Propagation Of Cosmic Ray Nuclei Research Articles

Cosmic ray propagation with CRPropa 3

Solving the question of the origin of ultra-high energy cosmic rays (UHECRs) requires the development of detailed simulation tools in order to interpret the experimental data and draw conclusions on the UHECR universe. CRPropa is a public Monte Carlo code for the galactic and extragalactic propagation of cosmic ray nuclei above ∼ 1017 eV, as well as their photon and neutrino secondaries. In this contribution the new algorithms and features of CRPropa 3, the next major release, are presented. CRPropa 3 introduces time-dependent scenarios to include cosmic evolution in the presence of cosmic ray deflections in magnetic fields. The usage of high resolution magnetic fields is facilitated by shared memory parallelism, modulated fields and fields with heterogeneous resolution. Galactic propagation is enabled through the implementation of galactic magnetic field models, as well as an efficient forward propagation technique through transformation matrices. To make use of the large Python ecosystem in astrophysics CRPropa 3 can be steered and extended in Python.

Lorentz invariance violation and chemical composition of ultra-high energy cosmic rays

Motivated by experimental indications of a significant presence of heavy nuclei in the cosmic ray flux at ultra high energies (≳ 1019 eV), we consider the effects of Planck scale suppressed Lorentz Invariance Violation (LIV) on the propagation of cosmic ray nuclei. In particular we focus on LIV effects on the photodisintegration of nuclei onto the background radiation fields. We apply our formalism to a simplified model where the LIV parameters of the various nuclei are assumed to kinematically result from a single LIV parameter for the constituent nucleons, η, and we show constraints on η.

Lorentz invariance violation and chemical composition of ultra high energy cosmic rays

Motivated by experimental indications of a significant presence of heavy nuclei in the cosmic ray flux at ultra high energies (≳1019 eV), we consider the effects of Planck scale suppressed Lorentz Invariance Violation (LIV) on the propagation of cosmic ray nuclei. In particular we focus on LIV effects on the photodisintegration of nuclei onto the background radiation fields. After a general discussion of the behavior of the relevant quantities, we apply our formalism to a simplified model where the LIV parameters of the various nuclei are assumed to kinematically result from a single LIV parameter for the constituent nucleons, η, and we derive constraints on η. Assuming a nucleus of a particular species to be actually present at 1020 eV the following constraints can be placed: −3 × 10−2≲η≲4 for 56Fe, −2 × 10−3≲η≲3 × 10−2 for 16O and −7 × 10−5≲η≲1 × 10−4 for 4He, respectively.

Galactic propagation of cosmic ray nuclei in a model with an increasing diffusion coefficient at low rigidities: A comparison of the new interstellar spectra with Voyager data in the outer heliosphere

Using both a Monte Carlo Diffusion Model and a Leaky Box Model for propagation in the galaxy, we have determined the interstellar spectra of H, He, and heavier nuclei with emphasis on energies below ∼1–2 GeV nucleon−1. This calculation uses diffusion coefficients that are increasing at rigidities below ∼2–3 GV and which are based on those used to fit the interstellar electron spectrum to the galactic nonthermal radio synchrotron spectrum by Webber and Higbie (2008). The resulting interstellar spectra of the cosmic ray nuclei are thus reduced at low energies in a charge‐dependent way from those derived using a diffusion coefficient = constant as was the case in some earlier calculations. The resulting interstellar intensities at ∼200 MeV nucleon−1 near the peak in the differential spectrum have been reduced by factors of 2.00 and 1.46 for H and He nuclei, respectively. These new interstellar intensities are then compared with recent Voyager measurements beyond the heliospheric termination shock. Solar modulation effects, corresponding to values of ϕ between 60 and 80 MV in simple force field models, are still evident in the 2008.5 Voyager 1 H and He spectra at 107 AU. In 2009, when the 11‐year solar modulation effects are expected to be a minimum in the outer heliosphere, a comparison of future Voyager measurements at ∼110 AU and beyond and these new interstellar spectra along with the corresponding electron spectrum measured by Voyager 1 will provide an important test of both modulation and interstellar propagation models.

