Numerical Simulations of Jet's Instabilities in a Star

Instabilities in a Hydrodynamic Jet

The jet is launched into the stellar envelope following the collapse of the stellar core. The jet propagation inflates a hot pressurized bubble, known as "the cocoon". Due to the lateral motion of the relativistically heavy jet into the lighter cocoon in the first collimation shock. Then the jet becomes instable to Rayleigh-Taylor instabilities (RTI) that form on the plane perpendicular to the jet's axis. As soon as the first collimation shock is closed, forms a new shock that expands radially, inducing Richtmeyer-Meshkov instabilities that develop on the same plane with the previous RTI. This behavior repeats, albeit at a smaller extent, at the second collimation shock.

Energy density colormap of a 3D simulation. Left: Edge on view of the jet. Right: Face on view of the jet. The movie depicts different heights along the jet (indicated by the dashed white line) at time of breakout. Units are arbitrary and colorbar scale is logarithmic. Download video

Instabilities in a Weakly Magnetized Jet

The collimation shock of the magnetic jet is narrower in comparison to the hydrodynamic jet, due to the higher pressure at the base of the cocoon. As a result the lateral motion of the jet is limited, and instabilities are inhibited on the jet-cocoon interface.

Terminal 4-velocity colormap of a 3D simulation. Left: Edge on view of the jet. Right: Face on view of the jet. The movie depicts different heights along the jet (indicated by the dashed white line) at time of breakout. Colorbar scale is logarithmic. Download video

For more videos of jets in various cosmic explosions,
including the double NS merger GW170817
click here

The simulations have been conducted with the public code PLUTO (Mignone et al. 2007)