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

Papers by Pantea Davoudifar

We announce PHIT as a numerical model for simulating of hadroproduction and compare our results w... more We announce PHIT as a numerical model for simulating of hadroproduction and compare our results with other models and experimental data. Our code, although very simple, imitates the expected results acceptably compared to other more detailed physical models. Moreover, PHIT is fast and easily executable on an ordinary PC. These advantages make PHIT an ideal choice for practical applications of an event generator.

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.

Monthly Notices of the Royal Astronomical Society, 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 mag...

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.

In the present work, with analyzing EGRET data, considering a gamma ray flux for Virgo supper clu... more In the present work, with analyzing EGRET data, considering a gamma ray flux for Virgo supper cluster and a detailed analysis on our postulates, with a new method a gamma ray flux in Coma direction results. First, we have noted some points about Gamma Ray flux in Virgo direction, from other's works. We have used here, A-Model from Wolfendale et al. [3] for calculating Gamma Ray flux in Virgo direction. The flux that we have calculated in Coma direction is considerable. Some analogy between the works has made before, is done. A flux index for Coma direction gamma rays has resulted which is in the favor of our information from Coma super cluster.

The damages and logical failures in different parts of a satellite may occur during a solar event... more The damages and logical failures in different parts of a satellite may occur during a solar event, when a bulk of solar energetic particles approaching the Earth. During solar events, these particles may cause extensive damages which are even permanent (hard errors). A way of damage reduction is designing a proper coating as the fuselage. As protons are the major component of solar particles and because the most of hard errors are caused by neutrons, in this work, we evaluated different shielding material against these type of errors. To avoid hard errors due to neutrons, we need to know solar energetic particles flux. During a solar flare a satellite receives the maximum flux of protons, so we used protons with an energy range of 100 MeV to 1 GeV which is the most sensitive energy range to the Sun activities. In the present work, we have calculated the flux of solar energetic particles which collides a typical satellite in low earth orbit. Using OMERE software, coordinates and spec...

Journal of Physics G: Nuclear and Particle Physics, 2019

Journal of Physics: Conference Series, 2017

Cosmic rays propagation within the Galaxy is simulated considering a fractallike distribution of ... more Cosmic rays propagation within the Galaxy is simulated considering a fractallike distribution of matter and magnetic fields. In such an anomalous diffusion process, the sources of ultra-high energy particles were considered to be galactic pulsars. The coordinate and birth times of sources were chosen from SN and pulsar catalogues. From these sources the primary spectrum of cosmic rays (H, He, CNO, Ne-Si, Fe) in energy range EeV and above were reproduced. The resulted spectrum is used to discuss about the change in cosmic ray sources form Galactic to Extragalactic.

Advances in Space Research, 2017

In General, the flux of low energy cosmic rays varies with time due to solar activities. The cosm... more In General, the flux of low energy cosmic rays varies with time due to solar activities. The cosmic particle fluxes were studied using data of satellites near the Earth. In this work, first we studied the variations of particle fluxes from 1 Jan to 31 Dec 2000 and 35 events were selected. Then we proposed a relation for cosmic particle flux as a function of time and rigidity in the time of approaching ejecta to the Earth. The coefficients of the relation were calculated using experimental data of particle fluxes from ACE satellite. Finally, we compare time variations of these coefficients for different events.

Journal of Astrophysics and Astronomy, 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.

Astrophysics and Space Science, 2017

Due to the high energy interactions of cosmic ray particles, progressive showers of secondary par... more Due to the high energy interactions of cosmic ray particles, progressive showers of secondary particles initiate in the atmosphere. Several models are suggested to describe the longitudinal development of extensive air showers, for example the Heitler model. The Heitler model also is written for hadronic showers. Anyhow, the predicted values of Xmax$X_{max}$ may differ significantly with the values from detailed simulations by up to about 100(g/cm2)$100~(\mbox{g}/\mbox{cm}^{2})$. In the present work, the mean depth of shower maximum is calculated using a variable interaction length. New equations for Xmax$X_{max} $ in the electromagnetic and hadronic showers have been obtained.

Iranian Journal of Science and Technology, Transactions A: Science, 2016

Theoretically, Forbush effect is highly connected to solar activity. Persistent presence of solar... more Theoretically, Forbush effect is highly connected to solar activity. Persistent presence of solar wind, magnetic storms and any types of solar flares with or without coronal mass ejections cause the occurrence of Forbush effect as cosmic ray’s flux. In this work by using some data from OMNIWEB and Izmiran observatory, we explore the relation between Forbush effect, solar wind and local parameters during one of the most massive coronal mass ejections of the century and define a new quantity which is in strong correlation with Forbush effect magnitude.

