Sputtering in oblique C-type shocks

TL;DR

This paper models sputtering in C-type shocks, revealing thresholds for mantle and core vaporization, and how shock speed, angle, and density influence grain destruction and SiO formation.

Contribution

First self-consistent multifluid hydromagnetic models of sputtering in C-type shocks, detailing threshold speeds and angular effects on grain mantle and core vaporization.

Findings

Mantle sputtering threshold at ~10 km/s, independent of density.

Complete mantle vaporization occurs at 20-25 km/s.

Gas-phase SiO forms after core sputtering begins.

Abstract

We present the first results for the sputtering of grain mantles and cores obtained with self-consistent multifluid hydromagnetic models of C-type shocks propagating through dusty media. The threshold shock speed for mantle sputtering is about 10 km/s and is independent of density. The mantles are completely vapourised in shocks with speeds of 20-25 km/s. At such shock speeds core sputtering commences and gas-phase SiO forms. Core destruction is not total in any C-type shock because grains are not completely destroyed in shocks with speeds near the minimum speeds at which J-type shocks appear. Due to the density-dependence of the critical shock speed for this transition, higher gas-phase SiO fractional abundances are produced behind shocks propagating in lower density gas. For shock speeds near the threshold speeds for both core and mantle sputtering, sputtering is much greater for shock velocities at smaller angles relative to the upstream magnetic field. At higher shock speeds, the angular variation is still present but less pronounced.