Laboratory investigation of the interaction between the jet and background, from collisionless to strong collision

TL;DR

This study uses laser-driven experiments and simulations to explore how supersonic jets interact with backgrounds under different collision conditions, revealing shock structures, filament formations, and electron acceleration relevant to astrophysical phenomena.

Contribution

It provides new experimental and simulation data on jet-background interactions across collision regimes, elucidating shock formation, filament instability, and electron dynamics in plasma jets.

Findings

Double-shock structures observed in collision cases.

Jet deflection of 50 degrees by high-density background.

Filament structures with widths comparable to ion skin depth.

Abstract

The interaction between the supersonic jet and background can influence the process of star formation, and this interaction also results in a change of the jet's velocity, direction and density through shock waves. However, due to the limitations of current astronomical facilities, the fine shock structure and the detailed interaction process still remain unclear. Here we investigate the plasma dynamics under different collision states through laser-driven experiments. A double-shock structure is shown in the optical diagnosis for collision case, but the integrated self-emitting X-ray characteristic is different. For solid plastic hemisphere obstacle, two-layer shock emission is observed, and for the relatively low-density laser-driven plasma core, only one shock emission is shown. And the plasma jets are deflected by $50 ^{\circ}$ through the interaction with the high-density background in both cases. For collisionless cases, filament structures are observed, and the mean width of filaments is roughly the same as the ion skin depth. High-energy electrons are observed in all interaction cases. We present the detailed process of the shock formation and filament instability through 2D/3D hydrodynamic simulations and particle-in-cell simulations respectively. Our results can also be applied to explain the shock structure in the Herbig-Haro (HH) 110/270 system, and the experiments indicate that the impact point may be pushed into the inside part of the cloud.