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Astron. Astrophys. 355, 1138-1145 (2000)

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H[FORMULA] polarimetry of the solar limb

D. Clarke and V. Ameijenda

University Observatory, Acre Road, Glasgow, G20 0TL, Scotland, UK (d.clarke@astro.gla.ac.uk)

Received 6 September 1999 / Accepted 21 January 2000


A prototype H[FORMULA] imaging polarimeter has been used to make measurements of the solar disk. Within the H[FORMULA] line, the polarization at the solar limb is significantly greater than the nearby continuum reflecting resonance scattering effects, with [FORMULA] achieving [FORMULA] at the line-core. Comparative measurements have been made of the form of polar and equatorial center-to-limb variations (CLVs). Face value results indicate that the polarization emanating from the pole is marginally greater than from the equator. This finding is explainable, however, in terms of instrumental, experimental and data reduction effects with the conclusion that no disparity between the polar and equatorial [FORMULA]- CLVs has been detected to polarimetric accuracies [FORMULA] or 2 parts in [FORMULA] and to a spatial accuracy [FORMULA] arcsec. Some of the recorded CLVs show departures from a smooth curve, these associated with magnetic structures and the Hanle effect.

Key words: polarization – scattering – instrumentation: polarimeters – techniques: polarimetric – Sun: chromosphere – Sun: photosphere

Send offprint requests to: D. Clarke

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© European Southern Observatory (ESO) 2000

Online publication: March 21, 2000