Parametric Study of Flow Patterns behind the Standing Accretion Shock Wave for Core-Collapse Supernovae

TL;DR

This study systematically investigates flow patterns behind accretion shock waves in core-collapse supernovae using 3D simulations, revealing how different parameters influence the emergence of various hydrodynamical instabilities.

Contribution

It classifies flow patterns behind shock waves and analyzes their dependence on neutrino luminosity and accretion rate, providing new insights into supernova hydrodynamics.

Findings

Identified three basic flow patterns: sloshing, spiral, and buoyant bubbles.

Flow pattern depends on neutrino luminosity and accretion rate.

Pattern realization is robust across different initial perturbations.

Abstract

In this study, we conduct three-dimensional hydrodynamic simulations systematically to investigate the flow patterns behind the accretion shock waves that are commonly formed in the post-bounce phase of core-collapse supernovae. Adding small perturbations to spherically symmetric, steady, shocked accretion flows, we compute the subsequent evolutions to find what flow pattern emerges as a consequence of hydrodynamical instabilities such as convection and standing accretion shock instability (SASI) for different neutrino luminosities and mass accretion rates. Depending on these two controlling parameters, various flow patterns are indeed realized. We classify them into three basic patterns and two intermediate ones; the former includes sloshing motion (SL), spiral motion (SP) and multiple buoyant bubble formation (BB); the latter consists of spiral motion with buoyant-bubble formation (SPB) and spiral motion with pulsationally changing rotational velocities (SPP). Although the post-shock flow is highly chaotic, there is a clear trend in the pattern realization. The sloshing and spiral motions tend to be dominant for high accretion rates and low neutrino luminosities, and multiple buoyant bubbles prevail for low accretion rates and high neutrino luminosities. It is interesting that the dominant pattern is not always identical between the semi-nonlinear and nonlinear phases near the critical luminosity; the intermediate cases are realized in the latter case. Running several simulations with different random perturbations, we confirm that the realization of flow pattern is robust in most cases.