On the Moat-Penumbra Relation

Abstract

Proper motions in a sunspot group with a delta-configuration and close to the solar disc center have been studied by employing local correlation tracking techniques. The analysis is based on more than one hour time series of G-band images. Radial outflows with a mean speed of 0.67 km s^{-1} have been detected around the spots, the well-known sunspots moats. However, these outflows are not found in those umbral core sides without penumbra. Moreover, moat flows are only found in those sides of penumbrae located in the direction marked by the penumbral filaments. Penumbral sides perpendicular to them show no moat flow. These results strongly suggest a relation between the moat flow and the well-known, filament aligned, Evershed flow. The standard picture of a moat flow originated from a blocking of the upward propagation of heat is commented in some detail.

4 pages, 4 figures, To appear in ApJ Letters

References in corpus (1)

• Evershed clouds as precursors of moving magnetic features around sunspots

Cited by in corpus (23)

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• The Current State-Of-The-Art In Active Region Seismology
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• Chromospheric and photospheric properties of sunspots as inferred from Stokes inversions under magneto-hydrostatic and non-local-thermodynamic equilibrium
• Rapid Disappearance of Penumbra-Like Features Near a Flaring Polarity Inversion Line: The Hinode Observations