A Comparison of 2D Magnetohydrodynamic Supernova Simulations with the CoCoNuT-FMT and Aenus-Alcar Codes

TL;DR

This paper compares two different MHD supernova simulation codes, CoCoNuT-FMT and Aenus-Alcar, to evaluate their consistency and identify uncertainties in modeling supernova explosions, magnetic fields, and nucleosynthesis outcomes.

Contribution

It provides the first detailed comparison of these two codes, highlighting similarities, differences, and the impact of numerical choices on supernova simulation results.

Findings

Qualitative similarity in explosion dynamics across codes.

Significant differences in explosion energy and magnetic energy.

Sensitivity of certain features to numerical details.

Abstract

Code comparisons are a valuable tool for the verification of supernova simulation codes and the quantification of model uncertainties. Here we present a first comparison of axisymmetric magnetohydrodynamic (MHD) supernova simulations with the CoCoNuT-FMT and Aenus-Alcar codes, which use distinct methods for treating the MHD induction equation and the neutrino transport. We run two sets of simulations of a rapidly rotating 35M gamma-ray burst progenitor model with different choices for the initial field strength, namely 10^12 G for the maximum poloidal and toroidal field in the strong-field case and 10^10 G in the weak-field case. We also investigate the influence of the Riemann solver and the resolution in CoCoNuT-FMT. The dynamics is qualitatively similar for both codes and robust with respect to these numerical details, with a rapid magnetorotational explosion in the strong-field case and a delayed neutrino-driven explosion in the weak-field case. Despite relatively similar shock trajectories, we find sizeable differences in many other global metrics of the dynamics, like the explosion energy and the magnetic energy of the proto-neutron star. Further differences emerge upon closer inspection, for example, the disk-like surface structure of the proto-neutron star proves highly sensitives to numerical details. The electron fraction distribution in the ejecta as a crucial determinant for the nucleosynthesis is qualitatively robust, but the extent of neutron- or proton-rich tails is sensitive to numerical details. Due to the complexity of the dynamics, the ultimate cause of model differences can rarely be uniquely identified, but our comparison helps gauge uncertainties inherent in current MHD supernova simulations.