Pantea Davoudifar - Profile on Academia.edu (original) (raw)

Papers by Pantea Davoudifar

ICRC, 2011

Time delays of Cosmic Rays (CRs) have been the subject of many researches in different fields. Co... more Time delays of Cosmic Rays (CRs) have been the subject of many researches in different fields. Cosmic rays with the highest energies propagate in their paths with small deflections relative to the straight line propagation of light. The supposed structure of magnetic fields: galactic, intergalactic and the large scale cluster magnetic fields, has an important role on the deflection angles and the time delays of the highest energy particles. In the present work using a simulation based on Auger events and suggestions about magnetic fields, discuss about the range of deflection angles and the resulted time delays which is important on identifying the origin of CR particles.

Development of a Galactic Magnetic Field Model and its application in identifying sources of Ultra-High-Energy Cosmic Rays in Northern Sky

Journal of physics, Sep 21, 2015

New physical conditions were applied to our previous Galactic Magnetic Field model. The relative ... more New physical conditions were applied to our previous Galactic Magnetic Field model. The relative motion of a Galactic source were also considered. We simulated the propagation of Ultra-High-Energy particles under the influence of Galactic Magnetic Field. In this research the particles were originated from millisecond pulsars located in the northern sky. Considering the relative motion of Galactic sources for a proper time interval, sample test images of millisecond pulsars were produced using cosmic rays of energies ranged in 1018 – 1019, 1019 – 1020, and 1020 – 1021 eV. The results were compared with our previous ones. For each part of the sky considering the structure of Galactic Magnetic Field, the source location and its relative motion to the observer, one may use these images as a guide to find possible sources of the Ultra-High-Energy Cosmic Ray' events. Consequently, a possible method of identifying the sources of these particles were introduced. Some physical limits were discussed.

Modeling the Galactic Magnetic Field and its Application in verifying a Pulsar Origin of Very High Energy Cosmic Rays

Journal of physics, Mar 11, 2014

ABSTRACT Deflection of Cosmic Ray charged particles under the influence of magnetic fields (Galac... more ABSTRACT Deflection of Cosmic Ray charged particles under the influence of magnetic fields (Galactic and Extragalactic) causes a nearly isotropic distribution of their observed fluxes especially in lower energy ranges. Anyhow, as very high energy cosmic rays experience less deflections in their paths, they may point out the direction of their sources within a few degrees. We used a Galactic magnetic field model to study the possible Galactic sources of these cosmic rays. The propagation of cosmic rays in this Galactic magnetic field is simulated to estimate average deflection angles into their straight-line paths from their sources. Pulsars with suitable characteristics are selected and deflection regions around them are defined. Compared with the observational data (i.e. detected directions of observed CRs), the possibility of a Galactic origin of ultra high energy cosmic rays is examined. We defined deflection angles in terms of energies for sources in a distance d into center and anti-center directions. The probability of observing cosmic rays of di?erent energies from the direction of a source in a distance d is studied and the possibility of a pulsar origin of very high energy cosmic rays due to some recent models, is discussed.

Iranian Journal of Physics Research, Dec 15, 2009

Journal of physics, Feb 8, 2013

The maximum development of an Extensive Air Shower (EAS) is an important parameter which is possi... more The maximum development of an Extensive Air Shower (EAS) is an important parameter which is possible to be studied with EAS simulation programs. This parameter is also related to hadronic interaction models in high and low energy ranges. A Detailed study been considered to investigate the effects of zenith angle and interaction models as well as thinning parameters on the maximum development of an EAS and its mean values. Diagrams of Maximum shower development vs. energy being used to recognize the masses of the primary particles initiated those EASs. An empirical formula presented to remove the effects of zenith angle.

The Effect of a Non-Isotropic Flux of Very High Energy Cosmic Rays on the values of Mean Shower Maxima

Journal of physics, Jan 21, 2015

ABSTRACT In our previous works we described a statistical method to interpret the results of exte... more ABSTRACT In our previous works we described a statistical method to interpret the results of extensive air shower simulations. For an isotropically distributed flux of cosmic rays, we used this method to deduce diagrams of mean values of shower maxima versus energy decades. To have a more realistic result, we considered the effect of a non-isotropic flux of cosmic rays at different energy ranges. This effect was considered as a weight factor deduced from a set of observed data. We discussed about the effect of this weight factor on our final resulted diagrams of mean shower maxima and for different interaction models compared the resulted distributions of very high energy cosmic ray's mass composition.

ira-davoudifar-P-abs1-og12-poster For so many years origin of anti protons above the atmosphere h... more ira-davoudifar-P-abs1-og12-poster For so many years origin of anti protons above the atmosphere has been the subject of much research and very discussions, and it was not clear whether anti protons are galactic or extragalactic. In this paper we compare the Leaky Box model and also a model of galactic anti protons with constant grammage (The amount of matter traversed by particles before they escape from the galaxy) with experimental data and because of observed differences we compute the anti protons produced in p-p collisions with a correction on grammage and take an energy dependence for grammage due to Berezhko model of supernova, so our new predicted model of galactic anti protons is comparable with the experimental data. The findings show that taking a correction due to energy dependence of grammage, reflects a galactic origin for anti protons.

