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Saint Petersburg, Russia

Makarenko N.G.,Institute for Problems of Informatics and Control | Nagovitsyn Y.A.,Central Pulkovo Astronomical Observatory | Karimova L.M.,Institute for Problems of Informatics and Control | Kruglun O.A.,Institute for Problems of Informatics and Control
Geomagnetism and Aeronomy | Year: 2013

The possibility to apply long-term regional series to reconstruct the Earth's global temperature in the past is considered. It is shown using symbolic analysis methods that significant (on the so-called order patterns) are relations of time series of St. Petersburg temperature with certain regional and global series. New sets of global temperature reconstructions, starting from the mid-18th century, are constructed on the basis of the previously proposed MSR and DPS methods. © 2013 Pleiades Publishing, Ltd.

Bobylev V.V.,Saint Petersburg State University | Bajkova A.T.,Central Pulkovo Astronomical Observatory
Astronomische Nachrichten | Year: 2013

We tested distances derived from the equivalent widths of interstellar Ca II spectral lines by Megier et al. (2009). To this end, we used a sample of nearby 126 young OB3 stars (r < 1 kpc) with known proper motions and line-of-site velocities. We shown that these stars are closely associated with the Gould Belt structure. The bulk of the sample (about 100 stars) shows the same kinematics as the sample of distant OB3 stars. Their galactocentric radial velocities agree well with the following spiral density wave parameters: the amplitude of radial perturbations fR ≈ 12 km s-1, wavelength λ ≈ 2.3 kpc, and phase of the Sun in spiral wave χ⊙ ≈ -90°. However, we revealed 20 stars with absolutely unusual kinematical features. Their galactocentric radial velocities show a wave shifted by ≈180° with respect to the wave found from the entire sample. The superposition of two spiral patterns seems to be a likely explanation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bajkova A.T.,Central Pulkovo Astronomical Observatory | Bobylev V.V.,Saint Petersburg State University
Astronomische Nachrichten | Year: 2013

The parameters of the Galactic spiral wave are re-determined using a modified periodogram (spectral) analysis of the galactocentric radial velocities of 58 masers with known trigonometric parallaxes, proper motions, and line-of-site velocities. The masers span a wide range of galactocentric distances, 3 < R < 14 kpc, which, combined with a large scatter of position angles θ of these objects in the Galactic plane required an accurate account of logarithmic dependence of spiral-wave perturbations on both the galactocentric distance and position angle. A periodic signal was detected corresponding to a spiral density wave with wavelength of λ = 2.4 ± 0.4 kpc, peak velocity of wave perturbations of fR = 7.5 ± 1.5 km s-1, phase of the Sun of χ⊙ = -160 ± 15°, and pitch angle of -5.5 ± 1°. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tsap Y.T.,Crimean Astrophysical Observatory | Stepanov A.V.,Central Pulkovo Astronomical Observatory
Proceedings of the International Astronomical Union | Year: 2010

Based on the three-fluid approximation the influence of the neutral component of hydrogen plasma on Joule dissipation of electric currents are considered. As distinguished from Mestel & Spitzer (1956) and Parker (1963) it has been shown that the magnetic flux may be not conserved in the case of the "ambipolar diffusion" due to collisions between ions and neutrals. This is explained by the ion acceleration under the action of Ampere's force. Joule dissipation is determined by electron and ion collisions in a partially ionized plasma. Plasma evacuation from current sheets is the effective mechanism of its cooling. Thickness of a current sheet can achieve up to hundreds of kilometers in the solar chromosphere. The origin of the solar chromospheric jets observed with the Hinode satellite are discussed. © 2011 International Astronomical Union.

Efremov V.I.,Central Pulkovo Astronomical Observatory | Parfinenko L.D.,Central Pulkovo Astronomical Observatory | Solov'ev A.A.,Central Pulkovo Astronomical Observatory
Solar Physics | Year: 2010

We applied special data-processing algorithms to the study of long-period oscillations of the magnetic-field strength and the line-of-sight velocity in sunspots. The oscillations were investigated with two independent groups of data. First, we used an eight-hour-long series of solar spectrograms, obtained with the solar telescope at the Pulkovo Observatory. We simultaneously measured Doppler shifts of six spectral lines, formed at different heights in the atmosphere. Second, we had a long time series of full-disk magnetograms (10 - 34 hour) from SOHO/MDI for the line-of-sight magnetic-field component. Both ground- and space-based observations revealed long-period modes of oscillations (40 - 45, 60 - 80, and 160 - 180 minutes) in the power spectrum of the sunspots and surrounding magnetic structures. With the SOHO/MDI data, one can study the longer periodicities. We obtained two new significant periods (> 3σ) in the power spectra of sunspots: around 250 and 480 minutes. The power of the oscillations in the lower frequencies is always higher than in the higher ones. The amplitude of the long-period magnetic-field modes shows magnitudes of about 200 - 250 G. The amplitude of the line-of-sight velocity periodicities is about 60 - 110 m s -1. The absence of low-frequency oscillations in the telluric line proves their solar nature. Moreover, the absence of low-frequency oscillations of the line-of-sight velocity in the quiet photosphere (free of magnetic elements) proves their direct connection to magnetic structures. Long-period modes of oscillation observed in magnetic elements surrounding the sunspot are spread over the meso-granulation scales (10″ - 12″), while the sunspot itself oscillates as a whole. The amplitude of the long-period mode of the line-of-sight velocity in a sunspot decreases rapidly with height: these oscillations are clearly visible in the spectral lines originating at heights of approximately 200 km and fade away in lines originating at 500 km. We found a new interesting property: the low-frequency oscillations of a sunspot are strongly reduced when there is a steady temporal trend (strengthening or weakening) of the sunspot's magnetic field. Another important result is that the frequency of long-period oscillations evidently depends on the sunspot's magnetic-field strength. © 2010 Springer Science+Business Media B.V.

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