Observations of the Hanle Effect in the Ca I 4227 and Sr II 4078 Å lines
The Hanle effect in the second solar spectrum has been explored with a beam splitter based polarimeter at IRSOL in Locarno. It is the only existing imaging solar polarimeter system that is sensitive to the ultraviolet part of the spectrum, where the scattering-polarization effects are the largest. We discuss results of full vector polarimetry (all four Stokes parameters) in the Ca I 4227 and Sr II 4078 A lines in quiet and active solar regions, and show how the signatures of Hanle depolarization in Stokes Q, Hanle rotation in Stokes U, and the longitudinal Zeeman effect in Stokes V can exhibit strong spatial variations over a few arcsec. We further illustrate how the Hanle observations can be used to derive information on both the spatially unresolved and partially resolved weak magnetic fields outside the supergranulation network.
Key wordspolarization scattering Sun: magnetic fields techniques: polarimetric
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