The Void Probability Function in MDI magnetograms

We investigate the spatial distribution of reticular clusters of magnetic features on the solar surface. For this purpose, we develop a void searching algorithm, such as those used in cosmology to study galaxy spatial distributions. We apply this method to a temporal series of large FoV MDI (Michelson Doppler Imager) magnetograms, to identify voids between magnetic structures and to extract their normalized Void Probability Function, which characterizes the scale distribution of magnetic inter-cluster voids. The histogram of the void dimensions shows a pronounced peak for small dimensions (1.76 Mm) and a large spread in the individual cell sizes, up to ' 60 Mm.