THE SATURATION OF SASI BY PARASITIC INSTABILITIES
THE SATURATION OF SASI BY PARASITIC INSTABILITIES
复制标题
寄生不稳定性导致 SASI 饱和
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
T. Foglizzo
中科院分区：
文献类型：
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作者：
J. Guilet;J. Sato;T. Foglizzo
通常认为，静止吸积激波不稳定性（SASI）是导致核心坍缩期间失速激波的大振幅偶极振荡的原因，可能导致不对称超新星爆炸。非对称性的程度取决于SASI的幅度，但非线性饱和机制尚未阐明。我们调查的寄生不稳定性的作用，作为一个可能的原因，非线性SASI饱和。由于激波振荡产生涡度和熵梯度，我们表明，开尔文-亥姆霍兹和瑞利-泰勒类型的不稳定性能够增长的SASI模式，如果它的振幅足够大。我们得到简单的估计，他们的增长率，考虑到平流和熵分层的影响。在对流声学循环的背景下，我们使用数值模拟来演示如何可以减少声反馈，如果寄生不稳定性扭曲的平流结构。在这种情况下，冲击变形的振幅估计解析。当应用到Fernández & Thompson的装置中时，这种饱和机制能够解释当核解离能和冷却速率都变化时SASI功率的急剧下降。我们的研究结果为预测坍缩星星模型中的物理成分对SASI振幅的影响开辟了新的视角。
The standing accretion shock instability (SASI) is commonly believed to be responsible for large amplitude dipolar oscillations of the stalled shock during core collapse, potentially leading to an asymmetric supernovae explosion. The degree of asymmetry depends on the amplitude of SASI, but the nonlinear saturation mechanism has never been elucidated. We investigate the role of parasitic instabilities as a possible cause of nonlinear SASI saturation. As the shock oscillations create both vorticity and entropy gradients, we show that both Kelvin–Helmholtz and Rayleigh–Taylor types of instabilities are able to grow on a SASI mode if its amplitude is large enough. We obtain simple estimates of their growth rates, taking into account the effects of advection and entropy stratification. In the context of the advective–acoustic cycle, we use numerical simulations to demonstrate how the acoustic feedback can be decreased if a parasitic instability distorts the advected structure. The amplitude of the shock deformation is estimated analytically in this scenario. When applied to the set up of Fernández & Thompson, this saturation mechanism is able to explain the dramatic decrease of the SASI power when both the nuclear dissociation energy and the cooling rate are varied. Our results open new perspectives for anticipating the effect, on the SASI amplitude, of the physical ingredients involved in the modeling of the collapsing star.
DOI：
10.1088/0004-637x/694/1/664
发表时间：
2007-08
期刊：
The Astrophysical Journal
影响因子：
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作者：
A. Marek;H. Janka
通讯作者：
A. Marek;H. Janka