skip to main content

SciTech ConnectSciTech Connect

Title: Instability of evaporation fronts in the interstellar medium

The neutral component of the interstellar medium is segregated into the cold neutral medium (CNM) and warm neutral medium (WNM) as a result of thermal instability. It was found that a plane-parallel CNM-WNM evaporation interface, across which the CNM undergoes thermal expansion, is linearly unstable to corrugational disturbances, in complete analogy with the Darrieus-Landau instability (DLI) of terrestrial flames. We perform a full linear stability analysis as well as nonlinear hydrodynamic simulations of the DLI of such evaporation fronts in the presence of thermal conduction. We find that the DLI is suppressed at short length scales by conduction. The length and time scales of the fastest growing mode are inversely proportional to the evaporation flow speed of the CNM and its square, respectively. In the nonlinear stage, the DLI saturates to a steady state where the front deforms to a finger-like shape protruding toward the WNM, without generating turbulence. The evaporation rate at nonlinear saturation is larger than the initial plane-parallel value by a factor of ∼2.4 when the equilibrium thermal pressure is 1800 k {sub B} cm{sup –3} K. The degrees of front deformation and evaporation-rate enhancement at nonlinear saturation are determined primarily by the density ratio between themore » CNM and WNM. We demonstrate that the Field length in the thermally unstable medium should be resolved by at least four grid points to obtain reliable numerical outcomes involving thermal instability.« less
Authors:
;  [1]
  1. Center for the Exploration of the Origin of the Universe (CEOU), Astronomy Program, Department of Physics and Astronomy,Seoul National University, Seoul 151-742 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22348518
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPUTERIZED SIMULATION; DEFORMATION; DENSITY; DISTURBANCES; EQUILIBRIUM; EVAPORATION; GALAXIES; HYDRODYNAMICS; INSTABILITY; INTERFACES; INTERSTELLAR SPACE; SATURATION; STABILITY; STEADY-STATE CONDITIONS; THERMAL EXPANSION; THERMODYNAMICS; TURBULENCE