Article Published by Ilia State University Scientists in High Ranked International Journal “Astronomy & Astrophysics”

Ilia State University scientists, Eka Gurgenishvili, Ph.D. student of Iliauni Lehmann-Haupt International Doctoral SchoolProfessors Teimuraz Zakarashvili and Vasil Kukhianidze, together with their European colleagues, published an article: „Rieger-type periodicity in the total irradiance of the Sun as a star during solar cycles 23–24“ in the high-ranking international journal “Astronomy & Astrophysics”.

About the Article

In prestigious scientific journal “Astronomy and Astrophysics”, an international team with leadership of the scientists from Ilia State University presented the estimation of the magnetic field strength in the solar interior using the periodic variations observed in total solar irradiance. The total solar irradiation is an analog of the stellar light curves, so this research is essential in studying other Sun-like stars. Examining solar-type stars younger or older than the Sun can help explain the past or future of our Sun.

The Sun, our nearest star, has a tremendous influence on the atmosphere of our planet and future technological development of our civilisation. Total solar irradiance data observed from different space missions show that the brightness of the Sun varies from minutes to several years due to the solar magnetic field. In addition to the known 11-year cycle, the solar activity undergoes shorter, 150-200-day periodicity, known as the Rieger-type cycles. Their existence has been known for almost 40 years and is characterized by many enigmatic features. This periodic variation is only seen in structures associated with a strong surface magnetic field, which is linked with solar interior. Therefore, the periodicity can be related with Rossby waves in internal magnetic field.

“Using periodic variations observed in total solar irradiation and the properties of the Rossby waves, we have estimated the magnetic field strength in the solar interior, which is impossible task with other observations.” says the leading author, PhD student at Ilia State University and Gottingen University (Germany), scientist at Abastumani Astrophysical Observatory, Eka Gurgenashvili.  “To detect the Rieger cycles, we now study the light curves of other stars, which will allow us to estimate the magnetic field strength in stelar interiors.”

Future studies are important to estimate the magnetic field of solar-type stars at different stages of evolution observed by various space missions (Kepler, CoRoT, TESS).

The study was conducted within the framework of the Lehmann-Haupt International Doctoral Program, jointly implemented by Ilia State University and the Georg-August-University of Göttingen. The donors of the program are Shota Rustaveli Georgian National Science Foundation and Volkswagen Foundation.

Scientific Article

Gurgenashvili, T. V. Zaqarashvili, V. Kukhianidze, A. Reiners, R. Oliver, A. F. Lanza and T. Reinhold, Rieger-type periodicity in the total irradiance of the Sun as a star during solar cycles 23-24, Astronomy & Astrophysics, 10.1051/0004-6361/202141370



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