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Nonlinear instability of accelerating shock waves with application to supernovaeWe consider the stability of a planar accelerating shock front in an exponential atmosphere, a situation that can be described by a self-similar solution. A previous linear instability analysis showed that there are three regimes, depending on the wavelength of the perturbation along the direction of the shock front: at long wavelengths the shock is unstable, at intermediate wavelengths it is overstable, and at short wavelenghts it is stable, where the characteristic length is set by the initial density scale height. We have carried out numerical simulations of such an accelerating shock front and have confirmed the results of the semianalytic linear analysis in the linear regime. In the nonlinear regime, the evolution again depends on the three wavelength domains. At long wavelengths, the instability continuously grows but the flow remains smooth, and at short wavelengths, the flow is stable. The intermediate wavelength, overstable regime shows more complex evolution. The growing linear oscillations saturate soon after entering the nonlinear regime and the oscillations continue with the same approximate period. The shock front develops moving points of intersection, which generate weak shock fronts and density and pressure structure in the immediate postshock flow. The density fluctuations, with a contrast of a factor of 2-3, become frozen into the downstream flow. The growth of the instability is slow, so substantial initial perturbations are needed; thesemay be present in Type II supernovae with red supergiant progenitor stars which have outer convective regions. The clumping in the outer supernova atmosphere may affect spectral line formation and may play a role in the formation of fast knots.
Document ID
19950038838
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Luo, Ding
(Univ. of Virginia, Charlottesville, VA United States)
Chevalier, Roger A.
(Univ. of Virginia, Charlottesville, VA United States)
Date Acquired
August 16, 2013
Publication Date
November 10, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 435
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A70437
Funding Number(s)
CONTRACT_GRANT: NSF AST-90-16687
CONTRACT_GRANT: NSF AST-93-14724
CONTRACT_GRANT: NSF AST-92-0010P
CONTRACT_GRANT: NAGW-2376
Distribution Limits
Public
Copyright
Other

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