Magneto-Hydrodynamical Effects on Nuclear Deflagration Fronts in Type Ia Supernovae

TL;DR

This study investigates how magnetic fields influence nuclear burning fronts in Type Ia supernovae, revealing that strong magnetic fields can suppress instabilities and potentially trigger detonations, offering insights into supernova explosion mechanisms.

Contribution

The paper introduces magneto-hydrodynamic models of nuclear flames in white dwarfs, highlighting the role of magnetic fields in altering flame stability and speed, which was not previously explored in detail.

Findings

Magnetic fields above 10^9 G suppress Rayleigh-Taylor instabilities.

Fields up to 10^11 G decrease flame front speed.

Fields above 10^{11} G induce structures that increase burning speed by 3-4 times.

Abstract

This article presents the study of the effects of magnetic fields on non-distributed nuclear burning fronts as a possible solution to a fundamental problem for the thermonuclear explosion of a Chandrasekhar mass ($M_{Ch}$) white dwarf (WD), the currently favored scenario for the majority of Type Ia SNe (SNe~Ia). All existing 3D hydrodynamical simulations predict strong global mixing of the burning products due to Rayleigh-Taylor (RT) instabilities, which is in contradiction with observations. As a first step and to study the flame physics we present a set of computational magneto-hydrodynamic (MHD) models in rectangular flux tubes, resembling a small inner region of a WD. We consider initial magnetic fields up to $10^{12}\,\,\mathrm{G}$ of various orientations. We find an increasing suppression of RT instabilities starting at about $10^9\,\,\mathrm{G}$. The front speed tends to decrease with increasing magnitude up to about $10^{11}\,\,\mathrm{G}$. For even higher fields new small scale finger-like structures develop, which increase the burning speed by a factor of 3 to 4 above the field-free RT-dominated regime. We suggest that the new instability may provide sufficiently accelerated energy production during the distributed burning regime to go over the Chapman-Jougey limit and trigger a detonation. Finally we discuss the possible origins of high magnetic fields during the final stage of the progenitor evolution or the explosion.