Rieger-type periodicity in the total irradiance of the Sun as a star during solar cycles 23-24

Abstract

<p><em>[eng] Context. Total solar irradiance allows for the use of the Sun as a star for studying observations of stellar light curves from recent space</em></p><p><em>missions.</em></p><p><em>Aims. We aim to study how the mid-range periodicity observed in solar activity indices influences the total solar irradiance.</em></p><p><em>Methods. We studied periodic variations of total solar irradiance based on SATIRE-S and SOHO/VIRGO data during solar</em></p><p><em>cycles 23–24 on timescales of Rieger-type periodicity. Then we compared the power spectrum of oscillations in the total solar irradiance</em></p><p><em>to those of sunspot and faculae data to determine their contributions.</em></p><p><em>Results. Wavelet analyses of TSI data reveal strong peaks at 180 days and 115 days in cycle 23, while cycle 24 showed periods of</em></p><p><em>170 days and 145 days. There are several periods in the sunspot and faculae data that are not seen in total solar irradiance as they</em></p><p><em>probably cancel each other out through simultaneous brightening (in faculae) and darkening (in sunspots). Rieger-type periodicity is</em></p><p><em>probably caused by magneto-Rossby waves in the internal dynamo layer, where the solar cyclic magnetic field is generated. Therefore,</em></p><p><em>the observed periods in the total solar irradiance and the wave dispersion relation allow us to estimate the dynamo magnetic field</em></p><p><em>strength as 10–15 kG.</em></p><p><em>Conclusions. Total solar irradiance can be used to estimate the magnetic field strength in the dynamo layer. This tool can be of</em></p><p><em>importance in estimating the dynamo magnetic field strength of solar-like stars using light curves obtained by space missions.</em></p>