Supersonic Evershed flow outside Sunspots

Abstract

We report on the discovery of mostly horizontal field channels just outside sunspot penumbrae (in the so-called `moat' region) that are seen to sustain supersonic flows (line-of-sight component of 6 km s{-1}). The spectral signature of these supersonic flows corresponds to circular polarization profiles with an additional, satellite, third lobe of the same sign as the parent sunspot' Stokes V blue lobe, for both downflows and upflows. This is consistent with an outward directed flow that we interpret as the continuation of the magnetized Evershed flow outside sunspots at supersonic speeds. In Stokes Q and U, a clear signature of a transverse field connecting the two flow streams is observed. Such an easily detectable spectral signature should allow for a clear identification of these horizontal field channels in other spectropolarimetric sunspot data. For the spot analyzed in this paper, a total of 5 channels with this spectral signature have been unambiguously found.

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Cited by in corpus (8)

• Peripheral downflows in sunspot penumbrae
• Structure of sunspot penumbral filaments: a remarkable uniformity of properties
• A geometrical height scale for sunspot penumbrae
• A new type of small-scale downflow patches in sunspot penumbrae
• Local Helioseismology of Sunspots: Current Status and Perspectives (Invited Review)
• Supersonic Downflows at the Umbra-Penumbra Boundary of Sunspots
• Temporal Evolution of the Inverse Evershed Flow
• Velocity fields in and around sunspots at the highest resolution