Differential rotation of main-sequence dwarfs and its dynamo efficiency

Kitchatinov, L. L.; Olemskoy, S. V.

doi:10.1111/j.1365-2966.2010.17737.x

Cited by 90 publications

(100 citation statements)

References 50 publications

(77 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Kitchatinov & Olemskoy (2011) studied differential rotation along the lower ZAMS for fixed rotation rate and found that the surface shear is a function of the effective temperature alone. Using some artificial models, we find that for the same effective temperature the depth of the convection zone has a significant impact on stellar rotation.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

The differential rotation of G dwarfs

Küker

Rüdiger

Kitchatinov

2011

A&A

Self Cite

108

View full text Add to dashboard Cite

A series of stellar models of spectral type G is computed to study the rotation laws resulting from mean-field equations. The rotation laws of the slowly rotating Sun, the rapidly rotating MOST stars Eri and κ 1 Cet, and the rapid rotators R58 and LQ Lup can be easily reproduced. We also find that differences in the depth of the convection zone cause large differences in the surface rotation law and that the extreme surface shear of HD 171488 can only be explained with an artificially shallow convection layer. We verify the thermal wind equilibrium in rapidly rotating G dwarfs and find that the polar subrotation (dΩ/dz < 0) is due to the baroclinic effect and the equatorial superrotation (dΩ/dr > 0) is caused by the Reynolds stresses. In the bulk of the convection zones where the meridional flow is slow and smooth, the thermal wind equilibrium holds between the centrifugal and the pressure forces. It does not hold, however, in the bounding shear layers including the equatorial region where the Reynolds stresses dominate.

show abstract

Section: Discussionmentioning

confidence: 99%

“…For the G5 V star κ 1 Cet, Walker et al (2007) found P eq = 8.77 days and k = 0.09 +0.006 −0.005 corresponding to δΩ = 0.064 rad/day. Kitchatinov & Olemskoy (2011) computed rotation laws for model stars with 0.8 and 1.0 solar masses for Eri and κ 1 Cet. The results were k = 0.127 for Eri and k = 0.13 for κ 1 Cet.…”

Section: Most Stars: Eri and κ 1 Cetmentioning

confidence: 99%

The differential rotation of G dwarfs

Küker

Rüdiger

Kitchatinov

2011

A&A

Self Cite

108

View full text Add to dashboard Cite

show abstract

“…Krause & Rädler 1980) and numerical simulations (e.g. Kitchatinov & Olemskoy 2011;Cole et al 2014) indicate that the magnetic fields of rapidly rotating solar-type stars are only weakly influenced by differential rotation, and they are therefore expected to have very small values of k. Thus, and especially since we simultaneously retrieve both the magnetic field and surface brightness, we did not apply any surface differential rotation in this study.…”

Section: Observed Stars and Their Adopted Stellar Parametersmentioning

confidence: 99%

Zeeman-Doppler imaging of active young solar-type stars

Hackman

Lehtinen

Rosén

et al. 2016

A&A

View full text Add to dashboard Cite

Context. By studying young magnetically active late-type stars, i.e. analogues to the young Sun, we can draw conclusions on the evolution of the solar dynamo. Aims. We determine the topology of the surface magnetic field and study the relation between the magnetic field and cool photospheric spots in three young late-type stars. Methods. High-resolution spectropolarimetry of the targets was obtained with the HARPSpol instrument mounted at the ESO 3.6 m telescope. The signal-to-noise ratios of the Stokes IV measurements were boosted by combining the signal from a large number of spectroscopic absorption lines through the least squares deconvolution technique. Surface brightness and magnetic field maps were calculated using the Zeeman-Doppler imaging technique.Results. All three targets show clear signs of magnetic fields and cool spots. Only one of the targets, V1358 Ori, shows evidence of the dominance of non-axisymmetric modes. In two of the targets, the poloidal field is significantly stronger than the toroidal one, indicative of an α 2 -type dynamo, in which convective turbulence effects dominate over the weak differential rotation. In two of the cases there is a slight anti-correlation between the cool spots and the strength of the radial magnetic field. However, even in these cases the correlation is much weaker than in the case of sunspots. Conclusions. The weak correlation between the measured radial magnetic field and cool spots may indicate a more complex magnetic field structure in the spots or spot groups involving mixed magnetic polarities. Comparison with a previously published magnetic field map shows that on one of the stars, HD 29615, the underlying magnetic field changed its polarity between 2009 and 2013.

show abstract

“…The flow V is specified using the differential rotation model of Kitchatinov & Olemskoy (2011b. A peculiarity of the model is that the eddy transport coefficients are not prescribed but expressed in terms of the entropy gradient, the entropy being one of the dependent variables of the model.…”

Section: Dynamo Modelmentioning

confidence: 99%

How supercritical are stellar dynamos, or why do old main-sequence dwarfs not obey gyrochronology?

Kitchatinov

Nepomnyashchikh

2017

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Asteroseismological determinations of stellar ages have shown that old main-sequence dwarfs do not obey gyrochronology. Their rotation is slow compared to young stars but faster than gyrochronology predicts. This can be explained by the presence of a maximum rotation period beyond which the large-scale dynamo switches off and stops providing global magnetic fields necessary for stellar spindown. Assuming this explanation, the excess of stellar dynamo parameters over their marginal values can be estimated for given spectral type and rotation rate. The estimation gives the dynamo number for the Sun about 10% above its critical value. The corresponding dynamo model provides -though with some further tuning -reasonable results for the Sun. Following the same approach, the differential rotation and marginal dynamo modes are computed for stars between 0.7 and 1.2 solar masses. With increasing stellar mass, the differential rotation and the ratio of toroidal-to-poloidal field are predicted to increase while the field topology changes from dipolar to mixed quadrupolar-dipolar parity.

show abstract

Differential rotation of main-sequence dwarfs and its dynamo efficiency

Cited by 90 publications

References 50 publications

The differential rotation of G dwarfs

The differential rotation of G dwarfs

Zeeman-Doppler imaging of active young solar-type stars

How supercritical are stellar dynamos, or why do old main-sequence dwarfs not obey gyrochronology?

Contact Info

Product

Resources

About