  In situ measurements of ion charge states can provide unique insight into the
heating and evolution of coronal mass ejections when tested against realistic
non-equilibrium ionization modeling. In this work we investigate the
representation of the CME magnetic field as an expanding spheromak
configuration, where the plasma heating is prescribed by the choice of
anomalous resistivity and the spheromak dynamics. We chose as a test case, the
19 May 2007 CME observed by STEREO and ACE. The spheromak is an appealing
physical model, because the location and degree of heating is fixed by the
choice of anomalous resistivity and the spheromak expansion rate which we
constrain with observations. This model can provide the heating required
between 1.1$R_{\sun}$ and earth orbit to produce charge states observed in the
CME flux rope. However this source of heating in the spheromak alone has
difficulty accounting for the rapid heating to Fe$^{8 - 11+}$ at lower heights,
as observed in STEREO EUVI due to the rapid radiative cooling that occurs at
the high densities involved. Episodes of heating and cooling clearly unrelated
to spheromak expansion are observed prior to the eruption, and presumably still
play a role during the eruption itself. Spheromak heating is also not capable
of reproducing the high Fe charge states (Fe$^{16+}$ and higher) seen in situ
exterior to the flux rope in this CME. Thus while the spheromak configuration
may be a valid model for the magnetic topology, other means of energization are
still required to provide much of the rapid heating observed.
