The Structure of Winds in AGB Stars
  Most dusty winds are described by a set of similarity functions of a single independent variable that can be chosen as the overall optical depth at visual. The self-similarity implies general scaling relations among the system parameters, in agreement with observations. Dust drift through the gas has a major impact on the structure of most winds. 
Moshe Elitzur, Zeljko Ivezic and Dejan Vinkovic