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Electric current density and related sigmoid in an active region

Published online by Cambridge University Press:  27 June 2012

V. Joulin
Affiliation:
Institut d’Astrophysique Spatiale, CNRS-UMR 8617, Université Paris-Sud 11, 91405 Orsay Cedex, France
B. Schmieder
Affiliation:
Observatoire de Paris, LESIA, CNRS-INSU-UMR 8109, UPMC Univ. Paris 06, Université Paris Diderot, Paris 7, 5 place Jules Janssen, 92190 Meudon, France
G. Aulanier
Affiliation:
Observatoire de Paris, LESIA, CNRS-INSU-UMR 8109, UPMC Univ. Paris 06, Université Paris Diderot, Paris 7, 5 place Jules Janssen, 92190 Meudon, France
V. Bommier
Affiliation:
Observatoire de Paris, LESIA, CNRS-INSU-UMR 8109, UPMC Univ. Paris 06, Université Paris Diderot, Paris 7, 5 place Jules Janssen, 92190 Meudon, France
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Abstract

Using THEMIS vector magnetograms we measured vertical electric current density in the leading sunspot of NOAA 11127 active region during its disk passage. The current structures evolve versus time. MHD modelling allows us to explain the spiral pattern by torsion. We found observational visible counterparts in the SDO/AIA 335 A images. The field lines are visible as loops in the AIA images. When the torsion is increasing, a sigmoid is observed. In the present event observed on November 24th 2010, we find that reconnection is also necessary to explain their sigmoidal shape.

Type
Research Article
Copyright
© EAS, EDP Sciences 2012

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References

Aulanier, G., Démoulin, P., Grappin, R., 2005, A&A, 430, 1067
Bommier, V., Landi Degl’Innocenti, E., Landolfi, M., & Molodij, G., 2007, A&A, 464, 323
Bommier, V., Landi Degl’Innocenti, E., Schmieder, B., & Gelly, B., 2012, A&A, submitted