Special relativistic magnetohydrodynamic simulation of twocomponent outflow powered by magnetic explosion on compact stars
Abstract
The nonlinear dynamics of the outflow driven by magnetic explosion on the surface of compact object is investigated through special relativistic magnetohydrodynamic simulations. We adopt, as an initial equilibrium state, a spherical stellar object embedded in the hydrostatic plasma which has a density ρ(r) ~ r^{α} and is threaded by a dipole magnetic field. The injection of magnetic energy at the surface of compact star breaks the dynamical equilibrium and triggers twocomponent outflow. At the early evolutionary stage, the magnetic pressure increases rapidly in time around the stellar surface, initiating a magnetically driven outflow. Then it excites a strong forward shock, shock driven outflow. The expansion velocity of the magnetically driven outflow is characterized by the Alfvén velocity on the stellar surface, and follows a simple scaling relation υ_{mag} ~ υ_{A}^{1/2}. When the initial density profile declines steeply with radius, the strong shock is accelerated selfsimilarly to relativistic velocity ahead of the magnetically driven component. We find that the evolution of the strong forward shock can be described by a selfsimilar relation Γ_{sh} ~ r_{sh}, where Γ_{sh} is the Lorentz factor of the plasma measured at the shock surface r_{sh}. It should be stressed that the pure hydrodynamic process is responsible for the acceleration of the shock driven outflow. Our twocomponent outflow model, which is the natural outcome of the magnetic explosion, would deepen the understanding of the magnetic active phenomena on various magnetized stellar objects.
 Publication:

Advances in Plasma Astrophysics
 Pub Date:
 June 2011
 DOI:
 10.1017/S1743921311006971
 Bibcode:
 2011IAUS..274..220M
 Keywords:

 relativistic;
 MHD;
 neutron stars;
 numerical