Bihelical Spectrum of Solar Magnetic Helicity and Its Evolution

Using a recently developed two-scale formalism to determine the magnetic helicity spectrum, we analyze synoptic vector magnetograms built with data from the Vector Spectromagnetograph instrument on the Synoptic Optical Long-term Investigations of the Sun telescope during 2010 January-2016 July. In c...

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Bibliographic Details
Published in:The Astrophysical journal 2018-08, Vol.863 (2), p.182
Main Authors: Singh, Nishant K., Käpylä, Maarit J., Brandenburg, Axel, Käpylä, Petri J., Lagg, Andreas, Virtanen, Ilpo
Format: Article
Language:English
Subjects:
Astrophysics
dynamo
Helicity
magnetohydrodynamics (MHD)
Solar cycle
Sun: magnetic fields
Turbulence
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Summary:Using a recently developed two-scale formalism to determine the magnetic helicity spectrum, we analyze synoptic vector magnetograms built with data from the Vector Spectromagnetograph instrument on the Synoptic Optical Long-term Investigations of the Sun telescope during 2010 January-2016 July. In contrast to an earlier study using only three Carrington rotations (CRs), our analysis includes 74 synoptic CR maps. We recover here bihelical spectra at different phases of solar cycle 24, where the net magnetic helicity in the majority of the data is consistent with a large-scale dynamo with helical turbulence operating in the Sun. More than 20% of the analyzed maps, however, show violations of the expected sign rule.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.3847/1538-4357/aad0f2