Non-linear Evolution of Rayleigh-Taylor Instability in a Radiation Supported Atmosphere

TL;DR

This study numerically investigates the non-linear evolution of Rayleigh-Taylor instability in radiation-supported atmospheres, revealing how radiation pressure and anisotropy influence instability growth, structure formation, and gas displacement.

Contribution

It introduces a numerical approach using a variable Eddington tensor to analyze RTI in radiation-dominated environments, highlighting the impact of radiation anisotropy on non-linear development.

Findings

Radiation reduces RTI growth and mixing when radiation pressure exceeds gas pressure.

Anisotropic radiation fields significantly alter RTI evolution.

RTI can limit gas displacement in radiation-driven outflows.

Abstract

The non-linear regime of Rayleigh-Taylor instability (RTI) in a radiation supported atmosphere, consisting of two uniform fluids with different densities, is studied numerically. We perform simulations using our recently developed numerical algorithm for multi-dimensional radiation hydrodynamics based on a variable Eddington tensor as implemented in Athena, focusing on the regime where scattering opacity greatly exceeds absorption opacity. We find that the radiation field can reduce the growth and mixing rate of RTI, but this reduction is only significant when radiation pressure significantly exceeds gas pressure. Small scale structures are also suppressed in this case. In the non-linear regime, dense fingers sink faster than rarefied bubbles can rise, leading to asymmetric structures about the interface. By comparing the calculations that use a variable Eddington tensor (VET) versus the Eddington approximation, we demonstrate that anisotropy in the radiation field can affect the non-linear development of RTI significantly. We also examine the disruption of a shell of cold gas being accelerated by strong radiation pressure, motivated by models of radiation driven outflows in ultraluminous infrared galaxies. We find that when the growth rate of RTI is smaller than acceleration time scale, the amount of gas that would be pushed away by the radiation field is reduced due to RTI.