Nonaxisymmetric Poynting Jets

TL;DR

This paper develops a theoretical framework for analyzing nonaxisymmetric, stationary, force-free plasma jets from misaligned black hole-accretion disk systems, revealing new solutions including self-confined jets with zero electromagnetic pressure.

Contribution

It derives a comprehensive stream equation for nonaxisymmetric jets, introduces a class of self-confined solutions, and connects these to numerical models of black hole jets in misaligned magnetic fields.

Findings

Derived a solvable stream equation for nonaxisymmetric jets.

Identified a class of self-confined jets with zero electromagnetic pressure.

Provided solutions approximating black hole jet simulations.

Abstract

The relativistic plasma jets from a misaligned black hole-accretion disk system will not be axially symmetric. Here we analyze nonaxisymmetric, stationary, translation invariant jets in the force-free approximation where the field energy dominates the particle energy. We derive a stream equation for these configurations involving the flux function $\psi$ for the transverse magnetic field, the linear velocity $v(\psi)$ of field lines along the jet, and the longitudinal magnetic field $B_z(\psi)$. The equations can be completely solved when $|v|=1$, and when $|v|<1$ the problem can be reduced to the pure magnetic case $v=0$ by a "field line dependent boost". We also find a large class of nonaxisymmetric solutions with arbitrary dependence on the longitudinal retarded time. A subclass of these constitutes a novel type of jet that has vanishing electromagnetic pressure $\tfrac{1}{2}(B^2-E^2)$ and requires no external pressure for confinement. We prove that such self-confinement is impossible when $B^2>E^2$. Finally, we write down specific solutions approximating numerical results for the nonaxisymmetric jet produced by a spinning black hole in an external, misaligned magnetic field.