CRA Seminar: Dr Jane Pratt

Title: Stellar Physics: from Plasma Dynamics to Stellar Evolution

Abstract:
New data available from recent space-missions Kepler and GAIA, as well
as up-coming missions TESS and PLATO, has introduced a new era for
stellar physics. New theoretical/computational models are needed to
interpret the wealth of detailed new data. This includes fundamental
theories of stellar convection, overshooting and pulsation, differential
rotation, chemical mixing, and the dynamo. It also includes
instabilities that occur in binary stars evolving close to a companion.
The forefront of theoretical modeling is to expand models of the stellar
interior into the stellar atmosphere, to include mass accretion and mass
loss from stellar winds, as well as stellar spots and stellar flares. I
will describe the multi-dimensional, time implicit, fully compressible,
hydrodynamic, implicit large eddy simulation code MUSIC, and outline the
ongoing development of this computational tool designed for realistic
stellar hydrodynamics and magnetohydrodynamics. I will discuss how I
have used MUSIC to study convection during an early stage in the
evolution of our sun where the convection zone covers approximately half
of the solar radius. I interpret simulation data using extreme value
theory and derive a new model for convective overshooting and
penetration, targeted for use in one-dimensional stellar evolution
calculations. My model provides a scenario that can explain the observed
lithium abundance on the surface of the Sun and other solar-like stars
at a range of ages. The motivation for this program of work is to derive
new models based on realistic fluid simulations, to be implemented in
stellar evolution codes and broadly used for stellar and galactic
astrophysics.