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[3.04] Comparison of Helicity Proxies Observed by Haleakala Stokes Polarimeter and Huairou Solar Observing Station Vector Magnetograph

A. A. Pevtsov (National Solar Observatory, U.S.A.), J. P. Dun, H. Zhang (National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China)

We conduct detailed comparison of the current helicity measurements derived using observations from two vector magnetographs - Haleakala Stokes Polarimeter (HSP) at Mees Solar Observatory, and Solar Magnetic Fields Telescope (SMFT) at Huairou Solar Observing Station. The data, -- 269 pairs of vector magnetograms -- are observed in 1997-2000. We apply the same procedure to both data sets to resolve 180\arcdeg\ azimuth ambiguity and compute the linear force free field coefficient \alpha. We find that in 205 (76%) of 269 cases the SMFT and HSP data show the same sign of \alpha. Remaining 64 (24%) magnetograms that exhibit opposite sign of helicity in two instruments can be explained by several reasons including incorrect heliographic coordinates of active regions, lack of persistence in polarimetric measurements, spatial misalignment between Stokes I, Q, U and V maps, difference in noise level and active regions evolution.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.