angles can be generated by large differences between the gas density in the jet and
the surroundings leading to significant lateral expansion. Kitamura (1986) used
Gaussian distributions of enhancement to model a jet with the maximum being a
factor of ten higher than the background. The width of the Gaussian was varied. The
opening angle is, unsurprisingly, a strong function of the jet strength with respect to
the background. There is a weaker dependence upon the dust particle size. An
example showing the basic features of the behaviour in simplified geometry is
shown in Fig. 4.42 (from S.-B. Gerig, PhD thesis in preparation) and its similarity
to the contour plots of Kitamura is qualitatively quite striking.
Fig. 4.42 Log particle number density of a simulation of a dusty gas jet emanating from the
sub-solar point and illustrating the dust distribution. Note the rarefaction forming a conical shape.
On the outside of this is a narrow region where the density is enhanced over the background.
(Courtesy of S.-B. Gerig)
4.9 Observation of Non-uniform Dust Emission
349