Damghan University PressIranian Journal of Astronomy and Astrophysics2322-49247220201001Effect of Latitude of Sunspots on Earth-Intersecting Trajectory of Plasma576518610.22128/ijaa.2020.398.1078ENAlan HobackUniversity of Detroit Mercy0000-0003-4609-9715Journal Article20210405Solar flares and Coronal Mass Ejections form around the edges of sunspots. If the plasma from such events is incident on the Earth’s magnetosphere, significant disruptions to electrical systems can occur. However, sunspots occur around the surface of the Sun and don’t always produce plasma that reaches the Earth. The latitude and longitude of the source of the plasma on the Sun will be evaluated to determine the likelihood that random events will intersect with the Earth. The size of the typical plasma balloon will be found to find its path. Comparing data from locations of sunspots to data of Earth’s orbit will provide a likelihood of incidence based on latitude or origin. The latitudes of sunspot centroids vary significantly through the solar cycle as they tend to migrate from mid-latitudes towards the equator. Sunspots from all latitudes are capable of producing plasma that reaches the Earth. However, as a solar event rotates in longitude away from the Earth, events at higher latitudes are less likely to have a trajectory that intersects the Earth. From analysis, 27% of dangerous events on the Sun should have trajectories towards Earth. The latitude has a small effect on this. It was determined that that the plasma balloon released from the Sun had a large spread of impact. Plasma from all latitudes could reach the Earth. However, if the Sun is rotated away, the combined effects of latitude and longitude can make the plasma trajectory pointed away from Earth.https://ijaa.du.ac.ir/article_186_cf1939c20e29c80cc982926a692a6a28.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49247220201001The Radiative Transfer in Accretion Discs with Linear Plank Function: Role of Scattering Effect677618710.22128/ijaa.2020.429.1091ENFahimeh HabibiDepartment of Physics, University of Birjand,
Birjand, Iran0000-0001-7991-5964Maryam SamadiDepartment of Physics‎, ‎Faculty of Sciences‎, ‎Ferdowsi University of Mashhad‎, ‎Mashhad‎, ‎91775-1436‎, ‎Iran0000-0002-1178-9305Journal Article20210619Radiative transfer in a geometrically thin accretion disc with fnite optical depth is considered under the plane-parallel approximation. The Eddington factor that is defned as the ratio of the mean intensity to radiation stress tensor, is assumed be constant. We have focused our attention on the scattering effect and the optical depth. The emergent intensity as well as other radiative quantities are analytically obtained related to the vertical structure of disc while a linear Planck function is applied. The effect of scattering on the radiative quantities is considered for two cases: (i) isothermal and (ii) temperature gradient and both cases are assumed to be in local thermodynamical equilibrium (LTE), too. Our results show the scattering for an isothermal atmosphere is more signifcant than an atmosphere with temperature gradient. Moreover, the emergent intensity is changed by the disc optical depth. We also explore the limb-darkening effect for the both thick and thin optically discs, separately.https://ijaa.du.ac.ir/article_187_0d47c6a09254f4f1862499a41051cbe5.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49247220201001Simulation of a Simple Wolter Telescope of Type I by Geant4 for Some Widely Used Materials778318810.22128/ijaa.2020.405.1084ENMehdi Abbasian MotlaghFaculty of Physics, Semnan University, Semnan, Iran0000-0002-4315-5665Gohar RastegarzadehFaculty of Physics ,Semnan University, Semnan, IranJournal Article20210420At the present work, the reflection of X-rays from surfaces composed of silicon, gold, iridium, and nickel is simulated in the range of E ≤ 5 keV energy for the two cases, which includes raw mirror surfaces and a typical Wolter-I optics-based X-ray telescope. We used Geant4 and a proper optical extension to use Geant4 as a general purpose X-ray tracing package. The reflectivity of the materials and the efficiency of the telescope for the materials have been obtained as a function of energy. Except for silicon, the efficiencies are close to each other for the materials. Of course, we generally see a larger value for nickel. Due to the importance of Wolter-I optics in the simulation of the X-ray telescopes and enhancement of the sensitivity of X-ray telescopes by increasing the reflectivity, the results of the present study have particular use in the manufacturing process of an X-ray telescope.https://ijaa.du.ac.ir/article_188_b9cf7d7b2612ff190bf67050577936b8.