The Evershed Effect with SOT/Hinode

TL;DR

This paper discusses high-resolution observations of the Evershed flow in sunspot penumbra, revealing its fine structure, dynamics, and relation to magnetic fields, suggesting a convective origin influenced by magnetic inclination.

Contribution

It provides new detailed observations of the Evershed flow's structure and dynamics using Hinode's Solar Optical Telescope, advancing understanding of penumbral magnetic and flow configurations.

Findings

Evershed flow confined in narrow, nearly horizontal magnetic channels

Flow channels associated with hot upflows and cool downflows

Twisting motions suggest convective processes in penumbral filaments

Abstract

The Solar Optical Telescope onboard Hinode revealed the fine-scale structure of the Evershed flow and its relation to the filamentary structures of the sunspot penumbra. The Evershed flow is confined in narrow channels with nearly horizontal magnetic fields, embedded in a deep layer of the penumbral atmosphere. It is a dynamic phenomenon with flow velocity close to the photospheric sound speed. Individual flow channels are associated with tiny upflows of hot gas (sources) at the inner end and downflows (sinks) at the outer end. SOT/Hinode also discovered ``twisting'' motions of penumbral filaments, which may be attributed to the convective nature of the Evershed flow. The Evershed effect may be understood as a natural consequence of thermal convection under a strong, inclined magnetic field. Current penumbral models are discussed in the lights of these new Hinode observations.