SS Cygni in outburst and quiescence

EXOSAT has been used to carry out a series of observations of the dwarf nova SS Cygni covering both quiescent and outburst states which provide a detailed picture of its behaviour at X-ray wavelengths. These results provide strong support for a new coronal model for the X-ray emission from non-magnetic white dwarf systems.     

Turbulence, Magnetic Reconnection in Turbulent Fluids and Energetic Particle Acceleration

Turbulence is ubiquitous in astrophysics. It radically changes many astrophysical phenomena, in particular, the propagation and acceleration of cosmic rays. We present the modern understanding of compressible magnetohydrodynamic (MHD) turbulence, in particular its decomposition into Alfvén, slow and fast modes, discuss the density structure of turbulent subsonic and supersonic media, as well as other relevant regimes of astrophysical turbulence. All this information is essential for understanding the energetic particle acceleration that we discuss further in the review. For instance, we show how fast and slow modes accelerate energetic particles through the second order Fermi acceleration, while density fluctuations generate magnetic fields in pre-shock regions enabling the first order Fermi acceleration of high energy cosmic rays. Very importantly, however, the first order Fermi cosmic ray acceleration is also possible in sites of magnetic reconnection. In the presence of turbulence this reconnection gets fast and we present numerical evidence supporting the predictions of the Lazarian and Vishniac (Astrophys. J. 517:700–718, 1999) model of fast reconnection. The efficiency of this process suggests that magnetic reconnection can release substantial amounts of energy in short periods of time. As the particle tracing numerical simulations show that the particles can be efficiently accelerated during the reconnection, we argue that the process of magnetic reconnection may be much more important for particle acceleration than it is currently accepted. In particular, we discuss the acceleration arising from reconnection as a possible origin of the anomalous cosmic rays measured by Voyagers as well as the origin cosmic ray excess in the direction of Heliotail.     

Source and loss processes in the magnetotail

Space Science Reviews -     

Variations of Protons and Doubly Ionized Helium Ions in the Solar Wind

Cosmic Research - We investigated variations on scales of 104–105 km and local spatial inhomogeneities in the density of protons Np, doubly ionized helium ions (α-particles) Nα, and...     

Shear flow energy redistribution stipulated by the internal-gravity wavy structures in the dissipative ionosphere

The linear mechanism of generation, intensification and further nonlinear dynamics of internal gravity waves (IGW) in stably stratified dissipative ionosphere with non-uniform zonal wind (shear flow) is studied. In case of the shear flows the operators of linear problem are non-selfadjoint, and the corresponding Eigen functions – nonorthogonal. Thus, canonical – modal approach is of less use studying such motions. Non-modal mathematical analysis becomes more adequate for such problems. On the basis of non-modal approach, the equations of dynamics and the energy transfer of IGW disturbances in the ionosphere with a shear flow is obtained. Exact analytical solutions of the linear as well as the nonlinear dynamic equations of the problem are built. The increment of shear instability of IGW is defined. It is revealed that the transient amplification of IGW disturbances due time does not flow exponentially, but in algebraic – power law manner. The effectiveness of the linear amplification mechanism of IGW at interaction with non-uniform zonal wind is analyzed. It is shown that at initial linear stage of evolution IGW effectively temporarily draws energy from the shear flow significantly increasing (by an order of magnitude) own amplitude and energy. With amplitude growth the nonlinear mechanism turns on and the process ends with self-organization of nonlinear solitary, strongly localized IGW vortex structures (the monopole vortex, the transverse vortex chain or the longitudinal vortex street). Accumulation of these vortices in the ionospheric medium can create the strongly turbulent state.     

Gamma-ray detector on board lunar mission Chang’E-1

Gamma-ray spectrometer (GRS) is included in the payload of Chinese first lunar mission Chang’E-1 that will be launched in 2007. Specific objectives of the GRS are to map abundance of O, Si, Fe, Ti, U, Th, K, and perhaps, Mg, Al, and Ca to depths of about 20 cm. There are remarkable advantages for GRS application to remote sensing elemental materials over the entire lunar surface: large effective area and good ability for background rejection. We will describe the design of GRS and present its performance in this paper. Moreover, the GRS calibration will also be introduced.     

Conjecture on superrotation in planetary atmospheres: A diffusion model with mixing length theory

Superrotation on Venus is discussed in the context of comparative planetary atmospheres. In our planetary system, the rigid shell component (global average) of superrotation is ubiquitous (Jupiter, Saturn, Earth, Venus, Mars, Titan). The largest equatorial values of the component are between 25 and 150 m/sec. We present a simplified, heuristic analysis, utilizing mixing length theory to describe the small scale non-linear advections of energy and angular momentum, thereby providing a closure of the dynamic system. This leads to the conjecture that the zonal velocity may be crudely estimated by

, approximating the observed planetary trends; with c the speed of sound, the parameter a being 1 or 2 for geostrophic or cyclostrophic conditions respectively, P_α an effective Prandtl number which becomes less than one when radiative cooling is important, S_o the average stability, Γ the adiabatic lapse rate and γ the ratio of specific heats.     

Evaluation of the contribution of different types of galaxies to the cosmic diffuse background based on γ-ray observations

The relative contribution to the γ-ray background of different types of sources, namely Seyfert Galaxies, Quasars, BL Lac objects, radio galaxies and field galaxies is estimated under the hypothesis that the cosmic diffuse flux is the result of a superposition of many unresolved galaxies. The γ-ray data indicate that the Seyfert volume emissivity matches that of the diffuse background at few hundred keV and exceeds it at higher energies by as much as a factor of about 4. Whilst normal galaxies contribute less than 0.1%, BL Lac objects, Quasars and Radio Galaxies may contribute as much as 5–10% each, even without significant evolution. In this paper we explore different ways of reconciling the observational data on active galaxies with the measured diffuse background level.     

Study of microaccelerations onboard the <Emphasis Type="Italic">International Space Station</Emphasis> with the DAKON-M convection sensor

The results of experiments with the DAKON-M convection sensor onboard the Russian orbital segment of the International Space Station are described. A comparison of the sensor measurements with the results of calculation of the quasistatic microacceleration component at the point of installation is made. For this comparison we have used three measurement intervals of the experiments in 2009, during which spacecraft were docked with the station, undocked from it, and actuation of jet engines of the attitude control system took place. When calculating microacceleration, we use the measurement data of the low-frequency MAMS accelerometer, installed on the American segment, and the telemetry data on the ISS rotational motion. This information allowed one to convert the MAMS measurements to the point of installation of the DAKON-M convection sensor. A comparison of sensor measurements with calculated microaccelerations showed sufficiently accurate coincidence between the calculated and measured data.