Florida Agricultural and Mechanical University College of Science and Technology

摘要

This dissertation 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 ( MCh ) 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. A set of computational magneto-hydrodynamic (MHD) models were ran as a first step and to study the flame physics in rectangular flux tubes, resembling a small inner region of a WD. The initial magnetic fields are up to 1012 G of various orientation. Observed is an increasing suppression of RT instabilities starting at about 109 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 5 above the field-free RT-dominated regime. Discussed are important aspects of the small-scale dynamo and field amplification during the final stages of the progenitor evolution possibly leading to magnetic fields as high as used in our models. We point out what improvements of the current models are needed to overcome some of the systemic limitations and a road map for the future of this research is outlined. Finally we are excited by the possibility that in a different setup the new instability may provide sufficient burning acceleration so that the local front speed goes over the Chapman-Jougey limit and triggers a detonation. Should this be proven possible, it will become a transition-to-detonation mechanism alternative to the Zel'dovich mechanism, which has not been shown to work in hydrodynamical simulations so far.