Dissertation/Thesis Abstract

Numerical modelling of convective instability in a stratified shear layer and wave-like properties of solar supergranulation
by Green, Cristina, Ph.D., Stanford University, 2008, 86; 3313816
Abstract (Summary)

Gizon, Duvall and Schou (2003) have observed that solar supergranulation demonstrates wavelike behaviour, with a non-advective phase speed of ∼ 65 m/s. Using numerical models, we tested the proposed explanation that supergranular waves are caused by the steep shear gradient at the solar surface.

A linearized nonviscous compressible hydrodynamic model produces supergranular waves; however, they have slower phase speeds than the observed 65 m/s. Further linear models including viscosity and/or toroidal magnetic fields produce modes at the observed phase speed, for an appropriate choice of parameters. Switching to a nonlinear model increases the phase speed, for the same choice of parameters.

The alternative proposed explanation that the supergranular waves are caused by the Coriolis force is evaluated, using both a linear model and data from nonlinear modelling by Miesch et al., but no evidence of wave-like behaviour was found.

Indexing (document details)
Advisor: Kosovichev, Alexander
Commitee:
School: Stanford University
School Location: United States -- California
Source: DAI-B 69/05, Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Astronomy, Astrophysics
Keywords: Convective instability, Solar physics, Supergranulation
Publication Number: 3313816
ISBN: 978-0-549-62982-5
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