The impact of non-dipolar magnetic fields in core-collapse supernovae

TL;DR

This study explores how complex, non-dipolar magnetic field topologies influence the dynamics and outcomes of core-collapse supernovae, revealing that multipolar fields generally lead to less energetic explosions and different proto-neutron star properties.

Contribution

It provides the first systematic comparison of core-collapse supernovae simulations with various magnetic field topologies, highlighting the impact of multipolar magnetic configurations on explosion characteristics.

Findings

Higher multipolar magnetic fields lead to less energetic explosions.

Small-scale magnetic fields produce more massive, faster-rotating proto-neutron stars.

Dipolar fields are more efficient in extracting rotational energy.

Abstract

The magnetic field is believed to play an important role in at least some core-collapse supernovae if its magnitude reaches $10^{15}\,\rm{G}$, which is a typical value for a magnetar. In the presence of fast rotation, such a strong magnetic field can drive powerful jet-like explosions if it has the large-scale coherence of a dipole. The topology of the magnetic field is, however, probably much more complex with strong multipolar and small-scale components and the consequences for the explosion are so far unclear. We investigate the effects of the magnetic field topology on the dynamics of core-collapse supernovae and the properties of forming proto-neutron star (PNS) by comparing pre-collapse fields of different multipolar orders and radial profiles. Using axisymmetric special relativistic MHD simulations and a two-moment neutrino transport, we find that higher multipolar magnetic configurations lead to generally less energetic explosions, slower expanding shocks and less collimated outflows. Models with a low order multipolar configuration tend to produce more oblate PNS, surrounded in some cases by a rotationally supported toroidal structure of neutron-rich material. Moreover, magnetic fields which are distributed on smaller angular scales produce more massive and faster rotating central PNS, suggesting that higher-order multipolar configurations tend to decrease the efficiency of the magnetorotational launching mechanism. Even if our dipolar models systematically display a far more efficient extraction of the rotational energy of the PNS, fields distributed on smaller angular scales are still capable of powering magnetorotational explosions and shape the evolution of the central compact object.