  Photoionization models frequently assume constant temperature or density
within HII regions. We investigate this assumption by measuring the detailed
temperature and density structures of four HII regions in the Large Magellanic
Cloud and the Small Magellanic Cloud, using integral-field spectroscopic data
from the Wide-Field Spectrograph on the ANU 2.3m telescope. We analyse the
distribution of emission-lines of low-ionization species,
intermediate-ionization species and high-ionization species. We present the
complex electron temperature and density structures within HII regions. All
four nebulae present a negative gradient in the electron density profile. Both
positive and negative temperature gradients are observed in the nebulae. We
create a series of nebula models with a constant ISM pressure and varying
temperature and density distributions. Comparison of the line ratios between
our HII regions and models suggests that none of the simple nebula models can
reproduce the observed temperature and density structures. Comparison between
the models and the data suggests that the ISM pressure of nebulae in LMC and
SMC is between log(P/k)=6-7.5. Complex internal structures of the nebulae
highlight the importance of future Monte-Carlo photoionization codes for
accurate nebula modeling, which include a comprehensive consideration of
arbitrary geometries of HII regions.
