1997A&A...319.1025F

There is common belief that superluminal jet motion from active galactic nuclei and from galactic high energy sources originates in the magnetized environment of a rotating black hole surrounded by an accretion disk. The structure of these jet magnetospheres follows from solutions of the so called stream equation for the force-balance between axisymmetric magnetic surfaces. In this paper, two-dimensional force-free solutions of the stream equation are numerically obtained in a general relativistic context (3+1 formalism on Kerr geometry). We apply the numerical method of finite elements. In this approach, the regularity conditions along the light surfaces are automatically satisfied. After an iterative adjustment of the poloidal current distribution and the shape of the jet boundary, we find magnetic field configurations without kinks at the outer light surface. The solutions extend from the inner light surface of the Kerr black hole to the asymptotic regime of a cylindrically collimated jet with a finite radius. Different magnetic flux distributions along the disk surface were investigated. There is strong evidence for a hollow jet structure.