In this paper, we show that if the broad-line region clouds are in approximate energy equipartition between the magnetic field and gravity, as hypothesized by Rees, there will be a significant effect on the shape and smoothness of broad emission-line profiles in active galactic nuclei. Linewidths of contributing clouds or flow elements are much wider than their thermal widths, because of the presence of non-dissipative magnetohydrodynamic waves and their collective contribution produce emission-line profiles broader and smoother than would be expected if a magnetic field were not present. As an illustration, a simple model of isotropically emitting clouds, normally distributed in velocity, is used to show that smoothness can be achieved for less than ∼8×104 clouds and may even be as low as a few hundred. We conclude that magnetic confinement has far-reaching consequences for observing and modelling active galactic nuclei.

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Published in Monthly Notices of the Royal Astronomical Society, v. 316, issue 1, p. 103-106.

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2000 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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