Iranian Journal of Astronomy and Astrophysic
Volume:7 Issue: 2, Autumn 2020

Solar 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.

Radiative transfer in a geometrically thin accretion disc with fnite optical depth is considered under the plane-parallel approximation. The Eddington factorthat is defned as the ratio of the mean intensity to radiation stress tensor, is assumedbe constant. We have focused our attention on the scattering effect and the opticaldepth. The emergent intensity as well as other radiative quantities are analyticallyobtained 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 anisothermal atmosphere is more signifcant than an atmosphere with temperature gradient. Moreover, the emergent intensity is changed by the disc optical depth. We alsoexplore the limb-darkening effect for the both thick and thin optically discs, separately.

At the present work, the reflection of X-rays from surfaces composed ofsilicon, gold, iridium, and nickel is simulated in the range of E ≤ 5 keV energy for thetwo cases, which includes raw mirror surfaces and a typical Wolter-I optics-based X-raytelescope. We used Geant4 and a proper optical extension to use Geant4 as a general purposeX-ray tracing package. The reflectivity of the materials and the efficiency ofthe telescope for the materials have been obtained as a function of energy. Except forsilicon, the efficiencies are close to each other for the materials. Of course, we generallysee a larger value for nickel. Due to the importance of Wolter-I optics in the simulationof the X-ray telescopes and enhancement of the sensitivity of X-ray telescopes by increasingthe reflectivity, the results of the present study have particular use in the manufacturingprocess of an X-ray telescope.

The 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 more

Evaluating 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.

Observatory 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.