Reply to comment on the paper “ on a role of quadruple component of magnetic field in defining solar activity in grand cycles” by Usoskin (2017)

Abstract

In this communication we provide our answers to the comments by Usoskin (2017) on our recent paper (Popova et al, 2017a). We show that Principal Component Analysis (PCA) allows us to derive eigen vectors with eigen values assigned to variance of solar magnetic field waves from full disk solar magnetograms obtained in cycles 21-23 which came in pairs. The current paper (Popova et al, 2017a) adds the second pair of magnetic waves generated by quadruple magnetic sources. This allows us to recover a centennial cycle, in addition to the grand cycle, and to produce a closer fit to the solar and terrestrial activity features in the past millennium.

RETRACTED ARTICLE: Oscillations of the baseline of solar magnetic field and solar irradiance on a millennial timescale

“…Although, it was noted 17,18 that Sporer minimum (1460–1550) is not present in our summary curve, which instead during the same period of time shows a standard grand cycle, the previous one to the modern grand cycle (17–21 centuries). Zharkova et al .…”

“…The resulting summary curve, which is linked to the solar activity curve defined by the averaged sunspot numbers 5 , restored backward for 3000 years shows about 9 grand cycles of 350–400 years, with the times of their grand minima having remarkable resemblance to those reported from the sunspot and terrestrial activity in the past millennia 17 : Maunder (grand) Minimum (1645–1715), Wolf grand minimum (1200), Oort grand minimum (1010–1050), Homer grand minimum (800–900 BC), combined with the warming periods: medieval (900–1200), Roman (400–10 BC) and other ones occurred between the grand minima. This approach allowed us to predict the modern grand solar minimum (GSM) approaching the Sun in 2020–2055 6 .…”

“…Zharkova et al . 17,18 reasonably argued that Sporer minimum is an artifact of the strongly increased at that time background radiation on the Earth caused by the explosion of a very close (about 600–700 light years) supernova Vela Junior occurred in the southern sky. The radiation induced by this explosion for this period has not been considered in the background radiation required for the carbon dating method 19,20 that could shift the dates by a few hundred years.…”

“…12 , so that their interference naturally leads to a beating effect with the envelope oscillations (grand cycles) occurring at the frequency equal to a difference of frequencies of the individual waves 6 . The lengths of the individual grand cycles depend on a real time as shown in the summary curve of the solar activity extrapolated backward by two 6,21 and three millennia 17,18 making some grand cycles shorter with higher amplitudes and the other ones longer with smaller amplitudes.

Figure 1Top plot: solar activity prediction backwards 3000 years with a summary curve (blue line) of the two principal components (PCs) of solar background magnetic field (SBMF) 6 versus the reconstruction by Solanki et al . 27 (red line).

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A review of the SCOSTEP’s 5-year scientific program VarSITI—Variability of the Sun and Its Terrestrial Impact

“…This forecast was an example of the methods based on spectral analysis in which it is assumed that the sunspot time series is a superposition of periodicities. This article was criticized by Usoskin (2018), which the authors disagreed with Zharkova et al (2018).…”