University of Oulu

Mikhail Vokhmyanin and Nadezhda Zolotova 2022 ApJ 928 56,

Long-term north–south asymmetry of the heliospheric current sheet

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Author: Vokhmyanin, Mikhail1,2; Zolotova, Nadezhda1
Organizations: 1Saint Petersburg State University, Universitetskaya nab. 7/9, 198504, Saint Petersburg, Russia
2Space physics and astronomy research unit, University of Oulu, PO Box 3000, Fl-90014 Oulu, Finland
Format: article
Version: published version
Access: open
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Language: English
Published: IOP Publishing, 2022
Publish Date: 2022-05-04


In this paper, we evaluate the heliospheric current sheet (HCS) north–south asymmetry using the ecliptical sector structure of the interplanetary magnetic field (IMF) reconstructed since the second half of the 19th century. During the last five solar cycles, the inferred IMF polarities fairly reproduce the observed dominance of the sectors with the polarity of the northern solar hemisphere, i.e., the prolonged southward shift of the HCS. For the presatellite era, we found that the northward shift of the HCS was more common in cycles 10, 15, and 17–19, and the southward HCS shift was more common in cycles 9, 11–14, and 16. We also analyzed the north–south asymmetry in sunspot group numbers since 1749 and found that the northern hemisphere dominated in cycles 2–3, 7–9, and 15–20, and the southern hemisphere activity was stronger in cycles 4, 9–14, and 21–24. Moreover, other solar phenomena bear similar long-term asymmetry variations. The regularity of these variations is not clear. According to the available proxies of the solar data, the dominance of the northern hemisphere is found in the ascending phase of the secular solar cycle, and the dominance of the southern hemisphere coincides with the descending phase.

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Series: Astrophysical journal
ISSN: 0004-637X
ISSN-E: 1538-4357
ISSN-L: 0004-637X
Volume: 928
Issue: 1
Article number: 56
DOI: 10.3847/1538-4357/ac5630
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Copyright information: © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.