Photophoresis in protoplanetary disks: a numerical approach

TL;DR

This paper investigates how photophoresis, a force caused by thermal creep on illuminated particles, can influence dust dynamics in protoplanetary disks, potentially preventing inward migration and affecting planet formation.

Contribution

The study introduces a numerical model incorporating photophoresis into protoplanetary disk simulations, demonstrating its significant impact on dust sorting and disk morphology.

Findings

Photophoresis causes size and density-dependent dust sorting.

It can counteract radial drift of solid particles.

Disk morphology is significantly affected by photophoretic forces.

Abstract

It is widely accepted that rocky planets form in the inner regions of protoplanetary disks (PPD) about 1 - 10 AU from the star. However, theoretical calculations show that when particles reach the size for which the radial migration is the fastest they tend to be accreted very efficiently by the star. This is known as the radial-drift barrier. We explore the photophoresis in the inner regions of PPD as a possible mechanism for preventing the accretion of solid bodies onto the star. Photophoresis is the thermal creep induced by the momentum exchange of an illuminated solid particle with the surrounding gas. Recent laboratory experiments predict that photophoresis would be able to stop the inward drift of macroscopic bodies (from 1 mm to 1 m in size). This extra force has been included in our two-fluid (gas+dust) SPH code in order to study its efficiency. We show that the conditions of pressure and temperature encountered in the inner regions of PPD result in strong dynamical effects on the dust particles due to photophoresis. Our simulations show that there is a radial and a vertical sorting of the dust grains according to their sizes and their intrinsic densities. Thus, our calculations support the fact that photophoresis is a mechanism which can have a strong effect on the morphology of the inner regions of PPD, ultimately affecting the fate of planetesimals.