We have investigated the optical design for the Japan astrometry satellite mission (JASMINE). In order to accomplish measurements of astrometric parameters with high accuracy, optics with a long focal length and a wide focal plane for astrometry are required. In 1977 Korsch proposed a three mirror system with a long focal length and a wide focal plane. The Korsch system is one of the convincing models. However, the center of the field is totally vignetted because of the fold mirror. Therefore we consider an improved Korsch system in which the center of the field is not vignetted. Finally, we obtain the diffraction limited optical design with small distortion. Our project needs a common astrometric technique to obtain precise positions of star images on solid state detectors to accomplish its objectives. In order to determine the centers of stars, an image of the point source must be focused onto the CCD array with a spread of a few pixels. The distribution of photons (photoelectrons) over a set of pixels enables us to estimate positions of stars with sub-pixel accuracy. We modify the algorithm to estimate the real positions of stars from the photon weighted mean, which was originally developed by the FAME (Full-Sky Astrometric Mapping Explorer) group. Finally, we obtain the results from the experiment that the accuracy of estimation of distance between two stars has a variance of about 1/300 pixel; that is, the error for one measurement is about 1/300 pixel, which is almost an ideal result given by Poisson photon noise. We also investigate the accuracy of estimation of positions with a different size of PSF. In this case also, we find that the accuracy of estimation has a variance of about 1/300 pixel.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A sufficiently thick and dense flaring magnetic loop is shown to be able to support global sausage magnetoacoustic modes. The oscillation period of this mode, calculated in the straight cylinder approximation, is determined by the length of the loop, not by its diameter, as it has previously been assumed. For the existence of this mode, the ratio of the loop length to its diameter is to be less than about a half of the square root of the density contrast ratio. This mode has a maximum of the magnetic field perturbation at the loop apex and nodes at the footpoints. We demonstrate that the 14-17 sec quasi-periodical pulsations of microwave emission, oscillating in phase at a loop apex and at its legs, as observed with the Nobeyama Radioheliograph, are interpreted in terms of the global sausage mode.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present observations of the dynamic evolution of photospheric magnetic elements in the G-band, magnetograms and Dopplergrams. The observations were obtained with the Swedish 1m Solar Telescope on La Palma at close to the diffraction limit of $0{\hbox{.\!\!^{\prime\prime}}}1$. In the most quiet regions we observe individual bright points in the G-band with corresponding magnetic signal in the magnetograms. Where the filling factor of the magnetic field is larger, the bright points interact when advected by the granular and super-granular flow-fields, flux sheets form and fragment. The plage region of the decaying active region is filled with more complex topologies like ribbon structures with darker interior and bright, knotted edges. These change into flower-like shape when small in extent and into micro-pores when the flux region is larger in extent. The magnetic elements in the plage region are associated with upflows with strong downflows in the immediate vicinity in the low-field region.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

One of the main characteristics of Mercury is its 3:2 spin-orbit resonance, combined with a 1:1 resonance between the orbital node of its orbit and the angle describing the precession of the rotation axis, both measured on the ecliptic plane. We build an analytical model, using Hamiltonian formalism, that takes into account this phenomenon thanks to the introduction of three resonant variables and conjugated momenta. We calculate the equilibria corresponding to four different configurations, which means four completely different values of the (ecliptic) obliquity; in particular, we focus on the present (stable) situation of Mercury, and thanks to several canonical transformations, we obtain, near the equilibrium, three pairs of angle-action variables, and consequently, three basic frequencies. Let us note that the model is as simple as possible: the gravitational potential is limited to the second degree terms (the only ones for which a value can be presently given), and the orbit of Mercury is Keplerian. The numerical values obtained by our simplified model are validated by the coherence with existing complete numerical models.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A revolution is taking place in the research of extra-solar planets with the discovery of the first exoplanets only a decade ago to the more than 100 systems known to date. Almost all of these extrasolar planets have been discovered using the radial velocity technique. Unfortunately, this limits the amount of information which can be obtain from these systems, with a $\sin i$ ambiguity in the planet's mass, and no further measurements of fundamental parameters as long as these planets can not be detected directly. This situation is very different in the rare case that the orbit of a planet has an inclination such that it occults its host star, as in the case of HD 209458b. Not only can the mass and radius of the planet be accurately determined, but it makes the system also suitable for many detailed follow-up studies, in particular atmospheric transmission spectroscopy. This has resulted in the detection of the atmosphere of HD 209458b in Sodium, and the discovery of an evaporating exosphere in Hydrogen, Carbon and Oxygen using the Hubble Space Telescope. In this paper I briefly review transiting exoplanets and methods to probe their atmospheres, with the emphasis on a new method of transmission spectroscopy making use of the Rossiter effect, which may be more suitable for the large ground-based telescopes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This paper is devoted to the investigation of the synchronous enhancements of the solar source fluxes according to the RATAN-600 Southern Sector observations at the 1.92 cm, 2.24 cm, 2.74 cm, and 3.21 cm radio waves. The observations were carried out on 11.09.01 from 8:30 UT to 10:30 UT every 8 min. We use the term “synchronous bursts” or “synchronous brightenings” instead of the “sympathetic bursts” as the time resolution of the RATAN - 600 is not high. The solar source brightenings are synchronous if they are registered in 2 - 2.5 min time lag, i.e. in the time interval of passage of the Sun through the central part of the main lobe of the antenna power pattern. The high flux sensitivity of the radio telescope - radiometer system was 0.005 s.f.u. The solar sources were identified with the active regions: AR 9610, AR 9608, AR 9606, AR 9616, AR 9617, which widely separated from each other (up to $10^{6}$ km). According to our observations, the synchronous enhancements were observed at the moments of the soft X ray brightenings and X ray bursts (Figure 1a). The temporal variations of the relative fluxes of the solar sources $F/F_{0}$ were compared to the $X$-ray (GOES 8,10; $H_{\alpha}$ - flares and to the radio bursts at 9100 MHz, $F_{0}$ - the radio emission flux from the “quiet” Sun, $F$ - the radio emission flux from the solar source). It turned out that the interrelationships of the active regions AR 9610, AR 9608, AR 9606 were the most interesting. It was registered 4 synchronous brightenings of solar sources AR 9610, AR 9608 at the moment of the observations: 8:38 UT, 9:02 UT, 9:50 UT, 10:30 UT. We recorded synchronous brightenings of solar sources at 1.92 cm, 2.24 cm, 2.74 cm, and 3.21 cm radio waves: at $\lambda=2.24 cm$ – $\Delta(F)=(0.24 \div 0.88)$ s.f.u. and at $\lambda=3.21$ cm – $\Delta(F)=(0.21 \div 0.94)$ s.f.u. The detailed halo solar source is the magnetosphere, which was identified with all extensive AR 9608 region excepting the primary the most strong solar source of the active region radio emission. The angular size of halo is closed to the angular size of AR 9608 ($7.7 \arcmin$). The comparison of the brightening onset of the AR 9610, AR 9608 interacting active regions in the time interval (9:26 - 9:58 UT) and the discovered forestalling of the halo flux quick intensification at $\lambda=2.24$ cm and $\lambda=3.21$ cm pointed to the active process start in the AR 9608 solar source at $\lambda=3.21$ cm. As it was shown, the dynamics of the time intensity variation of solar sources at $\lambda=3.21$ cm, $\lambda$=2.74 cm is more complicated. It is demonstrated by against of the synchronous of the moments of the AR 9610 relative flux maxima with the $\lambda$ increase (Figure 1b).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

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