We show that the latitudinal distribution of the coronal bright points (BPs) changes between the solar minimum and the rising phase of solar cycle 23. In 1996, the number of BPs peaks near the disk center. In 1998, the distribution shows bands of increased BPs' number at the ARs' latitudes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a method how to describe analytically a magnetic field distribution in the vicinity of a large interplanetary flux rope. The field consists of the pre-existing one and an additional current-free part. This work was supported by INTAS grant 03-51-6206, AV ČR project S1003006, and RFBR grant 03-02-16340.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

From observations of the Sun as a star made at Kitt Peak it is known that MnI 539.5 nm line exhibits unusually big (for a photospheric line) variations during a solar activity cycle. Doyle et al. 2001 suggested that it is because of optical pumping. This work aims particularly to check this hypothesis with help of observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Helioseismic analysis of solar global oscillations allows investigation of the internal structure and dynamics of the sun. I summarize the recent observational results, putting emphasis on the bands of slower- and faster-than-average rotation migrating in latitude over the solar cycle in a manner similar to the zones of solar activity. I also review theoretical considerations so far proposed as a cause of the periodic oscillation of the rotation profile.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Dutch Open Telescope (DOT) on La Palma is an innovative solar telescope combining open telescope structure and an open support tower with a multi-wavelength imaging assembly and with synchronous speckle cameras to generate high-resolution movies which sample different layers of the solar atmosphere simultaneously and co-spatially at high resolution over long durations. The DOT test and development phase is nearly concluded. The installation of an advanced speckle processor enables full science utilization including “Open-DOT” time allocation to the international community. Co-pointing with spectropolarimeters at other Canary Island telescopes and with TRACE furnishes valuable Solar-B precursor capabilities.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results of a study of the morphology and evolution of active regions using solar acoustic holography. These include acoustic signatures of large far-side active regions and their relationship to near-side activity indices a half rotation before and after the farside image, and the direct comparison of near-side acoustic signatures with the standard activity indicators, not only in their own right but also to calibrate the farside acoustic signature.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss a new program to measure the parallaxes of a number of L and T dwarfs, objects that bridge the gap between M dwarfs and planets. This pilot project tests the feasibility of using large telescopes with infrared detectors to determine parallaxes at the level of milli-arcseconds (mas). First results show that we are able to achieve the required centroiding precision and simulations indicate that when the final observations come in we should be able to achieve our goal of parallaxes with accuracies of 2 mas. The main problems will be focal plane astrometric distortions and stability.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss the polarization signals produced in recent realistic 3D simulations of solar magnetoconvection. The Stokes profiles of the Fe I 6301.5, 6302.5, 15648 and 15652 $\mathrm{\AA}$ Zeeman-sensitive spectral lines are synthesised and smeared to simulate the image degradation caused by the Earth's atmosphere and finite telescope resolution. A Principal Component Analysis approach is applied to classify the profiles. We find that the classes of Stokes $V$ profiles as well as their amplitude and area asymmetries are very close to the observations in the network and inter-network regions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Cyclic variations of the coronal green line brightness (CGLB) are investigated analysing a series of synoptic charts and a special movie assembled of them, covering 1943-2001. Regular changes of the large-scale CGLB distribution in dependence on the phase in the solar cycle are presented. A quantitative relation between the coronal green line intensity $I$ and the total magnetic field strength $B$ is derived for the period 1977-2001; the $B$ was calculated under potential approximation. A simple exponential relation of type $I \propto B^q$ was found to exist between the above two quantities. It is shown that the $q$ exponent may have opposite sign in the equatorial and polar zones. During phases of the solar cycle maxima the $I$ versus $B$ relation is much more complicated and cannot be expressed by such a simple formula.