Magnetic reconnection, breaking and reorganization of magnetic field topology, is a fundamental process for rapid release of magnetic energy into plasma particles that occurs pervasively throughout the universe. In most natural circumstances, the plasma properties on either side of the reconnection layer are asymmetric, in particular for the collision rates that are associated with a combination of density and temperature and critically determine the reconnection mechanism. To date, all laboratory experiments on magnetic reconnections have been limited to purely collisional or collisionless regimes. Here, we report a well-designed experimental investigation on asymmetric magnetic reconnections in a novel hybrid collisional-collisionless regime by interactions between laser-ablated Cu and CH plasmas. We show that the growth rate of the tearing instability in such a hybrid regime is still extremely large, resulting in rapid formation of multiple plasmoids, lower than that in the purely collisionless regime but much higher than the collisional case. In addition, we, for the first time, directly observe the topology evolutions of the whole process of plasmoid-dominated magnetic reconnections by using highly-resolved proton radiography.

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 • through the interaction with the high-density background in both cases. For collisionless case, 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 detail 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.