On the solar differential rotation - Meridional motions associated with a slowly varying angular velocity

1993 ◽  
Vol 407 ◽  
pp. 367 ◽  
Author(s):  
Bernard R. Durney
Keyword(s):  
Angular Velocity ◽  
Differential Rotation ◽  
Solar Differential Rotation

scholarly journals Differential Rotation as an Axisymmetric Resonant Mode of Convection

1991 ◽  
Vol 130 ◽  
pp. 178-181
Author(s):  
Kwing L. Chan ◽  
Hans G. Mayr
Keyword(s):  
Angular Velocity ◽  
Differential Rotation ◽  
Rotation Axis ◽  
Numerical Models ◽  
Resonant Mode ◽  
Analytical Models ◽  
Resonance Model ◽  
Solar Convection Zone ◽  
Solar Differential Rotation ◽  
Solar Convection

Recent results from helioseismology (see Goode, these Proceedings) have shown that the inferred contours of the solar angular velocity are more or less radial in the convection region, and the rotation becomes uniform below. These observations contradict the prevailing numerical models of Taylor columns which predict angular velocity contours parallel to the rotation axis of the Sun. Thus, an alternative explanation of solar differential rotation is called for.Presently, it is not feasible to construct a thermally-relaxed, dynamically self-consistent numerical model of the solar convection zone (see Chan and Serizawa, these Proceedings). It is then appropriate to explore simplified models that may shed some light. A number of analytical models have been proposed for the solar differential rotation, and the reader is referred to the book by Rüdiger (1989) for a comprehensive review of this subject. Here, we report on some recent development on the convective resonance model proposed by Chan et al. (1987; hereafter referred as CSM).

scholarly journals Generators of Solar Differential Rotation and Implications of Helioseismology

1990 ◽  
Vol 138 ◽  
pp. 315-320
Author(s):  
G. Rüdiger ◽  
I. Tuominen
Keyword(s):  
Angular Velocity ◽  
Orthogonal Polynomials ◽  
Turbulence Model ◽  
Differential Rotation ◽  
Heat Conductivity ◽  
Solar Rotation ◽  
Meridional Flow ◽  
Reynolds Stresses ◽  
Solar Differential Rotation ◽  
In Series

We interpret the helioseismological results for the solar rotation law as implying a uniform Ω0 in depth, if the angular velocity Ω(θ) is expanded in series of orthogonal polynomials. One of the possibilities to ensure uniformity of Ω0 is to exclude any anisotropy from the generating turbulence field, so that only the rotationally originated part of the heat conductivity tensor survive as a generator of meridional flow and consequently equatorial acceleration is produced. In addition to this simplest possible turbulence model, we discuss some possible forms of the nondiffusive parts of the Reynolds stresses which may be compatible with the uniformity of Ω0.

scholarly journals Spin Down of Boussinesq Fluid in the Circular Cylinder, as a Simulation of the Solar Spin-Down Procedure

1970 ◽  
Vol 4 ◽  
pp. 329-339
Author(s):  
Takeo Sakurai
Keyword(s):  
Angular Velocity ◽  
Circular Cylinder ◽  
Asymptotic Distribution ◽  
Differential Rotation ◽  
Boussinesq Approximation ◽  
Geometrical Configuration ◽  
Solar Differential Rotation ◽  
Frame Work ◽  
Boussinesq Fluid

AbstractAs the simplest model to simulate the solar spin down procedure from the hydrodynamical viewpoint, a spin down problem with a simple geometrical configuration within the frame work of the Boussinesq approximation is investigated. A new proposal of the origin of the solar differential rotation is made on the basis of the calculated asymptotic distribution of the angular velocity. A comment on the present day solar spin down controversy is also made.

scholarly journals On Theories of Solar Rotation

1976 ◽  
Vol 71 ◽  
pp. 243-295 ◽  
Author(s):  
B. R. Durney
Keyword(s):  
Angular Velocity ◽  
Differential Rotation ◽  
Large Scale ◽  
Convection Zone ◽  
Solar Rotation ◽  
Turbulent Convection ◽  
Viscosity Approximation ◽  
Coriolis Forces ◽  
Solar Differential Rotation ◽  
Stabilizing Effect

