Magnetic field effects on the thermonuclear combustion front of Chandrasekhar mass white dwarfs

The explosion of a Type Ia supernova (SN Ia) starts in a white dwarf as a l aminar deflagration at the center of the star, and soon several hydrodynami c instabilities, in particular, the Rayleigh-Taylor instability, begin to a ct. A cellular stationary combustion and a turbulent combustion regime are rapidly achieved by the flame and maintained up to the end of the so-called flamelet regime when the transition to detonation is believed to occur. Th e burning velocity at these regimes is well described by the fractal model of combustion. Using a semianalytic approach, we describe the effect of mag netic fields on the fractalization of the front by considering a white dwar f with a nearly dipolar magnetic field. We find an intrinsic asymmetry on t he velocity field that may be maintained up to the free-expansion phase of the remnant. Considering the strongest values inferred for a white dwarf's magnetic fields with strengths up to 10(8)-10(9) G at the surface and assum ing that the field near the center is roughly 10 times greater, asymmetries in the velocity field higher than 10%-20% are produced between the magneti c polar and the equatorial axis of the remnant that may be related to the a symmetries found from recent spectropolarimetric observations of very young SN Ia remnants. The dependence of the asymmetry with a white dwarf composi tion is also analyzed.