Two-fluid dusty shocks: simple benchmarking problems and applications to protoplanetary discs

TL;DR

This paper develops simple benchmark problems for two-fluid dusty gas shocks, enabling testing of numerical codes and applying them to protoplanetary disc accretion shocks, highlighting the importance of dust size and dust-to-gas ratio.

Contribution

It introduces benchmark problems for dusty gas shock simulations and applies them to study accretion shocks in protoplanetary discs, emphasizing two-fluid effects.

Findings

Two-fluid effects are significant for grains larger than 1 μm.

Peak dust temperature indicates the dust-to-gas ratio.

Benchmark problems help test dust-gas coupling models.

Abstract

The key role that dust plays in the interstellar medium has motivated the development of numerical codes designed to study the coupled evolution of dust and gas in systems such as turbulent molecular clouds and protoplanetary discs. Drift between dust and gas has proven to be important as well as numerically challenging. We provide simple benchmarking problems for dusty gas codes by numerically solving the two-fluid dust-gas equations for steady, plane-parallel shock waves. The two distinct shock solutions to these equations allow a numerical code to test different forms of drag between the two fluids, the strength of that drag and the dust to gas ratio. We also provide an astrophysical application of J-type dust-gas shocks to studying the structure of accretion shocks onto protoplanetary discs. We find that two-fluid effects are most important for grains larger than 1 um, and that the peak dust temperature within an accretion shock provides a signature of the dust-to-gas ratio of the infalling material.