Magnetohydrodynamical Effects on Nuclear Deflagration Fronts in Type Ia Supernovae

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 10(12) G of various orientations. We find an increasing suppression of RT instabilities starting at about 10(9) G. The front speed tends to decrease with increasing magnitude up to about 1011 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 fieldfree 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.