  The thermodynamics of ``horizon brightened acceleration radiation'' (HBAR),
due to a random atomic cloud freely falling into a black hole in a
Boulware-like vacuum, is shown to mimic the thermodynamics of the black hole
itself. The thermodynamic framework is developed in its most general form via a
quantum optics master equation, including rotating (Kerr) black holes and for
any set of initial conditions of the atomic cloud. The HBAR field exhibits
thermal behavior at the Hawking temperature and an area-entropy-flux relation
that resembles the Bekenstein-Hawking entropy. In addition, this general
approach reveals:(i) the existence of an HBAR-black-hole thermodynamic
correspondence that explains the HBAR area-entropy-flux relation;(ii) the
origin of the field entropy from the near-horizon behavior, via conformal
quantum mechanics (CQM).
