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Tlatov A.G.,Kislovodsk Mountain Astronomical Station of Pulkovo Observatory
Advances in Space Research | Year: 2015

Our analysis of groups of sunspots since the year 1610 till indicates that the Gnevyshev-Ohl rule (GO) displays cycles of inversion with the period of 200 years. The latest inversion occurred in the Hale double cycle 22-23. Due to that, in several subsequent double cycles the odd cycles should be weaker than their preceding even cycles. Gleissberg cycles with the period of about 100 years and variations with the period of 200 years are manifested in variations of physical parameters of sunspots and are interconnected. We suggested that the secular minima of the solar activity occur in the vicinity of the extreme points of the 200-year cycles of inversion of the GO rule. The peak of the next secular minimum is expected between the years 2025 ÷ 2035. We studied the variations of the physical parameters of sunspots in a Gleissberg cycle. At the maximum phase of the Gleissberg cycle, the average area of groups and the average number of spots in a group reach their maximum. According to our forecast, the amplitude of the 25th solar activity cycle will be somewhat lower than that of the 24th. © 2014 COSPAR.

Tlatov A.G.,Kislovodsk Mountain Astronomical Station of Pulkovo Observatory
Astrophysical Journal Letters | Year: 2013

We perform an analysis of the number of sunspot groups in activity cycles from 1610 through the present. Here we use the Gn index, which is defined as the average daily number of sunspot groups in cycle n. There is a high positive correlation between the parameter Gn in the current cycle and an analogous parameter in the following cycle G n + 1 both for pairs of even-odd cycles and odd-even activity cycles. In cycle Nos. 10-21 for pairs of even-odd cycles, the ratio of parameter Gn corresponds to the GO rule Godd n+1/Geven n > 1. However, during the period ∼1745-1850, odd cycles were less than the preceding even cycles Godd n+1/Geven n < 1. The ratio of the parameter Godd n+1/Geven n has a long-term variation within the range 0.5-1.5 with a period of about 21 activity cycles, and it proves the reversal of the GO rule. © 2013. The American Astronomical Society. All rights reserved.

Tlatov A.G.,Kislovodsk Mountain Astronomical Station of Pulkovo Observatory | Tlatova K.A.,Kislovodsk Mountain Astronomical Station of Pulkovo Observatory | Vasil'eva V.V.,Kislovodsk Mountain Astronomical Station of Pulkovo Observatory | Pevtsov A.A.,U.S. National Solar Observatory | Mursula K.,University of Oulu
Advances in Space Research | Year: 2015

Using the software developed by us, we produced a digitized (tabulated) database of sunspot umbrae and pores observed at Mount Wilson Observatory (MWO) in 1917-2013. The database includes the heliographic coordinates, areas and the polarity and strength of magnetic fields of umbrae and pores in the MWO sunspot drawings. Using this database we study here the properties and long-term variation of sunspot umbrae and pores, separately for leading and trailing polarity spots. We find that the leading sunspots have tendency for larger umbrae and stronger magnetic field strength than the trailing spots. The average field strength and area of sunspot umbrae vary with sunspot cycle. Furthermore, the mean magnetic field strength in sunspot umbrae exhibits a gradual increase from early 1960s to 1990s. The nature of this increase is discussed. © 2014 COSPAR.

Tlatov A.,Kislovodsk Mountain Astronomical Station of Pulkovo Observatory | Tavastsherna K.,Russian Academy of Sciences | Vasil'eva V.,Kislovodsk Mountain Astronomical Station of Pulkovo Observatory
Solar Physics | Year: 2014

We present identifications of coronal holes (CHs) from observations in the He i 10 830 Å line made at Kitt Peak Observatory (from 1975 to 2003) and in the EUV 195 Å wavelength with SOHO/EIT (from 1996 to 2012). To determine whether a feature is a CH we have developed semi-automatic techniques for delineating CH borders on synoptic charts and for subsequent mapping of these borders on magnetic-field charts. Using these techniques, we superimposed CH borders on magnetic-field charts over the time interval from 1975 to 2012. A major contribution to the total area was made by high-latitude CHs, but in the declining phase of solar cycle 23, the contribution from low-latitude CHs increased substantially. Variations in the flux of Galactic cosmic rays and those in the inclination angle of the heliospheric current sheet followed the cyclic variations of CH areas. High-latitude CHs affect the properties of the solar wind in the ecliptic plane. © 2013 Springer Science+Business Media Dordrecht.

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