Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.     

Characteristics and performance of thin LaBr3(Ce) crystal for hard X-ray astronomy

We have developed a new detector using thin lanthanum bromide crystal (32 × 3 mm) for use in X-ray astronomy. The instrument was launched in high altitude balloon flight on two different occasions, December 21, 2007, which reached a ceiling altitude of 4.3 mbs and April 25, 2008 reaching a ceiling altitude 2.8 mbs. The observed background counting rate at the ceiling altitude of 4 mbs was ∼4 × 10⁻³ ct cm⁻² s⁻¹ keV⁻¹ sr⁻¹. This paper describes the details of the experiment, the detector characteristics, and the background behaviour at the ceiling altitude.     

Observations of auroral kilometric radio emission on the <Emphasis Type="Italic">Interball-1</Emphasis> satellite in the active Sun period 1999–2000

Results of almost two years (January 1999–October 2000) of continuous observations of auroral kilometric radio emission with the instrument AKR-X onboard the high-apogee satellite of the Earth Interball-1 are presented. The observations were conducted at the growth stage (in 1999) and in the maximum (2000) of solar activity within the 100–1500 kHz frequency band. The results of AKR detection in the vicinity of the maximum of its spectrum at a frequency of 252 kHz are presented. Both similarity (for example, the character of global directivity) and important differences from the AKR emission observed during the solar activity minimum [5] are found. Together with very high sporadicity, strong seasonal changes in the intensity are typical for the emission. It is completely absent in the spring-summer period in the Northern Hemisphere and is strongly suppressed in this period in the Southern Hemisphere. Probable nature of these features of AKR is discussed.     

Kink-like mode of a double gradient instability in a compressible plasma current sheet

A linear MHD instability of the electric current sheet, characterized by a small normal magnetic field component, varying along the sheet, is investigated. The tangential magnetic field component is modeled by a hyperbolic function, describing Harris-like variations of the field across the sheet. For this problem, which is formulated in a 3D domain, the conventional compressible ideal MHD equations are applied. By assuming Fourier harmonics along the electric current, the linearized 3D equations are reduced to 2D ones. A finite difference numerical scheme is applied to examine the time evolution of small initial perturbations of the plasma parameters. This work is an extended numerical study of the so called “double gradient instability”, – a possible candidate for the explanation of flapping oscillations in the magnetotail current sheet, which has been analyzed previously in the framework of a simplified analytical approach for an incompressible plasma. The dispersion curve is obtained for the kink-like mode of the instability. It is shown that this curve demonstrates a quantitative agreement with the previous analytical result. The development of the instability is investigated also for various enhanced values of the normal magnetic field component. It is found that the characteristic values of the growth rate of the instability shows a linear dependence on the square root of the parameter, which scales uniformly the normal component of the magnetic field in the current sheet.     

On the concept of a future carrier-based light fighter

The peculiarities of future light fighter concept generation, reflecting tendencies of fighter aviation development and potentialities of scientific and research background are considered.     

On the uncertainties in the measurement of absolute (true) TEC over Indian equatorial and low latitude sectors

The Indian sector encompasses the equatorial and low latitude regions where the ionosphere is highly dynamic and is characterized by the equatorial ionization anomaly (EIA) resulting in large latitudinal electron density gradients causing errors and uncertainties in the estimation of range delays in satellite based navigation systems. The diurnal and seasonal variations of standard deviations in the TEC data measured during the low sunspot period 2004–2005 at 10 different Indian stations located from equator to the anomaly crest region and beyond are examined and presented. The day-to-day variability in TEC is found to be lowest at the equatorial station and increases with latitude up to the crest region of EIA and decreases beyond.     

Structural regularities of stress-strain state variations in a hardened surface of turbine blade roots at service conditions

Some results obtained in the course of structural investigations with the use of the methods of scanning electron microscopy and X-ray structure analysis of operating temperature influence upon dynamics of the hardened state relaxation in the turbine blade roots are discribed. Also considered are the data on determining the residual surface stresses by Davidenkov’s method and that of the X-ray diffractometry.