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

The radiation environment encountered in space by satellites is extremely variable and depends mainly on the satellite position and space weather. Although models for the concerned processes are available, most of them only represent the average conditions and neglect the dynamics of the system. Accurate prediction of the radiation environment remains an unsolved problem. Space weather can cause manifold problems to spacecraft (S/C) components, such as degradation of sensors and solar arrays and changes in on-board memories by Single Event Upsets (SEU). The final effect is a degradation of the S/C overall performance and in extreme cases complete unavailability of services. When certain alarm conditions are reached, risk avoidance procedures may be invoked, e.g. switching off high voltages/biases/filters etc. and transition to protected operating modes. Once the detectors are off, there is just a rough estimation of when the conditions are safe again. Better prediction of radiation conditions and more accurate information could greatly improve these operations. Therefore it is necessary to monitor and predict the space weather effects and improve the space weather services.

Valuable large archive of solar radio observations has been accumulated by the Pulkovo solar radio group. But big part of data is recorded on paper. We describe a method and software for transferring data recorded on paper to FITS format.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

An aestimate of a typical life time of zebra pattern associated with escaping of fast particles from the trap into the loss-cone, is given. Besides, we estimate a number of fast electrons that is necessary to be injected into the trap in order to provide the observed brightness temperature of zebra stripes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The 11-year cycle represents a simultaneous parallel change in both the activity level and the total irradiance of the Sun. So, in case of variations of the amplitude of the activity level - a power of a cycle - the amplitude of solar irradiance variations is expected to change correspondingly. The identical correlated course of the long-term variations of activity and luminosity of the Sun on the secular timescale has been observed earlier by Eddy (1976), and Borisenkov (1988). Moreover, according to the data of Borisenkov (1988), in each of 18 deep Maunder-type minima of solar activity, revealed over the span of the last 7500 years, the cooling of climate had been observed, while warming occurred during the periods of high maxima. Thus, the integral radiation has always been essentially higher at the maximum, and it had noticeably decreased at the minima. Therefore, quasi-periodic variations of the solar activity during both the 11-year cycle and 80- and 200-year cycles are accompanied by proportional variations of the integral flux of solar radiation, which result in geophysical effects. The main cause of climate change during the last millennia is the corresponding cyclic variation of the 80- and 200-year component of irradiance correlated with activity. That is why, the contemporary is not anomalous but is ordinary secular global warming (Aguilar 2003; Reid 2000), as well as previous similar cases of warming during the periods of secular activity growth is still mainly connected with an increase of the secular component of solar irradiance variation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The coincidence was observed between the places with weak (probably inverse) photospheric longitudinal magnetic fields in the big spot of the AR NOAA 8340 prior to the start of the flare and a common base of the giant arches (loops) and centers of emission visible in the HeI 10830Å line core during the flare. A number of observational facts compel us to make a supposition that the flare was the consequence of an injection of plasma from the places with marked peculiarity of the photospheric magnetic field into the expanding magnetic arcade.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The East-West asymmetry of sunspot areas has been analyzed on the basis of the Debrecen Photoheliographic Data (DPD). This material provides the opportunity to scrutinize the fine details in the distributions of the East-West differences depending on spot size and central meridional distance during the ascending and the descending phase of 22th cycle.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Series of H$_\alpha$ spectra and slit-jaw H$_\alpha$ filtergrams of a quiescent prominence (QP) taken at Pic du Midi Observatory on 7 November 1977 are studied. The image processing of the H$_\alpha$ filtergrams reveals an internal structure of the prominence consisting of several arches. Series of high-resolution H$_\alpha$ spectra obtained with the slit located on selected parts of one of the prominence arches chosen for Doppler shift analysis. The prominence arch show cyclic displacement along the line-of-sight (L.O.S.) direction implying Alfven string-mode oscillations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In the past 10 years, observations from space have generated a genuine revolution in our understanding of the Sun. Its interior is now “observed” down to a few % of the solar radius, its internal dynamics, its rotation and the large scale flows that are found to exist under its “surface” are studied continuously for over nearly a complete solar cycle. The mechanisms that underlie solar activity are better understood as well as their effects on the heliosphere and on the planets of the Solar System, in particular on the Earth.

However, there are still opened questions that deserve to be answered through a new generation of space instruments, requiring the best experts in the world and an extended fleet of space missions that no single country is able today to undertake alone. In this context, the International Living with a Star programme is a key element that must be pursued with full strength. At the same time, new missions that are not part of that programme should begin to be studied. They will provide the ultimate resolution and accuracy that are necessary to go a step further in the knowledge of the Sun and of its effects on our planet.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Eclipsing binary light curves have provided the ‘royal road’ (Russell 1948) to fundamental astrophysical information on stars. If radial velocities of the components and a reliable colour/temperature/flux relation are available, parallaxes may be determined and compared with direct measures, e.g. by Hipparcos. Accuracies of existing measures are considered and aspects of the development of this and other methods of distance determination reviewed. Roles for multiwavelength techniques (e.g. VLBA, broad-spectrum photometry) are noted. The recovery of information on new planets orbiting remote stars by transit phenomena will be looked into within this context.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html