Turbulence and thermal instability in the neutral and atomic interstellar medium : a numerical approach
type: Distribution
access URL: https://theses.hal.science/tel-00784196
format: HTML
issued: 2026-05-14T17:49:14.008385
modified: 2026-05-14T17:49:13.925635

test_moissonnage_selune
type: Agent

Turbulence and thermal instability in the neutral and atomic interstellar medium : a numerical approach
type: Dataset
contact point: Organization
  fn: CCSD
keyword: interstellar-medium
keyword: hydrodynamique
keyword: instabilite-thermique
keyword: theses
keyword: simulations-numeriques
keyword: thermal-instability
keyword: hydrogene-atomique
keyword: turbulence
keyword: structure
keyword: infoeu-reposemanticsdoctoralthesis
keyword: atomic-hydrogen
keyword: milieu-interstellaire
keyword: sduothersciences-of-the-universe-physicsother
keyword: hydrodynamics
keyword: numerical-simulations
landing page: https://theses.hal.science/tel-00784196
description: One of the main current questions in Astrophysics is the understanding of the star formation process, directly related to the processes involved in the cooling and the condensation of the gas yielding to intricate filamentary structures of molecular clouds. Thermal instability and turbulence are playing dominant roles in this complex dynamics. The work presented here is focused on the evolution of the atomic and diffuse interstellar medium that provides the initial conditions to the formation of molecular clouds and is based on the comparison of hydrodynamical numerical simulations and observations. To understand the roles of thermal instability and turbulence in the WNM (warm neutral medium, T ~ 8000 K, n = 0.5 cm-³) to CNM (cold neutral medium, T ~ 80 K, n = 50 cm-³) transition, I produced 90 hydrodynamical numerical simulations of thermally bistable HI and used them to study the impact of the WNM initial density and the compressibility of the turbulent stirring on the efficiency of the CNM production. The main result here is that the warm gas in the observed turbulent conditions do not transit naturally to cold gas whatever the amplitude of turbulent motions. These small resolution simulations also allowed me to determine which initial conditions lead to the reproduction of the observed properties, as the Mach number, the amount of CNM or the amplitude of the turbulent motions. A compression is needed to trigger this transition either by increasing the initial density (n ≥ 1.5 cm-³) or by stirring with a compressive field. These initial conditions have been used to produce two high resolution simulations (1024³). I showed that these two simulations reproduce well the properties of the turbulence and the thermal instability. The temperature histograms present the evidences of a bistable gas and the pressure distributions are in agreement with the observations. On the other hand, the power spectra of the density are characteristic of a high contrasted medium while …
identifier: NNT: 2012PA112107
issued: 2026-05-14T17:49:13.958813
language: fr
modified: 2026-05-14T17:49:13.958818