Exact equilibrium state for pair plasmas near the horizon of a Schwarzschild black hole

Abstract

A pair plasma in hidrostatic equilibrium near the horizon of a Schwarzschild black hole is an exact state. In this work, we show that an exact non--hidrostatic equilibrium state can be sustained for a pair plasma, in which its constituents are moving near the horizon of the black hole. This equilibrium state solution is not due to a vortical formalism, but by the balance of forces in the plasma. This new equilibrium state has a pressure for the hydrostatic equilibrium, although the plasma moves. The equilibrium is achieved by the generation of a magnetic field that emerges by the interplay between the plasma dynamics and the gravitational field, having no flat spacetime analogue. No electric fields are needed to sustain the equilibria. The magnetic field shows an exponential decaying behavior, governed by a function that depends on the properties of the pair plasma and the black, and that plays the role of a characteristc length of the dynamics of the magnetic field.