Excitation of stellar p-modes by turbulent convection: 1. Theoretical formulation

TL;DR

This paper develops a comprehensive theoretical model for the stochastic excitation of stellar p-modes by turbulent convection, accounting for Reynolds stresses and entropy fluctuations, and generalizes previous formulations.

Contribution

It introduces a generalized expression for mode excitation that includes both Reynolds stresses and entropy fluctuations, applicable to various turbulence spectra.

Findings

Entropy fluctuations dominate mode excitation at most frequencies.

The derived formulation aligns with previous models under Kolmogorov spectrum assumptions.

Numerical results suggest entropy source is more significant than Reynolds stress in the Sun.

Abstract

Stochatic excitation of stellar oscillations by turbulent convection is investigated and an expression for the power injected into the oscillations by the turbulent convection of the outer layers is derived which takes into account excitation through turbulent Reynolds stresses and turbulent entropy fluctuations. This formulation generalizes results from previous works and is built so as to enable investigations of various possible spatial and temporal spectra of stellar turbulent convection. For the Reynolds stress contribution and assuming the Kolmogorov spectrum we obtain a similar formulation than those derived by previous authors. The entropy contribution to excitation is found to originate from the advection of the Eulerian entropy fluctuations by the turbulent velocity field. Numerical computations in the solar case in a companion paper indicate that the entropy source term is dominant over Reynold stress contribution to mode excitation, except at high frequencies.