University of Oulu

Singh, N., Käpylä, M., Brandenburg, A., Käpylä, P., Lagg, A., Virtanen, I. (2018) Bihelical Spectrum of Solar Magnetic Helicity and Its Evolution. Astrophysical Journal, 863 (2), 182. doi:10.3847/1538-4357/aad0f2

Bihelical spectrum of solar magnetic helicity and its evolution

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Author: Singh, Nishant K.1; Käpylä, Maarit J.1,2; Brandenburg, Axel3,4,5,6;
Organizations: 1Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany
2ReSoLVE Centre of Excellence, Department of Computer Science, Aalto University, PO Box 15400, FI-00076 Aalto, Finland
3NORDITA, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden
4Department of Astronomy, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
5JILA and Department of Astrophysical and Planetary Sciences, Box 440, University of Colorado, Boulder, CO 80303, USA
6Laboratory for Atmospheric and Space Physics, 3665 Discovery Drive, Boulder, CO 80303, USA
7Leibniz Institute for Astrophysics Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany
8ReSoLVE Centre of Excellence, Space Climate research unit, University of Oulu, P.O.Box 3000 FI-90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.9 MB)
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Language: English
Published: IOP Publishing, 2018
Publish Date: 2019-03-26


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.

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Series: Astrophysical journal
ISSN: 0004-637X
ISSN-E: 1538-4357
ISSN-L: 0004-637X
Volume: 863
Issue: 2
Article number: 182
DOI: 10.3847/1538-4357/aad0f2
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: Financial support from the Academy of Finland grant no. 272157 to the ReSoLVE Center of Excellence (M.J.K., P.J.K., and I.V.) and through the Max-Planck-Princeton Center for Plasma Physics (N.S.) is gratefully acknowledged. This research was further supported by the NSF Astronomy and Astrophysics Grants Program (grant 1615100) and the University of Colorado through its support of the George Ellery Hale visiting faculty appointment (A.B.).
Academy of Finland Grant Number: 272157
Detailed Information: 272157 (Academy of Finland Funding decision)
Copyright information: © 2018. The American Astronomical Society. All rights reserved. Published in this repository with the kind permission of the publisher.