Very long baseline interferometry (VLBI) is a radio astronomy technique that allows imaging and astrometry at milliarcsecond or better resolution. The last decade has seen improvements in VLBI techniques and equipment which have enabled precision astrometry of pulsars. Most notably, VLBI arrays have become more sensitive and calibration has become more accurate. Pulsar astrometry using VLBI can readily yield a proper motion and in many cases a trigonometric parallax as well. These observables have have numerous applications which justify the difficulty of the measurements. The goals of pulsar astrometry include: 1. determination of the distribution of pulsar birth velocities, a critical probe of supernova asymmetry; 2. improvement in understanding of the ISM through observations of pulsar bow shocks, interstellar scattering, and timing dispersion measures; and 3. understanding characteristics of individual pulsars though knowledge of their distance and velocity. I will discuss these science cases, some recent results, and prospects for better astrometry in the near future.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We explain simulation tools in the JASMINE project (JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Therefore it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations of error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. We find that new software technologies, such as Object Oriented (OO) methodologies, are ideal tools for the simulation system of JASMINE (the JASMINE simulator). In this article, we explain the framework of the JASMINE simulator.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Solar flare on 26 June 1999 was accompanied by radio bursts giving an indirect evidence of accelerated superthermal particle beams. It is generally believed that this effect can stimulate an impact linear polarization in Balmer series spectral lines. The flare was observed simultaneously by the Ondřejov Multichannel Flare Spectrograph (MFS) and by the Large Solar Vacuum Telescope (LSVT) using the polarization optics in the H$\alpha$ line. Spectropolarimetric data obtained by the two instruments are analyzed, however no substantial linear polarization was detected. Both spectral and auxiliary data, including radio and X-ray observations are analyzed to discuss possible reasons of the lack of linear polarization.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study variations of the solar large-scale magnetic field (LMF) with period $\approx$1.0–1.3 years by observational data of Stanford (1976–2004) and Kitt-Peak (1970–1984).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Since its launch on 2 December 1995, the joint ESA/NASA SOHO mission has provided a wealth of information about the Sun, from its interior, through the hot and dynamic atmosphere, to the solar wind and its interaction with the interstellar medium. At the same time, SOHO's easily accessible images and movies have captured the imagination of the science community and the general public alike. This article summarizes some of the key findings from 8 years of SOHO.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The temperature, velocity and magnetic field structures of solar atmosphere are extremely in-homogeneous under consideration on a small spatial scales. This fact is the reason of significant difficulties in the attempts of disambiguous interpretation of observations. Particularly informative for investigation of the complex polarized radiation formation processes in the dynamic solar atmosphere with a fine-structured organization of magnetic fields are the distributions across the solar disk of the amplitude asymmetry ($\delta a$) and area asymmetry ($\delta A$) of Stokes profiles, as well as of the strength ratios $R$ in different combinations of spectral lines. At this paper such information has been obtained using the Stokesmeter of the STOP telescope at the Sayan observatory. It was found that for some Fraunhofer lines the distribution of $R$ has an evident equatorial-polar asymmetry, which is difficult to explain yet. Additionally this paper presents some new results of the theoretical simulation (with different parameters of magnetic flux tubes models and of the medium in their neighborhood) of the center-to-limb variations of $\delta A$ on the example of the FeI $\lambda 525.02$ nm spectral line and of the $R = B_{525.02}/B_{524.70}$. The conclusion is made that a reasonably good agreement theory and experimental data can be achieved, for the time being, only for the central regions of the disk.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

How do you make a sunspot?

Douglass Gough (UK) and Alexander Stepanov(Russia)To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

