Two-dimensional Particle-in-Cell simulations of axisymmetric black hole magnetospheres

TL;DR

This study uses two-dimensional particle-in-cell simulations to explore the dynamics of axisymmetric black hole magnetospheres, revealing energy extraction patterns, the breakdown of MHD approximations, and implications for jet collimation.

Contribution

It introduces a novel 2D particle-in-cell simulation approach to study black hole magnetospheres, highlighting the limitations of MHD in such environments.

Findings

Energy is extracted mainly from middle latitudes.

Magnetohydrodynamic approximations are invalid in magnetically-dominated regimes.

Charge-separated plasmas are highly non-neutral, affecting jet formation.

Abstract

We investigate the temporal evolution of an axisymmetric magnetosphere around a rapidly rotating, stellar-mass black hole, applying a two-dimensional particle-in-cell simulation scheme. Adopting a homogeneous pair production, and assuming that the mass accretion rate is much less than the Eddington limit, we find that the black hole's rotational energy is preferentially extracted from the middle latitudes, and that this outward energy flux exhibits an enhancement that lasts approximately 160 dynamical time scales. It is demonstrated that the magnetohydrodynamic approximations cannot be justified in such a magnetically-dominated magnetosphere, because the Ohm's law completely breaks down, and because the charge-separated electron-positron plasmas are highly non-neutral. An implication is given regarding the collimation of relativistic jets.