We provide an observational proof of the existence of the global sausage mode oscillations in a flaring loop studying a microwave burst with quasi-periodical pulsations observed with the Nobeyama Radioheliograph (NoRH).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The map of the large-scale chromospheric Doppler velocities ($VD$) on the solar disk, obtained from 2D-spectroscopy within the HeI 10830 Å line for June 4 2002, is presented. Velocity field structures larger than the supergranulation cells are studied. Statistical relations between $VD$ and 1) the intensity in the core of the HeI 10830 Å line and 2) the sign and strength of the longitudinal photospheric magnetic field are obtained and discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We describe two flares of GOES class M5.7 and 1.5 which were observed simultaneously by RHESSI (Ramaty High Energy Solar Spectroscopic Imager) and NoRH (Nobeyama Radio Heliograph). Both flares exhibit slow motions suggestive of changing magnetic shear, loop expansion, or gradual reconnection. One flare is clearly a coronal hard X-ray and microwave flare.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study a simple model for the solar dynamo in the framework of the Parker dynamo, with a nonlinear dynamo saturation mechanism based on magnetic helicity conservation arguments. We find a parameter range in which the model demonstrates a cyclic behaviour with properties similar to that of Parker dynamo with the simplest form of algebraic $\alpha$-quenching. We compare the nonlinear current helicity evolution in this model with data for the current helicity evolution obtained during 10 years of observations at the Huairou Solar Station of China. We conclude that, in spite of the very preliminary state of the observations and the crude nature of the model, the idea of using observational data to constrain our ideas concerning magnetic field generation in the framework of the solar dynamo appears promising.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Analyzing the long-term evolution of active regions (ARs) permits to quantify the link between their atmospheric emission (from optical to X-rays) and the magnetic field. Multi-wavelength studies provide the full story, and not just a snapshot, of the phenomena and they allow us analyze how the atmosphere changes as the field strength decreases (with the dispersion of the AR).

The evolution of the emitted flux in various wavelength ranges contains information on the heating mechanism(s) of the different atmospheric levels. I review what we can learn from such long-term (months) multi-wavelength observations, and compare the results to other solar and stellar studies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We determine a location of a source of a main acceleration of relativistic particles during the flare on July 14, 2000, adopting that the time of acceleration coincides with a burst of the hard linear and continuum gamma-radiation. The process of this effective acceleration starts when one of flare ribbons reaches the large spot of the group, as it follows from the TRACE data. An estimation shows that the source of acceleration locates on the height of 15–20 thousands of km above the photosphere. Comparison these results with those for other large flares allows us to conclude that during almost 30 powerful events in the last three cycles an additional effective “accelerator” of a moderate scale turns on in diluted regions with large magnetic fields and their gradients.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Geomagnetic activity variations are closely related to the global magnetic field of the Sun and could serve as useful proxies to reconstruct the solar wind history and evolution of the inner heliosphere. Historical geomagnetic records reveal trends in the solar wind and interplanetary magnetic field variability resulting from topological changes of the heliospheric current sheet and solar corona viewed from the Earth. Predictions of the solar cycle based on geomagnetic trends are presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have developed the technique and software to observe and process spectral data obtained with the CCD camera. It makes possible to construct two-dimensional maps of Doppler velocity and intensity in solar features simultaneously at two levels in the solar atmosphere. We present some results derived from study of the structure and space-time variations of the Doppler velocity in the region of quiescent filaments in the chromosphere (the $H_{\beta}$ $\lambda 486.1$ nm line) and under filaments in the photosphere (the Fe I $\lambda$ 486.3 nm. and Fe I $\lambda$ 485.9 nm lines). We came to a conclusion that motions in quiescent filaments consist of both the stationary and oscillatory components and follow helical trajectories.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The voyage of the Mexican commission to observe the transit of Venus on 8 December 1874 in Japan is briefly recounted. The five-man expedition was led by Francisco Díaz Covarrubias. They succeeded in establishing two observing stations near Yokohama, one in Nogue-no-Yama and one on a hill called “The Bluff”, and also in determining precise geographical positions for them. Clear skies allowed the observation of the transit at both stations. The results were presented in Paris in 1875, and published on the same year. They were meant as a contribution to be processed along with all other data obtained by different missions. The importance of the expedition for the development of early modern science in Mexico – particularly astronomy – is examined in the broad context of the social and political conditions then prevailing in the country. The relevance of the mission for the establishment of scientific, cultural and even commercial ties between Japan and Mexico is emphasized.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The one-dimensional relaxation of a spatially bounded electron stream in non-uniform background plasma is simulated. The corresponding system of quasi-linear equations is \begin{equation}\frac{\partial f}{\partial t}+V\frac{\partial f}{\partial x}=\frac \partial {\partial V}\left( D\frac{\partial f}{\partial V}\right),\, \frac{\partial W}{\partial t}=2\gamma W,\, \gamma =\frac \pi 2\frac{\omega _p}{n_p}V^2\frac{\partial f}{\partial V},\, D=\frac{8\pi ^2e^2}{m^2}\frac WV. \end{equation} Here $f$ - the electron distribution function, $D$ - diffusion coefficient, and $\gamma$ and $W$ - are the growth rate and spectral energy density of plasma waves respectively, $n$ - background plasma density, $\omega_p$ - plasma frequency. Initial conditions (the electron distribution function at $t = 0$): \begin{equation}f(x,V,t=0)=An_{b}\exp \left(-\frac{(V-V_b)^2}{2V_{Tb}^2}\right)\exp \left(-\left(\frac xd\right)^2\right)\end{equation}To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In Eselevich V. and M. Solar Phys. 195, 319, 2000 is shown that in brightness rays of the streamer belt from time to time there exist additional plasma streams of enhanced density moves antisunward and occupies a separate ray. The duration of additional streams can range from a few hours to several days. For that reason, some of them may be categorized as sporadic SW streams and the others as quasi-stationary SW streams. Preliminary investigations showed that the leading edge of such streams can be extremely small in width. The purpose of this paper is to verify the conclusions about the existence of additional plasma streams with steep fronts in streamer belt rays, based on analyzing the calibrated data from LASCO/SOHO C2 and C3.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Angular positions of the brightest coronal streamers observed during the total solar eclipses (TSEs) in 1870-2001 are compared with calculated tilts of the heliospheric current sheet (HCS) in 1976-2001 and with reconstructed ones in 1870-1976.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The new SOHO/MDI data (1996-2003) reveal an interesting result that the total polar magnetic fluxes do not vary significantly during the polar magnetic field reversals in both hemispheres, while the positive and negative parts of the total fluxes do change.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present calculations of helicity based on our solar dynamo model and show that the results are consistent with observational data.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A new information resource to study solar magnetic field variations and their influence on the Earth extending ordinary lengths of some traditional indices of solar activity is introduced.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