JASMINE (Japan Astrometry Satellite Mission for INfrared Exploration) is a mission to determine positions and parallaxes accurate to $\sim 10$$\mu$arcsec, with proper motion errors $\sim 10$$\mu$arcsec yr$^{-1}$ for Galactic stars observed in the z-band (0.9 $\mu$m). In this article, we report some technical investigations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Torsional oscillations of sunspots were investigated in a penumbra on the observations in the photosphere of the longitudinal magnetic and velocity fields.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The short-term periodicities of the flare index (FI) which is roughly proportional to the total energy emitted by the flare, are investigated in detail using Fourier transform (FT) for the full-disc and for the northern and the southern hemispheres of the Sun separately over the epoch of almost 4 cycles (1966-2002) which covers 13392 days. Figure 1 shows the power spectra of the three time series of FI calculated for the 289-771 nHz (15-40 days) range with 0.24 nHz interval. The uncertainty in each frequency is ±0.4 nHz due to the 36.5-year data length. The dashed lines indicate the false alarm probability significance levels. In this figure, there are several pronounced power peaks whose significances are enough high. These are at 25.6, 27.0, 30.2 days for the full-disc, 27.0 days for the northern hemisphere and 27.5 and 33.8 days for the southern hemisphere. Since commonly used FT is not able to disclose the possible changes in the periodicities over the period studied, the wavelet transform (WT) was applied to search for temporal variability. The wavelet transform results show that the occurence of periodicities of flare index power is highly intermittent in time. All three FI time series show that the major periods, obtained by Fourier transform are localised in short time intervals (typically up to half of a year).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the preliminary results of study of the coronal bright points (BPs) using the SoHO/EIT data. We show that the number of BPs in quiet Sun areas does not vary between 1996 and 1997. In 1998 the BPs number (full disk) increases by about 20%.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The results of research of halfwidhts ($\Delta\lambda$) and intensities (W) of Fe X $\lambda 6374 \AA$ and Fe XIV $\lambda 5303\AA$ spectral lines using observations obtained with the Large coronagraph of the Sayan observatory in 1968-1983 show the inverse correlation between $\Delta\lambda$ and W always exists for Fe X $\lambda 6374 \AA$; it takes place at all latitudes at the same height as well as with height irrespectively of activity level. For Fe XIV $\lambda 5303 \AA$ this correlation varies from direct to inverse depending on activity level. It is shown that relation type between $\Delta\lambda$ and W for different spectral lines is determined by different coronal structurednesses in these lines.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The latitudinal time distribution of sunspots (butterfly diagram) was studied by Becker (1959) and Antalová & Gnevyshev (1985). Our goal is to revisit these studies. In the first case we check whether there is a poleward migration in sunspot activity. In the second case we confirm the results, and make more quantitative statements concerning their significance and the position of the activity peaks.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Observations of the Sun are always complicated by the thermal influence of the integral flux of its radiation on the optical-mechanical and photo-detecting units of the telescope. This influence manifests itself especially strong and can be even amplified while observing the Sun from the space, and mostly while observing its full disk. However, the existing optical solar telescopes produce an image of either full disk of the Sun or only one individual region. In the latter case, the radiation of almost full disk of the Sun is cut off from the telescope, and emission from a small region on its surface propagate through a small aperture on the optical axis of the telescope (see, for example, Popov (1988); Stix (1991). The third variant is a solar coronagraph, which constructs an image of the solar corona, cutting off radiation of the whole disk of the Sun, thus imitating a total solar eclipse (Lyott, 1939; Nikolsky 1966; Smartt 1998). This solution determines success of the solar experiment in the space, particularly, if it is connected with long-term high-precision photometric and coordinate measurements of temporal variations of the diameter and shape of the solar disk limb.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The accomplishments of space flights and introduction of new astrometric methods (radar ranging, lunar laser-ranging, VLBI measurements) in the 1960s required considerably more precise planetary ephemerides than it was possible with classical analytical theories by Leverrier, Hill, Newcomb and Clemence. On the other hand, these modern data made possible the creation of such ephemerides. Two series of numerical ephemerides of planets most complete up to now, and of the same level of accuracy, are considered in this paper. There are the well-known numerical DE ephemerides of JPL as well as the EPM (Ephemerides of Planets and the Moon) ephemerides produced at the Institute of Applied Astronomy. The description of the dynamical models, the brief characteristics of DE118, DE200, DE403, DE405, DE410, EPM87, EPM98, EPM2000, EPM2004 ephemerides, and the comparison between DE410 and EPM2004 are given. The latest DE410 and EPM2004 ephemerides have resulted from a least squares adjustment to observational data totaling about 300000 position observations (1911–2003) of different types. The accurate radar observations of planets and spacecraft have made it possible not only to improve the orbital elements of planets but to determine a broad set of astronomical constants from the value of the astronomical unit (AU) to parameters of PPN formalism. Recent estimates of different astronomical constant are presented, and progress is shown in the improvement of the AU value, the parameters $\beta, \gamma $, as well as possible variability of the gravitational constant $G$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The properties of the magnetic field in the coronal holes (CH) were considered during 1996-2002. The daily observations from the Kitt Peak observatory in the line HeI 10830Å were compiled. The measurement of the magnetic fields in the CH was carried out by comparing the data obtained from the Kitt Peak telescope and the magnetograms of SOHO/MDI. The dependence between the brightness of CH from intensity of the magnetic field and distributions of CH depending from the magnetic field and latitude were presented for minimum and maximum of the cycle. The latitude and the unipolarity degree of the magnetic field that influence on the brightness of the CH were examined. It was shown that the average magnetic field was 1-2G, the unipolarity degree of the magnetic field was 0.1-0.3 and brightness of the coronal holes increases with the average magnetic field. The latitude-time distributions of CH for different polarity were obtained.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We are considering below some complex problems which arise in theoretical description of the processes developing in convective zones of rotating stars. It is common knowledge that the solutions of the starting nonlinear equations of equilibrium or motion may have singularities at the rotation axis, whose elimination in the case of equations of an even more general nature including spins was treated in quantum mechanics by invoking a numerical procedure (see, e.g., Varshalovich et al. (1988)). If spin effects are disregarded, these equations, which describe general representations of conventional and Alfven velocities as expansions in orthogonal vector spherical harmonics can be cast in an analytical form Vandakurov (1999).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Hard X-ray radiation from several powerful solar flares was detected in October-November, 2003 by the SPR-N hard X-ray polarimeter onboard CORONAS-F satellite. In the October, 29 solar flare (20:40 - 21:00 UT) the X-ray radiation was strongly polarized (more than 70% of photons with energies 40-100 keV). In the flares 28.10.03 and 04.11.03 the emission was not polarized. The upper limits for the part of polarized photons at the level of tens percents were obtained in these flares.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Using local helioseismology, we construct maps of the horizontal divergence of the velocity field near the solar surface and study the spectrum of solar supergranulation during the period from 1996 to 2002. Supergranulation oscillates and propagates like a wave interference pattern. The variations of the oscillation frequency with latitude and time are less than 5%. We find significant solar-cycle variations in the lifetime and the anisotropic distribution of power. We also measure the time-dependent zonal and meridional flows that advect supergranules.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have used most recent archaeomagnetic and ice core $CO_2$ records for the long-term trend correction in global tree ring radiocarbon concentration ($\Delta^{14}C$). The short-term $CO_2$ exchange system was approximated via first order differential equation with frequency dependent coefficients. A generalized multi-scale box model was constructed and used for the reservoir effect correction.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html