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Kitchatinov, L. L.; Пипин, В. В.; Макаров, В. И.; Tlatov, A. G.

doi:10.1023/a:1005260008532

Cited by 74 publications

(66 citation statements)

References 9 publications

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“…Rüdiger et al (1995) employed the rotationally induced anisotropy in their accretion disc dynamo. The equatorial drift due to the diffusion anisotropy was even obtained in the solar-type dynamo model (Kitchatinov et al 1999) but not understood that time.…”

Section: Resultsmentioning

confidence: 99%

Do dynamo-waves propagate along isorotation surfaces?

Kitchatinov

2002

A&A

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Abstract. It is shown that the basic rule of the dynamo theory on the propagation of dynamo-waves along surfaces of constant angular velocity is restricted to the case of isotropic magnetic diffusion. The influence of rotation on convective turbulence induces an anisotropy in the eddy diffusivity. The anisotropy makes the direction of travel of the dynamo wave deviate from the isorotation surfaces. The deviation is towards the equator for solar conditions. This finding may help to resolve the old problem of solar dynamo theory concerning the incompatibility between the helioseismological rotation law and equatorward migration of solar activity. A qualitative explanation for the inclined propagation is suggested. The derived properties of the dynamo waves are illustrated by 2D dynamo models in spherical geometry. The model with anisotropic diffusion shows a pronounced equatorial drift of toroidal fields even with a depth independent rotation.

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Section: Resultsmentioning

confidence: 99%

Do dynamo-waves propagate along isorotation surfaces?

Kitchatinov

2002

A&A

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“…Earlier studies have already noted that the rotation parameters depict long-term trends and long-term oscillations (see, e.g., Makarov et al 1997;Kitchatinov et al 1999;Javaraiah et al 2005;Brajsa et al 2006, and references therein). For instance, Javaraiah et al (2005) found that the Ω 0 parameter depicts a fairly systematic decline during cycles 12 to 23 from roughly Ω 0 = 14.55 deg/day to Ω 0 = 14.45 deg/day, with some evidence of weak century-scale oscillation superimposed.…”

Section: Discussionmentioning

confidence: 96%

Global analysis of active longitudes of sunspots

Zhang

Мурсула

Usoskin

et al. 2011

A&A

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Context. Active longitudes have been found in various manifestations of solar activity. The longitudinal distribution of, e.g., sunspots and solar X-ray flares shows two persistent preferred longitudes separated by roughly 180 degrees. We previously studied solar X-ray flares using an improved version of a dynamic, differentially rotating coordinate system and found enhanced rotational asymmetry and rotation parameter values that are consistent for the three classes of X-ray flares. Aims. We aim to find the optimal values of rotation parameters of active longitudes of sunspots for several different time intervals and separately for the two solar hemispheres. Methods. We perform a global study of the longitudinal location of sunspots (all sunspots and first appearance sunspots) using a refined version of a dynamic, differentially rotating coordinate system. Results. We find that the rotation parameters for sunspots are in good agreement with those obtained for X-ray flares using the same method. The improved method typically finds somewhat faster equatorial rotation with better accuracy. The improved treatment also leads to a larger non-axisymmetry. Rotation parameters for all sunspots and first appearances closely agree with each other, but nonaxisymmetry is systematically larger for all sunspots than for first appearances, suggesting that strong fields follow more closely the pattern of active longitudes. The refined method emphasizes hemispheric differences in rotation. Over the whole interval, the mean rotation in the southern hemisphere is slower than in the north. We also find significant temporal variability in the two rotation parameters over the 136-year interval. Interestingly, the long-term variations (trends and residual oscillations) in solar rotation are roughly the opposite in the northern and southern hemispheres. Conclusions. Rotation parameters vary differently with time in the northern and southern hemispheres. Both sunspots and flares strongly suggest that the northern hemisphere rotated considerably faster but the southern hemisphere slightly slower than the Carrington rotation rate during the last three solar cycles.

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“…Candidates for the driving mechanism are Lorentz force feedback (e.g., Schüssler 1981;Yoshimura 1981), thermal feedback (Spruit 2003), and magnetic quenching of turbulent angular momentum transport (Kitchatinov & Pipin 1998;Kitchatinov et al 1999). Most models of torsional oscillations to date are based on Lorentz force feedback, most of them use a simplified momentum equation only considering zonal flows (see, e.g., Covas et al 2000Covas et al , 2004Covas et al , 2005Chakraborty et al 2009aChakraborty et al , 2009b.…”

Section: Introductionmentioning

confidence: 99%

High-Latitude Solar Torsional Oscillations During Phases of Changing Magnetic Cycle Amplitude

Rempel

2012

ApJ

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Torsional oscillations are variations of the solar differential rotation that are strongly linked to the magnetic cycle of the Sun. Helioseismic inversions have revealed significant differences in the high-latitude branch of torsional oscillations between cycle 23 and cycle 24. Here we employ a non-kinematic flux-transport dynamo model that has been used previously to study torsional oscillations and simulate the response of the high-latitude branch to a change in the amplitude of the magnetic cycle. It is found that a reduction of the cycle amplitude leads to an increase in the amplitude of differential rotation that is mostly visible as a drop in the high-latitude rotation rate. Depending on the amplitude of this adjustment the high-latitude torsional oscillation signal can become temporarily hidden due to the unknown changing mean rotation rate that is required to properly define the torsional oscillation signal.

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Untitled

Cited by 74 publications

References 9 publications

Do dynamo-waves propagate along isorotation surfaces?

Do dynamo-waves propagate along isorotation surfaces?

Global analysis of active longitudes of sunspots

High-Latitude Solar Torsional Oscillations During Phases of Changing Magnetic Cycle Amplitude

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