scholarly journals Simulations of Turbulent Convection in Rotating Young Solarlike Stars: Differential Rotation and Meridional Circulation

2007 ◽  
Vol 669 (2) ◽  
pp. 1190-1208 ◽  
Author(s):  
Jerome Ballot ◽  
Allan Sacha Brun ◽  
Sylvaine Turck‐Chieze
Keyword(s):  
Differential Rotation ◽  
Meridional Circulation ◽  
Turbulent Convection

scholarly journals On turbulent mixing

1984 ◽  
Vol 105 ◽  
pp. 519-521
Author(s):  
Ian W. Roxburgh
Keyword(s):  
Angular Momentum ◽  
Differential Rotation ◽  
Turbulent Mixing ◽  
Time Scale ◽  
Meridional Circulation ◽  
Neutrino Flux ◽  
Gravitational Energy ◽  
Solar Neutrino Flux ◽  
Angular Momentum Loss ◽  
Image Position

Several authors (myself included!) have suggested that turbulent mixing takes place in some, if not all, stars, and in particular that such mixing can explain the low solar neutrino flux. This turbulence is thought to be caused by differential rotation produced by braking due to angular momentum loss in a stellar wind, and/or to the effect of meridional circulation currents in redistributing angular momentum. Whilst such instabilities may exist even in the presence of a stabilizing distribution of chemical composition, they do not necessarily cause mixing. To be effective in mixing, the energy available to the instability be it differential rotation or any other mechanism, has to be sufficient to lift the helium rich matter in the interior of the star to the outer regions. This requires where Erot is the kinetic energy in rotation, Eg the gravitational energy, τth the thermal time scale and τnuc the nuclear evolution time scale of the star.

scholarly journals A Quantitative Study of Magnetic Flux Transport on the Sun

1983 ◽  
Vol 102 ◽  
pp. 273-278 ◽  
Author(s):  
N.R. Sheeley ◽  
J.P. Boris ◽  
T.R. Young ◽  
C.R. DeVore ◽  
K.L. Harvey
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Quantitative Study ◽  
Differential Rotation ◽  
Meridional Circulation ◽  
Diffusion Constant ◽  
The Sun ◽  
Flux Transport ◽  
Field Reversal ◽  
Best Fit

A computational model, based on diffusion, differential rotation, and meridional circulation, has been developed to simulate the transport of magnetic flux on the Sun. Using Kitt Peak magnetograms as input, we have determined a best-fit diffusion constant by comparing the computed and observed fields at later times. Our value of 730 ± 250 km2/s is consistent with Leighton's (1964) estimate of 770–1540 km2/s and is significantly larger than Mosher's (1977) estimate of 200–400 km2/s. This suggests that diffusion may be fast enough to account for the observed polar magnetic field reversal without requiring a significant assist from meridional currents.

scholarly journals Angular Velocity Distribution in Rotating Massive Stars

1967 ◽  
Vol 20 (6) ◽  
pp. 651
Author(s):  
MPC Legg
Keyword(s):  
Angular Velocity ◽  
Velocity Distribution ◽  
Radiation Pressure ◽  
Electron Scattering ◽  
Differential Rotation ◽  
Meridional Circulation ◽  
Massive Stars ◽  
Effects Of Radiation ◽  
Uniform Composition

The angular velocity distribution in rotating massive stars with uniform composition and opacity due to electron scattering is calculated on the assumption that meridional circulation is neglible. The effects of radiation pressure are taken into account in the determination of the differential rotation and the angularvelocity is assumed to be ndependent of latitude.

scholarly journals On the Equatorial Acceleration of the Sun

1970 ◽  
Vol 4 ◽  
pp. 318-320 ◽  
Author(s):  
Ian W. Roxburgh
Keyword(s):  
Angular Momentum ◽  
Steady State ◽  
Energy Transport ◽  
Meridional Circulation ◽  
Turbulent Energy ◽  
Convective Zone ◽  
Turbulent Convection ◽  
The Sun ◽  
Viscous Transport ◽  
Gradient Models

AbstractThe interaction of rotation and turbulent convection gives rise to a latitude dependent turbulent energy transport. Energy conservation demands a slow meridional circulation in the solar outer convective zone. The transport of angular momentum by this circulation is balanced in a steady state by the turbulent viscous transport across an angular velocity gradient. Models are constructed which give equatorial acceleration as observed on the sun.

scholarly journals Dynamo Processes Constrained by Solar and Stellar Observations

2018 ◽  
Vol 13 (S340) ◽  
pp. 275-280
Author(s):  
Maria A. Weber
Keyword(s):  
Differential Rotation ◽  
Meridional Circulation ◽  
Mean Field ◽  
Magnetic Activity ◽  
Flux Emergence ◽  
Dynamo Theory ◽  
M Dwarfs ◽  
Dynamo Action ◽  
Solar Type ◽  
Stellar Dynamo

AbstractOur understanding of stellar dynamos has largely been driven by the phenomena we have observed of our own Sun. Yet, as we amass longer-term datasets for an increasing number of stars, it is clear that there is a wide variety of stellar behavior. Here we briefly review observed trends that place key constraints on the fundamental dynamo operation of solar-type stars to fully convective M dwarfs, including: starspot and sunspot patterns, various magnetism-rotation correlations, and mean field flows such as differential rotation and meridional circulation. We also comment on the current insight that simulations of dynamo action and flux emergence lend to our working knowledge of stellar dynamo theory. While the growing landscape of both observations and simulations of stellar magnetic activity work in tandem to decipher dynamo action, there are still many puzzles that we have yet to fully understand.

scholarly journals The Boussinesq approximation in rapidly rotating flows

2013 ◽  
Vol 737 ◽  
pp. 56-77 ◽  
Author(s):  
Jose M. Lopez ◽  
Francisco Marques ◽  
Marc Avila
Keyword(s):  
Differential Rotation ◽  
Fluid Flows ◽  
Boussinesq Approximation ◽  
Accretion Disc ◽  
Rotating Flows ◽  
Turbulent Convection ◽  
Rotating Cylinders ◽  
New Approach ◽  
Type Approximation ◽  
Straightforward Approach

AbstractIn commonly used formulations of the Boussinesq approximation centrifugal buoyancy effects related to differential rotation, as well as strong vortices in the flow, are neglected. However, these may play an important role in rapidly rotating flows, such as in astrophysical and geophysical applications, and also in turbulent convection. Here we provide a straightforward approach resulting in a Boussinesq-type approximation that consistently accounts for centrifugal effects. Its application to the accretion-disc problem is discussed. We numerically compare the new approach to the typical one in fluid flows confined between two differentially heated and rotating cylinders. The results justify the need of using the proposed approximation in rapidly rotating flows.

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