skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: PHOTOPHORETIC LEVITATION AND TRAPPING OF DUST IN THE INNER REGIONS OF PROTOPLANETARY DISKS

Abstract

In protoplanetary disks, the differential gravity-driven settling of dust grains with respect to gas and with respect to grains of varying sizes determines the observability of grains, and sets the conditions for grain growth and eventually planet formation. In this work, we explore the effect of photophoresis on the settling of large dust grains in the inner regions of actively accreting protoplanetary disks. Photophoretic forces on dust grains result from the collision of gas molecules with differentially heated grains. We undertake one-dimensional dust settling calculations to determine the equilibrium vertical distribution of dust grains in each column of the disk. In the process we introduce a new treatment of the photophoresis force which is consistent at all optical depths with the representation of the radiative intensity field in a two-stream radiative transfer approximation. The levitation of large dust grains creates a photophoretic dust trap several scale heights above the mid-plane in the inner regions of the disk where the dissipation of accretion energy is significant. We find that differential settling of dust grains is radically altered in these regions of the disk, with large dust grains trapped in a layer below the stellar irradiation surface, where the dust to gasmore » mass ratio can be enhanced by a factor of a hundred for the relevant particles. The photophoretic trapping effect has a strong dependence on particle size and porosity.« less

Authors:
 [1];  [2]
  1. Niels Bohr International Academy, The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100 Copenhagen Ø (Denmark)
  2. European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748, Garching bei München (Germany)
Publication Date:
OSTI Identifier:
22661412
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 834; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; AUGER ELECTRON SPECTROSCOPY; EQUILIBRIUM; GRAIN GROWTH; GRAIN SIZE; GRAVITATION; INTERSTELLAR GRAINS; IRRADIATION; LAYERS; LEVITATION; MASS; MOLECULES; PARTICLE SIZE; PLANETS; PROTOPLANETS; RADIANT HEAT TRANSFER; SATELLITES; SCALE HEIGHT; STARS; TRAPPING

Citation Formats

McNally, Colin P., and McClure, Melissa K., E-mail: cmcnally@nbi.dk, E-mail: mmcclure@eso.org. PHOTOPHORETIC LEVITATION AND TRAPPING OF DUST IN THE INNER REGIONS OF PROTOPLANETARY DISKS. United States: N. p., 2017. Web. doi:10.3847/1538-4357/834/1/48.
McNally, Colin P., & McClure, Melissa K., E-mail: cmcnally@nbi.dk, E-mail: mmcclure@eso.org. PHOTOPHORETIC LEVITATION AND TRAPPING OF DUST IN THE INNER REGIONS OF PROTOPLANETARY DISKS. United States. doi:10.3847/1538-4357/834/1/48.
McNally, Colin P., and McClure, Melissa K., E-mail: cmcnally@nbi.dk, E-mail: mmcclure@eso.org. Sun . "PHOTOPHORETIC LEVITATION AND TRAPPING OF DUST IN THE INNER REGIONS OF PROTOPLANETARY DISKS". United States. doi:10.3847/1538-4357/834/1/48.
@article{osti_22661412,
title = {PHOTOPHORETIC LEVITATION AND TRAPPING OF DUST IN THE INNER REGIONS OF PROTOPLANETARY DISKS},
author = {McNally, Colin P. and McClure, Melissa K., E-mail: cmcnally@nbi.dk, E-mail: mmcclure@eso.org},
abstractNote = {In protoplanetary disks, the differential gravity-driven settling of dust grains with respect to gas and with respect to grains of varying sizes determines the observability of grains, and sets the conditions for grain growth and eventually planet formation. In this work, we explore the effect of photophoresis on the settling of large dust grains in the inner regions of actively accreting protoplanetary disks. Photophoretic forces on dust grains result from the collision of gas molecules with differentially heated grains. We undertake one-dimensional dust settling calculations to determine the equilibrium vertical distribution of dust grains in each column of the disk. In the process we introduce a new treatment of the photophoresis force which is consistent at all optical depths with the representation of the radiative intensity field in a two-stream radiative transfer approximation. The levitation of large dust grains creates a photophoretic dust trap several scale heights above the mid-plane in the inner regions of the disk where the dissipation of accretion energy is significant. We find that differential settling of dust grains is radically altered in these regions of the disk, with large dust grains trapped in a layer below the stellar irradiation surface, where the dust to gas mass ratio can be enhanced by a factor of a hundred for the relevant particles. The photophoretic trapping effect has a strong dependence on particle size and porosity.},
doi = {10.3847/1538-4357/834/1/48},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 834,
place = {United States},
year = {2017},
month = {1}
}