scholarly journals The Sun’s Internal Differential Rotation From Helioseismology

1991 ◽  
Vol 130 ◽  
pp. 157-171
Author(s):  
Philip R. Goode
Keyword(s):  
Solar Cycle ◽  
Internal Rotation ◽  
Differential Rotation ◽  
Convection Zone ◽  
Body Rotation ◽  
Solid Body Rotation ◽  
Weak Evidence ◽  
Observational Techniques ◽  
Cycle Dependence ◽  
Outer Half

AbstractWell-confirmed helioseismic data from several groups using various observational techniques at different sites have allowed us to determine the differential rotation in the outer half of the Sun’s interior. The resulting rotation law is simple – the surface differential rotation persists through much of the convection zone with a transition toward solid body rotation beneath. To date there is no appealing evidence for a rapidly rotating core. There is however, weak evidence for a solar cycle dependence of the Sun’s internal rotation.

scholarly journals The Sun’s Rotation Near the Interface Between its Convective and Radiative Zones: 1986 to 1990

1993 ◽  
Vol 141 ◽  
pp. 545-548
Author(s):  
Philip R. Goode
Keyword(s):  
Magnetic Field ◽  
Internal Rotation ◽  
Convection Zone ◽  
Solar Observatory ◽  
Private Communication ◽  
Solar Oscillation ◽  
Body Rotation ◽  
Solid Body Rotation ◽  
Temporal And Spatial ◽  
The Magnetic Field

The Sun’s rotation rate near the base of its convection zone might be expected to vary over the solar cycle because of related changes there in the magnetic field. Helioseismic analyses have taught us that much of the Sun’s convection zone rotates with surface-like differential rotation and a transition toward solid body rotation beneath. For a review of what we know about the Sun’s internal rotation, see Goode, et al.(1991). We now have sufficient solar oscillation data to look for changes in the internal rotation near the base of the convection zone. The relevant data are from the 1986, 1988, 1989 and 1990 Big Bear Solar Observatory( BBSO) sets, Libbrecht and Woodard(1992, private communication). These four datasets were gathered at the same site for roughly the same number of days, reduced in the same way and span the same temporal and spatial frequency ranges—the differences between the sets should arise primarily because they were obtained in different years.

Measurements of Differential Rotation in Cool Stars

2004 ◽  
Vol 215 ◽  
pp. 138-143 ◽  
Author(s):  
A. Reiners ◽  
J.H.M.M. Schmitt
Keyword(s):  
Differential Rotation ◽  
Rotation Parameter ◽  
High Signal ◽  
Body Rotation ◽  
Signal To Noise ◽  
Transform Method ◽  
Solid Body Rotation ◽  
Cool Stars ◽  
Show Evidence ◽  
The Fourier Transform

We have obtained high resolution (R ≈ 220000) - high signal-to-noise (S/N > 500) spectra of 142 field dwarfs of spectral types F–K and v sin i ≤ 45 km s–1. Using the Fourier Transform Method (FTM) we precisely determined rotational velocities (Δ v sin i < 1.0 km s–1). For stars with v sin i ≥ 12.0 km s–1 this method allows the detection of deviations from solid body rotation. In the case of symmetric profiles the differential rotation parameter α = (ωequator – ωpole) / ωequator can be determined. This was possible for 32 of our sample stars; ten stars show evidence for solar-like differential rotation with α > 0.0. Thus it becomes possible to search for connections between differential rotation, rotational velocities and other stellar parameters. Signatures of differential rotation could be found on stars rotating as fast as v sin i = 42 km s–1. Particularly the Li-depleted stars turned out to show strong signatures of differential rotation. Our measurements support the idea, that Li-depletion in fast rotators (v sin i > 15 km s–1) is closely connected to differential rotation.

Three-dimensional instabilities and inertial waves in a rapidly rotating split-cylinder flow

2016 ◽  
Vol 800 ◽  
pp. 666-687 ◽  
Author(s):  
Juan M. Lopez ◽  
Paloma Gutierrez-Castillo
Keyword(s):  
Solid Body ◽  
Differential Rotation ◽  
Three Dimensional ◽  
Side Wall ◽  
Wall Layer ◽  
Bulk Flow ◽  
Body Rotation ◽  
Rotating Waves ◽  
Solid Body Rotation ◽  
Inertial Wave

The nonlinear dynamics of the flow in a differentially rotating split cylinder is investigated numerically. The differential rotation, with the top half of the cylinder rotating faster than the bottom half, establishes a basic state consisting of a bulk flow that is essentially in solid-body rotation at the mean rotation rate of the cylinder and boundary layers where the bulk flow adjusts to the differential rotation of the cylinder halves, which drives a strong meridional flow. There are Ekman-like layers on the top and bottom end walls, and a Stewartson-like side wall layer with a strong downward axial flow component. The complicated bottom corner region, where the downward flow in the side wall layer decelerates and negotiates the corner, is the epicentre of a variety of instabilities associated with the local shear and curvature of the flow, both of which are very non-uniform. Families of both high and low azimuthal wavenumber rotating waves bifurcate from the basic state in Eckhaus bands, but the most prominent states found near onset are quasiperiodic states corresponding to mixed modes of the high and low azimuthal wavenumber rotating waves. The frequencies associated with most of these unsteady three-dimensional states are such that spiral inertial wave beams are emitted from the bottom corner region into the bulk, along cones at angles that are well predicted by the inertial wave dispersion relation, driving the bulk flow away from solid-body rotation.

