Magnetic collimation of relativistic outflows in jets with a high mass flux

Self-collimation of relativistic magnetohydrodynamic (MHD) plasma outflows is inefficient in a single-component model consisting of a wind from a stellar object or an accretion disc, in the sense that the collimated portion of the mass and magnetic fluxes is uncomfortably low. The theory of magnetic collimation is applied here to a two-component model consisting of a relativistic wind-type outflow from a central source and a non-relativistic wind from the surrounding disc. Through a direct numerical simulation of the MHD flow in the nearest zone by the relaxation method and a solution of the steady-state problem in the far zone, it is shown that in this two-component model it is possible to collimate into cylindrical jets, in principle, up to all the mass and magnetic fluxes that are available from the central source. In such a case the non-relativistic disc-wind plays the role of the jet collimator. It is also shown that this collimation is accompanied by the formation of a sequence of shock waves at the interaction interface of the relativistic and non-relativistic outflows.