Prior to the explosive burning of a white dwarf ( WD ) that makes a Type Ia supernova ( SN Ia ) , the star “ simmers ” for \sim 10 ^ { 3 } yrs in a convecting , carbon burning region .
I estimate the excitation of g -modes by convection during this phase and explore their possible affect on the WD .
As these modes propagate from the core of the WD toward its surface , their amplitudes grow with decreasing density .
Once the modes reach nonlinear amplitudes , they break and deposit their energy into a shell of mass \sim 10 ^ { -4 } M _ { \odot } .
This raises the surface temperature by \approx 6 \times 10 ^ { 8 } { K } , which is sufficient to ignite a layer of helium , as is expected to exist for some SN Ia scenarios .
This predominantly synthesizes ^ { 28 } Si , ^ { 32 } S , ^ { 40 } Ca , and some ^ { 44 } Ti .
These ashes are expanded out with the subsequent explosion up to velocities of \sim 20 , 000 { km s ^ { -1 } } , which may explain the high velocity features ( HVFs ) seen in many SNe Ia .
The appearance of HVFs would therefore be a useful discriminant for determining between progenitors , since a flammable helium-rich layer will not be present for accretion from a C/O WD as in a merger scenario .
I also discuss the implications of ^ { 44 } Ti production .