Twist and writhe of Delta island active regions

LOPEZ FUENTES, M.; MANDRINI, C.H.; DÉMOULIN, P.

Ventura

Simposio; IAU Symposium 273 - Physics of Sun and Star Spots; 2010

IAU

We study the magnetic helicity properties of a set of peculiar active regions (ARs) including Delta-islands and 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 that originates deformed flux tubes.