A Mechanism to Produce the Small Dust Observed in Protoplanetary Disks

TL;DR

This paper proposes a novel mechanism involving light-induced erosion, such as Knudsen compression and photophoresis, to continuously generate small dust particles in protoplanetary disks, addressing the depletion issue.

Contribution

It introduces a new dust production mechanism based on laboratory experiments demonstrating light-induced erosion processes in protoplanetary disks.

Findings

Light-induced erosion can produce small dust particles.

The mechanism prevents immediate re-aggregation of dust.

Laboratory results support the viability of this process.

Abstract

Small (sub)-micron dust is present over the entire lifetime of protoplanetary disks. As aggregation readily depletes small particles, one explanation might be that dust is continuously generated by larger bodies in the midplane and transported to the surface of the disks. In general, in a first step of this scenario, the larger bodies have to be destroyed again and different mechanisms exist with the potential to accomplish this. Possible destructive mechanisms are fragmentation in collisions, erosion by gas drag or light induced erosion. In laboratory experiments we find that the latter, light induced erosion by Knudsen compression and photophoresis, can provide small particles. It might be a preferred candidate as the dust is released into a low particle density region. The working principle of this mechanism prevents or decreases the likelihood for instant re-accretion or re-growth of large dense aggregates. Provided that there is a particle lift, e.g. turbulence, these particles might readily reach the surface of the disk.