Widespread Occurrence of Trenching Patterns in the Granulation Field: Evidence for Roll Convection - AstrophysicsReport as inadecuate




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Abstract: Time-averaged series of granulation images are analysed using COLIBRI, apurpose-adapted version of a code originally developed to detect straight orcurvilinear features in aerospace images. The algorithm of image processingutilises a nonparametric statistical criterion that identifies a straight-linesegment as a linear feature lineament if the photospheric brightness at acertain distance from this line is on both sides stochastically lower or higherthan at the line itself. Curvilinear features can be detected as chains oflineaments, using a criterion modified in some way. Once the input parametersused by the algorithm are properly adjusted, the algorithm highlights``ridges- and ``trenches- in the relief of the brightness field, drawingwhite and dark lanes. The most remarkable property of the trenching patterns isa nearly-universally-present parallelism of ridges and trenches. Since thematerial upflows are brighter than the downflows, the alternating parallellight and dark lanes should reflect the presence of roll convection in thesubphotospheric layers. If the numerous images processed by us arerepresentative, the patterns revealed suggest a widespread occurrence of rollconvection in the outer solar convection zone. In particular, the roll systemscould form the fine structure of larger-scale, supergranular and-ormesogranular convection flows. Granules appear to be overheated blobs ofmaterial that could develop in convection rolls due to some instabilities ofroll motion.



Author: A. V. Getling, A. A. Buchnev

Source: https://arxiv.org/







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