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Astron. Astrophys. 331, 383-391 (1998)

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An ambiguity-free determination of Jz in solar active regions

M. Semel and A. Skumanich *

DASOP, Section de Meudon, URA 326, Observatoire de Paris, Place Jules Janssen, F-92195 Meudon Cedex, France

Received 11 July 1996 / Accepted 24 July 1997


We propose a way to derive a radial electric current density from vector magnetograms that is free of any particular choice of the two possible azimuths for the plane of the sky field. The method is applied to active region data obtained with the Advanced Stokes Polarimeter (ASP). A comparison of this current density with that derived for two particular sets of possible azimuth assignments allows one to evaluate the appropriateness of each set. In addition one may verify the detection of currents in general and the occurrence of current sheets, i.e. field discontinuities, in particular.

Key words: Sun: magnetic fields; plages; sunspots

* On leave from the High Altitude Observatory of the National Center for Atmospheric Research (NCAR) Boulder, Colo, USA. The NCAR is sponsored by the National Science Foundation.

Send offprint requests to: M. Semel


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© European Southern Observatory (ESO) 1998

Online publication: February 4, 1998