Traveling Waves of Magnetoconvection and the Origin of the Evershed Effect in Sunspots

TL;DR

This paper uses realistic numerical simulations to demonstrate that traveling waves in non-linear magnetoconvection under strong, inclined magnetic fields can explain the Evershed effect observed in sunspots, including flow structures and dynamics.

Contribution

It introduces a novel simulation-based explanation for the Evershed effect, linking traveling wave magnetoconvection to observed sunspot flow features.

Findings

Simulations reproduce high-speed Evershed clouds

Flow structures match filamentary patterns observed

Predicts large-scale organization of outflows

Abstract

Discovered in 1909 the Evershed effect represents strong mass outflows in sunspot penumbra, where the magnetic field of sunspots is filamentary and almost horizontal. These flows play important role in sunspots and have been studied in detail using large ground-based and space telescopes, but the basic understanding of its mechanism is still missing. We present results of realistic numerical simulations of the Sun's subsurface dynamics, and argue that the key mechanism of this effect is in non-linear magnetoconvection that has properties of traveling waves in the presence of strong, highly inclined magnetic field. The simulations reproduce many observed features of the Evershed effect, including the high-speed "Evershed clouds", the filamentary structure of the flows, and the non-stationary quasi-periodic behavior. The results provide a synergy of previous theoretical models and lead to an interesting prediction of a large-scale organization of the outflows.