Cosmic‐Ray Propagation in the Galaxy: Techniques and the Mean Matter Traversal

After examining the techniques used for solving the equations describing the propagation of cosmic-ray nuclei in the Galaxy, we have introduced a technique that yields exact numerical solutions for the steady state equations. We have implemented this in a new code, which uses the Runge-Kutta numerical method and incorporates current knowledge of relevant physical parameters to carry out simultaneous integration of the steady state equations. Comparing results from the steady state solution with those obtained using the weighted-slab approximation, we find that the weighted slab underestimates the equilibrium flux at low energies for all nuclei and does so most severely for secondary nuclei. At high energies, the fluxes of secondary nuclei also differ from the steady state results, depending upon the value of the parameter U, the ratio of the of the daughter and parent nuclei (A/Z). Rasy, the high-energy asymptotic ratio of the secondary fluxes obtained from the weighted-slab and steady state solutions, is well parameterized by the useful relationship Rasy = U-0.53. Our results are in qualitative, but not quantitative, agreement with the seminal work of Ptuskin, Jones & Ormes. We have determined the path length traversed by cosmic rays by making use of the steady state technique and the observed B/C ratio for various compositions of interstellar gas. Our results agree well with those derived by Webber, but vary from those of Heinbach & Simon.

The Formation of Galactic Cosmic Rays Spectrum

The cosmic ray spectrum can be formed in source by an acceleration process or by the effects of propagation in photons and magnetic fields of galactic and/or extragalactic space. The influence of magnetic field turbulence on the propagation of cosmic ray nuclei has been investigated. We have found that the regular component of galactic magnetic field should be equal to (0.35 μ G) but turbulent component have a mean strange value (4.65 μ G) for description whole feature observed in spectrum of cosmic rays. The propagation paths of nuclei in the galactic magnetic field are changed at the same energies where Extensive Air Shower (EAS) experiments observes alteration in the energy spectrum of cosmic ray. The ‘knee’ in the energy spectrum is due to two processes photo disintegration of nuclei in a soft photon field, type thermal bremsstrahlung with (kT=20) eV and leakage from Galaxy. A concave down among (2 ÷ 5 · 1018) eV observed in the energy spectrum is caused because above this energy the trajectories of protons are strike line in galactic magnetic field, so the propagation length is simple geometric path and do not depend from energy. The trajectories of iron are bending by magnetic field up to energy (1020) eV suffering the photo disintegration, so the secondary protons from destruction of heavy nuclei are isotropic. Only neutrons super high energy can provide some anisotropy. A good agreement with total cosmic ray spectrum can be obtained for parameters widely accepted for the galactic space. The model explain the data set, that the fraction of heavy nuclei increases up to (1016) eV. At energies (1016 ÷ 3 · 1018) eV the mixed mass compositions do not varies so much, but above this energy mass composition become lighter due to photo disintegration process of heavy nuclei. The secondary protons and spectra of light nuclei originating from the destruction of heavy nuclei have the maximum just above the ‘knee’. We suggest that secondary protons (PS) and nuclei of groups (He and CNO) make up the second component of cosmic ray spectrum proposed recently by Wdowczyk (1984), Wdowczyk and Wolfendale (1989), Fichtel and Linsley (1986), and discussed by Gaisser (1991). Verification of the proposed model by the observations of UHE neutrons and VHE/UHE gamma rays from point sources is possible.

SOME PRELIMINARY RESULTS FROM THE NEW 10.6 GeV/NUCLEON GOLD BEAM AT BROOKHAVEN

Preliminary results are described from three separate experiments observing the interactions of gold nuclei accelerated to 10.6 GeV/nucleon at the Brookhaven AGS. Nuclear emulsion results present a global picture of the various interaction modes and reveal the production of mesons, copious multifragmentation and the angular distributions of the emitted particles. Electronic detectors make a more precise measurement of the heavy fragments emitted from interactions in a wide range of well defined targets. Etchable glass detectors provide unique charge resolution of these heavy fragments but give results that are discordant with those from the other detectors. Very significant differences are seen between these interactions and those observed at energies of ≤1.0 GeV/nucleon. Fission appears to be almost entirely suppressed while charge pickup is reduced by a factor of two to three. Total charge changing cross-sections are increased but partial cross sections for small charge changes are reduced. Frequent examples of multifragmentation are observed and central collisions result in copious particle production with total multiplicities as great as 370 singly charged particles being emitted from a single interaction. Other interactions show the emission of as many as 15 alpha particles or 7 heavier fragments. The implications of these results on the problem of the propagation of cosmic ray nuclei through the interstellar medium are considered.

