The flow field in the sunspot canopy

Abstract

We investigate the flow field in the sunspot canopy using simultaneous Stokes vector spectropolarimetry of three sunspots ($\theta$ = 27, 50, 75 deg) and their surroundings in visible (630.15 and 630.25 nm) and near infrared (1564.8 and 1565.2 nm) neutral iron lines.} {To calibrate the Doppler shifts, we compare an absolute velocity calibration using the telluric $O_2$-line at 630.20 nm and a relative velocity calibration using the Doppler shift of Stokes V profiles in the umbra under the assumption that the umbra is at rest. Both methods yield the same result within the calibration uncertainties (~150 m/s). We study the radial dependence of Stokes V profiles in the directions of disk center and limb side. Maps of Stokes V profile shifts, polarity, amplitude asymmetry, field strength and magnetic field azimuth provide strong evidence for the presence of a magnetic canopy and for the existence of a radial outflow in the canopy. Our findings indicate that the Evershed flow does not cease abruptly at the white-light spot boundary, but that at least a part of the penumbral Evershed flow continues into the magnetic canopy.

10 pages, accepted to A&A

Cited by in corpus (7)

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• Relation between photospheric magnetic field and chromospheric emission
• Evidence of magnetic field wrapping around penumbral filaments
• Temporal evolution of the Evershed flow in sunspots. I. Observational characterization of Evershed clouds
• Sunspots: from small-scale inhomogeneities towards a global theory
• Temporal evolution of the Evershed flow in sunspots. II. Physical properties and nature of Evershed clouds
• Opposite magnetic polarity of two photospheric lines in single spectrum of the quiet Sun