MHD Simulations of Magnetized Rotating Jets

The results of MHD simulations of supersonic astrophysical and laboratory jets in an external poloidal magnetic field ( $${{B}_{r}}$$ , $${{B}_{z}}$$ ) taking into account the rotation of the matter, are presented. The ejected matter is collimated by the magnetic field, the degree of collimation and the flow structure depend on the relation between of the magnetic field induction and the angular velocity of the matter. For a strong magnetic field and moderate rotation, a barrel-shaped structure of an elongated shape is formed, which leaves behind a stable outflow. Inside the jet ejection, a barrel-shaped a periodic shock-wave structure is observed. For a moderate magnetic field and rapid rotation, the ejected matter at first significantly expands, but then gradually collimates into a jet due to the appearance of a toroidal magnetic field $${{B}_{\phi }}$$ . A cocoon-shaped structure is formed. It spreads to the boundary of the computational domain. Inside the jet cocoon, a cavity with a low density of matter, quasi-stationary in time near is formed. In all cases, the rotation of the matter in the jet is transmitted to neighboring regions, which ultimately leads to the generation of magneto-torsional oscillations associated with the appearance of a toroidal component of the field. The toroidal field $${{B}_{\phi }}$$ arises during the twisting of the poloidal magnetic field due to the dependence of the jet matter angular velocity on the radial ( $$r$$ ) and axial ( $$z$$ ) coordinates. The toroidal field also participates in the collimation of the jet.