Energy Conservation and Gravity Waves in Sound-proof Treatments of Stellar Interiors: Part I Anelastic Approximations

Дата и время публикации : 2012-07-11T22:19:49Z

Авторы публикации и институты :
Benjamin P Brown (Department of Astronomy and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison)
Geoffrey M Vasil (Canadian Institute for Theoretical Astrophysics, University of Toronto, Canada)
Ellen G Zweibel (Department of Astronomy and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison)

Ссылка на журнал-издание: 2012, ApJ, 756, 109
Коментарии к cтатье: Accepted for publication in ApJ. 20 pages emulateapj format, 7 figures
Первичная категория: astro-ph.SR

Все категории : astro-ph.SR, physics.flu-dyn

Краткий обзор статьи: Typical flows in stellar interiors are much slower than the speed of sound. To follow the slow evolution of subsonic motions, various sound-proof equations are in wide use, particularly in stellar astrophysical fluid dynamics. These low-Mach number equations include the anelastic equations. Generally, these equations are valid in nearly adiabatically stratified regions like stellar convection zones, but may not be valid in the sub-adiabatic, stably stratified stellar radiative interiors. Understanding the coupling between the convection zone and the radiative interior is a problem of crucial interest and may have strong implications for solar and stellar dynamo theories as the interface between the two, called the tachocline in the Sun, plays a crucial role in many solar dynamo theories. Here we study the properties of gravity waves in stably-stratified atmospheres. In particular, we explore how gravity waves are handled in various sound-proof equations. We find that some anelastic treatments fail to conserve energy in stably-stratified atmospheres, instead conserving pseudo-energies that depend on the stratification, and we demonstrate this numerically. One anelastic equation set does conserve energy in all atmospheres and we provide recommendations for converting low-Mach number anelastic codes to this set of equations.

Category: Physics