Analysis of the resonance and ways of its elimination at the descent of spacecrafts in the rarefied atmosphere

In this paper uncontrolled motions of blunt-shaped spacecrafts of small elongation descended in the rarefied atmosphere is considered. Such spacecrafts can have three balancing position of a spatial angle of attack. It can result in a resonance at change of a dynamic pressure at the descend. It is shown, that numerical integration of equations of perturbed motion does not allow to receive authentic results because of stochastic character of transients. Procedure of calculation of the upper and lower estimates of parameters of motion with use of received averaged equations and a stability criteria is developed. Efficiency of this procedure is shown on an example of hypothetical spacecraft descent. The analysis of ways of the resonance elimination is executed. In result, analytical formulas for the initial angular velocity of the spacecraft and for spacecraft's geometrical parameters are obtained.     

Vertical plasma transport in the ionosphere over Irkutsk during St. Patrick’s Day geomagnetic storm: Observations and modeling

The St. Patrick’s Day storm being the strongest geomagnetic storm of Solar Cycle 24 caused strong changes in ionospheric and thermospheric dynamics. The paper presents a study of vertical plasma transport in the ionosphere during the St. Patrick’s Day storm with using both observations and modeling. The observations give the ionospheric peak height obtained with the chirp vertical sounding ionosonde and the neutral wind velocities obtained with the Fabry-Perot interferometer. The ionospheric peak height is an indicator of the total vertical plasma transport, while meridional wind and electromagnetic drift are the two main drivers of the vertical plasma transport. The Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere used in this study gives the total set of ionospheric and thermospheric parameters including F2-layer peak height, neutral wind velocities, electric field, and neutral composition. The model/data comparison allows us to obtain two main results. The first one is an estimation of the model prediction possibilities under storm conditions. The second result is an indirect assessment of the neutral wind and electric field contribution into the changes in the ionospheric peak height in the case of the St. Patrick’s Day geomagnetic storm.     

X-Ray and extreme ultraviolet emissions from comets

There is significant progress in the observations, theory, and understanding of the x-ray and EUV emissions from comets since their discovery in 1996. That discovery was so puzzling because comets appear to be more efficient emitters of x-rays than the Moon by a factor of 80000. The detected emissions are general properties of comets and have been currently detected and analyzed in thirteen comets from five orbiting observatories. The observational studies before 2000 were based on x-ray cameras and low resolution (E/E1.5–3) instruments and focused on the morphology of x-rays, their correlations with gas and dust productions in comets and with the solar x-rays and the solar wind. Even those observations made it possible to choose uniquely charge exchange between the solar wind heavy ions and cometary neutrals as the main excitation process. The recently published spectra are of much better quality and result in the identification of the emissions of the multiply charged ions of O, C, Ne, Mg, and Si which are brought to comets by the solar wind. The observed spectra have been used to study the solar wind composition and its variations. Theoretical analyses of x-ray and EUV photon excitation in comets by charge exchange, scattering of the solar photons by attogram dust particles, energetic electron impact and bremsstrahlung, collisions between cometary and interplanetary dust, and solar x-ray scattering and fluorescence in comets have been made. These analyses confirm charge exchange as the main excitation mechanism, which is responsible for more than 90% of the observed emission, while each of the other processes is limited to a few percent or less. The theory of charge exchange and different methods of calculation for charge exchange are considered. Laboratory studies of charge exchange relevant to the conditions in comets are reviewed. Total and state-selective cross sections of charge exchange measured in the laboratory are tabulated. Simulations of synthetic spectra of charge exchange in comets are discussed. X-ray and EUV emissions from comets are related to different disciplines and fields such as cometary physics, fundamental physics, x-rays spectroscopy, and space physics.     

