Vortices in simulations of solar surface convection

TL;DR

This paper investigates small-scale vortices in solar surface convection simulations, revealing their properties, dynamics, and potential observability, contributing to understanding solar surface turbulence.

Contribution

It introduces an eigenanalysis method to identify swirling plasma regions and characterizes the properties and behavior of vortices in solar surface simulations.

Findings

Vortices form an unsteady, tangled network in turbulent downflow lanes.

Vertical vortices are underdense and cause local surface depressions.

Vortices typically last a few minutes and are influenced by plasma motion.

Abstract

We report on the occurrence of small-scale vortices in simulations of the convective solar surface. Using an eigenanalysis of the velocity gradient tensor, we find the subset of high vorticity regions in which the plasma is swirling. The swirling regions form an unsteady, tangled network of filaments in the turbulent downflow lanes. Near-surface vertical vortices are underdense and cause a local depression of the optical surface. They are potentially observable as bright points in the dark intergranular lanes. Vortex features typically exist for a few minutes, during which they are moved and twisted by the motion of the ambient plasma. The bigger vortices found in the simulations are possibly, but not necessarily, related to observations of granular-scale spiraling pathlines in "cork animations" or feature tracking.