Thermal instability revisited

ABSTRACT Field’s linear analysis of thermal instability is repeated using methods related to Whitham’s theory of wave hierarchies, which brings out the physically relevant parameters in a much clearer way than in the original analysis. It is also used for the stability of non-equilibrium states and...

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Veröffentlicht in:Monthly notices of the Royal Astronomical Society 2020-03, Vol.492 (3), p.4484-4499
Hauptverfasser: Falle, S A E G, Wareing, C J, Pittard, J M
Format: Artikel
Sprache:eng
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Zusammenfassung:ABSTRACT Field’s linear analysis of thermal instability is repeated using methods related to Whitham’s theory of wave hierarchies, which brings out the physically relevant parameters in a much clearer way than in the original analysis. It is also used for the stability of non-equilibrium states and we show that for gas cooling behind a shock, the usual analysis is only quantitatively valid for shocks that are just able to trigger a transition to the cold phase. A magnetic field can readily be included and we show that this does not change the stability criteria. By considering steady shock solutions, we show that almost all plausible initial conditions lead to a magnetically dominated state on the unstable part of the equilibrium curve. These results are used to analyse numerical calculations of perturbed steady shock solutions and of shocks interacting with a warm cloud.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/staa131