Inner dusty regions of protoplanetary discs - III. The role of non-radial radiation pressure in dust dynamics

Abstract

Abstract We explore dynamical behaviour of dust particles that populate the surface of inner optically thick protoplanetary discs. This is a disc region with the hottest dust and of a great importance for planet formation and dust evolution, but we still struggle to understand all the forces that shape this environment. In our approach we combine results from two separate numerical studies - one is the wind velocity and density distributions obtained from magnetohydrodynamical simulations of accretion discs, and the other is a high-resolution multigrain dust radiation transfer. In our previous paper in the series, we described the methodology for utilising these results as an environmental input for the integration of dust trajectories driven by gravity, gas drag, and radiation pressure. Now we have two improvements - we incorporate time changes in the wind density and velocity, and we implement the non-radial radiation pressure force. We applied our analysis on Herbig Ae and T Tau stars. We confirm that the radiation pressure force can lead to dust outflow, especially in the case of more luminous stars. Additionally, it opposes dust accretion at the inner disc edge and reduces dust settling. These effects are enhanced by the disc wind, especially in the zone where the stellar and the disc magnetic fields meet. Our results suggest that dust grains can stay in the hottest disc region for an extended period and then can end up ejected into the outer disc regions.