Magnetic Field Structure in Spheroidal Star-Forming Clouds
  A model of magnetic field structure is presented to help test the prevalence
of flux freezing in star-forming clouds of various shapes, orientations, and
degrees of central concentration, and to estimate their magnetic field
strength. The model is based on weak-field flux freezing in centrally condensed
Plummer spheres and spheroids of oblate and prolate shape. For a spheroid of
given density contrast, aspect ratio, and inclination, the model estimates the
local field strength and direction, and the global field pattern of hourglass
shape. Comparisons with a polarization simulation indicate typical angle
agreement within 1 - 10 degrees. Scalable analytic expressions are given to
match observed polarization patterns, and to provide inputs to radiative
transfer codes for more accurate predictions. The model may apply to
polarization observations of dense cores, elongated filamentary clouds, and
magnetized circumstellar disks.