IR properties of AGN and SB

Evaluation the effect of energetic particles in solar flares on satellite's life time

Journal of Astrophysics and Astronomy, Mar 1, 2017

In this paper, we used CORSIKA code to understand the characteristics of cosmic ray induced showe... more In this paper, we used CORSIKA code to understand the characteristics of cosmic ray induced showers at extremely high energy as a function of energy, detector distance to shower axis, number, and density of secondary charged particles and the nature particle producing the shower. Based on the standard properties of the atmosphere, lateral and longitudinal development of the shower for photons and electrons has been investigated. Fluorescent light has been collected by the detector for protons, helium, oxygen, silicon, calcium and iron primary cosmic rays in different energies. So we have obtained a number of electrons per unit area, distance to the shower axis, shape function of particles density, percentage of fluorescent light, lateral distribution of energy dissipated in the atmosphere and visual field angle of detector as well as size of the shower image. We have also shown that location of highest percentage of fluorescence light is directly proportional to atomic number of elements. Also we have shown when the distance from shower axis increases and the shape function of particles density decreases severely. At the first stages of development, shower axis distance from detector is high and visual field angle is small; then with shower moving toward the Earth, angle increases. Overall, in higher energies, the fluorescent light method has more efficiency. The paper provides standard calibration lines for high energy showers which can be used to determine the nature of the particles.

Determination of local muon flux using astronomical Charge Coupled Device

Journal of Physics G, Feb 6, 2020

Astronomy Letters, Dec 1, 2014

To study phenomenological properties of extensive air showers initiated by different particles (i... more To study phenomenological properties of extensive air showers initiated by different particles (i.e., γ, p, Fe), CORSIKA simulations were used. We adopted a statistical method to produce diagrams of mean values of depth of shower maxima, X max , versus energy decades. To be compared with other works, this method were applied for Yakutsk array and the resulted diagrams were used to calculate the mass composition of a set of published data from this array. The mass composition of cosmic rays (from 10 17 eV up to the highest energies) in different combinations of QGSJET-II-04, SYBILL 1.6, and SYBILL 2.1 with FLUKA were discussed and upper limits for the observed proton flux were calculated. Due to these results a tendency to light nuclei was proposed and the predicted value of upper limit for the observed proton flux was close to GZK cutoff in a combination of FLUKA and QGSJET-II-04 models.

The Study of Relativistic AGN Jets and Experimental Survey of AGN Properties

Proceedings of Armenian-Iranian Astronomical Workshop (AIAW), Sep 1, 2016

Magnetic Fields at Large Scales and Their Connection with Ultra High Energy Cosmic Rays

journal of sciences islamic republic of iran, 2011

Cosmic Rays (CR) travel at speeds essentially indistinguishable from the speed of light. However ... more 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.

Modeling a Kolmogorov-Type Magnetic Field in the Galaxy and its Effect on an Extragalactic Isotropic Flux of Ultra High Energy Cosmic Rays

Journal of Physics: Conference Series, 2016

A model of turbulent galactic magnetic fields was developed in which, the type of turbulence were... more A model of turbulent galactic magnetic fields was developed in which, the type of turbulence were considered to be Kolmogorov. We tested the effect of this model on an isotropically distributed flux of ultra high energy cosmic ray in the extragalactic space. To do this, a giant Galactic halo (radius of ~ 100Mpc) was considered. Regular and random components of the Galactic Magnetic Fields were considered to have the mean observed relevant values and also satisfy a Kolmogorov field type. The deviation from isotropy then were calculated considering the propagation of ultra high energy protons in such a magnetic field and results were discussed to show how isotropic is the flux of ultra high energy cosmic rays in the extragalactic space. It is seen that considering an isotropic flux of ultra high energy cosmic rays in the intergalactic space for different choices of galactic magnetic field is not consistence with the distribution of observed ultra high energy events.

Thermal instability in the presence of the cosmic ray and ambipolar diffusion

Monthly Notices of the Royal Astronomical Society, Dec 11, 2021

The aim of this study is to investigate the impact of the cosmic ray and the ambipolar diffusion ... more The aim of this study is to investigate the impact of the cosmic ray and the ambipolar diffusion on the thermal instability in a weakly ionized gas. The cosmic ray propagates along the magnetic-field line where the ambipolar diffusion is present. The weakly ionized gas and the cosmic ray are considered as two different interacting fluids. Using the linear perturbation analysis, we consider the occurrence of the thermal instability to obtain a dispersion relation in the presence of both phenomena. This equation describes the stable and unstable modes in the terms of some parameters, which depend on the cosmic ray and the ambipolar diffusion. The results show that the angle between the direction of the perturbation propagation and the magnetic-field lines plays an important role on the domains of stability and instability. Furthermore, we found that there is a characteristic wavelength related to the ambipolar diffusivity that explains whether the ambipolar diffusion increases the magnetic support of the cloud against the collapse, or decreases it against the collapse. Finally, the results address some new points in the study of the structure formation within the clumpy molecular clouds as well as the formation of the low-mass stars in the interstellar medium.

Thermal instability in the presence of the cosmic-ray and ambipolar diffusion

Monthly Notices of the Royal Astronomical Society, 2021

In the present work, after our work about the extragalactic gamma ray flux in direction of Coma s... more In the present work, after our work about the extragalactic gamma ray flux in direction of Coma super-cluster, with considering the Virgo proton flux and considering a constant gamma to proton ratio for the very high energy cosmic rays in first approximation, the extragalactic proton flux in Coma direction is calculated. We have considered the available theoretical models for gamma ray flux from Virgo supper-cluster and compared the result for Coma supper-cluster with KUO et al. model. [3] We have studied that is it possible that the coma super-cluster be an origin for the highest energy protons in cosmic rays flux or not. a detailed analysis has made.