Spectral characteristic of mid-term quasi-periodicities in sunspots data. (arXiv:1911.06881v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Frick_P/0/1/0/all/0/1">P. Frick</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sokoloff_D/0/1/0/all/0/1">D. Sokoloff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stepanov_R/0/1/0/all/0/1">R. Stepanov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pipin_V/0/1/0/all/0/1">V. Pipin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Usoskin_I/0/1/0/all/0/1">I. Usoskin</a>
Numerous analyses suggest the existence of various quasi-periodicities in
solar activity. The power spectrum of solar activity recorded in sunspot data
is dominated by the $sim$11-year quasi-periodicity, known as the Schwabe
cycle. In the mid-term range (1 month — 11 years) a pronounced variability
known as a quasi-biennial oscillation (QBO) is widely discussed. In the shorter
time scale a pronounced peak, corresponding to the synodic solar rotation
period ($sim$ 27 days) is observed. Here we revisited the mid-term solar
variability in terms of statistical dynamic of fully turbulent systems, where
solid arguments are required to accept an isolated dominant frequency in a
continuous (smooth) spectrum. For that, we first undertook an unbiased analysis
of the standard solar data, sunspot numbers and the F10.7 solar radioflux
index, by applying a wavelet tool, which allows one to perform a frequency-time
analysis of the signal. Considering the spectral dynamics of solar activity
cycle by cycle, we showed that no single periodicity can be separated, in a
statistically significant manner, in the specified range of periods. We examine
whether a model of solar dynamo can reproduce the mid-term oscillation pattern
observed in solar data. We found that a realistically observed spectrum can be
explained if small spatial (but not temporal) scales are effectively smoothed.
This result is important because solar activity is a it global feature,
although monitored via small-scale tracers like sunspots.
Numerous analyses suggest the existence of various quasi-periodicities in
solar activity. The power spectrum of solar activity recorded in sunspot data
is dominated by the $sim$11-year quasi-periodicity, known as the Schwabe
cycle. In the mid-term range (1 month — 11 years) a pronounced variability
known as a quasi-biennial oscillation (QBO) is widely discussed. In the shorter
time scale a pronounced peak, corresponding to the synodic solar rotation
period ($sim$ 27 days) is observed. Here we revisited the mid-term solar
variability in terms of statistical dynamic of fully turbulent systems, where
solid arguments are required to accept an isolated dominant frequency in a
continuous (smooth) spectrum. For that, we first undertook an unbiased analysis
of the standard solar data, sunspot numbers and the F10.7 solar radioflux
index, by applying a wavelet tool, which allows one to perform a frequency-time
analysis of the signal. Considering the spectral dynamics of solar activity
cycle by cycle, we showed that no single periodicity can be separated, in a
statistically significant manner, in the specified range of periods. We examine
whether a model of solar dynamo can reproduce the mid-term oscillation pattern
observed in solar data. We found that a realistically observed spectrum can be
explained if small spatial (but not temporal) scales are effectively smoothed.
This result is important because solar activity is a it global feature,
although monitored via small-scale tracers like sunspots.
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