Abstract
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.