Astrometry from Space: New Design of the GAIA Mission

An interferometric astrometric mission, aiming at accuracies at around the10 microarcsec level, was recommended as a high priority concept within thenew ESA Horizon 2000+ scientific programme. The original outline concept forsuch a mission, GAIA, presented its general feasibility but did not addressmany questions of implementation or optimisation. Another concept of aninterferometer for a scanning astrometric satellite is presented. It containsa simpler optical telescope and a more efficient detector system. The designutilizes the full resolution of all light in the dispersed fringes of aFizeau interferometer. A preliminary optimization of the satellite indicatesthat two telescope units with a baseline of 100 cm will achieve a precisionof 3, 8, 22, 68, 302 microarcsec for parallaxes of stars with V = 12, 14, 16, 18, 20 mag, respectively, from a 5 year mission. Simultaneousspectrophotometry of the entire spectrum of each star will be obtained with aresolution corresponding to intermediate band photometry. The expectedprecision of this photometry is about 0.003 mag for V = 16. The performance is good in crowded fields, at least up to one star per 5 arcsec2. A Hipparcos-type beam combiner of 150 cm width is placed in front of atelescope with 4 square apertures of 50 cm. The assumed focal length is f = 60 m and the field 0.5 degree diameter. The detector consists of CCDs used for time delayed integration (drift-scan.)     

Rotation cycles of the sector structure of the solar magnetic field and its activity

We study the rotation of the sector structure of the solar magnetic field by using Stanford magnetographic observations from 1975 until 2000 and magnetic synoptic Hα-maps obtained from 1904 until 2000. The two independent series of observations yielded the same rotation periods of the two-sector (26.86 days) and four-sector (13.64 days) structures. We introduce a new index of the solar rotation, SSPM(t). The spectral power density of the sector structure of the magnetic field is shown to exhibit a 22-year cyclicity. The two-and four-sector structures of the magnetic field rotate faster at the maxima of even 11-year sunspot cycles. This phenomenon may be called the Gnevyshev-Ohl rule for the solar rotation. The 11-year sector-structure activity cycles are shown to lead the 11-year sunspot cycles (Wolf numbers) by 5.5 years. A 55-year component with the slowest rotation in the 18th cycle (1945–1955) was distinguished in the sector-structure rotation.     

Geologo-geomorphological study of modern tectonic movements

In studying, and especially in interpreting, modern movements of the Earth's crust, one should take into account its tectonic variability, its layering and the deformations exposed at the Earth's surface, which reflect the evolution of deep processes. No less important is the solution of the opposite problem, i.e., the study of deep tectonic processes, using data on modern movements of the surface. In both cases, analysis of the distribution of types of movement and regions along (active) faults is essential. Active faults in Asia between 20° and 60° are taken as examples.     

The behaviour of prominence areas in the 11-Year cycle and their relationship with other solar events

On the basis of the data on prominence areas for 1880–1976 and positions of the boundary background magnetic field for 1955–1982 it is shown that the maximum development of prominences and their poleward migration, accompanied by the magnetic field reversal, concides with the first maximum of the 11-year solar cycle, which is characterized by an enhancement of solar activity at all latitudes. The second maximum is an increase of all features, including prominences but in the low latitudes only. That prominence zone migrates poleward in the following 11-year solar cycle.     

Chaos and Wavefront Reversal for Long-Range Sound Propagation

Doklady Earth Sciences - Long-range sound propagation in the deep ocean is considered. Attention is concentrated on the procedure of acoustic wavefield refocusing by means of the wavefront...     

Ultra-flat galaxies selected from RFGC catalog. I. The sample properties

We used the Revised Flat Galaxy Catalog (RFGC) to create a sample of ultra-flat galaxies (UFG) covering the whole northern and southern sky apart from theMilkyWay zone. It contains 817 spiral galaxies seen edge-on, selected into theUFG sample according to their apparent axial ratios (a/b)_B ≥ 10.0 and (a/b)_R ≥ 8.53 in the blue and red bands, respectively. Within this basic sample we fixed an exemplary sample of 441 UFG galaxies having the radial velocities of V_LG < 10000 km s^?1, Galactic latitude of | b |> 10° and the blue angular diameter of a_B > 1.′0. According to the Schmidt test the exemplary sample of 441 galaxies is characterized by about (80–90)% completeness, what is quite enough to study different properties of the ultra-flat galaxies. We found that more than 3/4 of UFGs have the morphological types within the narrow range of T = 7± 1, i.e. the thinnest stellar disks occur among the Scd, Sd, and Sdm types. The average surface brightness of UFG galaxies tends to diminish towards the flattest bulge-less galaxies. Regularly shaped disks without signs of asymmetrymake up about 2/3 both among all the RFGC galaxies, and the UFG sample objects. About 60% of ultra-flat galaxies can be referred to dynamically isolated objects, while 30% of them probably belong to the scattered associations (filaments, walls), and only about 10% of them are dynamically dominating galaxies with respect to their neighbours.     

Parameter Variations in the Subsoil Radon Field at the Paratunka Station of the Petropavlovsk-Kamchatsky Geodynamic Test Site in 2011–2016

A network of stations for subsoil radon monitoring is in operation at the Petropavlovsk-Kamchatsky geodynamic testing area and is aimed at detection of strong earthquake precursors. At all stations, measurements are carried out using gas-discharge counters located at different depths within aeration zones of soft sediments. The volume activity of radon (VA Rn) is monitored at the most equipped station Paratunka (PRT) at three measurement sites located across the regional fault. The radon flux density (RFD) is measured from the surface. The article reviews responses in the dynamics of VA Rn and RFD from the surface at the PRT station prior to the Kamchatka earthquakes with magnitudes М _W > 5 that occurred over the period of 2011–2016. The revealed RFD seasonal cycle is likely related to the seasonal variations in air temperature. The postseismic effect caused by the strongest deep Okhotsk earthquake (May 24, 2013, М _W = 8.3) is detected in the RFD data. The behavior of VA Rn dynamics during time periods of the strong earthquakes is different. The results confirm the existing opinion on the formation of narrowly localized zones of Rn runoff to the atmosphere owing to both vertical and horizontal irregularities in the top layer of soil, which can react differently to changes in the geoenvironment stress–strain. On the basis of the real-time radon monitoring data, the authors have issued partially successful short-term prediction for several earthquakes. The results of this work confirm the opinion of many researchers that radon monitoring can be used in the short-term prediction of strong earthquakes.     

A study of heat transport at the ice base and structure of the under-ice water layer in Southern Baikal

Experimental data and a new model of ice buildup are used to assess and to study variations of heat flux at the water–ice interface. The latter plays an important part in ice cover formation but still is poorly known because of the lack of field temperature measurements with sufficient spatial and temporal resolution along the phase transition boundary, which knowledge gap is filled by this study.     

Determination of Thermophysical Characteristics of the Surface Layer of the Lunar Soil under Natural Conditions

Solar System Research - The schemes of unburied thermal probes and the principles of their operation are considered. The efficiency of each scheme is evaluated.     

Sea Level Fluctuations as a Key Factor in Delta Formation

Water Resources - Based on studies of the geological and geomorphological structure of the mouth areas of the Ob, Pyasina, Khatanga, and Lena rivers, a model for delta development as a result of...