Collisionless Magnetic Reconnection in Curved Spacetime and the Effect of Black Hole Rotation

TL;DR

This paper investigates how the gravitational field and rotation of black holes influence collisionless magnetic reconnection, revealing that black hole rotation generally decreases reconnection rates unless collisionless effects are considered, which can enhance it.

Contribution

It introduces a general relativistic model for collisionless magnetic reconnection near rotating black holes, combining gravity and plasma effects for the first time.

Findings

Black hole rotation increases azimuthal reconnection layer length.

Collisionless effects can enhance reconnection rates near black holes.

Gravity influences magnetic reconnection in the vicinity of compact objects.

Abstract

Magnetic reconnection in curved spacetime is studied by adopting a general relativistic magnetohydrodynamic model that retains collisionless effects for both electron-ion and pair plasmas. A simple generalization of the standard Sweet-Parker model allows us to obtain the first order effects of the gravitational field of a rotating black hole. It is shown that the black hole rotation acts as to increase the length of azimuthal reconnection layers, per se leading to a decrease of the reconnection rate. However, when coupled to collisionless thermal-inertial effects, the net reconnection rate is enhanced with respect to what would happen in a purely collisional plasma due to a broadening of the reconnection layer. These findings identify an underlying interaction between gravity and collisionless magnetic reconnection in the vicinity of compact objects.