The main theories of solar rotation are critically reviewed.The interaction of large-scale convection with rotation gives rise to a transport of angular momentum towards the equator and therefore to differential rotation with equatorial acceleration. (Large-scale convection is defined as follows: in a highly turbulent fluid, the small-scale turbulence acts as a viscosity and organizes fluid motions on a much larger scale.) This transport of angular momentum towards the equator arises because of the highly non-axisymmetric character of the large-scale convective motions in the presence of rotation. These motions tend to be concentrated near the equator. It is not surprising, therefore, that for magnitudes of large-scale convection which are needed to generate the observed solar differential rotation, largeand unobservedpole-equator differences in flux appear in the Boussinesq approximation.It is important, therefore, to take the variations in density into account. Studies of large-scale convection in a compressible rotating medium are still in a very early stage; these studies suggest, however, that the surface layers must indeed rotate differentially.The interaction of rotation with convection appears to be especially efficient in generating a pole-equator difference in flux,Such adrives meridional motions, and the action of Coriolis forces on these motions gives rise to differential rotation. In the ‘large-viscosity’ approximation the problem separates; the meridional motions can be determined first (from the radial and latitudinal equations of motions, and the energy equation) and the angular velocity can be determined next from the azimuthal equation of motion. Since very little is known about compressible large-scale convection, it has been assumed in the development of this theory that the stabilizing effect of rotation onturbulent convectiondepends on the polar angle θ and on depth. The solution for the angular velocity in the large viscosity approximation gives a differential rotation that varies slowly with depth. As a consequence, the large viscosity approximation is not valid over most of the convection zone, the Coriolis term being larger than the viscous term; a thin layer at the top excepted. (It appears, however, that if the angular velocity, ω, is a slowly varying function of depth and the azimuthal stresses vanish at both ends of the convection zone, then the general behavior of ω will be very much like that predicted by the large viscosity approximation.)The stabilizing effect of rotation on turbulent convection is neglected; if differential rotation is significant over the entire convection zone, and if the meridional and large-scale convective velocities are not too large, then in the radial and latitudinal equations of motion, the main balance of forces is between pressure gradients, buoyancy and Coriolis forces. If rotation is not constant along cylinders, then the differential rotation gives rise to latitudinal variations in the convective flux which are proportional to(whereTis the temperature andgis gravity). In the lower part of the convection zone,is of the order of the superadiabatic gradient itself. Therefore large pole-equator differences in flux,will be present unless the angular velocity is constant along cylinders. The meridional velocities associated with this rotation law are not small, however, and could generate a significantIt could well be that larges can be avoided only if rotation is uniform in the lower part of the convection zone. (To be certain of these results, however, it is important to estimate the magnitude of the stabilizing effect of rotation on turbulent convection.)Turbulent convection is driven by the buoyancy force which thus introduces a preferred direction: gravity. In consequence, the turbulence in the sun should be anisotropic and if this is the case the convection zone cannot rotate uniformly. The degree of anisotropy is not known and must be determined from the observed solar differential rotation. The anisotropy is such that the horizontal exchange of momentum is larger than the vertical.The normal mode of vibrations and the inner rotation of the Sun are briefly discussed.

A model of solar differential rotation

Solar Physics ◽  
1991 ◽  
Vol 133 (2) ◽  
pp. 177-194
Author(s):  
L. L. Kichatinov
Keyword(s):  
Differential Rotation ◽  
Solar Differential Rotation

scholarly journals Measurements of Solar Differential Rotation Using the Century Long Kodaikanal Sunspot Data

Solar Physics ◽  
2021 ◽  
Vol 296 (1) ◽  
Author(s):  
Bibhuti Kumar Jha ◽  
Aditya Priyadarshi ◽  
Sudip Mandal ◽  
Subhamoy Chatterjee ◽  
Dipankar Banerjee
Keyword(s):  
Differential Rotation ◽  
Solar Differential Rotation ◽  
Sunspot Data

CCD-Doppler measurements of solar differential rotation

Solar Physics ◽  
1996 ◽  
Vol 167 (1-2) ◽  
pp. 441-444 ◽  
Author(s):  
Axel D. Wittmann
Keyword(s):  
Differential Rotation ◽  
Solar Differential Rotation

scholarly journals Long-Term Variations of Solar Differential Rotation and Sunspot Activity: Revisited

Solar Physics ◽  
2013 ◽  
Vol 289 (3) ◽  
pp. 759-768 ◽  
Author(s):  
K. J. Li ◽  
W. Feng ◽  
X. J. Shi ◽  
J. L. Xie ◽  
P. X. Gao ◽  
...  
Keyword(s):  
Differential Rotation ◽  
Sunspot Activity ◽  
Solar Differential Rotation ◽  
Long Term Variations
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