New methods of local area helioseismology provide three-dimensional maps of sound-speed variations and mass flows in the upper convection zone, giving important insight into the internal structure and dynamics of sunspots and active regions. Most of these results are obtained from SOHO/MDI data using the method of time-distance helioseismology (or acoustic tomography). Robustness of this method has been significantly improved by incorporating most important wave propagation effects and stochastic properties of solar oscillations. Time-distance helioseismology reveals that developed sunspots have a two layer structure: a relatively thin sub-photospheric layer of lower sound speed, and a deeper layer of higher sound speed. The mass flows in the upper layer are typically converging and directed downward, while in the deeper interior the flows are mostly diverging. These results support the cluster model of sunspots suggested by Parker. New observations also provide interesting information about emerging magnetic flux, formation and evolution of active regions and complexes of activity, and allow us to investigate effects of sub-photospheric dynamics of active regions on the global circulation of the Sun and also small-scale rapid shear flows associated with flares and CME.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

High resolution optical spectra of hydrogen and calcium lines observed with the Echelle spectrograph of the VTT at Sacramento Peak Observatory were analyzed. The observed line profiles in some parts of dark chromospheric mottles are to be matched with theoretical ones using the cloud model and several parameters (e.g. the temperature, gas pressure, flow velocity) are to be derived. Individual steps of the procedure, as well as crucial problems are discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The black-drop effect bedeviled attempts to determine the Astronomical Unit from the time of the transit of Venus of 1761, until dynamical determinations of the AU obviated the need for transit measurements. By studying the 1999 transit of Mercury, using observations taken from space with NASA's Transition Region and Coronal Explorer (TRACE), we have fully explained Mercury's black-drop effect, with contributions from not only the telescope's point-spread function but also the solar limb darkening. Since Mercury has no atmosphere, we have thus verified the previous understanding, often overlooked, that the black-drop effect does not necessarily correspond to the detection of an atmosphere. We continued our studies with observations of the 2004 transit of Venus with the TRACE spacecraft in orbit and with ground-based imagery from Thessaloniki, Greece. We report on preliminary reduction of those data; see http://www.transitofvenus.info for updated results. Such studies are expected to contribute to the understanding of transits of exoplanets. Though the determination of the Astronomical Unit from studies of transit of Venus has been undertaken only rarely, it was for centuries expected to be the best method. The recent 8 June 2004 transit of Venus provided an exceptionally rare opportunity to study such a transit and to determine how modern studies can explain the limitations of the historical observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This investigation is devoted to the study of time variations and spatial peculiarities of radio local radio sources associated with the solar active regions (AR) on the basis of microwave observations in September–October 2002. During this period the most interesting results have been obtained for the AR NOAA 0139. So, in this paper an analysis of this radio source is presented. The observations were made with the radio telescopes RT–22 (Crimea), RATAN–600, the Siberian Solar Radio Telescope (SSRT) and Nobeyama. Observations with the RT–22 (wavelengths 2.0, 2.3, 3.5 cm) were carried out by the quasi–zero method with the flux sensitivity of 0.1 s.f.u and the temporal resolution of about 0.1 s. The typical length of realization was about 6.5 hours. The spatial resolution of few arc minutes allowed to limit the analysis by the particular AR but was not enough to distinguish any details. Nevertheless spectral analysis of the AR made using observations with high one–dimensional resolution of the RATAN–600 shows that at short cm wavelengths for this AR at the period of the RT–22 observations dominated thermal cyclotron emission of above the largest sunspot of the group. This result was also confirmed by radio maps of the Nobeyama at wavelength 1.76 cm.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Archival full disk observations of the central depth of Mn 539.467, a photospheric line, have been found to correlate with chromospheric Ca K intensity. In this paper we present spectroheliograms taken in Mn I 539.467 and 542.32 nm lines and other nearby lines to see if the other photospheric lines show chromospheric structures. We see both Mn images and also Si I 542.118 mimic magnetograms the similar way, while strong Fe and Ti lines only faintly reveal magnetic features, and weak Fe lines of comparable strength to Mn show nothing.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html