The Sun's Supergranulation

TL;DR

This paper reviews the complex phenomenon of solar supergranulation, discussing observational, numerical, and theoretical advances that shed light on its origin and dynamics in the solar photosphere.

Contribution

It provides an exhaustive review of recent progress in understanding supergranulation through observations, simulations, and theory, highlighting the role of large-scale thermal convection.

Findings

Supergranulation involves vigorous cellular flow patterns with specific scales and velocities.

Recent high-resolution observations and simulations have advanced understanding of its origin.

Large-scale nonlinear thermal convection is key to supergranulation dynamics.

Abstract

Supergranulation is a fluid-dynamical phenomenon taking place in the solar photosphere, primarily detected in the form of a vigorous cellular flow pattern with a typical horizontal scale of approximately 30--35~megameters, a dynamical evolution time of 24--48~h, a strong 300--400~m/s (rms) horizontal flow component and a much weaker 20--30~m/s vertical component. Supergranulation was discovered more than sixty years ago, however, explaining its physical origin and most important observational characteristics has proven extremely challenging ever since, as a result of the intrinsic multiscale, nonlinear dynamical complexity of the problem concurring with strong observational and computational limitations. Key progress on this problem is now taking place with the advent of 21st-century supercomputing resources and the availability of global observations of the dynamics of the solar surface with high spatial and temporal resolutions. This article provides an exhaustive review of observational, numerical and theoretical research on supergranulation, and discusses the current status of our understanding of its origin and dynamics, most importantly in terms of large-scale nonlinear thermal convection, in the light of a selection of recent findings.