Oral Presentation

The role of magnetic field for relativistic jets and black hole accretion disc

Author(s): Yosuke Mizuno (ITP, Goethe University Frankfurt)

Presenter: Yosuke Mizuno (ITP, Goethe University Frankfurt)

The most promising mechanisms for producing and accelerating relativistic jets, and maintaining collimated structure of relativistic jets from accretion discs onto black holes involve magnetohydrodynamical (MHD) processes. We have investigated the role of magnetic field in relativistic jets via general-relativistic MHD simulations. We found that relativistic jets involving helical magnetic field are unstable via a current-driven kink instability, which leads to helically distorted structure in relativistic jets and dissipates the jet's magnetic energy through magnetic reconnection. We also found that an over-pressured relativistic jet leads to the generation of a series of stationary recollimation shocks and rarefaction structures. The differences in the recollimation-shock structure due to different magnetic-field topologies and strengths may be observable through mm- and space-VLBI. We also present our new 3D AMR-GRMHD code BHAC and its application to black-hole accretion disc with the goal of extracting observational signatures of a black-hole horizon from future mm-VLBI and space VLBI observations.