Open AccessOn the linear analysis of unstable radiative shocks
Author(s) -
Ramachandran Babulakshmanan,
Smith Michael D.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.08691.x
Subject(s) - physics , monatomic gas , instability , radiative cooling , mechanics , monatomic ion , radiative transfer , range (aeronautics) , wavenumber , thermodynamics , classical mechanics , optics , quantum mechanics , materials science , composite material
We study the stability properties of strong hydrodynamic shocks and their associated radiative cooling layers. We explore a range of conditions which covers both molecular and atomic gas impacting against a rigid wall. Through a linear analysis employing a cooling function of the form Λ∝ρ β T α and a specific heat ratio of γ, we determine the overstability regime in the parameter space consisting of α, β and γ. In general, if α is sufficiently low, the fundamental mode leads to long‐wavelength growing oscillations. For the fundamental mode, we find that values of γ corresponding to molecular hydrodynamics lead to a significantly restricted instability range for α in comparison with the shocks in a monatomic medium. The conditions for the growth of higher‐order modes, however, are relatively unchanged. This predicts that certain molecular shocks are prone to displaying signatures of small‐scale rapid variability. Dissociative shocks, however, can be subject to a large‐scale overstability if subsequent molecule formation in the cooling layer abruptly increases the cooling rate. In contrast to the dynamical rippling overstability, the cooling overstability is suppressed for a sufficiently low specific heat ratio.