The Nicholas Central Astronomical Observatory in Pulkovo, near Saint-Petersburg, was inaugurated as Russia's principal astronomical institution on 19 (7) August 1839. Construction of the observatory had begun in 1834 following the edict of the Russian Emperor Nicholas I, who had invited as his adviser Professor Friedrich Georg Wilhelm Struve, the Director of the Dorpat Observatory. Emperor Nicholas I appointed Wilhelm Struve as the Director of the new observatory. With regard to funding, the emperor had given Struve a carte blanche to enable him to order from German telescope makers the best astrometric instruments designed according to Struve's own ideas. Hence Wilhelm Struve is to be considered as the co-founder of Pulkovo Observatory.

Even though comet 55P/Tempel-Tuttle has an orbital period of about 33 years it has only been recovered five times in the past 630 years. The earliest clearly documented return is that of 1366, with the others being in 1699, 1865, 1965 and 1998. The comet may have been briefly sighted in 1035 (indicative of a possible outburst) and in 1234 and it was conspicuous by its non-recovery in 901 (possibly indicating very low surface activity during that return). We review the absolute magnitude data for comet 55P /Tempel-Tuttle and find tentative evidence to suggest it underwent an outburst in 1699. If large meteoroids were ejected from the comet during the 1699 outburst numerical integration studies find that they would have been Earth-orbit crossing in 1832 and 1965 - years in which the Leonid shower was rich in bright fireballs. The Earth will also sample 1699 ejected material in November 2001.

Built toward the end of the 18th century on the last floor of a former Trinitarian church, the Astronomical Observatory in Alba Iulia (Romania) was equipped with instruments brought from Vienna and it was in activity until 1860. A description of the astronomical instruments of those existing at present is given.

The comet explorers at Kyiv University took part in numerous international observational programs for study of comets: C/1973 E1 Kohoutek in 1974, 27P/Crommelin in 1984, 1P/ Halley in 1986, 23P/Brorsen-Metcalf in 1989, D/Shoemaker-Levy 9 in 1994, C/1996 B2 Hyakutake in 1996, C/1995 O1 Hale-Bopp in 1997, C/1999 S4 (LINEAR) in 2000 and others. Two comets, 67P/Churyumov-Gerasimenko in 1969 and C/1986 N1 (Churyumov-Solodovnikov) in 1986, were discovered. During 1939-2000 more than 1000 scientific papers devoted to comets were published in different journals, books and proceedings.

Bessel proposed to the Berlin Academy that 24 astronomers should collaborate in mapping the sky within 15° of the equator. The projected completion date was 1829. The actual completion date was 1859.

There should be a driving layer on the Sun, in which the interaction between magnetic field and plasma motion would provide enough magnetic energy and necessary topology for the explosion of solar activity in the corona.

Although the exact location of the driving layer is not known, phenomenologically, the photosphere is acting, in many aspects, as the driving layer. Vector magnetic field measurements on the photosphere are greatly needed in clarifying the nature of the driving. Two elementary processes, flux emergence and cancellation, and one basic structure, magnetic interface between topology-independent magnetic loops, are key elements in the driving.

Computational seismic holography, applied to Solar Oscillations Investigation -Michelson Doppler Imager (SOI-MDI) data from SOHO, has recently given us the first images of an active region on the far side of the Sun(Lindsey & Braun 2000). The advent of phase-coherent seismic imaging is now allowing us quite literally to look into the solar interior from a local perspective, indeed to see through the solar interior acoustically to its far surface. Solar activity is critical to near-Earth space weather. A great deal of effort has been invested towards the prediction of flares and CMEs, based on the formidable presence of active regions on the near solar surface. Active regions can emerge rapidly from beneath the photosphere or appear on the east limb with relatively little warning. Because of this, the ability to anticipate the appearances of active regions will contribute substantially to forecasts of space weather on time scales of more than about a day. In collaboration with Dr. Phil Scherrer and the MDI team at Stanford University we are currently deriving far-side images from the lower resolution “medium-l” SOI-MDI Dopplergrams, which are obtained continuously through the year and arrive at MDI headquarters within 24 hours of their acquisition by the SOHO spacecraft. We are therefore already capable of locating large far-side active regions and predicting their appearance on the east solar limb to within a few hours more than a week in advance. In addition, ground-based networks such as GONG will soon have the capability for “real-time helioseismology”, and will be routinely monitoring the far surface of the Sun, and perhaps beneath the near surface, for emerging solar activity.

In this paper we discuss some recent observations of radio emission produced by high energy electrons resulting from solar flares. We discuss the spatial structure of simple weak spiky burst emissions observed simultaneously, at 17 and 34 GHz with the Nobeyama Radio Heliograph (NoRH). Using simultaneous imaging observations obtained by Yohkoh/HXT and SXT along with NoRH17 & 34 GHz observations, we attempt to model a relatively stronger and longer flare using gyrosynchrotron mechanism for the flaring radio emission.

