Radio emission of a pulsed cosmic source of X-rays with 1-keV energy

The generation of electromagnetic signals due to the interaction of a cosmic X-ray with the Earth's atmosphere is considered. The amplitude and frequency of the radio signal are calculated, and the possibility of its detection at the Earth's surface is shown.     

Reprise: partial chemical strain dislocations and their role in pinning dislocations to their atmospheres

A correct solution for a dislocation atmosphere is provided using Hirth's Standard Model, confirming the errors in Hirth and Lothe. Contrary to what is given there, concentration changes in Cottrell atmospheres reduce an edge dislocation's stress and its elastic energy, thereby reducing the magnitude of the concentration changes. The chemical and elastic strain fields from Cottrell atmospheres are again shown to behave as partial dislocations with variable Burgers vectors that are not crystal translation vectors. The reality of partial dislocations provides a simpler explanation for pinning of dislocations by atmospheres. Much of the literature on dislocation properties in solid solutions should be re-examined.     

Study of the turbulence and inner waves in the stratosphere based on the observations of stellar scintillations from space: A model of scintillation spectra

Abstract

Stellar scintillations observed from space through the atmosphere show that density inhomogeneities in the stratosphere are stretched along the Earth's surface. This is true for vertical scales above dozens of metres. The observations reveal the existence of locally isotropic small-scale structure with fluctuation sizes up to fractions of a metre. The subject of this paper is to find out how the rotation of inhomogeneities with respect to the passing ray affects scintillations. Another subject of this study is chromatic aberration in the atmosphere which distorts the scintillation spectra. Numerical modelling within the weak-fluctuation approximation showed that the characteristic value of the anisotropy parameter is equal to the square root of the Earth's radius divided by the atmospheric scale. After the anisotropy exceeds this value, the growth of scintillation variance quickly becomes saturated. Chromatic aberration suppresses the high-frequency branch of the scintillation spectrum. However, information on the structure of isotropic fluctuations with scales up to the Fresnel radius is retained in scintillation spectra for oblique occultations. The model of composing blocks is suggested to develop the approximation for a three-dimensional fluctuation spectrum in the stratosphere. Parameters of these blocks can be determined from the set of measured scintillation spectra.     

On hydrodynamic instability of the ozone layer

We show that instability may be arisen when the large-scale waves propagate in the ozone layer of Earth's atmosphere. The instability criterion suitable both for the acoustic waves and for the Rossby waves is found. Moreover, the possibility of the spatially located dissipative Rossby vortical structures formation in this layer is established.     

Communicating science

In this article we discuss the structure and dynamics of the Earth's plasma environment and how it is influenced by its interaction with the outer atmosphere of the Sun, as revealed by both space-based and ground-based observations over the past thirty years. We begin with a discussion of the basic physical principles involved, and then apply these principles to the solar wind and interplanetary magnetic field (IMF), and their interaction with the Earth's magnetic field. The structure and flow of magnetospheric plasma populations then follows, together with consequent magnetosphere-ionosphere interactions. The initial discussion applies to a steady-state magnetosphere driven by steady reconnection, which we then generalized to the time-dependent case resulting from variations in the direction of the IMF.     

Analysis of the charged particle radiation effect for a CubeSat transiting from Earth to Mars

This paper presents a computational estimation of the total ionizing dose from protons and electrons in the Earth's magnetosphere and interplanetary space for a hypothetical CubeSat transiting from Earth to Mars. An initial hyperbolic escape of the spacecraft from Earth's gravitation is assumed, followed by an elliptical transfer from Earth to Mars under the Sun's gravitation. The rapid traversal of the Earth's radiation belt yields a smaller ionizing dose, whereas high-energy solar protons in the interplanetary space have the greatest effect on the ionizing dose during the transfer between the planets. Variation in the heliocentric distance of the spacecraft is considered in the calculation. Calculation of the shielding distributions with Geant4 and the transport of the ionizing particles across the obtained distributions yields an estimation of the total ionizing dose as a function of position within the spacecraft as well as statistical confidence levels. With a moderate confidence level, this calculation shows that a practical exploration of Mars with a CubeSat is possible in terms of the expected total ionizing dose.     

Thermal conductivity: Recent developments

The detailed spectral energy distribution of the radiation emitted by stars provides information on their composition and physical parameters. Many of the astpophysically important spectral lines of neutral and ionized atoms whose study can lead to a better understanding of the processes occurring in stellar atmosphere and in the interstellar gas lie in the ultraviolet region of the spectrum.

