Investigating the influence of the radiative torque disruption on the size evolution of dust in the heliosphere

TL;DR

This study investigates how Radiative Torque Disruption (RATD) affects dust grain fragmentation in the heliosphere, showing it efficiently produces nanoparticles and influences the dust size distribution and water snow line location.

Contribution

It provides a detailed analysis of RATD's role in dust fragmentation, highlighting its efficiency and impact on dust size evolution and the water snow line in the heliosphere.

Findings

RATD effectively fragments micrometer-sized dust into nanoparticles.

RATD prevents micrometer-sized grains from being expelled by radiation pressure.

Size distribution modeling shows a decrease in larger grains and increase in smaller grains due to RATD.

Abstract

In this paper, we conduct a detailed study on the effect of Radiative Torque Disruption (RATD) mechanism on the fragmentation of micrometer-sized dust grains into nanoparticles within the heliosphere. We start by estimating the disruption timescales for dust grains under various centrifugal stresses. Our numerical calculations demonstrate that RATD is a highly effective mechanism for breaking down micrometer-sized grains, producing nanoparticles more efficiently than other fragmentation processes. RATD also prevents micrometer-sized grains from being expelled by radiation pressure. Our findings indicate that the location of the present water snow line depends not only on temperature but also on the size of dust grains. For smaller grains, the snow line can shift outward beyond the position defined by thermal sublimation. Furthermore, we model the size distribution of dust grains modified by the RATD mechanism using a simplified model, showing that rotational disruption significantly decreases the number density of micrometer-sized grains while substantially increasing the number density of sub-micrometer-sized grains. However, the fraction of dust grains aligned at high-$J$ attractors by radiative torques less than 80\% can considerably weaken the effect of RATD on the grain size distribution. Finally, we suggest several experiments that could potentially test the RATD mechanism and discuss the uncertainties of our model in more realistic applications to heliospheric dust.