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49247220201001Effects of Relativistic Maxwellian Distribution on the Dust Grain Electrical Potential859718910.22128/ijaa.2020.400.1080ENMasoud TaherimoghadamDepartment of Physics, Mashhad Branch, Islamic Azad University, Mashhad, IranIman MotieDepartment of Physics, Mashhad Branch, Islamic Azad University, Mashhad, IranAli BakhshayeshiDepartment of Physics, Mashhad Branch, Islamic Azad University, Mashhad, IranTaghi MirzayeDepartment of Physics, Mashhad Branch, Islamic Azad University, Mashhad, IranJournal Article20210412The effects of relativistic on the dust charging process and the dust electrical potential are investigated by taking into account the cross section of relativistic by the OLM theory (Orbit Limited Motion) theory, a kinetic model and the relativistic Maxwellian distribution function for currents carried by ions and electrons. The calculations are applied by the numerical analyses to finding the electrical potential of dust grain in the charging process. It is shown that the electrical potential of dust grain is increased in the relativistic regime, and the slope of the transition region to zero is much more severe than the non-relativistic state and also, the possible values for dust density are shifted to the larger amounts. The comparison of the results of the relativistic and nonrelativistic Maxwellian distribution functions shows in the low dust to ion density ratio, only the relativistic Maxwell distribution function can indicate the dust charging process. As another result the increase of the dust density shows the collective behavior, because of the dust grains behavior as a component from conventional multi-ionic plasma. In addition to, it is indicated that the role of mass is more colorful than the ion temperature in the light plasma such as hydrogen versa the heavy plasma such as oxygen in relativistic regime. Moreover, it is showed that, as ions are closer to the ultra-relativistic range, the dust grain electrical potential is increased and the difference between the dust grain electrical potential in oxygen, helium and hydrogen plasmas become more and morehttps://ijaa.du.ac.ir/article_189_895a4a8346f785016fc3e68512e96b4a.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49247220201001Collisional and Radiative Energy Loss in QED and QCD Plasmas9910619010.22128/ijaa.2020.426.1090ENJavad SheibaniPhysics Department, Yazd UniversityAbolfazl MirjaliliPhysics Department, Yazd UniversityKurosh JavidanPhysics Department, School of Science, Ferdowsi University of Mashhad, Mashhad, Iran0000-0002-7596-4280Reza GharaeiPhysics Department, Hakim Sabzevari UniversityShahin Atashbar TehraniSchool of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM),Journal Article20210611Evaluating the energy loss of an electrically (color) charged particle crossing a high-temperature QED (QCD) plasma at its thermal equilibrium is studied. The average energy loss depends on the particle characteristics, plasma parameters, and QED (QCD) coupling constant alpha (alpha s). All processes through which the energy of a particle changes can be categorized into two main mechanisms: elastic collisions and radiation through bremsstrahlung. We have introduced the final results of collisional and radiation energy loss for an electrically charged particle in a QED plasma, as well as a quark in a QCD plasma. The suppression due to radiation is presented using the Landau-Pomeranchuk-Migdal effect. Time evolution of particle distribution functions has been evaluated numerically through the Fokker-Planck equation. We have calculated the drag and diffusion coefficients using the collisional and radiation energy loss definitions. outcomes of different presented relations are different. We have compared differences and similarities in evolution of distribution functions.https://ijaa.du.ac.ir/article_190_ee3090018a2c35441fe0cfd1ddfcf16b.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-49247220201001Study the Effect of Perturbation in the Evolution of the Filamentary Molecular Clouds10711721610.22128/ijaa.2020.449.1102ENMaryam MesgaranSchool of Physics, Damghan University,
Damghan, IranKhodadad KokabiSchool of Physics, Damghan University, Damghan, IranJournal Article20210925Observatory studies indicate that stars are caused by the collapse of dense molecular clouds, and thermal instability can be a factor in creating this collapse. As the formation of stars occurs in molecular clouds, the evolution of molecular clouds is important. In this study, the stability of the magnetized filamentary molecular clouds and their instability growth rate has been investigated. We consider the linear thermal instability of magnetized filament. We showed that the magnetic field makes the filament more stable against thermal instability. Also, increasing the intensity of the magnetic field helps to reduce the growth rate of instability.https://ijaa.du.ac.ir/article_216_adcf961472d134a53b893b73206b86b8.pdf