Time sampling = 1.45 days CMEs ? larger characteristic size ✓ strength ? characteristic time Magnetic cycle of solar-like stars have an impact on modes properties such as frequency, amplitude, excitation and damping. [e.g. Broomhall et al. (2014) and references therein] While modes are thought to be stochastically excited by turbulent convection, observations reveal a power excess not fully explained by this mechanism. [Chaplin et al. 1997, Chang & Gough 1998] The role of magnetic cycles in mode excitation remains unclear — could magnetic activity features (flares, CMES,…) be responsible for this observed power excess? 2. Temporal evolution of mode energy VIRGO/SPMs and GOLF data from SoHO [Frölich et al. 1995, Gabriel et al. 1995, Domingo et al. 1995] Combinaison of the < 3 and n = 14 → 25 modes Selection of a mode 1 There are non-stochastic characteristics in the mode excitation mechanisms → Observed with several instruments → Can not only be attributed to noise → Not automatically correlated → Magnetic cycle dependent only for the with flares/CMEs 2620-3160 Hz frequency band 4. Distribution of the modes combined energy 2 5. Variations in Energy supply rate [Tapping 2013] Check the paper here! A study to continue on other stars with PLATO! Flares ✓ small characteristic size ✕ strength ? characteristic time [Foglizzo 1998] 3. Kolmogorov-Smirnov statistical tests Comparison of the energy distribution for each mode with theoretical exponential distributions ¹Université Paris Cité, Université Paris-Saclay, CEA, CNRS, AIM ²Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM ³INAF – Osservatorio Astrofisico di Catania, Italy ⁴Instituto de Astrofísica de Canarias (IAC), Tenerife, Spain ⁵Universidad de La Laguna (ULL), Departamento de Astrofísica, Tenerife, Spain Acknowledgements. The authors want to acknowledge Leila Bessila, Adam Finley, Kiran Jain, Barbara Perri and Antoine Strugarek for useful comments and discussions. The GOLF and VIRGO/SPMs instruments on board SoHO, are a cooperative effort of many individuals to whom we are indebted. SoHO is a project of international collaboration between ESA and NASA. The authors strongly acknowledge the French space agency, CNES, for its support to GOLF since the launch of SoHO. E.P. and R.A.G. acknowledge the support from the GOLF/SoHO and PLATO Centre National D’Études Spatiales grants. S.N.B acknowledges support from PLATO ASI-INAF agreement no. 202228-HH.0 "PLATO Fase D". Theoretical probability of observing these events over all data points: P < 10 1.6% observed → 108 high energy points over 6612 data points Compatible with a stochastic excitation by turbulent convection Maximum Cycle 25 High peaks = excitation of several modes at the same time IS TURBULENT CONVECTION THE ONLY EXCITING MECANISM OF ACOUSTIC MODES IN SOLAR-LIKE OSCILLATORS? Eva Panetier¹, Rafael A. García², Sylvain N. Breton³, Antonio Jiménez4,5, Thierry Foglizzo²
[email protected] Maximum Cycle 23 Maximum Cycle 24 [Inspired from Kurzgesagt] Not compatible with a stochastic excitation by turbulent convection → Very significant 1. INTRODUCTION Inverse Fourier-Transform The energy supply rate changes over time → seems to follow a QBO-like pattern → The variance of seems to be anti-correlated with the cycle TAKE AWAY MESSAGES [Foglizzo et al. 1998, Lazrek et al. 1997] General behaviour of the mode energy compatible with a stochastic excitation [Kiefer & Broomhall 2021] A proxy of the energy supply rate was computed: its mean and variance changes over time E = 2 |f (t)| n 2 v l -3 [Nigam & Kosovichev 1998]
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