Cool Stars 14 - Submitted Abstract # 273
This version created on 05 October 2006

Thermal instability of Irradiation-dominated protoplanetary disks


Sei-ichiro Watanabe, Nagoya University (Now in UC Santa Cruz)
Douglas Lin, University of California, Santa Cruz

The protoplanetary disks around many young stars are heated mostly by
surface dust grains which absorbed light from the central star.  Since
the irradiation heating is sensitive to the vertical disk structure,
the possibility of an unstable feedback is present.  Using a
long-wavelength approximation D'Alessio et al.  (1999) treated this
problem semi-analytically and concluded that disk are stable to
perturbations in vertically isothermal disks.  But validity of the
approximation was not clear.  We have performed quasi-static
calculations of thermal evolution of irradiated disks, using the
direct integration of optical depthes to determine the optical surface
and total emitting area-filling factor of superheated grains.  We find
that thermal waves are spontaniously excited and propagate inward
within a few times of thermal timescale in the region from 1AU to
10AU.  Peak mid-plane temparature of the wave is more than twice
compare to that of circumferance.  These waves may have an important
role to planetary formation.

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