The Dynamic Age of Centaurus A
  In this paper I present dynamic models of the radio source Centaurus A, and
critique possible models of in situ particle reacceleration (ISR) within the
radio lobes. The radio and gamma-ray data require neither homogeneous plasma
nor quasi-equipartition between plasma and magnetic field; inhomogeneous models
containing both high-field and low-field regions are equally likely. Cen A
cannot be as young as the radiative lifetimes of its relativistic electrons,
which range from a few to several tens of Myr. Two classes of dynamic models --
flow driven and magnetically driven -- are consistent with current
observations; each requires Cen A to be on the order of a Gyr old. Thus,
ongoing ISR must be occurring within the radio source. Alfven-wave ISR is
probably occurring throughout the source, and may be responsible for
maintaining the gamma-ray-loud electrons. It is likely to be supplemented by
shock or reconnection ISR which maintains the radio-loud electrons in
high-field regions.
