Acceleration of relativistic outflows with tangled magnetic field

Relativistic outflows are launched from compact stars, such as black holes and neutron stars. The flows are Poynting dominated at their origin because the rotational energy of the compact stars can be extracted by the magnetic braking mechanism. However, it is known that the efficient acceleration of the flows by converting the Poynting energy to kinetic one is not easy in the ideal magnetohydrodynamic (MHD) limit. Non-ideal MHD processes including dissipation of the magnetic field are discussed as an solution to the efficient flow acceleration. Here, we study the one-dimensional cylindrical relativistic outflow with non-ideal MHD effects. Radiative cooling (cooling effect), conversion of the ordered magnetic field into the turbulent one (conversion effect) and dissipation of the turbulent magnetic field (dissipation effect) are formulated according to our past study on pulsar wind nebulae. The cooling effect works as acceleration but the flow is not efficiently accelerated by the cooling effect alone. This is the same for the conversion effect. The dissipation effect rather works as deceleration. However, we find that the flow is efficiently accelerated to about a half of the maximum possible Lorentz factor when the cooling, conversion and dissipation effects work simultaneously. In this case, almost a half of the total luminosity of the flow is converted into the radiation.