Cosmic Ray research in Armenia

Cosmic Ray research on Mt. Aragats began in 1934 with the measurements of East-West anisotropy by the group from Leningrad Physical-Technical Institute and Norair Kocharian from Yerevan State University. Stimulated by the results of their experiments, in 1942 Artem and Abraham Alikhanian brothers organized a scientific expedition to Aragats. Since that time physicists were studying Cosmic Ray fluxes on Mt. Aragats with various particle detectors: mass spectrometers, calorimeters, transition radiation detectors, and huge particle detector arrays registering protons and nuclei accelerated in most violent explosions in Galaxy. Latest activities at Mt. Aragats include Space Weather research with networks of particle detectors located in Armenia and abroad, and detectors of Space Education center in Yerevan.     

Mechanisms of Cosmic Ray Generation

Physics of Atomic Nuclei - The origin of cosmic rays (CR) stays an open-ended question for over a hundred years. However, during the past decade, a wide range of new experimental data and...     

Non-Classical Diffusion of the Cosmic Rays in the Galaxy: Retrieval of Primary Nuclei Spectra in Sources

Physics of Atomic Nuclei - This study investigates the use of results from new-generation balloon-borne and satellite instruments and earthbound observatories for quantifying primary nuclei spectra...     

Variations of Cosmic Ray Muons during Thunderstorms

Journal of Experimental and Theoretical Physics - This article briefly reviews the results of an experiment initiated by A.E. Chudakov. The first results were obtained in pioneering works under his...     

Recent Results in Cosmic Ray Physics and Their Interpretation

The last decade has been dense with new developments in the search for the sources of Galactic cosmic rays. Some of these developments have confirmed the tight connection between cosmic rays and supernovae in our Galaxy, through the detection of gamma rays and the observation of thin non-thermal X-ray rims in supernova remnants. Some others, such as the detection of features in the spectra of some chemicals, opened new questions on the propagation of cosmic rays in the Galaxy and on details of the acceleration process. Here, I will summarize some of these developments and their implications for our understanding of the origin of cosmic rays. I will also discuss some new avenues that are being pursued in testing the supernova origin of Galactic cosmic rays.     

Cosmic Ray Nuclei: Results from AMS-02

Physics of Atomic Nuclei - AMS is a multi-purpose high-energy particle detector designed to perform high precision direct cosmic ray measurements onboard of the International Space Station. AMS can...     

Electromagnetic Interactions of High Energy Cosmic Ray Muons

This paper investigates the electromagnetic interactions of muons. The various processes such as knock-on electron-, bremsstrahlung-, direct electron pair production, and nuclear interactions are described in detail. The energy range concerned extends from 10⁹ eV up to 10¹⁵ eV for primary muons and from 10⁸ eV up to 10¹⁴ eV for energy transfers to the secondaries. On the one hand the measurement of muon interactions represents a test of quantum electrodynamics. On the other hand the high energies available in cosmic rays would possibly lead to the measurement of new processes or the detection of new particles. One hopes to find in the high energy domain the answer to the question why the muon exists at all and if there are properties (apart from differences in mass, lifetime, and lepton number) which distinguish it from a mere heavy electron. The different experimental techniques are described and the various experimental results on muon interactions are presented and compared with relevant QED-theories. Observed deviations between theory and experiment and anomalies in muon interactions are critically investigated and discussed in the light of experimental difficulties and interpretation problems. In general, agreement between theory and experiment is found, i.e. QED-theories describe the results adequately. However, some experiments claim to have detected anomalies in muon physics in the cosmic ray beam. But the hypotheses on new processes and new particles in the high energy range do not withstand a critical analysis. It is concluded that the observed deviations can be understood in the framework of conventional theories.     

Gamma Ray Astronomy and the Origin of Cosmic Rays

The classical production processes for high energy gamma radiation in the interstellar medium are discussed and confronted with recent satellite observations. It is shown that gamma ray data in their present form do not provide definite conclusions on the origin of cosmic rays. Some current ideas on the nature of gamma ray point sources are presented.     

EAS Phenomenology and Cosmic Ray Spectrum Ground Based Measurements

Primary cosmic ray energy spectrum around and above 1 PeV is of great interest due to its non-power-law behavior (“knee”) in PeV region found many years ago using the indirect EAS (Extensive Air Shower) method. The method is based on secondary particles measuring on Earth’s surface under a thick atmosphere. Traditionally, people use detectors sensitive to ionization produced mostly by secondary electromagnetic component and therefore any found changes in EAS size spectrum correspond to secondary components, which have to be recalculated to primary spectrum. Recently some new “knees” were claimed by high altitude experiments: at ∼45 TeV for all-particle spectrum (HAWC), for primary protons and helium: at ∼400 TeV (Tibet ASγ) and at ∼700 TeV (ARGO-YBJ) thus widening the “knee” region from ∼0.045 to 5 PeV. The natural explanation of such a strange spectrum behavior in a wide energy range could be found in the EAS phenomenological approach to the knee problem.

