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Twist and writhe of δ-island active regions

Published online by Cambridge University Press:  26 August 2011

M. C. López Fuentes ,
C. H. Mandrini  and
P. Démoulin
M. C. López Fuentes
Affiliation:
Instituto de Astronomía y Física del Espacio (CONICET-UBA), CC 67, Suc 28, 1428 Buenos Aires, Argentina e-mail: lopezf@iafe.uba.ar
C. H. Mandrini
Affiliation:
Instituto de Astronomía y Física del Espacio (CONICET-UBA), CC 67, Suc 28, 1428 Buenos Aires, Argentina e-mail: lopezf@iafe.uba.ar
P. Démoulin
Affiliation:
Observatoire de Paris, LESIA, UMR 8109 (CNRS), F-92195, Meudon Principal Cedex, France
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Abstract

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We study the magnetic helicity properties of a set of peculiar active regions (ARs) including δ-islands and other high-tilt bipolar configurations. These ARs are usually identified as the most active in terms of flare and CME production. Due to their observed structure, they have been associated with the emergence of magnetic flux tubes that develop a kink instability. Our main goal is to determine the chirality of the twist and writhe components of the AR magnetic helicity in order to set constrains on the possible mechanisms producing the flux tube deformations. We determine the magnetic twist comparing observations of the AR coronal structure with force-free models of the magnetic field. We infer the flux-tube writhe from the rotation of the main magnetic bipole during the observed evolution. From the relation between the obtained twist and writhe signs we conclude that the development of the kink instability cannot be the single mechanism producing deformed flux-tubes.

Keywords

Sun: magnetic fieldssun: activitysun: photospheresun: corona
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S273: The Physics of Sun and Star Spots , August 2010 , pp. 153 - 156
Copyright
Copyright © International Astronomical Union 2011

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