Velocity fields in and around sunspots at the highest resolution

Abstract

The flows in and around sunspots are rich in detail. Starting with the Evershed flow along low-lying flow channels, which are cospatial with the horizontal penumbral magnetic fields, Evershed clouds may continue this motion at the periphery of the sunspot as moving magnetic features in the sunspot moat. Besides these well-ordered flows, peculiar motions are found in complex sunspots, where they contribute to the build-up or relaxation of magnetic shear. In principle, the three-dimensional structure of these velocity fields can be captured. The line-of-sight component of the velocity vector is accessible with spectroscopic measurements, whereas local correlation or feature tracking techniques provide the means to assess horizontal proper motions. The next generation of ground-based solar telescopes will provide spectropolarimetric data resolving solar fine structure with sizes below 50 km. Thus, these new telescopes with advanced post-focus instruments act as a "zoom lens" to study the intricate surface flows associated with sunspots. Accompanied by "wide-angle" observations from space, we have now the opportunity to describe sunspots as a system. This review reports recent findings related to flows in and around sunspots and highlights the role of advanced instrumentation in the discovery process.

6 pages, 1 figure, to be published in "Physics of Sun and star spots", Proc. IAU Symp. 273, D.P. Choudhary and K.G. Strassmeier (eds.)

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