2018ApJ...858...13H

This article presents a 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. All existing 3D hydrodynamical simulations predict strong global mixing of the burning products due to Rayleigh-Taylor (RT) instabilities, which contradicts observations. As a first step toward studying the flame physics, we present a set of computational magnet-hydrodynamic models in rectangular flux tubes, resembling a small inner region of a WD. We consider initial magnetic fields up to 10¹²G of various orientations. We find an increasing suppression of RT instabilities starting at about 10⁹G. The front speed tends to decrease with increasing magnitude up to about 10¹¹G. 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.