Spatial Clustering of Photospheric Structures

Abstract

The study of large-scale structures existing in solar photospheric flows provides an essential tool for constraining the models of solar and stellar convection and for understanding physical processes that are at the basis of solar variability. Recent convection models and N-body dynamic simulations predict the evolution of small-scale features (i.e., granules) into large-scale ones. In this work we address the question of the emergence of large spatial scale patterns as a direct consequence of the organization of small-scale plasma flows on time periods longer than the mean granular lifetime. Our analysis reveals that the photospheric dynamics plays a key role in structuring stable intensity features and suggests that surface flows organize small-scale plasma structures, sweeping them up to form clusters of recurrent and stable granular features. Using a quite novel statistical method, the hexagonal normalized information entropy, we establish that sites where recurrent and stable granular features are observed exhibit a clustering spatial scale of about 8 Mm and timescale around 10 minutes.