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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. 相似文献
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F. H. Busse 《Solar physics》2007,245(1):27-36
Thermal convection in a horizontal fluid layer heated from below and rotating about an arbitrary axis is studied analytically
with the attention focused on mean flows and drifts generated by the convection velocity field. Mean flows occur in both horizontal
directions when the angle between the rotation vector and the vertical is finite but less than 90°. In the case of a hexagonal
convection pattern, a wavelike drift is found in the presence of a horizontal component of rotation. Applications to solar
convection are discussed. Considering the simplicity of the model the agreement with observations is surprisingly good. 相似文献
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