Abstract
Recently, Duvall and Hanasoge (Solar Phys. 287, 71, 2013) found that large-distance separation [Δ] travel-time differences from a center to an annulus [δt oi] implied a model of the average supergranular cell that has a peak upflow of 240 m s−1 at a depth of 2.3 Mm and a corresponding peak outward horizontal flow of 700 m s−1 at a depth of 1.6 Mm. In the present work, this effect is further studied by measuring and modeling center-to-quadrant travel-time differences [δt 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 oi] are found not to vary with heliocentric angle. A consistency check finds an increase of δt oi with the temporal frequency [ν] by a factor of two, which is not predicted by the ray theory.
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The data used here are courtesy of NASA/SDO and the HMI Science Team. We thank the HMI team members for their hard work. This work is supported by NASA SDO.
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The Many Scales of Solar Activity in Solar Cycle 24 as seen by SDO
Guest Editors: Aaron Birch, Mark Cheung, Andrew Jones, and W. Dean Pesnell
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Duvall, T.L., Hanasoge, S.M. & Chakraborty, S. Additional Evidence Supporting a Model of Shallow, High-Speed Supergranulation. Sol Phys 289, 3421–3433 (2014). https://doi.org/10.1007/s11207-014-0537-3
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DOI: https://doi.org/10.1007/s11207-014-0537-3