On mesogranulation, network formation and supergranulation

We present arguments which show that in all likelihood mesogranulation is n ot a true scale of solar convection but the combination of the effects of b oth highly energetic granules, which give birth to strong positive divergen ces (SPDs) among which we find exploders, and averaging effects of data pro cessing. The important role played by SPDs in horizontal velocity fields ap pears in the spectra of these fields where the scale similar to 4 Mm is mos t energetic; we illustrate the effect of averaging with a one-dimensional t oy model which shows how two independent non-moving (but evolving) structur es can be transformed into a single moving structure when time and space re solution are degraded. The role of SPDs in the formation of the photospheric network is shown by c omputing the advection of floating corks by the granular flow. The coincide nce of the network bright points distribution and that of the corks is rema rkable. We conclude with the possibility that supergranulation is not a pro per scale of convection but the result of a large-scale instability of the granular flow, which manifests itself through a correlation of the flows ge nerated by SPDs.