Bibcode
Rezaei, R.; Schlichenmaier, R.; Beck, C.; Bellot Rubio, L. R.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 454, Issue 3, August II 2006, pp.975-982
Fecha de publicación:
8
2006
Revista
Número de citas
36
Número de citas referidas
30
Descripción
Aims.We investigate the flow field in the sunspot canopy using
simultaneous Stokes vector spectropolarimetry of three sunspots
(θ=27°, 50°, 75°) and their surroundings in visible
(630.15 and 630.25 nm) and near infrared (1564.8 and 1565.2 nm) neutral
iron lines. Methods: .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-1). We study the radial dependence of Stokes V
profiles in the directions of disk center and limb side. Results:
.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. Conclusions: .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.