11266(  1) - 03/30/07 11:17  - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11266

Version: 1    Check-in Time: 30-Mar-2007 15:17:16       STScI Edit Number: 0

Title
Radiation-induced Grain Dynamics in Dust Disks: Radiation Pressure, Poynting-
Robertson Drag, and Photophoresis
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Type             Cycle     Parallel Pointing Tolerance
AR               16        <none>
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Investigators
                                                                                     Contact?
    PI: Dr. Aigen Li                      University of Missouri - Columbia
   CoI: Mr. Shunlin Liang                 University of Missouri - Columbia             N

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Abstract

We propose a theoretical program to rigorously calculate the radiation pressure and
Poynting-Robertson drag parameters for both porous and compact grains in dust disks
illuminated by stars of a wide range of spectral types, using the scattering
parameters obtained from our HST Cycle 15 theory project. We also propose to study
the rotational excitation of grains in gas-rich, optically thin disks (through
collisions with neutrals, ions, "plasma drag" which may drive them to rotate
suprathermally) to test the "photophoresis" hypothesis which was recently invoked to
explain the central clearing and the formation of narrow rings in dust disks. This
program will create a web-based library of radiation pressure and Poynting-Robertson
drag parameters for both porous dust and compact dust (including nano-sized grains)
as a function of size, composition, porosity (for porous dust), and stellar spectral
type. This library will be made publicly available via the WWW at
http://www.missouri.edu/~lia/. These parameters are essential (1) for modeling disk
dynamics to interpret the un-smooth structures (e.g. asymmetry, warps, inner holes,
clumps, rings) seen in scattered light images of disks obtained with HST, and (2)
for reliably determining the dust removal and replenishment rates of debris disks as
well as disk evolution.
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