The pattern of supergranular in a solar active region and the formation of filaments

The formation of filaments in solar bipolar active regions is investigated, giving particular attention to the relationship between this process and the pattern of supergranular convection. SOHO MDI and Kitt Peak magnetograms and Hα filtergrams are used. The large decaying active region NOAA 8525 is considered over the period May 4–7, 1999. The boundaries of supergranules are identified as concentrations of the line-of-sight photospheric field in magnetograms. Filaments in the central part of the active region are studied; as a whole, they are aligned with the supergranule boundaries. Variations in the magnetic field in this period were manifest primarily in the form of “cancellations” and spatial-redistribution processes consistent with the pattern of developing supergranules. These factors created the conditions necessary for the formation of a filament stretched across the entire active region; i.e., the straightening of the polarity-inversion line and reduction of the horizontal gradients of the magnetic field. One possible explanation of the results is that the magnetic-field component along the filament axis is associated with the vortical structure of horizontal flows in the supergranulation cells.     

Large-Scale Magnetic Field of the Sun and Evolution of Sunspot Activity

The evolution of the large-scale magnetic field of the Sun has been studied using an algorithm of tomographic inversion. By analyzing line-of-sight magnetograms, we mapped the radial and toroidal components of the Sun??s large-scale magnetic field. The evolution of the radial and toroidal magnetic field components in the 11-year solar cycle has been studied in a time?Clatitude aspect. It is shown that the toroidal magnetic field of the Sun is causally related to sunspot activity; i.e., the sunspot formation zones drift in latitude and follow the toroidal magnetic fields. The results of our analysis support the idea that the high-latitude toroidal magnetic fields can serve as precursors of sunspot activity. The toroidal fields in the current cycle are anomalously weak and also show a barely noticeable equatorward drift. This behavior of the toroidal magnetic field suggests low activity levels in the current cycle and in the foreseeable future.     

Dynamics of the magnetic field and velocity field in an emerging active region

The dynamics of the magnetic field and velocity field during the birth and an early development stage of a major active region is studied. SOHO MDI longitudinal-component magnetograms, Dopplergrams, and continuum images are used. The presence of an enhanced material upflow in the photosphere during the passing of the top of the magnetic flux loop, forming the active region, is revealed. The maximum upflow velosity is 2 km/s and the maximum size of the upflow area exceeds 20000 km. The lifetime of the upflow is about two hours. The undulating form of the magnetic flux tubes crossing the photosphere is confirmed. A structural-analysis technique is used to show that the trailing polarity field at the formation stage of the active region is more highly structured than the leading polarity field.     

A space-borne solar stereoscope experiment in solar physics

A space experiment project is proposed, with the main purpose of obtaining 3-dimensional images of the solar atmosphere. We give a list of problems and objectives which can be resolved through the space-borne solar stereoscope.     

The east-Siberian complex of SibIZMIR Solar Observatories

The Sayan Solar Observatory, the Tunkinskaya Radiophysical Observatory, and the Baikal Astrophysical Observatory of SibIZMIR have been described. Some results of the investigations carried out over the past years have been expounded. Clarifying solar activity mechanisms and the nature of solar magnetic fields, active regions and flares as well as solar wind are their main problems. In the interest of these investigations the Institute has initiated and developed laboratory-scale simulation of plasma processes.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Concerning five-minute variations of the global magnetic field of the Sun

For the purpose of identifying five-min oscillations we analyze long-term continuous observations of the solar magnetic field (with a duration from 3 to 11 hours) with 0.5 D spatial resolution obtained with the STOP telescope (Solar Telescope for Operative Predictions) at the Sayan observatory in 1987 and 1989. It is shown that global magnetic field fluctuations with such periods seem to be real, but the character of corresponding power spectra is strongly dependent on the mean field strength in the magnetograph aperture.     

An Investigation of the sun-as-a-Star Magnetic Field Through Spectropolarimetric Measurements

We discuss some properties of the Sun-as-a-star magnetic field (SSMF) from measurements of the Stokes I and V profiles observed in several spectral lines simultaneously at the Sayan Observatory during 1999–2001. The data are analyzed both in terms of the Stokesmeter and magnetographic measuring techniques. Using, together with the SSMF observations, quasi-simultaneous measurements of V-profile distributions across the solar surface with an angular resolution of 100 arc sec we have shown that the SSMF signal is determined largely by the central area of the disk within 0.5 solar radius. We have explored the correlation and regression relations in different combinations of four Fraunhofer lines near the line Fei 525.021 nm and concluded that fine-structure elements with kilogauss strengths are main sources of the SSMF signal. We have obtained statistical estimates of asymmetry parameters and relative shifts of the Stokes V-profiles, which indicate the presence of dynamic processes in the magnetic elements. The relation between the Sayan and Stanford SSMF measurements is analyzed.     

Deep electromagnetic sounding of the lithosphere in the eastern Baltic (fennoscandian) shield with high-power controlled sources and industrial power transmission lines (FENICS experiment)

The paper addresses the technique and the first results of a unique experiment on the deep tensor frequency electromagnetic sounding, the Fennoscandian Electrical conductivity from results of sounding with Natural and Controlled Sources (FENICS). In the experiment, Energy-1 and Energy-2 generators with power of up to 200 kW and two mutually orthogonal industrial 109- and 120-km-long power transmission lines were used. The sounding frequency range was 0.1–200 Hz. The signals were measured in the Kola-Karelian region, in Finland, on Svalbard, and in Ukraine at distances up to 2150 km from the source. The parameters of electric conductivity in the lithosphere are studied down to depths on the order of 50–70 km. A strong lateral homogeneity (the one-dimensionality) of a geoelectric section of the Earth’s crust is revealed below depths of 10–15 km. At the same time, a region with reduced transverse crustal resistivity spread over about 80 000 square kilometers is identified within the depth interval from 20 to 40 km. On the southeast the contour of the anomaly borders the zone of deepening of the Moho boundary down to 60 km in Central Finland. The results are compared with the AMT-MT sounding data and a geodynamic interpretation of the obtained information is carried out.     

Possibilities for the application of adaptive optics at solar telescopes

Possibilities for the application of adaptive optics at solar telescopes are studied. A modified correlation tracker to measure the image motion at the first focus of the Big Solar Vacuum Telescope (BSVT) at the Baikal Astrophysical Observatory of the Institute for Solar-Terrestrial Physics, the Siberian Branch of the Russian Academy of Sciences, has been investigated experimentally.