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A comparison between global proxies of the sun’s magnetic activity cycle : inferences from Helioseismology
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Broomhall, Anne-Marie and Nakariakov, V. M. (Valery M.) (2015) A comparison between global proxies of the sun’s magnetic activity cycle : inferences from Helioseismology. Solar Physics, 290 (11). pp. 3095-3111. doi:10.1007/s11207-015-0728-6 ISSN 1573-093X.
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Official URL: http://dx.doi.org/10.1007/s11207-015-0728-6
Abstract
The last solar minimum was, by recent standards, unusually deep
and long. We are now close to the maximum of the subsequent solar cycle, which is relatively weak. In this article we make comparisons between different global (unresolved) measures of the Sun’s magnetic activity, to investigate how they are responding to this weak-activity epoch. We focus on helioseismic data, which are sensitive to conditions, including the characteristics of the magnetic field, in the solar interior. Also considered are measures of the magnetic field in the photosphere (sunspot number and sunspot area), the chromosphere and corona (10.7 cm radio flux and 530.3 nm green coronal index), and two measures of the Sun’s magnetic activity closer to Earth (the
interplanetary magnetic field and the galactic cosmic-ray intensity). Scaled versions of the activity proxies diverge from the helioseismic data around 2000, indicating a change in relationship between the proxies. The degree of divergence varies from proxy to proxy with sunspot area and 10.7 cm flux showing only small deviations, while sunspot number, coronal index, and the two interplanetary proxies show much larger departures. In Cycle 24 the deviations in the solar proxies and the helioseismic data decrease, raising the possibility that the deviations observed in Cycle 23 are just symptomatic of a 22-year Hale cycle. However, the deviations in the helioseismic data and the
interplanetary proxies increase in Cycle 24. Interestingly the divergence in the solar proxies and the helioseismic data are not reflected in the shorter-term variations (often referred to as quasi-biennial oscillations) observed on top of the dominant 11-year solar
cycle. However, despite being highly correlated in Cycle 22, the short-term variations in the interplanetary proxies show very little correlation with the helioseismic data during Cycles 23 and 24.
Item Type: | Journal Article | ||||||||
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Subjects: | Q Science > QB Astronomy | ||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
Library of Congress Subject Headings (LCSH): | Helioseismology, Solar oscillations, Solar magnetic fields | ||||||||
Journal or Publication Title: | Solar Physics | ||||||||
Publisher: | Springer | ||||||||
ISSN: | 1573-093X | ||||||||
Official Date: | November 2015 | ||||||||
Dates: |
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Volume: | 290 | ||||||||
Number: | 11 | ||||||||
Number of Pages: | 17 | ||||||||
Page Range: | pp. 3095-3111 | ||||||||
DOI: | 10.1007/s11207-015-0728-6 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||
Date of first compliant deposit: | 19 April 2016 | ||||||||
Date of first compliant Open Access: | 28 July 2016 | ||||||||
Funder: | University of Warwick. Institute of Advanced Study (IAS), European Research Council (ERC), Science and Technology Facilities Council (Great Britain) (STFC) |
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