We describe numerical simulations , using the particle-in-cell ( PIC ) and hybrid-PIC code Lsp [ T. P. Hughes et al. , Phys .
Rev .
ST Accel .
Beams 2 , 110401 ( 1999 ) ] , of the head-on merging of two laboratory supersonic plasma jets .
The goals of these experiments are to form and study astrophysically relevant collisionless shocks in the laboratory .
Using the plasma jet initial conditions ( density \sim 10 ^ { 14 } – 10 ^ { 16 } cm ^ { -3 } , temperature \sim few eV , and propagation speed \sim 20 –100 km/s ) , large-scale simulations of jet propagation demonstrate that interactions between the two jets are essentially collisionless at the merge region .
In highly resolved one- and two-dimensional simulations , we show that collisionless shocks are generated by the merging jets when immersed in applied magnetic fields ( B \sim 0.1 –1 kG ) .
At expected plasma jet speeds of up to 100 km/s , our simulations do not give rise to unmagnetized collisionless shocks , which require much higher velocities .
The orientation of the magnetic field and the axial and transverse density gradients of the jets have a strong effect on the nature of the interaction .
We compare some of our simulation results with those of previously published PIC simulation studies of collisionless shock formation .