2001MNRAS.325..249B

Recent numerical simulations and analytical models of magnetically collimated plasma outflows from a uniformly rotating central gravitating object and/or a Keplerian accretion disc have shown that relatively low mass and magnetic fluxes reside in the produced jet. Observations, however, indicate that in some cases, as in jets of young stellar objects, the collimated outflow carries higher fluxes than these simulations predict. A solution to this problem is proposed here by assuming that jets with high mass flux originate in a central source which produces a non-collimated outflow provided that this source is surrounded by a rapidly rotating accretion disc. The relatively faster rotating disc produces a collimated wind, which then forces all the enclosed outflow from the central source to be collimated too. This conclusion is confirmed by self-consistent numerical solutions of the full set of the magnetohydrodynamic equations.