Is Strong SASI Activity the Key to Successful Neutrino-Driven Supernova Explosions?

TL;DR

This study investigates the role of SASI activity and dimensional effects in neutrino-driven supernova explosions, finding that large-scale SASI motions support explosions, with differences observed between 2D and 3D models related to turbulence and energy cascade.

Contribution

It provides a comparative analysis of 1D, 2D, and 3D supernova models, highlighting the importance of SASI activity and turbulence effects on explosion conditions.

Findings

2D models explode more easily with better angular resolution

3D models show less favorable conditions for explosion due to turbulence

Large-scale SASI motions support shock expansion and explosion readiness

Abstract

Following a simulation approach of recent publications we explore the viability of the neutrino-heating explosion mechanism in dependence on the spatial dimension. Our results disagree with previous findings. While we also observe that two-dimensional (2D) models explode for lower driving neutrino luminosity than spherically symmetric (1D) models, we do not find that explosions in 3D occur easier and earlier than in 2D. Moreover, we find that the average entropy of matter in the gain layer hardly depends on the dimension and thus is no good diagnostic quantity for the readiness to explode. Instead, mass, integrated entropy, total neutrino-heating rate, and nonradial kinetic energy in the gain layer are higher when models are closer to explosion. Coherent, large-scale mass motions as typically associated with the standing accretion-shock instability (SASI) are observed to be supportive for explosions because they drive strong shock expansion and thus enlarge the gain layer. While 2D models with better angular resolution explode clearly more easily, the opposite trend is seen in 3D. We interpret this as a consequence of the turbulent energy cascade, which transports energy from small to large spatial scales in 2D, thus fostering SASI activity. In contrast, the energy flow in 3D is in the opposite direction, feeding fragmentation and vortex motions on smaller scales and thus making the 3D evolution with finer grid resolution more similar to 1D. More favorable conditions for explosions in 3D may therefore be tightly linked to efficient growth of low-order SASI modes including nonaxisymmetric ones.