scholarly journals The traditional approximation of rotation for rapidly rotating stars and planets. II. Deformation and differential rotation

2021 ◽  
Author(s):  
H. Dhouib ◽  
V. Prat ◽  
T. Van Reeth ◽  
S. Mathis
Keyword(s):  
Differential Rotation ◽  
Rotating Stars ◽  
Rapidly Rotating Stars

scholarly journals Learning about Stellar Dynamos from Long–term Photometry of Starspots

1991 ◽  
Vol 130 ◽  
pp. 353-369 ◽  
Author(s):  
Douglas S. Hall
Keyword(s):  
Differential Rotation ◽  
Rotation Period ◽  
Turnover Time ◽  
Rotating Stars ◽  
Photometric Variability ◽  
Solar Type ◽  
Magnetic Cycles ◽  
The Many ◽  
Rapidly Rotating Stars

AbstractSpottedness, as evidenced by photometric variability in 277 late-type binary and single stars, is found to occur when the Rossby number is less than about 2/3. This holds true when the convective turnover time versus B–V relation of Gilliland is used for dwarfs and also for subgiants and giants if their turnover times are twice and four times longer, respectively, than for dwarfs. Differential rotation is found correlated with rotation period (rapidly rotating stars approaching solid-body rotation) and also with lobe-filling factor (the differential rotation coefficient k is 2.5 times larger for F = 0 than F = 1). Also reviewed are latitude extent of spottedness, latitude drift during a solar-type cycle, sector structure and preferential longitudes, starspot lifetimes, and the many observational manifestations of magnetic cycles.

scholarly journals Theory of differential rotation and meridional circulation

2012 ◽  
Vol 8 (S294) ◽  
pp. 399-410 ◽  
Author(s):  
Leonid L. Kitchatinov
Keyword(s):  
Angular Momentum ◽  
Boundary Layers ◽  
Differential Rotation ◽  
Rotation Rate ◽  
Convection Zone ◽  
Rotation Axis ◽  
Meridional Flow ◽  
Slow Rotation ◽  
Rotating Stars ◽  
Rapidly Rotating Stars

AbstractMeridional flow results from slight deviations from the thermal wind balance. The deviations are relatively large in the boundary layers near the top and bottom of the convection zone. Accordingly, the meridional flow attains its largest velocities at the boundaries and decreases inside the convection zone. The thickness of the boundary layers, where meridional flow is concentrated, decreases with rotation rate, so that an advection-dominated regime of dynamos is not probable in rapidly rotating stars. Angular momentum transport by convection and by the meridional flow produce differential rotation. The convective fluxes of angular momentum point radially inward in the case of slow rotation but change their direction to equatorward and parallel to the rotation axis as the rotation rate increases. The differential rotation of main-sequence dwarfs is predicted to vary mildly with rotation rate but increase strongly with stellar surface temperature. The significance of differential rotation for dynamos has the opposite tendency to increase with spectral type.

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