One of the basic features of solar activity is the quasi-biennial oscillations (QBOs)—variations with a period of about two years. The nature of the QBO remains unclear and the most puzzling is the high instability of the QBO period. We investigated a fine structure of the QBO period variability as manifested in sunspot area variations in Solar Cycles 19 – 23 using the wavelet transform with a real mother wavelet, Daubechies 10, that provided a high temporal resolution. We found that within every 11-yr solar cycle the QBO period varies not randomly, as it is widely accepted now, but it gradually decreases from the beginning of the solar cycle till the end, in phase with the shift of the average sunspots latitude to the equator. We have analyzed in a similar way the time series which were simulated using a combination of sine waves with different periods (constant and variable one) and red noise with a standard deviation as large as 40% of the sine amplitude. The analysis has shown that noise does not distort significantly the initial signal and noise itself does not form the structures with the properties which were observed in the case of the natural time series. We suppose that the revealed modification of the QBO period with the development of the solar cycle may be related to the latitudinal differential rotation in the solar convection zone and the possible influence of the rotational velocity in the region of the QBO generation on the QBO period value. Under this assumption, the process responsible for the QBO generation should operate in a layer with a substantial latitudinal shear which according to the helioseismology analysis is observed in the bulk of the convection zone and is getting smaller in the vicinity of the tachocline.

中文翻译：

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太阳黑子区准双年振荡的精细结构与太阳双磁循环

太阳活动的基本特征之一是准双年振荡（QBO）——周期约为两年的变化。QBO 的性质尚不清楚，最令人费解的是 QBO 时期的高度不稳定性。我们使用小波变换和真正的母小波 Daubechies 10 研究了 QBO 周期变化的精细结构，如太阳周期 19-23 中太阳黑子面积变化所体现的那样，提供了高时间分辨率。我们发现，在每 11 年太阳周期内，QBO 周期不是随机变化的，正如现在广泛接受的那样，但它从太阳周期开始到结束逐渐减少，与平均太阳黑子纬度向赤道。我们以类似的方式分析了使用不同周期（恒定和可变）的正弦波和标准偏差高达正弦幅度 40% 的红噪声的组合模拟的时间序列。分析表明，噪声不会显着扭曲初始信号，并且噪声本身不会形成具有在自然时间序列情况下观察到的特性的结构。我们推测QBO周期随太阳活动周期的发展所揭示的变化可能与太阳对流区的纬度差异旋转以及QBO产生区域的旋转速度对QBO周期值的可能影响有关. 在这个假设下，