RECOLLIMATION SHOCKS IN MAGNETIZED RELATIVISTIC JETS

Abstract

We have performed two-dimensional special-relativistic magnetohydrodynamic\nsimulations of non-equilibrium over-pressured relativistic jets in cylindrical\ngeometry. Multiple stationary recollimation shock and rarefaction structures\nare produced along the jet by the nonlinear interaction of shocks and\nrarefaction waves excited at the interface between the jet and the surrounding\nambient medium. Although initially the jet is kinematically dominated, we have\nconsidered axial, toroidal and helical magnetic fields to investigate the\neffects of different magnetic-field topologies and strengths on the\nrecollimation structures. We find that an axial field introduces a larger\neffective gas-pressure and leads to stronger recollimation shocks and\nrarefactions, resulting in larger flow variations. The jet boost grows\nquadratically with the initial magnetic field. On the other hand, a toroidal\nfield leads to weaker recollimation shocks and rarefactions, modifying\nsignificantly the jet structure after the first recollimation rarefaction and\nshock. The jet boost decreases systematically. For a helical field, instead,\nthe behaviour depends on the magnetic pitch, with a phenomenology that ranges\nbetween the one seen for axial and toroidal magnetic fields, respectively. In\ngeneral, however, a helical magnetic field yields a more complex shock and\nrarefaction substructure close to the inlet that significantly modifies the jet\nstructure. The differences in shock structure resulting from different field\nconfigurations and strengths may have observable consequences for disturbances\npropagating through a stationary recollimation shock.\n