The mid-term periodicities in sunspot areas

Getko, R.

doi:10.1017/s174392130902924x

Cited by 3 publications

(4 citation statements)

References 5 publications

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“…Prabhakaran Nayar et al (2002) showed a significant wavelet power of the daily Wolf numbers at periods around 11 -12 rotations for short time-intervals during several solar maxima. The auto-correlation and the wavelet analyses of rotational data for each solar hemisphere confirmed the dominance of this periodicity (Getko, 2009). …”

Section: Discussionmentioning

confidence: 59%

“…To verify the stationarity conditions of {X (Getko, 2009), the positive and negative fluctuations were considered separately. For {F n i } they can be defined as follows:…”

Section: The Stationary Version Of Sunspot Area Fluctuationsmentioning

confidence: 99%

“…A more up-to-date review is given by Obridko and Shelting (2007). Recently, Getko (2009) showed that these periods could be treated as subharmonics of the ten-rotation period. This was able to explain a wide range of periodicities in various solar indices at all levels from the tachocline to Earth.…”

Section: Introductionmentioning

confidence: 99%

“…It is known that for a time series that contains Gaussian white noise and a sinusoidal component, the probability distribution is symmetric and the autocorrelation functions [c τ ] of that time series, of its positive fluctuations, and of its negative fluctuations should be the same. Getko (2009) showed that these c τ -functions for one solar cycle are different. Therefore the positive and the negative fluctuations are considered separately.…”

Section: Introductionmentioning

confidence: 99%

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The Ten-Rotation Quasi-periodicity in Sunspot Areas

Getko

2013

Sol Phys

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Sunspot-area fluctuations over an epoch of 12 solar cycles (12 -23) are investigated in detail using wavelets. Getko (Universal Heliophysical Processes, IAU Symp. 257, 169, 2009) found three significant quasi-periodicities at 10, 17, and 23 solar rotations, but two longer periods could be treated as subharmonics of the ten-rotation quasi-periodicity. Therefore we focused the analysis on the occurrence of this quasi-periodicity during the low-and high-activity periods of each solar cycle. Because of the N -S asymmetry, each solar hemisphere was considered separately. The skewness of each fluctuation-probability distribution suggests that the positive and negative fluctuations could be examined separately. To avoid the problem that occurs when a few strong fluctuations create a wavelet peak, we applied fluctuation transformations for which the amplitudes at the high-and the low-activity periods are almost the same. The wavelet analyses show that the ten-rotation quasi-periodicity is mainly detected during the high-activity periods, but it also exists during a few low-activity periods. The division of each solar hemisphere into 30• -wide longitude bins and the wavelet calculations for the areas of sunspot clusters belonging to these 30• bins enable one to detect longitude zones in which the ten-rotation quasi-periodicity exists. These zones are present during the whole high-activity periods and dominate the integrated spectra.

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Section: Discussionmentioning

confidence: 59%

“…To verify the stationarity conditions of {X (Getko, 2009), the positive and negative fluctuations were considered separately. For {F n i } they can be defined as follows:…”

Section: The Stationary Version Of Sunspot Area Fluctuationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Ten-Rotation Quasi-periodicity in Sunspot Areas

Getko

2013

Sol Phys

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The rotation signal in daily sunspot areas

Wen

et al. 2010

Astrophys Space Sci

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The continuous complex Morlet wavelet transform is used to investigate temporal rotation cycle length of daily sunspot areas from May 9, 1874 to February 28, 2010, from a global point of view. The rotation cycle length of the Sun is found to have a secular trend: it decreased from the year of 1874 to 1950s, and since then the Sun is rotating more and more speedily in the long run. The rotation period appears around the maximum times of the Schwabe cycles with statistical significance, but in the minimum times it is always statistically insignificant, although it is found to have no relation with the Schwabe cycle. The period length of the rotation cycle displays the significant periods of 2.61 and 5.77 years.

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Quasiperiodic Variations of Coronal Mass Ejections with Different Angular Widths

Deng

Wang

et al. 2023

ApJS

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Coronal mass ejections (CMEs) are energetic expulsions of organized magnetic features from the Sun. The study of CME quasiperiodicity helps establish a possible relationship between CMEs, solar flares, and geomagnetic disturbances. We used the angular width of CMEs as a criterion for classifying the CMEs in the study. Based on 25 yr of observational data, we systematically analyzed the quasiperiodic variations corresponding to the CME occurrence rate of different angular widths in the northern and southern hemispheres, using frequency and time–frequency analysis methods. There are various periods for CMEs of different angular widths: 9 months, 1.7 yr, and 3.3–4.3 yr. Compared with previous studies based on the occurrence rate of CMEs, we obtained the same periods of 1.2 (±0.01), 3.1 (±0.04), and ≈6.1 (±0.4) months, and 1.2 (±0.1) and 2.4 (±0.4) yr. We also found additional periods of all CMEs that appear only in one hemisphere or during a specific solar cycle. For example, 7.1 (±0.2) months and 4.1 (±0.2) yr in the northern hemisphere, 1 (±0.004) and 5.9 (±0.2) months and 1 (±0.1), 1.4 (±0.1), and 2.4 (±0.4) yr in the southern hemisphere, 6.1 (±0.4) months in solar cycle 23, and 6.1 (±0.4) months and 1.2 (±0.1) and 3.7 (±0.2) yr in solar cycle 24. The analysis shows that quasiperiodic variations of the CMEs are a link among oscillations in coronal magnetic activity, solar flare eruptions, and interplanetary space.

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The mid-term periodicities in sunspot areas

Cited by 3 publications

References 5 publications

The Ten-Rotation Quasi-periodicity in Sunspot Areas

The Ten-Rotation Quasi-periodicity in Sunspot Areas

The rotation signal in daily sunspot areas

Quasiperiodic Variations of Coronal Mass Ejections with Different Angular Widths

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