Energy Conservation And Gravity Waves In Stellar Interior Simulations That Employ Sound-proof Treatments

Brown, Benjamin
(
Univ. of Wisconsin - Madison
);
Vasil, G. M.
(
Candian Institute for Theoretical Astrophysics, Canada
);
Lecoanet, D.
(
University of California, Berkeley
);
Zweibel, E. G.
(
Univ. of Wisconsin - Madison
)
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American Astronomical Society, AAS Meeting #220, id.328.02

Published in May 2012

In the deep stellar interiors, flows are typically much slower than the local speed of sound. Owing to this, simulations of stellar convection and dynamo action typically employ various "sound-proof" equations, which filter the fast sound waves but can follow the subsonic convective flows. These sound-proof equations include the anelastic equations, which typically are derived in adiabatically-stratified stellar convection zones, and the pseudo-incompressible equations. In stars like the Sun, the radiative zone underlying the convection zone is a region of stable subadiabatic stratification, where motions remain highly subsonic and gravity waves dominate the dynamics. We study the application of sound-proof equations to dynamics in stellar radiative zones. We find that some formulations fail to conserve energy in regions of stable stratification and consequently do not correctly capture the dynamics of gravity waves. We provide a mapping to equations that do conserve energy. We discuss gravity wave dynamics in stably-stratified stellar regions in the context of simulations of stars like the Sun, and also consider more massive stars, where the radiative envelope lies above a convective core.
(c) 2012: American Astronomical Society