SH002-0018
Rotation and Rieger-type periods in total irradiance of the Sun as a star during solar cycle 23

Monday, 7 December 2020
Poster
Eka Gurgenashvili, Ilia State University, Georg-August-Universitaet Goettingen, Astrophysics, Goettingen, Germany, Teimuraz Zaqarashvili, University of Graz, Institute of Physics, Graz, Austria, Vasili Kukhianidze, Ilia State University, Tbilisi, Georgia and Ansgar Reiners, Georg-August-Universitaet Goettingen, Institute of Astrophysics, Goettingen, Germany
Abstract:
Total solar irradiance permits to use the Sun as a star to study stellar light curves from recent space missions. We aim to study how the solar differential rotation and mid-ranged periods in the Sun’s activity influence total solar irradiance, which then can be used for a reverse task i. e. to reveal the stellar rotation and activity properties from their light curves. We study periodic variations of total solar irradiance based on SATIRE-S and SORCE data during solar cycle 23 on time scales of solar rotation and Rieger-type periodicity. Then we compare the power spectrum of oscillations in total solar irradiance to those of sunspot and faculae data in order to determine their contributions. Wavelet and Lomb-Scargle analyses show that a single rotation period in total solar irradiance can be determined only during minimum phase of the solar cycle. On the other hand, several periods between 27 and 38 days are seen in power spectra during the cycle maximum. There are two branches of periods drifting to smaller and longer values as the cycle progresses, which correspond to equatorward and poleward migrations of magnetic elements and torsional oscillation patterns. Observed difference between periods in total solar irradiance permits the estimation of the solar latitudinal differential rotation rate with 90 percent accuracy. Power spectrum shows the longer period oscillations at 180 days and 115 days in total solar irradiance. There are several periods in sunspot and faculae data canceling each other through simultaneous brightening (in faculae) and darkening (in sunspots), which are not seen in total solar irradiance. Rieger-type periodicity is probably caused by magneto-Rossby waves in internal dynamo layer, therefore the observed periods in total solar irradiance and the wave dispersion relation allow to estimate the dynamo magnetic field strength as 10-15 kG.

Total solar irradiance can be used to estimate the properties of solar latitudinal differential rotation and dynamo magnetic field strength. This tool can be of importance to estimate the similar properties of solar-like stars using light curves obtained by space missions.

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