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Numerical Simulations of a Laboratory Star
  • Fredy Ramirez,
  • Nicholas Featherstone,
  • Jonathan Aurnou
Fredy Ramirez
University of Colorado at Boulder

Corresponding Author:frra1220@colorado.edu

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Nicholas Featherstone
University of Colorado at Boulder
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Jonathan Aurnou
University of California Los Angeles
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The Sun’s deep-seated convective flows must ultimately sustain not just the efficient EMF from which solar magnetism derives, but also the large-scale shearing and circulatory flows thought to imbue that magnetism with its remarkable spatiotemporal ordering. Exploration of the dynamo process ultimately requires knowledge of how these flows are structured, and indeed, near-surface convective motions are imaged regularly using helioseismic observations. Those techniques reliably image flows throughout only the upper 15% of the convection zone, however, leaving us with a description of the interior that is heavily predicated on theoretical-computational results. Ideally, computational models would be validated directly against, or even applied in tandem with, laboratory experiments. Such investigations have been limited in the solar context due to the difficulty in creating a central force outside of a microgravity environment. Recent advances in acoustics have enabled the construction of an experimental apparatus that employs resonant sound waves to confine a plasma in spherical geometry. The plasma is heated internally using microwaves that are pulsed in resonance with the bulb’s fundamental acoustic mode. The resonant soundwave excited results in a central force over 1,000 times stronger than Earth’s gravity. In analog to the Sun, the resulting plasma state possesses layers that are both stable and unstable to convection. We discuss how this system’s behavior compares with numerical models run in comparable parameter regimes. Using the 3D-convection code, Rayleigh, we first model the spherically symmetric acoustic radiation pressure as a pseudo gravity. Following this initial incompressible treatment examine the behavior of a fully compressible model wherein the sound field is simulated directly. For each set of simulations, we examine the initial onset of thermal buoyancy instability and characterize the most unstable modes and their growth rate during the initial transient phase.