Non-adiabatic oscillations of the low- and intermediate-degree modes of the Sun

• Published in: Monthly notices of the Royal Astronomical Society Vol. 405; no. 4; pp. 2759 - 2767
• Main Authors: Xiong, D. R., Deng, L.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 11-07-2010; Wiley-Blackwell; Oxford University Press
• Subjects: Astronomy; convection; Earth, ocean, space; Exact sciences and technology; Oscillators; Sun; Sun: oscillations; convection; Sun: oscillations; Damping; Growth rate; Stabilization; p mode; Linear stability; Excitation; Sun; Convection
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2010.16662.x

Using a non-local time-dependent theory of convection, the linear stability is analysed for low- and intermediate-degree (l= 1–25) g4–p39 modes of the Sun. The results show that all the p modes with periods from ∼3 to ∼16 min are pulsationally unstable, while all the g, f and p modes with periods longer than ∼16 min and the high-frequency p modes with periods shorter than ∼3 min are stable except the low-degree (l= 1–5) p1 modes. The pulsation amplitude growth rates depend on only the frequency and almost do not depend on l. They achieve the maximum at ν∼ 3700 μHz (P∼ 270 s). The effects of radiation and convection on the stability are analysed in detail. The coupling between convection and oscillations plays a key role for stabilization of low-frequency f and p modes and excitation of intermediate- and high-frequency p modes. We propose that the solar 5-min oscillations are not excited by a single mechanism, but are resulted from the combined effects of the ‘regular’ coupling between convection and oscillations and the turbulent stochastic excitation. The coupling between convection and oscillations is the dominant excitation and damping mechanism for the low- and intermediate-frequency modes, and the turbulent stochastic excitation is the main excitation mechanism for high-frequency p modes.