Influence of the magnetic cycle on the excitation of solar-like acoustic modes

The Sun’s convective envelope generates, by dynamo effect, a surface magnetic field whose strength evolves on an 11-year cycle, with a change in polarity at the end of each cycle. Similar activity cycles exist in other solar-type stars, influencing the stars' dynamics, including the properties of acoustic oscillations, which are excited by convection. Therefore, the frequency, amplitude, excitation, and damping of the modes vary with the cycle over time. We need to understand the impact of magnetic activity on modes in order to characterise precisely stars that will be observed by PLATO, a mission to be launched in 2026 to find Earth-like planets orbiting solar-like stars. In this work, we investigate the variation of the modes' excitation during Cycles 23, 24 and the beginning of Cycle 25 for the Sun. To do so, we analyse data obtained since 1996 by two instruments onboard the SoHO satellite, namely, the GOLF spectrometer and the VIRGO/SPM photometer, according to a method reaching a better resolution than classical methods. Combining the variation of energy for several l=0−2 modes in three frequency bands (i.e., [1800, 2450], [2450, 3110], and [3110, 3790] μHz), our preliminary results show that more energy is associated to several modes during cycle minima, suggesting that there could be a second source of excitation other than turbulent convection that would excite several modes at a time during solar minima. We then extend the analysis to other solar-like stars observed by Kepler. In particular, to KIC 8006161 (aka Doris), a solar-like star whose cycle lasts 7.41 ± 1.16 years, observed during one of its cycle minima and the beginning of the ascending phase of a new cycle.