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.
|School Location:||United States -- California|
|Source:||DAI-B 69/05, Dissertation Abstracts International|
|Keywords:||Convective instability, Solar physics, Supergranulation|
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