In order to verify scenario of solar cycle suggested by Babcock and Leighton, a new index of activity is derived from observational data of bipolar spot groups by taking positions of magnetic poles of the groups into account. In agreement with the Babcock-Leighton scenario, this index reveals substantial correlation with amplitude of the axisymmetric magnetic field of the Sun measured at subsequent minimum of activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The reconstruction of sunspot numbers from the decadal radiocarbon series was made for the time interval 8005 B.C. - 1945 A.D using five-box carbon exchange model. Analyses showed apparent persistency in the reconstructed Wolf number series. It indicates the existence of long-term memory in solar activity. Nonlinear forecast of the mean value of Wolf number is made for the next 40 years using obtained radiocarbon proxy. Comparison of the results with the long-term forecasts of the other authors was performed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Recent observational work has shown that the emission in different layers of the solar atmosphere can de described statistically. For example, Pauluhn et al. (2000) show that the frequency distribution of quiet Sun emission in EUV lines is well fit by a lognormal distribution. In addition, Parnell (2002) has shown that the frequency distribution of discrete magnetic elements in the quiet Sun is well fit by a Weibull distribution. These distributions arise naturally from fragmentation studies of materials such as polymers and sediments. It is suggested that fragmentation and its related phenomena may be of use in describing the physics of how the above distributions appear on the Sun.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The solar cycle in photosphere and corona reflects the internal dynamics on the Sun. According to the modern understanding the observed behavior of solar activity is related to the dynamo process in convection zone and photosphere and it is closely connected with the evolution of the coronal structures. The observational data from ground and space allow us to investigate the solar cycle as a complex phenomenon and to clarify the most important features such as polar magnetic field reversals, non-uniform distributions of the solar activity complexes and fine structure of the solar cycle.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the catalog of data for 27 gamma-ray flares detected above 500 keV by the gamma-ray spectrometer SONG (Solar Neutrons and Gamma-Rays) onboard the Russian CORONAS-F satellite. These gamma-ray flares were collected during the period from August 14, 2001 till November 31, 2003 covering the latter half of the 23rd solar sunspot cycle.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Recent high-resolution observations provide us with key information that allows us to begin to assemble a coherent theoretical picture of the formation and maintenance of a sunspot and its complex thermal and magnetic structure. A new picture of penumbral structure has emerged from observations, involving two components having different magnetic field inclinations and remaining essentially distinct over the lifetime of the spot, with little interchange of magnetic flux. The darker component, with more nearly horizontal magnetic field, includes “returning” magnetic flux tubes that dive down below the surface near the outer edge of the penumbra and carry much of the Evershed flow. The configuration of these flux tubes can be understood to be a consequence of downward pumping of magnetic flux by turbulent granular convection in the moat surrounding a sunspot. This process has been demonstrated in recent three-dimensional numerical simulations of fully compressible convection. The process of flux pumping is an important key to understanding the formation and maintenance of the penumbra, the hysteresis associated with the transition from a pore to a sunspot, and the behavior of moving magnetic features in the moat.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The paper deals with some structural characteristics of sunspot magnetic fields.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

After the failure of the 1761 transit to provide a reliable value for the astronomical unit, the focus shifted to the 1769 event, and Britain mounted an ambitious program, with overseas observing parties dispatched to North Cape (Norway), Hudson Bay (Canada) and newly-discovered Tahiti in the Pacific. Lieutenant James Cook was in charge of the Tahitian expedition, ably assisted by fellow-astronomer, Charles Green, and they were supplied by the Royal Society and the Royal Observatory at Greenwich with telescopes and other scientific instruments. The main observing site was set up at Fort Venus, and supplementary transit stations were established on Irioa Island (Moorea) and Taaupiri Island (off the east coast of Tahiti). June 3 was warm and clear, and all observers successfully recorded the transit, but on the journey home ‘the curse of the transit’ prevailed and more than half of them fell ill and died. Back in England, Cook wrote up the transit observations for the Philosophical Transactions of the Royal Society, but for some inexplicable reason only used data obtained at Fort Venus. It was left to Oxford astronomer, Professor Thomas Hornsby, to derive a meaningful figure for the solar parallax, and he utilized the Tahitian data and observations made at four other sites to arrive at a figure of 8$\rlap . ^{\prime\prime}$78. But discordant results obtained by other researchers fuelled controversy over the effectiveness of transits of Venus as a valid means of determining the astronomical unit. In fact, the solar parallax obtained by Hornsby was remarkably similar to the currently-accepted value of 8$\rlap . ^{\prime\prime}$794148, thereby discrediting Beaglehole's oft-quoted claim that the Tahitian observations were a failure. Although more than a dozen men were involved in the Tahitian transit program, most of their records have been lost, and remarkably few of the instruments they employed can now be identified. Yet for those of us with Pacific affiliations, Cook's first voyage to the South Seas occupies a special place in transit of Venus history.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We investigate the series of the green corona (GC) intensity by the combined catalogues of Rybansky, Tlatov and the original series of Kislovodsk station.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We performed the study of a solar flare of GOES class X1.0 which occurred on 2002 August 21, peak time 05:34 UT. A new method was applied for temperature determination of the plasma seen in TRACE images. This method makes use of the detailed knowledge of the TRACE point spread function (PSF) function. Substantial dependence of TRACE PSF on wavelength allows for determination of temperature from a single TRACE image even in these portions of the image which are saturated. We also determined the average temperature of this flare from the soft X-ray spectra measured by RESIK Bragg spectrometer aboard CORONAS-F satellite. The results obtained from TARCE and RESIK data are compared.