The response of our space environment to the constantly changing Sun is known as ”Space Weather”. The Solar and Heliospheric Observatory (SOHO) has obtained significant new information about coronal mass ejections (CMEs), the source of the most severe disturbances in the Earth’s environment. Most of the time space weather is of little concern in our everyday lives. However, when the space environment is disturbed by the variable outputs of the Sun, technologies that we depend on both in orbit and on the ground can be affected. The increasing deployment of radiation-, current-, and field-sensitive technological systems over the last few decades and the increasing presence of complex systems in space combine to make society more vulnerable to solar-terrestrial disturbances. Thus, our society is much more sensitive to space weather activity today compared to the last solar maximum. By observing the Sun 24 hours per day, SOHO has proved to be an important “space weather watchdog”. The importance of real-time monitoring of the Sun will be pointed out and a number of enterprises affected by space weather will be discussed.

In 1967 Gordon made the revolutionary assumption that reflection of radar signal from the Sun can be explained by its scattering on microturbulence (Gordon 1973). In his first model it was ion-sound turbulence. Later he considered radar scattering on Langmuir turbulence. The principal opportunity to explain frequency displacements of radar echoes observed in James’ experiments (James 1966, 1970) was shown. However, it turned out (Gerasimova 1979) that the mechanism needed an impermissible high level of isotropic turbulence for the reflection with cross-sections σ = 10πR2ʘ.

The authors present evidence for a connection between solar activity and mean winter temperatures at Havana, Cuba, in observations covering the past 130 years. The colder-than-average winters tend to follow 2±1 years after years of maximum solar activity.

The origin of coronal mass ejections (CMEs) is an interesting, while still mysterious, subject in solar physics. As well, the relationship between CMEs and solar flares is poorly understood. This paper attempts to provide answers to these questions on the base of the flux rope model, and put forward a trigger mechanism for CMEs. The work is motivated by an interesting discovery of the relation between reconnection-favored emerging flux and CMEs (Feynman and Martin 1995), i.e., such emerging flux, either within the filament channel or on the outer edge of the channel, can trigger CMEs.

In the consideration of Aly’s constraint, a detached flux rope model was proposed for the pre-CME configuration. A quadrupolar magnetic field with a flux rope is introduced as the initial magnetic configuration in current research. Since our trigger mechanism is magnetic in nature, gravity is omitted. Emerging flux is simulated by changing the local magnetic flux at the bottom boundary.

The mechanism of flare energy build-up is one of the most fundamental questions in the solar flare study, but is still to be solved. From the review of the previous studies, we notice that the formation process of the magnetic shear in an active region should be essential for the flare energy build-up mechanism. Based on this idea, we make detailed studies of the active region evolutions using high resolution Hα images obtained with the 60 cm Domeless Solar Telescope at Hida Observatory, Kyoto University.

We study sunspot proper motions and evolutionary changes of Hα fine structures and magnetic fields in active regions NOAA 5395 (Ishii et al. 1998) and NOAA 4201 (Ishii et al. 2000). To explain the evolutionary characteristics found from the analysis of these two active regions, we propose schematic models of twisted flux bundles emerging from the convection zone. We also found that the occurrence of high flare activity in each active region was restricted to the rapidly emerging region of the twisted flux bundle. In conclusion, we suggest that the emergence of the twisted flux bundle should be the key to high flare-productivity of the sunspot group, or the flare energy build-up mechanism.

The authors propose a number of empirical criteria for prediction of solar flares based on many years of observations at Huairou Solar Observing Station of Beijing Astronomical Observatory.

The radio wave from distant radio sources will be scattered by the irregular structures of the solar wind plasma when propagating through the interplanetary space, resulting into a randomly fluctuating pattern of the radio wave in observation. This pattern is called interplanetary scintillation (IPS). Observation on IPS can give information of the solar wind speed and irregular structures in solar wind plasma. The IPS observations began at Miyun Station, Beijing Astronomical Observatory from the late half of 1999. The properties of the telescope and description of the data analysis can be found in the papers of Wang (1987) and Wu, Zhang and Zheng (2000) respectively.

Table 1 summarizes some observational results using IPS source 3C48 in April and May 2000. The Fresnel knees and the first minima in the IPS spectra were used to estimate solar wind speeds. Comparisons of our results with the unpublished data of Hiraiso Solar Terrestrial Research Center obtained from their web site, have been done and good agreement between the two systems was found. Since the collecting area of Miyun telescope is limited, the system noise is relatively high and dominates the high-frequency parts of the spectra. The Miyun IPS observation and data reduction procedures are still under developing and will soon be completed.

Determination of accurate oxygen abundances in old metal-poor stars is of importance for a variety of astronomical problems ranging from stellar evolution to cosmology. A brief review is given here of the four basic procedures from which values of [O/Fe] can be estimated.

From new high resolution spectra of metal-poor giants we use equivalent widths of [O I], Sc II, and Fe II lines to derive new values of [O/Sc] and [O/Fe]. These results are generally consistent with previous determinations of oxygen abundances from [O I] lines, but the star-to-star scatter is greatly reduced.

Permitted OI, forbidden [OI], electronic AΣ − XП UV OH and vib-rot IR OH lines often infer different oxygen abundances for cool stars. Which species should one use to determine the oxygen abundance in cool stars and how does one reconcile the different results for different species? Although there are uncertainties and systematic differences in the molecular gf values used by different authors, the main reason for the different results lies in the 1-D model atmosphere analyses that are used.