Additional Evidence Supporting a Model of Shallow, High-Speed Supergranulation

Recently, Duvall and Hanasoge ({\it Solar Phys.} {\bf 287}, 71-83, 2013) found that large distance $[Δ]$ separation travel-time differences from a center to an annulus $[δt_{\rm{oi}}]$ implied a model of the average supergranular cell that has a peak upflow of $240\rm{ms^{-1}}$ at a depth of $2.3\rm{Mm}$ and a corresponding peak outward horizontal flow of $700\rm{ms^{-1}}$ at a depth of $1.6\rm{Mm}$. In the present work, this effect is further studied by measuring and modeling center-to-quadrant travel-time differences $[δt_{\rm{qu}}]$, which roughly agree with this model. Simulations are analyzed that show that such a model flow would lead to the expected travel-time differences. As a check for possible systematic errors, the center-to-annulus travel-time differences $[δt_{\rm{oi}}]$ are found not to vary with heliocentric angle. A consistency check finds an increase of $δt_{\rm{oi}}$ with the temporal frequency $[ν]$ by a factor of two, which is not predicted by the ray theory.

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