  We here consider the pressure equilibrium during an intense magnetic flare
above the surface of a cold accretion disk. Under the assumption that the
heating source for the plasma trapped within the flaring region is an influx of
energy transported inwards with a group velocity close to $c$, e.g., by
magnetohydrodynamic waves, this pressure equilibrium can constrain the Thomson
optical depth $\tau_T$ to be of order unity. We suggest that this may be the
reason why $\tau_T\sim 1$ in Seyfert Galaxies. We also consider whether current
data can distinguish between the spectrum produced by a single X-ray emitting
region with $\tau_T\sim 1$ and that formed by many different flares spanning a
range of $\tau_T$. We find that the current observations do not yet have the
required energy resolution to permit such a differentiation. Thus, it is
possible that the entire X-ray/$\gamma$-ray spectrum of Seyfert Galaxies is
produced by many independent magnetic flares with an optical depth
$0.5<\tau_T<2$.

Astrophysics