COSMIC RAYs (CR) travel at speeds essentially indistinguishable from the speed of light. However whilst travelling through magnetic fields, both regular and turbulent, they are delayed behind the light since they are usually charged particles and their paths are not linear. Those delays can be so long that they are an impediment to correctly identifying sources which may be variable in time. Furthermore deduction of CR sources without knowing CR time delays is not possible, so the magnitude of such delays will be discussed and compared to the characteristic time variation of possible COSMIC RAY sources.

Muon-electron ratio and median zenith angle of Extensive Air Shower (EAS) is calculated for the energy range of 1019 to bigger than 1020 eV. The results are compared with the simulation work of Capdevielle et al. The results show a good correspondence with proton primary composition up to energy level of 7×1019 eV. In higher energies above GZK cut off, a considerable increase is calculated in COSMIC primary photons. In addition, event frequency distribution above energy 7×1019 eV shows increasing concentration towards super galactic plane.

In this research, using CORSIKA simulation code with QGSJETII04 and GHEISHA2002d as high and low energy interaction models respectively, proton and iron COSMIC RAY primaries with 10 17 eV energy and 20-60 o zenith angle are simulated at Tehran observation level (1200m above sea level). By using azimuth angle, arrival time and local coordinates of the muon and electron secondaries as well as rise times of received pulses are calculated. By investigating the rise time as a function of the distance to the Shower Core for different azimuth angle, it is shown that there is an azimuthal asymmetry in the rise time distribution which can be used for mass discrimination of primary COSMIC RAYs.

One of the common methods in the study of COSMIC RAYs induced extensive air shower on the Earth's surface is using an arRAY of scintillation detectors. Dimensions and distances between detectors are among the most important parameters that determine the energy range detectable by the arRAY. Furthermore, the geometry of the arRAY has an important role in determining of optimum distance Ropt, which is defined as the distance from the shower core, where uncertainty in lateral density of secondary particles is minimized. In the present work, dependence of Ropt on arRAY geometry and characteristics of COSMIC RAYs has been studied for the Alborz-1 arRAY. It is shown that the value of ropt is independent on shower characteristics like energy, incident angle and primary mass. On the other hand, according to our results, the ropt value has explicit dependence on arRAY geometry specially distances between detectors. Our investigation shows that the cluster layout is the best layout for the detectable energy range of ALBORZ-1 arRAY (1015 eV). We have found Ropt= 9 ± 1m for the ALBORZ-1 arRAY.

Monte Carlo simulation with CORSIKA code using QGSJET hadronic interaction model is applied on more than 5000 COSMIC RAY primaries to investigate dependence of maximum air shower development (Hmax) on mass and energy of, primaries.

Optimum distance is defined as a distance from the air-shower core in which the density of a number of particles calculated by the lateral distribution function at that distance has the least uncertainty. Furthermore, with a good approximation, this distance is independent of the characteristics of primitive RAY and it only depends on the geometric shape of arRAY. In this paper, by simulating 1000 vertical EAS of protons with the energy 300 TeV, using the CORSIKA Monte Carlo code and trigger condition, the calculated distance for the arRAY triggering ALBORZ-1 was found to be equal to 9± 1 m. Also, it was found that this distance as well as the density of the number of calculated particles was independent of the lateral distribution function used in the calculations.

Energetic secondary particles in gamma and hadron initiated showers can generate Cherenkov photons. Using CORSIKA code and simulation data, different characteristics of lateral distribution of Cherenkov photon density are studied. In particular, physical origin of these differences and also dependence of this distribution on primary energy and altitude of observation level are discussed. It is shown that the existence of a hump in lateral distribution of Cherenkov photon density in gamma initiated showers is a useful tool for separating gamma-hadron and rejecting hadron background in gamma RAY astronomy.

In this paper, using simulation code CRPropa3. 0, the propagation of 104 primary COSMIC RAYs of proton and iron with energy range of 1018 to 1021 eV was simulated. The spectra of the secondary photons and electron-positrons generated in the interactions of ultra-high energy COSMIC RAYs (UHECRs) with COSMIC background photons were investigated. The photon and electron spectra considered here are generated in photopion production, beta decay, and pair production. The minimum energy of primaries and the spectral index of source injection is changed separately and the effect of these changes on the spectra is investigated. Also, the total primary energy percent which transfers to secondaries, is calculated. It is found that for both primaries, lowering the minimum energy of the primaries leads to the decrease of the flux of secondaries. This also results in the decrease of the total energy percent carried by beta and photopion products and the increase of the energy percent of pair production. Finally, in is shown that by increasing the spectral index, the flux and the energy percent of all secondaries decreases for proton and iron primaries.

In this paper, after addressing various future singularities, predicted for Cosmos, an introductory note on Rastall theory is provided. Thereinafter, considering a flat Universe, the Friedmann equations of Rastall theory are derived, and the possibility of obtaining various singularities are studied in two cases. In the first case, the COSMIC fluid is an isotropic and homogenous fluid while the ratio of its pressure and density is constant. In the second case, the mentioned ratio is not always constant and Universe evolves with a specified rate. The study claims that whereas it is not predicted any future singularity for the first model of cosmos, some types of future singularities may be inevitable in the second one.

One of the main factors for satellite design is simulating of total ionizing dose due to space ionizing RAYs in devices used in space. By measurement of induced dose based on available data in different altitudes, expenses of designing, satellite weight and amount of needed fuel will be reduced. Optimum design of satellite for protecting satellite against ionizing radiation has considerable effect on reduction of manufacturing expenses. TID effect should be calculated for each mission separately. The main parameters for starting simulation are perigee and apogee altitudes, inclination, launch date and space environment condition. In this article, the induced dose for missions with equal apogee and perigee points and the most dangerous altitudes for launching satellites have been simulated. To gain this goal, simulations have been performed in different inclinations from 500km to 58000km. by plotting result of all these simulations for launching satellite in minimum solar activity, a dose map has been achieved for different altitudes and inclinations. Absorbed dose in this dose map is sum of absorbed dose of all radiations in space environment. Simulation results illustrate that the maximum dose are related to low inclinations in altitudes between 11000 and 12000. The result of calculated and simulated results have been confirmed and evaluated by ECSS documents. These results have been simulated by using the last version of OMERE radiation package.