Simulating Electromagnetic Cascades in Magnetospheres of Active Galactic Nuclei

Context: At the low accretion-rates typical for BL Lac-objects, magnetospheres of active galactic nuclei can develop vacuum gaps with strong electric fields accelerating charged seed particles parallel to the magnetic fields up to ultra-relativistic energies. The seed particles sustain electromagnetic cascades by inverse-Compton-scattering and subsequent pair-production in soft background-radiation- fields from the accretion-disk and/or photo-ionised clouds, along the direction of the primary particle beams. Method: The one-dimensional kinetic equation describing this linear inverse-Compton- Klein-Nishina-pair-cascade is inferred. We have developed a novel code, that can numerically solve this kinetic equation for an ample variety of input-parameters. By this, quasi-stationary particle-and photon-spectra are obtained.