  The burning speed of a thermonuclear supernova front could be described by
the fractal model of combustion. We have examined the effects of magnetic
fields on the fractalization of the front considering a white dwarf with a
nearly dipolar magnetic field and found an intrinsic asymmetry on the velocity
field of the expanding plasma. For white dwarf's magnetic fields of 10^8-10^9 G
at the surface, and assuming a field roughly 10 times greater near the center,
we have found asymmetries in the velocity field > 10-20 % at rho ~ 10^8 g
cm^(-3), produced between the magnetic polar and the equatorial axis of the
remnant. This effect may be related to the asphericities inferred from
spectro-polarimetric observations of very young SN Ia remnants (for example: SN
1999by). In the present work, we analyse the dependence of the asymmetry with
the composition of the white dwarf progenitor.