系统级电磁兼容分析的离散技术及应用综述

介绍了一种系统级电磁兼容(EMC)分析技术—离散非线性分析(Discrete Nonlinear Analysis,DNA)的发展现状,该技术起源于线性离散EMC分析技术,后者是为开发系统内电磁兼容分析程序(IntrasystemElectromagnetic Compatibility Analysis Program,IEMCAP)所提出的方法。DNA技术可应用于以下方面:在极端恶劣电磁环境(EME)中(调制信号数目高达100 000)对无线电发射和接收建模;在一次仿真中需要综合考虑各种效应,包括线性(增益、衰减、滤波等)和非线性(互调、减敏、交调、相互混频、调幅调相转换等)效应以及高阶的非线性响应(25阶或更高);进行快速EMC分析(电磁环境越复杂,非线性效应阶数越高,DNA方法相对于传统方法的计算优势越大;自动搜寻非线性干扰源。     

On ultra-high energy cosmic rays: Origin in AGN jets and transport in expanding universe

The cosmic ray source spectrum produced by AGN (active galactic nucleus) jets is calculated. A distinctive feature of these calculations is the account for the jet distribution on kinetic energy. The expected cosmic ray spectrum at the Earth is determined with the use of a simple numerical code which takes into account interactions of ultra-high energy protons and nuclei with the background radiation in an expanding universe.     

Convective Instability and Appearance of Structured Flows for Diffusion in Multicomponent Gas Mixtures

The main objective of this article is to investigate the behavior of gaseous systems with two and more in- dependent gradients or thermodynamic forces exhibiting complicated behavior, when the convective flows occur. The existence of structural formations in these systems is shown by the schlieren method and the fast-response transducers. The linear analysis of stability can explain reasons of the appearance of convective instability in multi component gas mixtures.     

X-ray and extreme ultraviolet emissions from comets

There is significant progress in the observations, theory, and understanding of the x-ray and EUV emissions from comets since their discovery in 1996. That discovery was so puzzling because comets appear to be more efficient emitters of x-rays than the Moon by a factor of 80 000. The detected emissions are general properties of comets and have been currently detected and analyzed in thirteen comets from five orbiting observatories. The observational studies before 2000 were based on x-ray cameras and low resolution (E/δE ≈ 1.5-3) instruments and focused on the morphology of xrays, their correlations with gas and dust productions in comets and with the solar x-rays and the solar wind. Even those observations made it possible to choose uniquely charge exchange between the solar wind heavy ions and cometary neutrals as the main excitation process. The recently published spectra are of much better quality and result in the identification of the emissions of the multiply charged ions of O, C, Ne, Mg, and Si which are brought to comets by the solar wind. The observed spectra have been used to study the solar wind composition and its variations. Theoretical analyses of x-ray and EUV photon excitation in comets by charge exchange, scattering of the solar photons by attogram dust particles, energetic electron impact and bremsstrahlung, collisions between cometary and interplanetary dust, and solar x-ray scattering and fluorescence in comets have been made. These analyses confirm charge exchange as the main excitation mechanism, which is responsible for more than 90% of the observed emission, while each of the other processes is limited to a few percent or less. The theory of charge exchange and different methods of calculation for charge exchange are considered. Laboratory studies of charge exchange relevant to the conditions in comets are reviewed. Total and state-selective cross sections of charge exchange measured in the laboratory are tabulated. Simulations of synthetic spectra of charge exchange in comets are discussed. X-ray and EUV emissions from comets are related to different disciplines and fields such as cometary physics, fundamental physics, x-rays spectroscopy, and space physics.This revised version was published online in July 2005 with a corrected cover date.     

Cosmic Rays in Galactic and Extragalactic Magnetic Fields

We briefly review sources of cosmic rays, their composition and spectra as well as their propagation in the galactic and extragalactic magnetic fields, both regular and fluctuating. A special attention is paid to the recent results of the X-ray and gamma-ray observations that shed light on the origin of the galactic cosmic rays and the challenging results of Pierre Auger Observatory on the ultra high energy cosmic rays. The perspectives of both high energy astrophysics and cosmic-ray astronomy to identify the sources of ultra high energy cosmic rays, the mechanisms of particle acceleration, to measure the intergalactic radiation fields and to reveal the structure of magnetic fields of very different scales are outlined.