The thermal radiation spectra of supermassive stars and X-ray sources

In the external layers of supermassive stars and thermal sources of X-ray radiation electron scattering contributes more to the opacity than free-free process. Therefore, the thermal radiation spectrum of supermassive stars must greatly differ from Planckian. The approximate formulae obtained for the radiation spectra are applicable to any objects with a predominant role of electron scattering in the opacity and power dependence of plasma temperature and density on geometrical depth of the layers.In thermal radiation sources with power dependence of plasma temperature on depth of the layer the formation of power radiation spectraF(v)v ^– with >0 with >0 is possible. Such spectra can imitate the presence of non-thermal radiation mechanisms. This effect takes place also in the case of small optical depth on the Thomson scattering. Possibly, this effect is of interest for the theories of X-ray sources and X-ray solar flares.This case was considered also in the final version of the paper (Felten and Rees, 1972).     

Reconstruction of Centennial Series of Solar Activity

Geomagnetism and Aeronomy - The results of the digitalization of the centennial series of solar activity are considered. The data contain information on sunspots since 1918, sunspot umbra since...     

Higher helicity invariants and solar dynamo

Modern models of nonlinear dynamo saturation in celestial bodies (specifically, on the Sun) are largely based on the consideration of the balance of magnetic helicity. This physical variable has also a topological meaning: it is associated with the linking coefficient of magnetic tubes. In addition to magnetic helicity, magnetohydrodynamics has a number of topological integrals of motion (the so-called higher helicity moments). We have compared these invariants with magnetic helicity properties and concluded that they can hardly serve as nonlinear constraints on dynamo action.     

Influence of the Change in the Relative Number of Pores in Activity Cycles on the Reconstruction of the Sunspot Index

Astronomy Reports - An analysis of the relative number of groups in cycles 21–24 based on the digitization of observations of sunspots at the Locarno Observatory (Locarno, Switzerland) was...     

Nature of the Kergelen Plateau and Its Place in the Structural Plan of the Southern Sector of the Indian Ocean

Izvestiya, Atmospheric and Oceanic Physics - The morphostructural characteristics of the main taxa of southern Indian Ocean, such as the Del Cano-Crozet, Conrad, and Kerguelen plateaus, are given...     

Statistical theory of thermal instability

A new statistical approach is presented to study the thermal instability of an optically thin unmagnetized plasma. In the framework of this approach the time evolution of the mass distribution function over temperature φ( T ) is calculated. Function φ( T ) characterizes the statistical properties of the multiphase medium of arbitrarily spaced three-dimensional structure of arbitrary (small or large) temperature perturbations. We construct our theory under the isobarical condition ( P  = constant over space), which is satisfied in the short-wavelength limit of the perturbations. The developed theory is illustrated for the case of the thermal instability of a slowly expanding interstellar cloud (smooth scenario). Numerical solutions of equations of the statistical theory are constructed and compared with hydrodynamical solutions. The results of both approaches are identical in the short-wavelength range when the isobarity condition is satisfied. Also the limits of applicability of the statistical theory are estimated. The possible evolution of the initial spectrum of perturbations is discussed. The proposed theory and numerical models can be relevant to the formation of the two-phase medium in the ∼ 1 pc region around quasars. Then small warm ( T  ≃ 10⁴  K ) clouds are formed as the result of thermal instability in an expanded gas fragment, which is a product of either star–star or star–accretion disc collision.     

The ocean floor morphostructure of the Bay of Bengal (Indian Ocean) and the problem of its origin

This study is based on the geological and geophysical data obtained in the Bay of Bengal and adjacent part of the Mid-Indian Ocean Basin by different Russian scientific and industrial institutions in the 1980s and 1990s. The results of the more recent foreign investigations are also involved. The analysis of the collected data provided a new insight into the geological structure and evolution of the region indicating that a large dry-land area—the Bengal elevation—existed in the Cretaceous at the location of the present-day Bay of Bengal. During the Cretaceous, the geological evolution of this area was controlled by epicontinental sedimentation and active volcanism. In the Late Cretaceous, progressive submersion with the inception of the Central Basin took place in the region. The subsidence of the basement was accompanied by active differentiated tectonic movements in the southern part of the Bay of Bengal. As a result, the basement experienced fragmentation into blocks with the formation of horst and graben structures. The horst relics eventually submerged to the current depths in the Late Miocene–Pliocene. The maximal amplitude of basement submersion within the bay is more than 11 km.     

Asymmetry in the form of solar spots

We have analyzed the geometric characteristics of sunspots. The form of sunspots has been studied by sunspot image normalization to obtain the average profile of spots and the profile relative to the position of cores. The deviation of the sunspot form from the axisymmetric configuration has been studied. We have found that the spots of leading and trailing polarities have a drop shape. The cores of leading and trailing sunspots are shifted toward the western and eastern edges of the photosphere–penumbra boundary, respectively. The strength of the magnetic field of the cores of leading spots in the eastern hemisphere exceeds the field strength in the western hemisphere. We considered the tilt of the form of sunspots as a function of size. The form of spots of a large area (S > 1000 ppm of solar hemisphere) is elongated along the magnetic axis of the bipole of a group of sunspots.     

A New Model of the Ninety East Ridge Formation,Indian Ocean

Izvestiya, Atmospheric and Oceanic Physics - The comprehensive analysis of geological, geophysical, and geochemical data makes it possible to obtain the most complete picture of the geological...     

Non-pulsed Emission from the Binary System B1259-63

PSR B1259-63 is the only known binary system with a radio pulsar from which the non-pulsed radio and X-ray emission was detected. The companion star in this system is a Be star SS 2883. A rapidly rotating radio pulsar is expected to produce a wind of relativistic particles. Be stars are known to produce highly asymmetric mass loss. Due to the interaction of the pulsar wind and the Be star wind the system of two shocks between the pulsar and the Be star forms. In this paper we show that the observed non-pulsed radio emission from the system is a result of the synchrotron emission of the relativistic particles in the outflow beyond the shock wave and that the non-pulsed X-ray emission is due to the inverse Compton scattering of the Be star photons on this particles. This revised version was published online in July 2006 with corrections to the Cover Date.