Advances in Space Research, 2016

Abstract Orbital debris are long-standing threats to space systems. They also contribute to the f... more Abstract Orbital debris are long-standing threats to space systems. They also contribute to the flux of macroscopic particles into the Earth’s atmosphere and eventually affects environmental processes across several other related regions. As impactful space debris may be, debris along with other Low Earth Orbit (LEO) orbiting objects, also serve as valuable long-monitoring probes to deduce the properties of geospace environment in-situ. We define the Daily Decay Rate (DDR) as a suitable indicator of how the Earth’s space–atmosphere interaction region (SAIR) responds to solar activity and how solar activity directly affects the orbital evolution of a LEO orbiter. We present a computationally simplified technique that simultaneously solves the motion equations for DDR and cross‐sectional area to mass ratio ( A / m ) from consecutive TLE records. By evaluating more than 50 million TLE records we estimate A / m of 15,307 NORAD-indexed objects and determine how DDR varies. We observe the thermospheric “natural thermostat” in our results, consistent with previous studies. We compare the observed DDRs with two models based on NRLMSISE‐00 and DTM-2013, and present evidence the models display a systemic altitudinal bias. We propose several possibilities to explain this altitudinal bias including the overestimated C D at low altitudes in our models (presumably due to the despinning effect of perturbing forces on the orbiting objects), and incomplete and limited coverage of in-situ observations at high solar activity. We conclude that the density models do not reliably reproduce the densities and atmospheric–thermospheric behaviors at high solar active conditions, especially for F10.7 cm above 300 sfu.

Journal of Physics: Conference Series, 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.

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.

For so many years origin of anti protons above the atmosphere has been the subject of much resear... more 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. We compute the antiprotons produced in p-p collisions with a correction on grammage (The amount of matter traversed by particles before they escape from the galaxy) and take an energy dependant function for grammage due to Axford and Berezhko models of supernova. Our new calculation of galactic antiprotons is comparable with the experimental data and reflects a galactic origin for antiprotons. The findings show that taking a correction due to energy dependence of grammage, reflects a galactic origin for anti protons.

Journal of Physics: Conference Series, 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.

Journal of Physics: Conference Series, 2015

In our previous works we described a statistical method to interpret the results of extensive air... more 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.

We announce PHIT as a numerical model for simulating of hadroproduction and compare our results w... more We announce PHIT as a numerical model for simulating of hadroproduction and compare our results with other models and experimental data. Our code, although very simple, imitates the expected results acceptably compared to other more detailed physical models. Moreover, PHIT is fast and easily executable on an ordinary PC. These advantages make PHIT an ideal choice for practical applications of an event generator.

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.

Monthly Notices of the Royal Astronomical Society, 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 mag...

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.

In the present work, with analyzing EGRET data, considering a gamma ray flux for Virgo supper clu... more In the present work, with analyzing EGRET data, considering a gamma ray flux for Virgo supper cluster and a detailed analysis on our postulates, with a new method a gamma ray flux in Coma direction results. First, we have noted some points about Gamma Ray flux in Virgo direction, from other's works. We have used here, A-Model from Wolfendale et al. [3] for calculating Gamma Ray flux in Virgo direction. The flux that we have calculated in Coma direction is considerable. Some analogy between the works has made before, is done. A flux index for Coma direction gamma rays has resulted which is in the favor of our information from Coma super cluster.

The damages and logical failures in different parts of a satellite may occur during a solar event... more The damages and logical failures in different parts of a satellite may occur during a solar event, when a bulk of solar energetic particles approaching the Earth. During solar events, these particles may cause extensive damages which are even permanent (hard errors). A way of damage reduction is designing a proper coating as the fuselage. As protons are the major component of solar particles and because the most of hard errors are caused by neutrons, in this work, we evaluated different shielding material against these type of errors. To avoid hard errors due to neutrons, we need to know solar energetic particles flux. During a solar flare a satellite receives the maximum flux of protons, so we used protons with an energy range of 100 MeV to 1 GeV which is the most sensitive energy range to the Sun activities. In the present work, we have calculated the flux of solar energetic particles which collides a typical satellite in low earth orbit. Using OMERE software, coordinates and spec...

