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.
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.
Instabilities in a Modulated Hydrodynamic Jet
Modulations in the jet's engine allow baryons to enter into the jet's spine, thereby increasing the loading and decelerating the flow.
including the double NS merger GW170817 click here The simulations have been conducted with the public code PLUTO (Mignone et al. 2007)