The global rotation of solar activity structures

Heristchi, D.; Mouradian, Z.

doi:10.1051/0004-6361/200809582

Cited by 28 publications

(32 citation statements)

References 25 publications

(30 reference statements)

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“…The main difference between the two methods seems to be so that the best-fit solution now tends to emphasize the hemispheric difference, especially in the latitudinal variation parameter B, more strongly than earlier. This contradicts the result of Heristchi & Mouradian (2009), who found no north-south asymmetry in solar rotation. Large B values for both hemispheres strongly suggest that sunspot groups follow the differential rotation law, which differs from the conclusion of Balthasar (2007).…”

Section: Discussioncontrasting

confidence: 92%

“…We found that the refined parameters describing the rotation of active longitudes are mutually consistent for the three flare classes and that the northern hemisphere rotates significantly faster than the southern hemisphere during the last three solar cycles. This contradicts the result of Heristchi & Mouradian (2009), who found no significant difference between the rotation rates of the two hemispheres. Moreover, the refined parameters yielded a consistently higher level of non-axisymmetry for the longitudinal distribution, thus increasing evidence for the existence of active longitudes.…”

Section: Introductioncontrasting

confidence: 89%

“…Balthasar (2007) noted, by analyzing sunspot numbers , that the rotation period varies over long timescales. Heristchi & Mouradian (2009) found an increase in the rotation rate from cycle 19 to cycle 23 by calculating sunspot numbers and the coronal radio flux at 10.7 cm. Pelt et al (2010), using a nonparametric statistical analysis of the longitude of sunspot groups in 1874-2008, proposed that the strong tendency for sunspot groups to cluster at a certain longitude peters out with time, the longest observable correlations reaching 10-15 Carrington rotations.…”

Section: Introductionmentioning

confidence: 96%

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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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Section: Discussioncontrasting

confidence: 92%

Section: Introductioncontrasting

confidence: 89%

Section: Introductionmentioning

confidence: 96%

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Global analysis of active longitudes of sunspots

Zhang

Мурсула

Usoskin

et al. 2011

A&A

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“…The secular deceleration of solar rotation was suggested by Brajša et al (2006) and Li et al (2011), while a secular acceleration trend was found by Heristchi & Mouradian (2009). A north-south asymmetry in solar rotation has been reported by many authors Balthasar et al 1986;Antonucci et al 1990;Rybák 1994Rybák , 2000Brajša et al 1997Brajša et al , 2000Javaraiah 2003;Georgieva et al 2005;Mursula & Hiltula 2004;Gigolashvili et al 2007;Zaatri et al 2009;Wöhl et al 2010), but there is so far no agreement on which of the two hemispheres is rotating faster, or how the difference between the hemispheric rotation rates is changing in time.…”

Section: Introductionmentioning

confidence: 93%

Consistent long-term variation in the hemispheric asymmetry of solar rotation

Zhang

Мурсула

Usoskin

2013

A&A

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Context. Solar active longitudes and their rotation have been studied for a long time using various forms of solar activity. However, the results on the long-term evolution of rotation rates and the hemispheric asymmetry obtained by earlier authors differ significantly from each other. Aims. We aim to find a consistent result on the long-term migration of active longitudes of sunspots in 1877−2008 separately for the two hemispheres. Methods. We used a dynamic, differentially rotating reference system to determine the best-fit values of the differential rotation parameters of active longitudes for each year in 1877−2008. With these parameters we determined the momentary rotation rates at the reference latitude of 17 • and calculated the non-axisymmetries of active longitudes. We repeated this with five different fit intervals and two weighting methods and compared the results. Results. The evolution of solar surface rotation in each hemisphere suggests a quasi-periodicity of about 80−90 years. The long-term variations of solar rotation in the northern and southern hemisphere have a close anti-correlation, leading to a significant 80−90-year quasi-periodicity in the north-south asymmetry of solar rotation. The north-south asymmetry of solar rotation is found to have an inverse relationship with the area of large sunspots. The latitudinal contrast of differential rotation is also found to be anti-correlated with the sunspot area. Different fit and weight methods yield similar results. Conclusions. Our results give strong evidence for the anti-correlation of the rotation of the two solar hemispheres. The long-term oscillation of solar rotation suggests that a systematic interchange of angular momentum takes place between the two hemispheres at a period of about 80−90 years.

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“…Changes in the solar rotation were also investigated by the helioseismological method using the GONG and SOHO-MDI data at the base of the convective zone (Howe et al 2000a(Howe et al ,b, 2001) and at high latitudes (Antia & Basu 2001). Recently, the time-series analysis was applied to investigate temporal changes of the solar rotation, especially using the radio data (Heristchi & Mouradian 2009;Chandra et al 2009). Various frequencies correspond to various altitudes in the solar corona and different methods have been used (e.g., the Sun analysed as a star with no latitudinal dependence, autocorrelation analysis with a time lag, etc.).…”

Section: Introductionmentioning

confidence: 99%