, we reveal a dramatic shift in the instability dynamics: the system undergoes a stratification mode instead of filamentation. This mode is rapidly quenched by magnetic reconnection, leading to a quasi-stable state with magnetic energy two orders of magnitude lower than in the counter-streaming case. This discovery establishes a new principle of passive instability control via geometric configuration, offering a new perspective on beam-plasma interactions in astrophysics and inertial confinement fusion. The underlying physics is verifiable in upcoming multi-laser experiments.