Differential Rotation and Meridional Flow for Fast‐rotating Solar‐Type Stars

Rüdiger, G.; Rekowski, B. von; Donahue, R. A.; Baliunas, S. L.

doi:10.1086/305216

Cited by 35 publications

(39 citation statements)

References 12 publications

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“…We found LO Peg (solid diamond) follows the same trend with the nearest candidate AB Dor. Including LO Peg, we derive the relation ∆P α P 1.4±0.1 rot , which is very similar to the relations derived from other observational evidences such as n = 1.4 ± 0.5 (Messina & Guinan, 2003), n = 1.30 (Donahue & Dobson, 1996), n = 1.15-1.30 (Rüdiger et al, 1998). This indicates the disagreement between the observational (n = 1.1-1.4) and the theoretical (n > 2) values of power-law index (Kitchatinov & Rüdiger, 1999).…”

Section: Discussionsupporting

confidence: 87%

LO Peg: surface differential rotation, flares, and spot-topographic evolution

Karmakar

Pandey

Саванов

et al. 2016

Mon. Not. R. Astron. Soc.

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Using the wealth of ∼24 yr multiband data, we present an in-depth study of the starspot cycles, surface differential rotations (SDR), optical flares, evolution of star-spot distributions, and coronal activities on the surface of young, single, main-sequence, ultrafast rotator (UFR) LO Peg. From the long-term V -band photometry, we derive rotational period of LO Peg to be 0.4231 ± 0.0001 d. Using the seasonal variations on the rotational period, the SDR pattern is investigated, and shows a solar-like pattern of SDR. A cyclic pattern with period of ∼2.7 yr appears to be present in rotational period variation. During the observations, 20 optical flares are detected with a flare frequency of ∼1 flare per two days and with flare energy of ∼10 31−34 erg. The surface coverage of cool spots is found to be in the range of ∼9-26 per cent. It appears that the high-and low-latitude spots are interchanging their positions. Quasi-simultaneous observations in X-ray, UV, and optical photometric bands show a signature of an excess of X-ray and UV activities in spotted regions.

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Section: Discussionsupporting

confidence: 87%

LO Peg: surface differential rotation, flares, and spot-topographic evolution

Karmakar

Pandey

Саванов

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The model, however, predicts an increase of the latitudinal shear with increasing rotation rate, in clear contradiction with the observational evidence. A consistent treatment of the rotation and the meridional flow yields qualitative agreement with observations but reproduces the solar rotation law only if a relatively large value of the turbulence viscosity is assumed (Rüdiger et al 1998). …”

Section: Introductionmentioning

confidence: 60%

Differential rotation of the present and the pre-main-sequence Sun

Küker¹,

Stix²

2001

A&A

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Abstract. We present a model for the differential rotation of the present Sun as well as a solar-type star during its pre-main-sequence evolution. The model is based on the mixing-length theory of convective heat transport and a standard solar model. The resulting rotation law is in good agreement with observations and only weakly dependent on the mixing-length parameter. For the present Sun, the normalized horizontal shear decreases with increasing rotation rate, but the total shear is roughly constant. We then follow the Sun's evolutionary track from the beginning of the contraction to the arrival on the ZAMS. While at an age of 30 Myr the total shear is very similar to that of the present Sun, it is much smaller on the Hayashi track.

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“…Disregarding the meridional flow altogether increases the surface shear to 0.18 rad/day. This is a well-known effect: meridional flows driven by differential rotation then act to reduce it (Rüdiger et al 1998). The baroclinic flow has the opposite direction and builds up the differential rotation along the polar axis.…”

Section: Thermal Wind Equilibriummentioning

confidence: 99%

The differential rotation of G dwarfs

Küker

Rüdiger

Kitchatinov

2011

A&A

108

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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.

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Differential Rotation and Meridional Flow for Fast‐rotating Solar‐Type Stars

Cited by 35 publications

References 12 publications

LO Peg: surface differential rotation, flares, and spot-topographic evolution

LO Peg: surface differential rotation, flares, and spot-topographic evolution

Differential rotation of the present and the pre-main-sequence Sun

The differential rotation of G dwarfs

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