     

Cosmic Ray Electrons and Protons,and Their Antiparticles

Cosmic rays are a sample of solar, galactic, and extragalactic matter. Their origin, acceleration mechanisms, and subsequent propagation toward Earth have intrigued scientists since their discovery. These issues can be studied via analysis of the energy spectra and composition of cosmic rays. Protons are the most abundant component of the cosmic radiation, and many experiments have been dedicated to the accurate measurement of their spectra. Complementary information is provided by electrons, which comprise about 1 % of the cosmic radiation. Because of their low mass, electrons experience severe energy losses through synchrotron emission in the galactic magnetic field and inverse Compton scattering of radiation fields. Electrons therefore provide information on the local galactic environment that is not accessible from the study of the cosmic ray nuclei. Antiparticles, namely antiprotons and positrons, are produced in the interaction between cosmic ray nuclei and the interstellar matter. They are therefore intimately linked to the propagation mechanisms of the parent nuclei. Novel sources of primary cosmic ray antiparticles of either astrophysical (e.g., positrons from pulsars) or exotic origin (e.g., annihilation of dark matter particles) may exist. The nature of dark matter is one of the most prominent open questions in science today. An observation of positrons from pulsars would open a new observation window on these sources. Several experiments equipped with state-of-the art detector systems have recently presented results on the energy spectra of electrons, protons, and their antiparticles with a significant improvement in statistics and better control of systematics. The status of the field will be reviewed, with a focus on these recent scientific results.     

Diagnostics for Electromagnetic Conditions in the Heliosphere by Cosmic Ray Effects

Physics of Atomic Nuclei - We review some results of diagnostics for the electromagnetic characteristics of the heliosphere and of the Earth magnetosphere within the model for cosmic ray modulation...     

Measurements of Cosmic Ray Muon Distributions with IceTop and IceCube

Physics of Atomic Nuclei - The IceTop detector is the surface component of the IceCube Observatory: an array of 81 ‘‘stations’’ of two frozen water tanks. Each tank contains...     

Simulation of the Galactic Cosmic Ray Shadow of the Sun

The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center of the Sun shadow is shifted from its nominal position due to the presence of magnetic fields in interplanetary space,and this shift is used indirectly as a probe to study the solar magnetic field that is difficult to measure otherwise.A detailed Monte Carlo simulation of galactic cosmic-ray propagation in the Earth–Sun system is carried out to disentangle the cumulative effects of solar, interplanetary and geomagnetic fields. The shadowing effects and the displacements results of the Sun shadow in different solar activities are reproduced and discussed.     

Global Characteristics of the Medium Produced in Ultra-High Energy Cosmic Ray Collisions

Physics of Atomic Nuclei - Estimations of some geometrical and bulk parameters are presented for the matter produced in various type collisions with ultra-high energy cosmic ray (UHECR) particles....     

Anomaly in the Spectrum of Galactic Cosmic Ray Nuclei in Olivine Crystals from Meteorites

Physics of Atomic Nuclei - An anomaly in the spectra of galactic cosmic ray nuclei in olivine crystals from meteorites that arises in the charge spectra upon studying crystals situated near the...     

Cosmic Ray Spectrum and Composition from Three Years of IceTop and IceCube

Physics of Atomic Nuclei - The IceCube Observatory includes both a deep in-ice array of 86 strings of sensors, and a surface array of 81 stations of frozen water tank detectors (IceTop). These...     

Supernova Remnants as Sources of Cosmic Rays and Nonthermal Emission

Physics of Atomic Nuclei - Cosmic ray acceleration by astrophysical shocks in supernova remnants is briefly reviewed. Results of numerical modeling taking into account magnetic field amplification...     

X射线激光器——新兴的短波长相干光源

Ｘ射线激光器是运行在电磁辐射波谱中Ｘ射线波段的短波长相干光源，通常，Ｘ射线激光器都采用高功率激光器作为泵浦源，强激光与靶相互使用形成的高温等离子体作为工作介质，并采用单程（或双程）行波放大的运行方式，近１０年来，Ｘ射线激光器的研制工作取得了重大进展，并开始了Ｘ射线激光应用的初步研究，现在正朝着提供高亮度，有较好相干性并且价格便宜的小型短波长Ｘ光光源的目标努力。