Automatic Recognition and Characterisation of Supergranular Cells from Photospheric Velocity Fields |
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| Authors: | H E Potts D A Diver |
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| Institution: | (1) Department of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK |
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| Abstract: | We have developed an exceptionally noise-resistant method for accurate and automatic identification of supergranular cell
boundaries from velocity measurements. Because of its high noise tolerance the algorithm can produce reliable cell patterns
with only very small amounts of smoothing of the source data in comparison to conventional methods. In this paper we describe
the method and test it with simulated data. We then apply it to the analysis of velocity fields derived from high-resolution
continuum data from MDI (Michelson Doppler Imager) on SOHO. From this, we can identify with high spatial resolution certain
basic properties of supergranulation cells, such as their characteristic sizes, the flow speeds within cells, and their dependence
on cell areas. The effect of the noise and smoothing on the derived cell boundaries is investigated and quantified by using
simulated data. We show in detail the evolution of supergranular cells over their lifetime, including observations of emerging,
splitting, and coalescing cells. A key result of our analysis of cell internal velocities is that there is a simple linear
relation between cell size and cell internal velocity, rather than the power law usually suggested.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. |
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| Keywords: | Photosphere Supergranulation Granules Photospheric flow |
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