English

The flow field in the sunspot canopy

Astrophysics 2007-05-23 v1

Abstract

We investigate the flow field in the sunspot canopy using simultaneous Stokes vector spectropolarimetry of three sunspots (θ\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 O2O_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.

Keywords

Cite

@article{arxiv.astro-ph/0604301,
  title  = {The flow field in the sunspot canopy},
  author = {Reza Rezaei and R. Schlichenmaier and C. A. R. Beck and L. R. Bellot Rubio},
  journal= {arXiv preprint arXiv:astro-ph/0604301},
  year   = {2007}
}

Comments

10 pages, accepted to A&A

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