Three-dimensional simulations of standing accretion shock instability in core-collapse supernovae

Wakana Iwakami, Kei Kotake, Naofumi Ohnishi, Shoichi Yamada, Keisuke Sawada

    Research output: Contribution to journalArticle

    109 Citations (Scopus)

    Abstract

    We have studied nonaxisymmetric standing accretion shock instabilities, or SASI, using three-dimensional (3D) hydrodynamical simulations. This is an extension of our previous study of axisymmetric SASI. We have prepared a spherically symmetric and steady accretion flow through a standing shock wave onto a proto-neutron star, taking into account a realistic equation of state and neutrino heating and cooling. This unperturbed model is meant to represent approximately the typical postbounce phase of core-collapse supernovae. We then added a small perturbation (∼1%) to the radial velocity and computed the ensuing evolutions. Both axisymmetric and nonaxisymmetric perturbations have been imposed. We have applied mode analysis to the nonspherical deformation of the shock surface, using spherical harmonics. We have found that (1) the growth rates of SASI are degenerate with respect to the azimuthal index m of the spherical harmonics Yl m, just as expected for a spherically symmetric background; (2) nonlinear mode couplings produce only m = 0 modes for axisymmetric perturbations, whereas m ≠= 0 modes are also generated in the nonaxisymmetric cases, according to the selection rule for quadratic couplings; (3) the nonlinear saturation level of each mode is lower in general for 3D than for 2D, because a larger number of modes contribute to turbulence in 3D; (4) low-l modes are dominant in the nonlinear phase; (5) equipartition is nearly established among different m modes in the nonlinear phase; (6) spectra with respect to l obey power laws with a slope slightly steeper for 3D; and (7) although these features are common to the models with and without a shock revival at the end of the simulation, the dominance of low-l modes is more remarkable in the models with a shock revival.

    Original languageEnglish
    Pages (from-to)1207-1222
    Number of pages16
    JournalAstrophysical Journal
    Volume678
    Issue number2
    DOIs
    Publication statusPublished - 2008 May 10

    Fingerprint

    supernovae
    shock
    accretion
    perturbation
    spherical harmonics
    simulation
    standing wave
    shock wave
    equation of state
    power law
    turbulence
    saturation
    heating
    cooling
    radial velocity
    coupled modes
    neutron stars
    shock waves
    equations of state
    neutrinos

    Keywords

    • Hydrodynamics
    • Instabilities
    • Neutrinos
    • Supernovae: general

    ASJC Scopus subject areas

    • Space and Planetary Science

    Cite this

    Three-dimensional simulations of standing accretion shock instability in core-collapse supernovae. / Iwakami, Wakana; Kotake, Kei; Ohnishi, Naofumi; Yamada, Shoichi; Sawada, Keisuke.

    In: Astrophysical Journal, Vol. 678, No. 2, 10.05.2008, p. 1207-1222.

    Research output: Contribution to journalArticle

    Iwakami, Wakana ; Kotake, Kei ; Ohnishi, Naofumi ; Yamada, Shoichi ; Sawada, Keisuke. / Three-dimensional simulations of standing accretion shock instability in core-collapse supernovae. In: Astrophysical Journal. 2008 ; Vol. 678, No. 2. pp. 1207-1222.
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    AU - Yamada, Shoichi

    AU - Sawada, Keisuke

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    AB - We have studied nonaxisymmetric standing accretion shock instabilities, or SASI, using three-dimensional (3D) hydrodynamical simulations. This is an extension of our previous study of axisymmetric SASI. We have prepared a spherically symmetric and steady accretion flow through a standing shock wave onto a proto-neutron star, taking into account a realistic equation of state and neutrino heating and cooling. This unperturbed model is meant to represent approximately the typical postbounce phase of core-collapse supernovae. We then added a small perturbation (∼1%) to the radial velocity and computed the ensuing evolutions. Both axisymmetric and nonaxisymmetric perturbations have been imposed. We have applied mode analysis to the nonspherical deformation of the shock surface, using spherical harmonics. We have found that (1) the growth rates of SASI are degenerate with respect to the azimuthal index m of the spherical harmonics Yl m, just as expected for a spherically symmetric background; (2) nonlinear mode couplings produce only m = 0 modes for axisymmetric perturbations, whereas m ≠= 0 modes are also generated in the nonaxisymmetric cases, according to the selection rule for quadratic couplings; (3) the nonlinear saturation level of each mode is lower in general for 3D than for 2D, because a larger number of modes contribute to turbulence in 3D; (4) low-l modes are dominant in the nonlinear phase; (5) equipartition is nearly established among different m modes in the nonlinear phase; (6) spectra with respect to l obey power laws with a slope slightly steeper for 3D; and (7) although these features are common to the models with and without a shock revival at the end of the simulation, the dominance of low-l modes is more remarkable in the models with a shock revival.

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