Overstable Convective Modes in a Polytropic Stellar Atmosphere

Within the convection zone of a rotating star, the presence of the Coriolis force stabilizes long-wavelength convective modes. These modes, which would have been unstable if the star lacked rotation, are called overstable convective modes or thermal Rossby waves. We demonstrate that the Sun’s rotati...

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Bibliographic Details
Published in:The Astrophysical journal 2023-02, Vol.943 (2), p.127
Main Authors: Hindman, Bradley W., Jain, Rekha
Format: Article
Language:English
Subjects:
Asteroseismology
Astrophysics
Atmospheric waves
Convection
Coriolis force
Exact solutions
Helioseismology
Internal waves
Photosphere
Planetary waves
Polytropes
Rossby waves
Solar convective zone
Solar interior
Solar oscillations
Solar rotation
Space telescopes
Stars
Stellar atmospheres
Stellar convective zones
Stellar oscillations
Stellar rotation
Visibility
Waves
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Summary:Within the convection zone of a rotating star, the presence of the Coriolis force stabilizes long-wavelength convective modes. These modes, which would have been unstable if the star lacked rotation, are called overstable convective modes or thermal Rossby waves. We demonstrate that the Sun’s rotation rate is sufficiently rapid that the lower half of its convection zone could possess overstable modes. Further, we present an analytic solution for atmospheric waves that reside within a polytropic stratification. We explore in detail the properties of the overstable and unstable wave modes that exist when the polytrope is weakly unstable to convective overturning. Finally, we discuss how the thermal Rossby waves that reside within the convection zone of a star might couple with the prograde branch of the g modes that are trapped within the star’s radiative zone. We suggest that such coupling might enhance the photospheric visibility of a subset of the Sun’s g modes.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/acaec4