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We examine statistical methods for calibrating trigonometric parallaxes to retrieve the absolute magnitudes of stars, using Monte Carlo simulations. Here we consider the case of the zero-point of the period-luminosity relation for Cepheid variables. The method originally proposed by Ratnatunga & Casertano was revisited by introducing a realistic density distribution of sample stars belonging to the catalogue through prior calculations of the photometric distance for each star. It is found that our method gives an unbiased estimate, regardless of any dispersions in their absolute magnitude. We further investigate the reliability of results which depend on the accuracy of parallax. Our finding is that the accuracy ($\sim$1 mas) of Hipparcos parallaxes is not enough to obtain a reliable result due to a large variation among different ensembles of stars. More precise determination of parallaxes to an accuracy of 200 $\mu$as at least, which will be easily realized by the ongoing astrometric space satellites, will give a precise zero-point together with a dispersion in absolute magnitude.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A new technique of nonlinear interrelations between time series developed by Marwan & Kurths, (2002) has been applied to the sunspot data. By using this tools we have investigated synchronization and phase difference in annual sunspot areas — time series available for Northern and Southern Hemispheres of the Sun.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a brief review of scientific milestones of the Russian Space Research Program for 2006-2015 in the field of solar and solar-terrestrial physics and describe several space projects: CORONAS-PHOTON, RESONANCE, CLIPPER, INTERHELIOPROBE, and THERION-F2.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The orbital distribution of asteroids and Kuiper-belt objects (KBOs) provides important information for the dynamical evolution of the solar system. Recent advances in modelling the dynamics of asteroids and KBOs have increased our understanding of the mechanisms responsible for the main features observed in the small-body belts. There are, however, several pieces left to complete the puzzle of the dynamical history of the solar system. In particular, we now understand that the solar system probably looked very different during the first $500-1000$ Myr than today, mainly because of two processes that took place during those times: (i) planetary formation and (ii) planetary migration. I will discuss observational and dynamical constraints that any model, attempting to reconstruct this early period, should obey. I will then present a new model for planetary migration, which successfully reproduces the observed orbital distribution of the trans-Neptunian objects. I will then discuss the implications of this model on the early evolution of the inner solar system, in particular the distribution of main-belt asteroids and the bombardment of the terrestrial planets by small bodies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We consider the Solar Cycle - the variation in any solar, heliospheric or cosmic ray parameter, related to the well-known 22-year dynamo-like process on the Sun - and discuss how it is influenced by the inner (the transformation of the solar activity in the basement of the heliosphere) and the external (the interaction between the solar and interstellar winds) factors. The corresponding approaches to the description of the long-term variations (the Solar Cycle, secular and longer ones) in the galactic cosmic ray intensity are outlined.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Signs of quasi-regular structures in time-averaged photospheric images are described.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Astronomical Unit is one of the most basic units of astronomy: the scale of the solar system. Yet its long and colorful history is sprinkled liberally with incorrect descriptions and mis-quoted definitions – today as much as ever. Over the last half century, the accuracy of the au determinations has improved dramatically: optical (triangulation) methods have given way to modern electronic observations, high-speed computers, and dedicated efforts to improve planetary ephemerides. Typical uncertainties in the value of the au have decreased from many tens of thousands of kilometers to the present level of only a few meters. With the solar system providing a very clean, undisturbed dynamical model, the ephemerides have been used for a variety of exotic physical tests: alternative theories of gravitation, $d({\rm G})/dt$, $d({\rm au})/dt$, etc. In the beginning of this modern era, the author happened to be a witness to a couple of rather key events; more lately, a participant. A couple of these personal experiences are related.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Halo CMEs represent the three-dimensional moving structures, located out of the plane of the sky (Howard et al. 1982, St. Cyr et al. 2000). At that one halo CMEs move toward the Earth (frontside Halo CMEs), other - away from the Earth, St. Cyr. Frontside halo CMEs play the special role in phenomena, associated with space weather, Crosby (2001). The largest geomagnetic storms are caused by influencing such CMEs on the magnetosphere of the Earth (Webb et al. 2000, St. Cyr et al. 2000). Using the images of halo CMEs in the field of view of a coronagraph it is possible to determine only their apparent characteristics in the plane of the sky. But in this case it is difficult define its important parameters such as directions of movement, angular sizes in various sections of CME, position of the CME “center” or of its front, velocities of CME elements along directions which are not located in the plane of the sky. Without these parameters it is impossible to find the mass of CME, it's kinetic and potential energy. In the present work the methods are offered and approved allowing the estimation of the listed above halo CMEs parameters, which are determined with difficulty.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Oscillations of the magnetic field in sunspot umbra have been detected by Pulkovo CCD spectroheliograph-magnetograph. The manifestations of 3- min oscillations in the power spectra of magnetic field variations are not very strong and can be seen only in a number of larger sunspots. Their power is concentrated in isolated small regions of the boundary between umbra and penumbre of large spots. The waves are produced in short bursts with coherence times of about 10 min. In the sunspot umbra, 30-40 min modes have been also confidently revealed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The change in the measured position due to the chromatic effect in the optical system is usually so small that it can be neglected. However, in the case of the Hipparcos mission, this effect is of the same magnitude as the targeted precision; it is therefore mandatory to correct for it. The different assumptions adopted to build up such corrections in the Hipparcos framework are presented. Some of their limitations and how they can be overcome to improve the results even today are described. The chromaticity mainly affects red stars and has its strongest impact on the astrometry of very red and highly variable stars such as Miras. Nevertheless, the implications on distance scale determination are rather small.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html