scholarly journals The Next Decade of Theoretical Solar Physics

1974 ◽  
Vol 3 ◽  
pp. 133-148
Author(s):  
M. Kuperus
Keyword(s):  
Differential Rotation ◽  
Convection Zone ◽  
70Th Birthday ◽  
Solar Physics ◽  
Direct Consequence ◽  
Interior Structure ◽  
Particle Detection ◽  
Convective Motions ◽  
Observational Techniques ◽  
Satisfactory Theory

Exactly a decade ago an international conference on solar physics took place in Utrecht on the occasion of the late Prof. Minnaert’s 70th birthday. Since then, much has happened. Many new instrumental devices were developed or refined. Completely new observational techniques were applied in the XUV and radio wavelengths and in particle detection.This all resulted in an explosion of new data. Moreover new problems appeared of course. It also resulted in an explosion of papers on solar physics. Actually many more contributions appear than reasonably can be absorbed by the periodical Solar Physics, of which the first volume appeared in 1967. At that time the editors were not at all sure that they would receive enough papers to maintain such a journal. But were there major problems solved recently?At first I would be inclined to think that, notwithstanding the enormous efforts spent in solar physics, little has been achieved and no spectacular breakthroughs have been found. This impression, probably shared by many more colleagues, becomes stronger if one tries to find a line of progress in ‘classical’ problems of solar physics. We still do not have a satisfactory theory of the Sun’s differential rotation and the Sun’s outer convection zone. One may argue that this is due to our bad knowledge of the interior structure which is not accessible to direct observation. Solar activity and the formation of sunspots is now believed to be a direct consequence of differential rotation and cyclonic convective motions and therefore suffers from the same uncertainties.

scholarly journals Solar-like differential rotation and equatorward migration in a convective dynamo with a coronal envelope

2012 ◽  
Vol 8 (S294) ◽  
pp. 307-312
Author(s):  
J. Warnecke ◽  
P. J. Käpylä ◽  
M. J. Mantere ◽  
A. Brandenburg
Keyword(s):  
Solar Cycle ◽  
Differential Rotation ◽  
Convection Zone ◽  
Meridional Circulation ◽  
Turbulent Dynamo

AbstractWe present results of convective turbulent dynamo simulations including a coronal layer in a spherical wedge. We find an equatorward migration of the radial and azimuthal fields similar to the behavior of sunspots during the solar cycle. The migration of the field coexist with a spoke-like differential rotation and anti-solar (clockwise) meridional circulation. Even though the migration extends over the whole convection zone, the mechanism causing this is not yet fully understood.

Solar-cycle dependence of the Sun's deep internal rotation shown by helioseismology

Nature ◽  
1991 ◽  
Vol 349 (6306) ◽  
pp. 223-225 ◽  
Author(s):  
Philip R. Goode ◽  
W. A. Dziembowski
Keyword(s):  
Solar Cycle ◽  
Internal Rotation ◽  
Cycle Dependence

scholarly journals Origin of solar magnetism

2010 ◽  
Vol 6 (S273) ◽  
pp. 28-36 ◽  
Author(s):  
Arnab Rai Choudhuri
Keyword(s):  
Solar Cycle ◽  
Differential Rotation ◽  
Convection Zone ◽  
Meridional Circulation ◽  
Solar Surface ◽  
Dynamo Model ◽  
Solar Cycles ◽  
Poloidal Field ◽  
Flux Transport ◽  
Solar Magnetism

AbstractThe most promising model for explaining the origin of solar magnetism is the flux transport dynamo model, in which the toroidal field is produced by differential rotation in the tachocline, the poloidal field is produced by the Babcock–Leighton mechanism at the solar surface and the meridional circulation plays a crucial role. After discussing how this model explains the regular periodic features of the solar cycle, we come to the questions of what causes irregularities of solar cycles and whether we can predict future cycles. Only if the diffusivity within the convection zone is sufficiently high, the polar field at the sunspot minimum is correlated with strength of the next cycle. This is in conformity with the limited available observational data.

Solar Internal Rotation and Dynamo Waves: A Two-Dimensional Asymptotic Solution in the Convection Zone

2000 ◽  
Vol 179 ◽  
pp. 379-380
Author(s):  
Gaetano Belvedere ◽  
Kirill Kuzanyan ◽  
Dmitry Sokoloff
Keyword(s):  
Magnetic Field ◽  
Asymptotic Solution ◽  
Internal Rotation ◽  
Convection Zone ◽  
General Idea ◽  
Dynamo Model ◽  
Axially Symmetric ◽  
Dynamo Action ◽  
Regeneration Rate ◽  
Dynamo Waves

Extended abstractHere we outline how asymptotic models may contribute to the investigation of mean field dynamos applied to the solar convective zone. We calculate here a spatial 2-D structure of the mean magnetic field, adopting real profiles of the solar internal rotation (the Ω-effect) and an extended prescription of the turbulent α-effect. In our model assumptions we do not prescribe any meridional flow that might seriously affect the resulting generated magnetic fields. We do not assume apriori any region or layer as a preferred site for the dynamo action (such as the overshoot zone), but the location of the α- and Ω-effects results in the propagation of dynamo waves deep in the convection zone. We consider an axially symmetric magnetic field dynamo model in a differentially rotating spherical shell. The main assumption, when using asymptotic WKB methods, is that the absolute value of the dynamo number (regeneration rate) |D| is large, i.e., the spatial scale of the solution is small. Following the general idea of an asymptotic solution for dynamo waves (e.g., Kuzanyan &amp; Sokoloff 1995), we search for a solution in the form of a power series with respect to the small parameter |D|–1/3(short wavelength scale). This solution is of the order of magnitude of exp(i|D|1/3S), where S is a scalar function of position.

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