Since ultraviolet radiation from the stars is absorbed by the Earth's atmosphere, observations must be made from space vehicles. In this article some scientific objectives of a programme in ultraviolet astronomy are considered, and a review made of the types of space vehicles and attitude control systems employed. A brief discussion is made of some recent results and their interpretation.     

Particle size analysis

Remote sensing is the popular name for the measurement of physical quantities at a distance, usually by quantitative spectroscopic methods. Its application to the study of the Earth's atmosphere and surface from satellites is a rapidly growing field, with many applications, and new or improved techniques are constantly being developed. In this article we look at some of the basic principles and technical challenges involved, and at the benefits which are accruing in a number of research areas in earth science, with particular emphasis on the use of remote sensing to understand global change.     

Geomagnetism and the dynamo: where do we stand?

We review recent developments both in the observation of the Earth's magnetic field (from the short, human life timescale, to the long, geological timescale) and in the modelling of its origin (using the numerical or the experimental approach). We attempt a confrontation of these results, coming from very different fields, and show how, when combined, they can yield a better understanding of the Earth's core dynamics. We assume prior knowledge of dynamo theory, but not of geophysics. To cite this article: E. Dormy, J.-L. Le Mouël, C. R. Physique 9 (2008).     

Accurate rotational constants of CO,HCl, and HF: Spectral standards for the 0.3- to 6-THz (10- to 200-cm−1) region

Accurate high-resolution spectroscopic measurements require secondary standards which can serve as convenient calibration references in laboratory and field research. We have measured the frequencies of a series of rotational transitions between 0.3 and 6 THz for several stable and readily obtainable gases (CO, HCl, and HF) to an accuracy better than one part in 10⁷ and present revised rotational constants for these molecules. The gases were selected (in part) due to their presence in the Earth's atmosphere in significant amounts and thus are convenient for the frequency calibration of atmospheric spectra.     

Physics and technology of sustainable energy

There falls on the Earth's atmosphere a rain of particles and photons the high energy part of which is termed the Cosmic Radiation. This article is concerned specifically with primary particles of the highest known energies, i.e. 10¹⁷-10²⁰eV and deals with the evidence for their existence, their nature and their origin.

Such particles are very rare but because they produce many millions of secondaries in the atmosphere they can be readily detected by large counter arrays at ground level. Some of the principal arrays in the world will be described including the giant array at Haverah Park, near Harrogate, England. The latest results on the energy spectrum and the incident directions of the primaries will be given and their astronomical significance critically assessed.

Finally, an account will be given of a novel array which promises to make a substantial contribution to our knowledge of primaries of energies even above 10²⁰ eV.     

Unveiling the secrets of gamma ray bursts

Gamma Ray Bursts are unpredictable and brief flashes of gamma rays that occur about once a day in random locations in the sky. Since gamma rays do not penetrate the Earth's atmosphere, they are detected by satellites, which automatically trigger ground-based telescopes for follow-up observations at longer wavelengths. In this introduction to Gamma Ray Bursts we review how building a multi-wavelength picture of these events has revealed that they are the most energetic explosions since the Big Bang and are connected with stellar deaths in other galaxies. However, in spite of exceptional observational and theoretical progress in the last 15 years, recent observations raise many questions which challenge our understanding of these elusive phenomena. Gamma Ray Bursts therefore remain one of the hottest topics in modern astrophysics.     

GRANADA: A Generic RAdiative traNsfer AnD non-LTE population algorithm

We present in this paper the Generic RAdiative traNsfer AnD non-LTE population Algorithm (GRANADA). This model is able to compute non-LTE populations for vibrational, rotational, spin (i.e., NO and OH), and electronic (i.e., O₂) states in a given planetary atmosphere. The model is very flexible and can be used for computing very accurate non-LTE populations or for calculating reasonably accurate but at high speed non-LTE populations in order to implement it into non-LTE remote sensing retrievals. We describe the model in detail and present an update of the non-LTE collisional processes and their rate coefficients for the most important molecules in Earth's atmosphere. In addition, we have applied the model to the most important atmospheric infrared emitters including 13 species (H₂O, CO₂, O₃, N₂O, CO, CH₄, O₂, NO, NO₂, HNO₃, OH, N₂, and HCN) and 460 excited vibrational or electronic energy levels. Non-LTE populations for all these energy levels have been calculated for 48 reference atmospheres expanding from the surface up to 200 km, including seasonal (January, April, July and October), latitudinal (75°S, 45°S, 10°S, 10°N, 45°N, 75°N) and diurnal (day and night) coverages. The effects of the most recent updates of the non-LTE collisional parameters on the non-LTE populations are briefly described. This climatology is available online to the community and it can be used for estimating non-LTE effects at specific conditions and for testing and validation studies.     

