The formation and large-scale propagation of Poynting-dominated jets produced by accreting , rapidly rotating black hole systems are studied by numerically integrating the general relativistic magnetohydrodynamic equations of motion to follow the self-consistent interaction between accretion disks and black holes .
This study extends previous similar work by studying jets till t \approx 10 ^ { 4 } GM / c ^ { 3 } out to r \approx 10 ^ { 4 } GM / c ^ { 2 } , by which the jet is super- fast magnetosonic and moves at a lab-frame bulk Lorentz factor of \Gamma \sim 10 with a maximum terminal Lorentz factor of \Gamma _ { \infty } \lesssim 10 ^ { 3 } .
The radial structure of the Poynting-dominated jet is piece-wise self-similar , and fits to flow quantities along the field line are provided .
Beyond the Alfvén surface at r \sim 10 – 100 GM / c ^ { 2 } , the jet becomes marginally unstable to ( at least ) current-driven instabilities .
Such instabilities drive shocks in the jet that limit the efficiency of magnetic acceleration and collimation .
These instabilities also induce jet substructure with 3 \lesssim \Gamma \lesssim 15 .
The jet is shown to only marginally satisfy the necessary and sufficient conditions for kink instability , so this may explain how astrophysical jets can extend to large distances without completely disrupting .
At large distance , the jet angular structure is Gaussian-like ( or uniform within the core with sharp exponential wings ) with a half-opening angle of \approx 5 ^ { \circ } and there is an extended component out to \approx 27 ^ { \circ } .
Unlike in some hydrodynamic simulations , the environment is found to play a negligible role in jet structure , acceleration , and collimation as long as the ambient pressure of the surrounding medium is small compared to the magnetic pressure in the jet .