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We explore a full sphere (2D axisymmetric) kinematic solar dynamo model based on the Babcock-Leighton idea that the poloidal field is generated in the surface layers from the decay of tilted bipolar solar active regions. This model incorporates the helioseismically deduced solar rotation profile and an algorithm for buoyancy motivated from simulations of flux tube dynamics. A prescribed deep meridional circulation plays an important role in the advection of magnetic flux. We specifically address the parity issue and show that – contrary to some recent claims – the Babcock-Leighton dynamo can reproduce solar-like dipolar parity if certain reasonable conditions are satisfied in the solar interior, the most important requirement being that the poloidal field of the two hemispheres be efficiently coupled across the equator.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Coronal mass ejections (CMEs) are a key aspect of coronal and interplanetary dynamics. They can inject large amounts of mass and magnetic fields into the heliosphere, causing major geomagnetic storms and interplanetary shocks, a key source of solar energetic particles. Studies over the past decade using the excellent data sets from the SOHO, TRACE, Wind, ACE and other spacecraft and ground-based instruments have improved our knowledge of the origins and early development of CMEs at the Sun and how they affect space weather at Earth. I review some key coronal properties of CMEs, their source regions, their manifestations in the solar wind, and their geoeffectiveness. Halo-like CMEs are of special interest for space weather because they suggest the launch of a geoeffective disturbance toward Earth. However, their correspondence to geomagnetic storms varies over the solar cycle. Although CMEs are involved with the largest storms at all phases of the cycle, recurrent features such as interaction regions and high speed wind streams can also be geoeffective. A new heliospheric experiment, the Solar Mass Ejection Imager, has completed its first year in orbit and I give some early results.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The results of photometric investigations of the eclipsing binary CM Dra are presented. The observations of CM Dra were taken with the 70-cm telescope and two-star photometer of the Ural State University Astronomical Observatory in 1996–1997 (the total duration was 155 hours). The solution of the composite lightcurve yielded some fundamental physical parameters of CM Dra components. Four flares were observed, the calculated flare rate was 0.026. The Flares power was about handred times larger than solar ones. The CM Dra composite lightcurve shows the outside-eclipse low-amplitude (0.024mag) brightness variations which appeared to be shifted by 120 degrees in phase over a 20-years period. It may be explained supposing an appearance of the star spots on another longitude.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Advanced Technology Solar Telescope (ATST) will perform high-resolution studies of the Sun's magnetic fields needed to understand their role in the fundamental processes responsible for solar variability. The generation of magnetic fields through dynamo processes, the amplification of fields through the interaction with plasma flows, and the destruction of fields remain poorly understood. There is incomplete insight as to what physical mechanisms are responsible for heating the corona, what causes variations in the radiative output of the Sun, and what mechanisms trigger flares and coronal mass ejections. Progress in answering these critical questions requires study of the interaction of the magnetic field and convection with a resolution sufficient to observe scales fundamental to these processes.

The 4-m aperture ATST is designed as a unique scientific tool, with excellent angular resolution, a large wavelength range, and low scattered light. With its integrated adaptive optics, the ATST will achieve a spatial resolution nearly 10 times better than any existing solar telescope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Solar magnetic field polarity reversal (SMFPR) happens every 10-11 years. However untill now there is no clear understanding in what way this process is carried out. Results represented here are a by-product of the coronal hole study based on taken from Web-archive XUV corona images (Yohkoh and EIT/SOHO), white-light corona pictures(SOHO/LASCO) and Kitt Peak coronal hole (CH) 1083 nm maps. Observations used cover the minimum, maximum and a part of declining phase of 23-d cycle (1996-2004).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

On 6 June 1761 the Dominican Giovanni Battista Audiffredi observed the transit of Venus in his little observatory at the Monastery of Santa Maria sopra Minerva in Rome. Soon after, he published an anonymous short report in Italian, and in the first months of 1762 he published a complete Latin essay about his transit observations. Late in 1762, and in 1765, the French abbé Alexandre-Gui Pingré, who had observed the transit at the Rodriguez Isle, to the south of the equator, presented to the French Royal Academy of Sciences the results of the solar parallax determination derived from comparison of observations made in different geographic places. He had excluded the Roman data because – he said – of the lack of a fundamental quantity, the longitude of the Monastery, concluding that the Roman observations were imperfect. In order to defend his scientific reputation, Audiffredi published two Latin essays concerning the solar parallax determination, the Investigatio parallaxis solaris in 1765, and the De Solis parallaxis Commentarius in 1766.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

