Variations of Solar Rotation and Sunspot Activity

Li, K. J.; Shi, X. J.; Hu, Liang; Zhan, L. S.; Xie, J. L.; Wen, Feng

doi:10.1088/0004-637x/730/1/49

Cited by 30 publications

(24 citation statements)

References 34 publications

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“…Intrinsic modes were found in the north-south sunspot time series (Zolotova & Ponyavin 2007). Acceleration and deceleration trends in the temporal variations of the rotational cycle length of the Sun were established (Li et al 2011). The first successful use of EMD in the analysis of QPPs in a solar flare was made in Nakariakov et al (2010b), where the technique was applied to the extraction of the high-frequency noise and low-frequency trend from the initial data set.…”

Section: Introductionmentioning

confidence: 87%

Multi-mode quasi-periodic pulsations in a solar flare

Kolotkov

Nakariakov

Kupriyanova

et al. 2015

A&A

102

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Context. Quasi-periodic pulsations (QPP) of the electromagnetic radiation emitted in solar and stellar flares are often detected in microwave, white light, X-ray, and gamma-ray bands. Mechanisms for QPP are intensively debated in the literature. Previous studies revealed that QPP may manifest non-linear, non-stationary and, perhaps, multi-modal processes operating in flares. Aims. We study QPP of the microwave emission generated in an X3.2-class solar flare on 14 May, 2013, observed with the Nobeyama Radioheliograph (NoRH), aiming to reveal signatures of the non-linear, non-stationary, and multi-modal processes in the signal. Methods. The NoRH correlation signal obtained at the 17 GHz intensity has a clear QPP pattern. The signal was analysed with the Hilbert-Huang transform (HHT) that allows one to determine its instant amplitude and frequency, and their time variation. Results. It was established that the QPP consists of at least three well-defined intrinsic modes, with the mean periods of 15, 45, and 100 s. All the modes have quasi-harmonic behaviour with different modulation patterns. The 100 s intrinsic mode is a decaying oscillation, with the decay time of 250 s. The 15 s intrinsic mode shows a similar behaviour, with the decay time of 90 s. The 45 s mode has a wave-train behaviour. Conclusions. Dynamical properties of detected intrinsic modes indicate that the 100 s and 15 s modes are likely to be associated with fundamental kink and sausage modes of the flaring loop, respectively. The 100 s oscillation could also be caused by the fundamental longitudinal mode, while this interpretation requires the plasma temperature of about 30 million K and hence is not likely. The 45 s mode could be the second standing harmonics of the kink mode.

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Section: Introductionmentioning

confidence: 87%

Multi-mode quasi-periodic pulsations in a solar flare

Kolotkov

Nakariakov

Kupriyanova

et al. 2015

A&A

102

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“…Thus, no secular trend is found to be statistically prominent. Li et al (2011a,b) have also found a secular decreasing trend in the length of the Sun’s rotation cycle by analysing sunspot activity. Furthermore, such a trend is statistically significant.…”

Section: Long‐term Variations Of the Coronal Rotation And Solar Actmentioning

confidence: 97%

Long-term variations of the coronal rotation and solar activity

Shi

Wen

et al. 2012

Monthly Notices of the Royal Astronomical Society

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Recently, Chandra and Vats have obtained the yearly period length of the solar coronal rotation cycle by analysing the daily adjusted solar radio flux at the 10.7‐cm wavelength for the years 1947–2009. In this paper, we use the time series (series I) of the yearly period length to investigate the long‐term variation of the rotation of radio emission corona, and we find a weak decreasing trend in the time series. We use the empirical mode decomposition to decompose both the yearly mean value (series II) of the solar radio flux at the 10.7‐cm wavelength and series I into different periodical components. There is a secular trend for each of the two series, and we find a negative correlation in the two trends. The decomposed 11‐yr‐cycle components of the two series show different and complicated periods and there is a phase relation between them. We investigate the cycle‐related variation of the coronal rotation length, and we find that there is no Schwable cycle of statistical significance for the long‐term variation of the rotation cycle length.

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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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Variations of Solar Rotation and Sunspot Activity

Cited by 30 publications

References 34 publications

Multi-mode quasi-periodic pulsations in a solar flare

Multi-mode quasi-periodic pulsations in a solar flare

Long-term variations of the coronal rotation and solar activity

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

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