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Successive injection of opposite magnetic helicity in solar active region NOAA 11928

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dc.contributor.author Vemareddy, P
dc.contributor.author Demoulin, P
dc.date.accessioned 2020-11-17T02:44:13Z
dc.date.available 2020-11-17T02:44:13Z
dc.date.issued 2017-01
dc.identifier.citation Astronomy & Astrophysics, Vol. 597, A104 en_US
dc.identifier.issn 0004-6361
dc.identifier.uri http://prints.iiap.res.in/handle/2248/7051
dc.description Open Access © ESO http://dx.doi.org/10.1051/0004-6361/201629282 en_US
dc.description.abstract Aims. Understanding the nature and evolution of the photospheric helicity flux transfer is crucial to revealing the role of magnetic helicity in coronal dynamics of solar active regions. Methods. We computed the boundary-driven helicity flux with a 12-min cadence during the emergence of the AR 11928 using SDO/HMI photospheric vector magnetograms and the derived flow velocity field. Accounting for the footpoint connectivity defined by nonlinear, force-free magnetic extrapolations, we derived and analyzed the corrected distribution of helicity flux maps. Results. The photospheric helicity flux injection is found to change sign during the steady emergence of the AR. This reversal is confirmed with the evolution of the photospheric electric currents and with the coronal connectivity as observed in EUV wavelengths with SDO/AIA. During approximately the three first days of emergence, the AR coronal helicity is positive while later on the field configuration is close to a potential field. As theoretically expected, the magnetic helicity cancellation is associated with enhanced coronal activity. Conclusions. The study suggests a boundary driven transformation of the chirality in the global AR magnetic structure. This may be the result of the emergence of a flux rope with positive twist around its apex while it has negative twist in its legs. The origin of such mixed helicity flux rope in the convective zone is challenging for models. en_US
dc.language.iso en en_US
dc.publisher EDP Sciences en_US
dc.subject Sun: magnetic fields en_US
dc.subject Sun: flares en_US
dc.subject Sun: activity en_US
dc.subject Sun: photosphere en_US
dc.subject Sun: corona en_US
dc.title Successive injection of opposite magnetic helicity in solar active region NOAA 11928 en_US
dc.type Article en_US


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