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Front. Astron. Space Sci. | doi: 10.3389/fspas.2018.00007

Magneto-Rossby waves and seismology of solar interior

  • 1Space Research Institute (OAW), Austria
  • 2Abastumani Astrophysical Observatory, Ilia State University, Georgia
  • 3Institute of Physics, Karl-Franzens-Universiy, Austria

11-year Schwabe cycle in solar activity is not yet fully understood despite of its almost two century discovery. It is generally interpreted as owing to some sort of magnetic dynamo operating below or inside the convection zone. The magnetic field strength in the dynamo layer may determine the importance of the tachocline in the model which is responsible for the cyclic magnetic field, but the direct measurement is not possible. On the other hand, solar activity also displays short term variations over time scale of months (Rieger-type periodicity), which significantly depend on solar activity level: stronger cycles (or more active hemisphere in each cycle) generally show shorter periodicity and vice versa. The periodicity is probably connected to Rossby-type waves in the dynamo layer, therefore alongside with wave dispersion relations it might be used to estimate the dynamo magnetic field strength. We performed the wavelet analysis of hemispheric sunspot areas during solar cycles 13-24 and corresponding hemispheric values of Rieger-type periodicity are found in each cycle. Two different Rossby-type waves could lead to observed periodicities: spherical fast magneto-Rossby waves and equatorial Poincare-Rossby waves. The dispersion relation of spherical fast magneto-Rossby waves gives the estimated field strength of > 40 kG in stronger cycles (or in more active hemisphere) and < 40 kG in weaker cycles (or in less active hemisphere). The equatorial Poincare-Rossby waves lead to > 20 kG and < 15 kG, respectively. Future perspectives of Rieger-type periodicities and Rossby-type waves in testing various dynamo models are discussed.

Keywords: Solar Activity, Rossby waves, Rieger-type periodicity, Solar interior, solar dynamo

Received: 15 Dec 2017; Accepted: 12 Feb 2018.

Edited by:

Scott W. McIntosh, National Center for Atmospheric Research (UCAR), United States

Reviewed by:

Juan Carlos Martínez Oliveros, Space Sciences Laboratory, UC Berkeley, United States
Mausumi Dikpati, High Altitude Observatory (UCAR), United States  

Copyright: © 2018 Zaqarashvili and Gurgenashvili. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Teimuraz V. Zaqarashvili, Space Research Institute (OAW), Graz, Austria, teimuraz.zaqarashvili@oeaw.ac.at