Photophoresis of dust particles in optically thin gas disks

Abstract

Photophoresis in optically thin disks is studied. Dust particles accumulate at the locations where Knudsen number (the ratio of the mean free path of gas molecules to the dust particle size) Kn>1. Photophoresis works to make a dust ring whose inner radius is determined by the condition Kn=1. The ring inner radius does not depend on particles' physical properties, and locates at 0.03-0.3 AU. The condition Kn=1 for inner ring radius provides us a method for the observational test to check if photophoresis actually occurs or not.