An analysis of the distribution of coronal brightness in the UV radiation according to SOHO/EIT in the wavelengths 171Å, 195Å and 304Å was carried out. A change of coronal brightness at the heights $1.02R-1.20R$ radius of the Sun was considered during 1996-2003. The distribution of brightness of the corona at the various heights depends on the phase of the solar cycle. Brightness of the corona at the heights more 1.05R in the wavelengths 171Å and 195Å has the greatest brightness during an epoch of the maximum activity. Brightness of the internal corona at the heights less $1.05R$ has the lowered brightness during this period. The maximum intensity of the corona 304Å was observed in the maximum activity at all heights. Comparison brightness of the corona with the number bright points in UV was carried out. For this purpose the bright points in the wavelength 304Å were allocated on the solar disk of the daily observations. The number of the bright points has the maximum on the phase of the minimum activity while the area of the bright regions has maximum in the maximum activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of Fourier and wavelet time series analysis for the high-cadence observations of an active region NOAA 8011, obtained with the Nobeyama Radioheliograph (NoRH) at the wavelength of 1.76 cm on 17.01.1997. Oscillations in brightness are found to be present with periods in the range from minutes to hours. The relationship between the active region oscillations in the microwave total intensity (I) and circular polarization (V) emission and changes of the magnetic field, deduced from the high-resolution magnetograms from MDI/SoHO, is investigated. We concentrate on the identification of different oscillation modes, the temporal behavior of the oscillations and the spatial distribution of different oscillating frequencies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The purpose of this investigation is a comparison of long-wave radiobursts, registered in the range of frequencies 100-1500 kHz with multi-channel radiometer AKR-X installed on INTERBALL-1, and hard X-ray fluxes in energy range 14-93 keV observed by YOHKOH/HXT during solar flares. We selected several events with flares of importance X and M, for which there were simultaneous observations in the hard X-ray and radio ranges during the impulsive phase of a flare. The temporal profiles of radiobursts are characterized by the rapid frequency drift, typical to the radiobursts of III type, caused by the motion of energetic electrons accelerated in the flare and which are spreading at the corona and interplanetary medium, up to the Earth orbit.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Coronagraphic spectral observations carried out with UVCS on SoHO above polar coronal holes have shown that the velocity distribution is highly anisotropic. Here we examine the influence of the density stratification on the interpretation of such observations. In particular, we investigate the profiles of O VI spectral lines emitted in polar coronal holes. We find that at distances greater than $1~R_{\odot}$ from the solar surface the widths of the emitted lines are significantly affected by the details of the adopted electron density profiles. In particular, the densities deduced by Doyle et al. (1999) from SoHO data result in O VI profiles whose widths and intensity ratio are relatively close to the values observed by UVCS although only isotropic velocity distributions are employed. Hence we expect that the magnitude of the anisotropy of the velocity distribution deduced from UVCS data depends strongly on the adopted density profile.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The investigation of coronal holes (CH) is in progress now thanks to a number of high precise experimental projects and a lot of observations (Ulysses, SOHO, Yohkoh and many others). Historical epoch of CH discovery and study is prolonged today on the new experimental materials. Our considerations of CH and its manifestations in SW near the Earth were connected with minimum, growth and maximum phases of solar cycle. In this work we deal with the descending phase of solar cycle 23. There was the interval of comparatively quite Sun in March 2004, when strong sporadic phenomena were not observed. The existence of long-lived transequatorial recurrent coronal holes on the solar disk allows the investigation it imprinting in SW flows, using Wind data in near Earth cosmic space, data SOHO, Yohkoh and others.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html