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arXiv · 2507.00919

The impact of differential rotation on the stochastic excitation of acoustic modes in solar-like pulsators

Gabriel Biscarrat·Leïla Bessila·Stéphane Mathis
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Abstract

Acoustic modes are excited by turbulent convection in the outer convective envelope of solar-like stars. Observational results from asteroseismic studies show that 44% of solar-like stars do not present detectable stochastically-excited acoustic modes. This phenomenon appears to be related to their rotation rate and magnetic activity. In a first paper, we showed that uniform rotation tends to diminish the mode amplitudes significantly. However, convective envelopes in solar-type stars are differentially rotating: the rotation rate difference between mid-latitudes and the equator can go up to 60%, as shown by recent asteroseismic works. In this paper, we examine the impact of differential rotation on the stochastic excitation of acoustic modes in solar-like stars. We provide theoretical predictions for the excitation of acoustic modes in a differentially rotating solar-like star. We use the Rotating Mixing-Length Theory approach to model the local influence of differential rotation on convection. We then estimate the resulting impact on power injection by turbulent convection into oscillation modes numerically, using a combination of the MESA stellar structure and evolution code and GYRE stellar pulsation code. We show that the power injected in acoustic modes differs by up to 30 % for stars with the same mean rotation rate $5 Ω_{\odot}$ but a distinct differential rotation rate. The excitation of axisymmetric acoustic modes is further inhibited in the anti-solar differential rotation regime where the pole of stars rotates faster than their equator when compared to the uniform rotation case. This could hinder mode detection in such configurations. This study permits a first prediction of the excitation of acoustic modes as a function of the differential rotation in solar-like pulsators.

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Gabriel Biscarrat, Leïla Bessila, Stéphane Mathis. 2025-07-01. The impact of differential rotation on the stochastic excitation of acoustic modes in solar-like pulsators. https://arxiv.org/abs/2507.00919

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