Supersonic Continuation of the Evershed Flow Outside a Sunspot as Observed with Hinode

Martínez Pillet, V.; Katsukawa, Y.; Puschmann, K. G.; Ruiz Cobo, B.
Referencia bibliográfica

The Astrophysical Journal Letters, Volume 701, Issue 2, pp. L79-L82 (2009).

Fecha de publicación:
8
2009
Número de autores
4
Número de autores del IAC
3
Número de citas
15
Número de citas referidas
9
Descripción
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 five channels with this spectral signature have been unambiguously found.
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