Two-dimensional numerical study of effect of magnetic field on evolution of laser-driven jets

Abstract

Astrophysical jets are highly collimated supersonic plasma beams distributed across various astrophysical backgrounds. The triggering mechanism, collimation transmission, and stability of jets have always been a research hotspot of astrophysics. In recent years, observations and laboratory research have found that the magnetic field plays a crucial role in jet collimation, transmission, and acceleration. In this work, the two-dimensional numerical simulation of the jet in front of the CH plane target driven by an intense laser is carried out by using the open-source MHD FLASH simulation program. We systematically investigate the dynamic behaviors of jet evolution caused by the Biermann self-generated magnetic field, the external magnetic field with different directions and initial strengths and compare them with each other. Simulation results show that the Biermann self-generated magnetic field does not affect the jet interface dynamics. The external magnetic field has a redirecting effect on the plasma outflow. The external magnetic field, which is parallel to the direction of the plasma outflow center in front of the target, is conducive to the generation and collimation of the jet. The evolution of the jet goes through three stages: antimagnetic ellipsoid cavity, conical nozzle, and collimated jet. Its formation process and evolution process result from competition among plasma thermal, magnetic, and ram pressure. In terms of force, plasma thermal pressure gradient and magnetic pressure forces play a decisive role in the jet evolution process. The presence of magnetic pressure significantly limits the radial expansion of the jet to achieve axial collimation transmission. The length-diameter ratio of the jet is positively correlated with the initial axial applied magnetic field intensity. In addition, we observe in the simulation that there are many node-like structures in the jet evolution zone, similar to the jet node in YSO. The results provide a reference for future experimental research related to jets and contribute to a more in-depth understanding of the evolution of celestial jets.