VUV photochemistry simulation of planetary upper atmosphere using synchrotron radiation

The coupling of a gas reactor, named APSIS, with a vacuum‐ultraviolet (VUV) beamline at the SOLEIL synchrotron radiation facility, for a photochemistry study of gas mixtures, is reported. The reactor may be irradiated windowless with gas pressures up to hundreds of millibar, and thus allows the effect of energetic photons below 100 nm wavelength to be studied on possibly dense media. This set‐up is perfectly suited to atmospheric photochemistry investigations, as illustrated by a preliminary report of a simulation of the upper atmospheric photochemistry of Titan, the largest satellite of Saturn. Titan's atmosphere is mainly composed of molecular nitrogen and methane. Solar VUV irradiation with wavelengths no longer than 100 nm on the top of the atmosphere enables the dissociation and ionization of nitrogen, involving a nitrogen chemistry specific to nitrogen‐rich upper atmospheres.     

Pressure dependence of melting temperature and shear modulus of hcp-iron

The pressure effects on melting temperature and shear modulus of hcp-iron have been studied based on the semi-empirical approach in the Debye model. The recent well-established pressure-dependent Grüneisen parameter has been applied to derive the analytical expressions of the Debye frequency, the Debye temperature, melting temperature and shear modulus which are of importance to geophysical implications. Numerical calculations have been performed for hcp-iron as functions of pressure up to the pressure of Earth's inner core. Our calculations are compared with those of previous experimental and theoretical data showing the good and reasonable agreements. The present results contribute to the database of high pressure melting, especially Earth's inner core boundary temperature, and could also be used to verify as well as analyze the future high pressure diamond-anvil cell experiments.     

Crucial role of the magnetic field in the evolution of life

The formation of a steady ozone layer in the earth’s atmosphere is the most significant event in the evolutionary cycle of the earth which, in turn, has been responsible for the development of life with an oxygen metabolism. In addition to protecting biological life from exposure to ultraviolet radiation the ozone layer has also been responsible for maintaining the water and oxygen balance in the atmosphere. It is argued that the magnetic field of the earth is really responsible for the formation of this steady ozone layer in the earth’s atmosphere. Because of the earth’s magnetic field and associated trapped charge particle belts and the magnetosphere, the earth’s atmosphere does not directly interact with the interplanetary space. Without such a shielding, the free oxygen atoms could have been depleted considerably causing a severe depletion in the ozone concentration to start with. The impact of charged particles from galactic and solar cosmic rays over the entire earth’s atmosphere and the consequent production of NO _x would have given rise to a major ozone sink, if earth were devoid of a magnetic field. The net result would have been the absence of a steady ozone layer and the absence of life with an oxygen metabolism, as in the case of the atmospheres of Venus and Mars, if the earth did not have a magnetic field.     

Effects of different annealing atmospheres on the surface and microstructural properties of ZnO thin films grown on p-Si (1 0 0) substrates

Effects of different annealing atmospheres on the surface and microstructural properties of ZnO thin films grown on Si (1 0 0) substrates were investigated. X-ray diffraction results showed that the crystallinity of the ZnO thin film annealed in an oxygen atmosphere was better than that annealed in a nitrogen atmosphere. Atomic force microscopy and transmission electron microscopy (TEM) images showed that the surfaces of the ZnO thin films annealed in a nitrogen atmosphere became very rough in contrast to those annealed in an oxygen atmosphere. High-resolution TEM images showed that many stacking faults and tilted grains could be observed in the ZnO thin films annealed in a nitrogen atmosphere in contrast to those annealed in an oxygen atmosphere. Surface morphology and microstructural property variations due to different annealing atmospheres in ZnO thin films are also described on the basis of the experimental results.     

Modified KdV equation for magnetized Rossby waves in a zonal flow of the ionospheric E-layer

Nonlinear interaction of magnetized Rossby waves with sheared zonal flow in the Earth's ionospheric E-layer is investigated. It is shown that in case of weak nonlinearity 2D Charney vorticity equation can be reduced to the one-dimensional modified KdV equation.