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Y. Nakagawa, M. Kohno (Kobe U.)
Particle settling in protoplanetary disks reduces the heights of photo-surfaces of those disks where the central stellar light is absorbed and their own thermal radiation is effectively emitted, i.e., the surfaces of the optical depth \tau = 1. It affects the temperature distribution in the disks and the spectral energy distribution of the disks also (Miyake and Nakagawa 1995). We examined how the photo-surfaces descend toward the central plane globally according to particle settling by numerical computation. We found that in the terrestrial planetary zone the typical descent time of the photo-surfaces is about 104 times the Keplerian time tK, which is about ten times larger than the particle settling time found by Weidenschilling 1980 and Nakagawa et al 1981, 1985 and that in Jovian planetary zone the descent time is just a little larger than or almost similar to the particle settling time (~103 tK). This is because the level of the photo-surfaces is significantly higher than the half-thickness of the main dust layer in the terrestrial planetary zone, while in the Jovian planetary zone where the density is lower the level is almost same as the half-thickness. We also found that there is a discontinuity or a gap in the photo-surfaces around the condensation front of ice at 2.7 AU, which formes a shadow zone around the gap against the central stellar light. It may affect the temperature structure around the gap.
The author(s) of this abstract have provided an email address for comments about the abstract: yoshi@whynot.phys.kobe-u.ac.jp