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Paper: Variations of Current Helicity in Active Region 10930 as Inferred from Hinode Spectropolarimeter Data and Cancellation Exponent
Volume: 454, The 3rd Hinode Science Meeting
Page: 311
Authors: Yurchyshyn, V.; Abramenko, V.; Watanabe, H.
Abstract: Current helicity derived from vector magnetograms possesses a well-pronounced scaling behavior, which can be studied by introducing a signed measure and calculating the power-law exponent (cancellation exponent). The time variations of this exponent seem to be related to flare activity of an active region. Here we focus on changes of current helicity in active region NOAA 10930 as derived from a set of Hinode spectropolarimeter data. Our findings are that the cancellation exponent first strongly increased on Dec 11 then rapidly decreased after a small sunspot-satellite developed. Afterward, the cancellation exponent began its gradual increase without significant new magnetic flux emergence. These two different modes of behavior may indicate different processes that ultimately led to an eruption: the first process is rapid injection of current helicity, while the second process is gradual redistribution of injected helicity over all spatial scales in the active region.
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