Journal of Physics G: Nuclear and Particle Physics, 2019

Journal of Physics: Conference Series, 2017

Cosmic rays propagation within the Galaxy is simulated considering a fractallike distribution of ... more Cosmic rays propagation within the Galaxy is simulated considering a fractallike distribution of matter and magnetic fields. In such an anomalous diffusion process, the sources of ultra-high energy particles were considered to be galactic pulsars. The coordinate and birth times of sources were chosen from SN and pulsar catalogues. From these sources the primary spectrum of cosmic rays (H, He, CNO, Ne-Si, Fe) in energy range EeV and above were reproduced. The resulted spectrum is used to discuss about the change in cosmic ray sources form Galactic to Extragalactic.

Advances in Space Research, 2017

In General, the flux of low energy cosmic rays varies with time due to solar activities. The cosm... more In General, the flux of low energy cosmic rays varies with time due to solar activities. The cosmic particle fluxes were studied using data of satellites near the Earth. In this work, first we studied the variations of particle fluxes from 1 Jan to 31 Dec 2000 and 35 events were selected. Then we proposed a relation for cosmic particle flux as a function of time and rigidity in the time of approaching ejecta to the Earth. The coefficients of the relation were calculated using experimental data of particle fluxes from ACE satellite. Finally, we compare time variations of these coefficients for different events.

Journal of Astrophysics and Astronomy, 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.

Astrophysics and Space Science, 2017

Due to the high energy interactions of cosmic ray particles, progressive showers of secondary par... more Due to the high energy interactions of cosmic ray particles, progressive showers of secondary particles initiate in the atmosphere. Several models are suggested to describe the longitudinal development of extensive air showers, for example the Heitler model. The Heitler model also is written for hadronic showers. Anyhow, the predicted values of Xmax$X_{max}$ may differ significantly with the values from detailed simulations by up to about 100(g/cm2)$100~(\mbox{g}/\mbox{cm}^{2})$. In the present work, the mean depth of shower maximum is calculated using a variable interaction length. New equations for Xmax$X_{max} $ in the electromagnetic and hadronic showers have been obtained.

Iranian Journal of Science and Technology, Transactions A: Science, 2016

Theoretically, Forbush effect is highly connected to solar activity. Persistent presence of solar... more Theoretically, Forbush effect is highly connected to solar activity. Persistent presence of solar wind, magnetic storms and any types of solar flares with or without coronal mass ejections cause the occurrence of Forbush effect as cosmic ray’s flux. In this work by using some data from OMNIWEB and Izmiran observatory, we explore the relation between Forbush effect, solar wind and local parameters during one of the most massive coronal mass ejections of the century and define a new quantity which is in strong correlation with Forbush effect magnitude.

Advances in Space Research, 2016

Abstract Orbital debris are long-standing threats to space systems. They also contribute to the f... more Abstract Orbital debris are long-standing threats to space systems. They also contribute to the flux of macroscopic particles into the Earth’s atmosphere and eventually affects environmental processes across several other related regions. As impactful space debris may be, debris along with other Low Earth Orbit (LEO) orbiting objects, also serve as valuable long-monitoring probes to deduce the properties of geospace environment in-situ. We define the Daily Decay Rate (DDR) as a suitable indicator of how the Earth’s space–atmosphere interaction region (SAIR) responds to solar activity and how solar activity directly affects the orbital evolution of a LEO orbiter. We present a computationally simplified technique that simultaneously solves the motion equations for DDR and cross‐sectional area to mass ratio ( A / m ) from consecutive TLE records. By evaluating more than 50 million TLE records we estimate A / m of 15,307 NORAD-indexed objects and determine how DDR varies. We observe the thermospheric “natural thermostat” in our results, consistent with previous studies. We compare the observed DDRs with two models based on NRLMSISE‐00 and DTM-2013, and present evidence the models display a systemic altitudinal bias. We propose several possibilities to explain this altitudinal bias including the overestimated C D at low altitudes in our models (presumably due to the despinning effect of perturbing forces on the orbiting objects), and incomplete and limited coverage of in-situ observations at high solar activity. We conclude that the density models do not reliably reproduce the densities and atmospheric–thermospheric behaviors at high solar active conditions, especially for F10.7 cm above 300 sfu.

Journal of Physics: Conference Series, 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.

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.

For so many years origin of anti protons above the atmosphere has been the subject of much resear... more 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. We compute the antiprotons produced in p-p collisions with a correction on grammage (The amount of matter traversed by particles before they escape from the galaxy) and take an energy dependant function for grammage due to Axford and Berezhko models of supernova. Our new calculation of galactic antiprotons is comparable with the experimental data and reflects a galactic origin for antiprotons. The findings show that taking a correction due to energy dependence of grammage, reflects a galactic origin for anti protons.

Journal of Physics: Conference Series, 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.

Journal of Physics: Conference Series, 2015

In our previous works we described a statistical method to interpret the results of extensive air... more 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.