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Title: North–South Asymmetry in Rieger-type Periodicity during Solar Cycles 19–23

Abstract

Rieger-type periodicity has been detected in different activity indices over many solar cycles. It was recently shown that the periodicity correlates with solar activity having a shorter period during stronger cycles. Solar activity level is generally asymmetric between northern and southern hemispheres, which could suggest the presence of a similar behavior in the Rieger-type periodicity. We analyze the sunspot area/number and the total magnetic flux data for northern and southern hemispheres during solar cycles 19–23, which had remarkable north–south asymmetry. Using wavelet analysis of sunspot area and number during the north-dominated cycles (19–20), we obtained the periodicity of 160–165 days in the stronger northern hemisphere and 180–190 days in the weaker southern hemisphere. On the other hand, south-dominated cycles (21–23) display the periodicity of 155–160 days in the stronger southern hemisphere and 175–188 days in the weaker northern hemisphere. Therefore, the Rieger-type periodicity has the north–south asymmetry in sunspot area/number data during solar cycles with strong hemispheric asymmetry. We suggest that the periodicity is caused by magnetic Rossby waves in the internal dynamo layer. Using the dispersion relation of magnetic Rossby waves and observed Rieger periodicity, we estimated the magnetic field strength in the layer as 45–49 kG in moremore » active hemispheres (north during cycles 19–20 and south during cycles 21–23) and 33–40 kG in weaker hemispheres. The estimated difference in the hemispheric field strength is around 10 kG, which provides a challenge for dynamo models. Total magnetic flux data during cycles 20–23 reveals no clear north–south asymmetry, which needs to be explained in the future.« less

Authors:
; ;  [1]; ;  [2]; ;  [3]
  1. Abastumani Astrophysical Observatory at Ilia State University, Tbilisi, Georgia (United States)
  2. Departament de Física, Universitat de les Illes Balears, E-07122, Palma de Mallorca (Spain)
  3. High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)
Publication Date:
OSTI Identifier:
22663221
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 845; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACTIVITY LEVELS; DISPERSION RELATIONS; DISPERSIONS; LAYERS; MAGNETIC FIELDS; MAGNETIC FLUX; NORTHERN HEMISPHERE; NORTH-SOUTH ASYMMETRY; PERIODICITY; SOLAR CYCLE; SOUTHERN HEMISPHERE; SUN; SUNSPOTS

Citation Formats

Gurgenashvili, Eka, Zaqarashvili, Teimuraz V., Kukhianidze, Vasil, Oliver, Ramon, Ballester, Jose Luis, Dikpati, Mausumi, and McIntosh, Scott W., E-mail: Eka.gurgenashvili.1@iliauni.edu.ge. North–South Asymmetry in Rieger-type Periodicity during Solar Cycles 19–23. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA830A.
Gurgenashvili, Eka, Zaqarashvili, Teimuraz V., Kukhianidze, Vasil, Oliver, Ramon, Ballester, Jose Luis, Dikpati, Mausumi, & McIntosh, Scott W., E-mail: Eka.gurgenashvili.1@iliauni.edu.ge. North–South Asymmetry in Rieger-type Periodicity during Solar Cycles 19–23. United States. doi:10.3847/1538-4357/AA830A.
Gurgenashvili, Eka, Zaqarashvili, Teimuraz V., Kukhianidze, Vasil, Oliver, Ramon, Ballester, Jose Luis, Dikpati, Mausumi, and McIntosh, Scott W., E-mail: Eka.gurgenashvili.1@iliauni.edu.ge. Sun . "North–South Asymmetry in Rieger-type Periodicity during Solar Cycles 19–23". United States. doi:10.3847/1538-4357/AA830A.
@article{osti_22663221,
title = {North–South Asymmetry in Rieger-type Periodicity during Solar Cycles 19–23},
author = {Gurgenashvili, Eka and Zaqarashvili, Teimuraz V. and Kukhianidze, Vasil and Oliver, Ramon and Ballester, Jose Luis and Dikpati, Mausumi and McIntosh, Scott W., E-mail: Eka.gurgenashvili.1@iliauni.edu.ge},
abstractNote = {Rieger-type periodicity has been detected in different activity indices over many solar cycles. It was recently shown that the periodicity correlates with solar activity having a shorter period during stronger cycles. Solar activity level is generally asymmetric between northern and southern hemispheres, which could suggest the presence of a similar behavior in the Rieger-type periodicity. We analyze the sunspot area/number and the total magnetic flux data for northern and southern hemispheres during solar cycles 19–23, which had remarkable north–south asymmetry. Using wavelet analysis of sunspot area and number during the north-dominated cycles (19–20), we obtained the periodicity of 160–165 days in the stronger northern hemisphere and 180–190 days in the weaker southern hemisphere. On the other hand, south-dominated cycles (21–23) display the periodicity of 155–160 days in the stronger southern hemisphere and 175–188 days in the weaker northern hemisphere. Therefore, the Rieger-type periodicity has the north–south asymmetry in sunspot area/number data during solar cycles with strong hemispheric asymmetry. We suggest that the periodicity is caused by magnetic Rossby waves in the internal dynamo layer. Using the dispersion relation of magnetic Rossby waves and observed Rieger periodicity, we estimated the magnetic field strength in the layer as 45–49 kG in more active hemispheres (north during cycles 19–20 and south during cycles 21–23) and 33–40 kG in weaker hemispheres. The estimated difference in the hemispheric field strength is around 10 kG, which provides a challenge for dynamo models. Total magnetic flux data during cycles 20–23 reveals no clear north–south asymmetry, which needs to be explained in the future.},
doi = {10.3847/1538-4357/AA830A},
journal = {Astrophysical Journal},
number = 2,
volume = 845,
place = {United States},
year = {Sun Aug 20 00:00:00 EDT 2017},
month = {Sun Aug 20 00:00:00 EDT 2017}
}