The ASTRONUM Conference is held annually and gathers researchers working on numerical methods and works related to space/astrophysical plasmas and fluids. This includes both astrophysicists as well as space scientists and solar physicists. Although there are some great differences in modeling the processes in the Sun, in the magnetosphere, collapsing neutron stars, and thermonuclear supernovae, there is great overlap in the numerical methods these areas require. In 2024, the conferece was held in La Rochelle, France.
My talk was the application of the low mach code MAESTROeX to simulate the Convective Urca process in simmering white dwarf.
## Abstract
### Low Mach Hydrodynamic Simulations of the Convective Urca Process in Type Ia Progenitors
Type Ia supernovae are bright thermonuclear explosions that play important roles in many areas of astronomy such as cosmology and galaxy evolution. The single degenerate paradigm is a potential model for the origins of these supernovae. This model entails a white dwarf accreting material from a companion and gaining mass to the point of carbon fusion in the core. The onset of carbon fusion, called the simmering phase, drives convection and alters the evolution of the white dwarf as it approaches the thermonuclear explosion. A key factor during this phase is the convective Urca process which links convection with weak nuclear reactions that leak energy from the star. To study the effects of the convective Urca process, it is vital to accurately model the turbulent convection in the core. We run 3D hydrodynamic simulations of the convection zone of a simmering white dwarf using the low-Mach hydrodynamic code MAESTROeX. A low-Mach method is necessary to capture the slow convective flow. From these simulations, we find the structure of convective mixing has a profound impact on the convective Urca process and that this mixing is not well characterized by a locally diffusive approximation (as assumed in Mixing Length Theory). We analyze these simulations to find energy loss rates due to neutrino emission. And finally, we place limits on how much the convective Urca process restricts the size of the convection zone
This research was supported in part by the US Department of Energy (DOE) under grant DE-FG02-87ER40317
The slides can be downloaded [here](/assets/Astronum_pres_2024.pdf).