Outward Motion of Porous Dust Aggregates by Stellar Radiation Pressure in Protoplanetary Disks

TL;DR

This study investigates how porous dust aggregates in protoplanetary disks are propelled outward by stellar radiation pressure, highlighting their efficient transport compared to compact grains and implications for comet formation.

Contribution

It introduces a calculation of radiation pressure effects on porous dust aggregates using the T-Matrix Method, revealing their significant outward flux in protoplanetary disks.

Findings

Porous dust aggregates are strongly affected by radiation pressure even at larger sizes.

Porous aggregates have an order of magnitude higher outward flux than compact grains at 1 AU.

Porous aggregates can efficiently transport crystalline silicates outward in the disk.

Abstract

We study the dust motion at the surface layer of protoplanetary disks. Dust grains in surface layer migrate outward due to angular momentum transport via gas-drag force induced by the stellar radiation pressure. In this study, we calculate mass flux of the outward motion of compact grains and porous dust aggregates by the radiation pressure. The radiation pressure force for porous dust aggregates is calculated using the T-Matrix Method for the Clusters of Spheres. First, we confirm that porous dust aggregates are forced by strong radiation pressure even if they grow to be larger aggregates in contrast to homogeneous and spherical compact grains to which efficiency of radiation pressure becomes lower when their sizes increase. In addition, we find that the outward mass flux of porous dust aggregates with monomer size of 0.1 $\mu$m is larger than that of compact grains by an order of magnitude at the disk radius of 1 AU, when their sizes are several microns. This implies that large compact grains like calcium-aluminum rich inclusions (CAIs) are hardly transported to outer region by stellar radiation pressure, whereas porous dust aggregates like chondritic-porous interplanetary dust particles (CP-IDPs) are efficiently transported to comet formation region. Crystalline silicates are possibly transported in porous dust aggregates by stellar radiation pressure from inner hot region to outer cold cometary region in the protosolar nebula.