Propagation of cosmic-ray nuclei in a diffusing galaxy with convective halo and thin matter disk

A diffusion model for cosmic-ray propagation in the galaxy that includes the effects of convection in the halo is presented. Calculations are made for 13 primary and secondary nuclei with rigidities between 1 and 1000 GV using interaction loss rates, secondary production rates, and radioactive decay on the basis of recent new cross-section measurements. It is found that, in order to fit the rather weak radial dependence of cosmic-ray protons derived from gamma-ray data, the radial profile of the cosmic-ray sources must also have a weak radial dependence. It is suggested that convection perpendicular to the disk of the Milky Way Galaxy may not be important even at rigidities less than a few GV. The obtained limits on halo thicknesses are consistent with what can be determined for the distribution of cosmic-ray electrons in the halo based on the distribution of radio synchrotron emission in this and other galaxies.

Features of the local galactic magnetic field

The propagation of cosmic ray nuclei in the Galaxy is strongly affected by the galactic magnetic field, and the derivation of information about the cosmic ray electron component, from studies of the synchrotron radiation, also requires a knowledge of the magnetic field. Inevitably knowledge is scanty but pulsar rotation measures hold out the prospect of improvement, and the authors discuss this, with particular reference being made to the 'local' region of the Galaxy; within about 1.5 kpc of the Sun. The results confirm the existence of an extragalactic component of cosmic ray nuclei above 1019 eV, and at much lower energies, approximately=109 eV, allow a good understanding of the propagation of the galactic electron component.

Propagation of cosmic ray nuclei above 50 GeV/amu

It is now well-known that the relative abundance of secondary cosmic ray nuclei which are produced by spallation in interstellar space depends on energies. The mechanism responsible for this energy dependence are not well understood because of the scarcity of data on the cosmic ray composition at energy above 50 GeV/amu. The University of Chicago experiment on the Spacelab-2 flown by the Space Shuttle in 1985 is aimed at the measurement of the elemental composition in this unexplored energy regime. Our latest results on the energy dependence of the secondary to primary abundance ratio using the pairs of elements B,C and N,O, are discussed.

The propagation of cosmic-ray nuclei in interstellar space and solar system

Cosmic ray nuclei propagation in interstellar space and solar system examined from balloon, rocket and satellite soundings

The energy spectrum of cosmic-ray heavy nuclei of chargeZ≥10 during a solar quiet time in July 1961

The energy spectrum of heavy nuclei (charge Z≥10) has been determined, in the energy interval from 200–700 Mev/nucleon, using a stack of nuclear emulsions, exposed on July 8, 1961, at a mean altitude of ∼2.4 g/cm2 of residual atmospheric depth on a balloon flown from Fort Churchill, Manitoba. The flight was preceded by a period of three months of low solar and geophysical activity. The charge and energy spectra were obtained principally from tracks of particles that ended in the detector by a combination of range and δ-ray density measurements. A second charge estimation for particles that stop in the emulsion was made from integral δ-ray counts as a function of range. The energy spectrum was measured up to 700 Mev/nucleon by also taking into consideration the tracks that pass through or interact within the stack using a combination of δ-ray density and multiple scattering measurements that determine the charge and energy of the nuclei. This energy spectrum was combined with the spectra measured for protons and helium nuclei in the same flight and with similar data obtained during 1963 with a view of arriving at a better understanding on the propagation of cosmic-ray nuclei in source regions, instellar space, and solar system.

Abundances and Energy Spectra of Galactic Cosmic-Ray Nuclei above 20 Mev Per Nucleon in the Nuclear Charge Range 2 ≤ Z ≤ 26

view Abstract Citations (73) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Abundances and Energy Spectra of Galactic Cosmic-Ray Nuclei above 20 Mev Per Nucleon in the Nuclear Charge Range 2 <= Z <= 26 Comstock, G. M. ; Fan, C. Y. ; Simpson, J. A. Abstract The individual abundances of the elements helium through silicon, as well as the nuclear-charge group 15 <Z < 25 and the Fe-Ni group, have been measured using a telescope composed of solid-state detectors on the OGO-I satellite in the period October, 1964, to June, 1965. Also measured were the differential energy spectra for He, B, C, and 0 over the energy range 201000 MeV per nucleon, with some integral measurements above 1000 MeV per nucleon. The spectra for Ne, Mg, and the Fe-Ni group were obtained over a narrower energy range. The experimental results are divided into two time intervals approximately 6 months apart in order to investigate the dependence of abundances and energy spectra upon changes in solar modulation. The abundances of the elements in the kinetic energy range 20 to 330 MeV per nucleon are normalized to oxygen with a flux of 5.4 X 10- nuclei ster (MeV/nucleon)-1. The ratio of abundances of nuclei with even-to-odd nuclear charge number Z, especially in the range 6 < Z < 14 is approximately 8:1. The elements Li, Be, and B are present down to the lowest observed energies in the approximate ratio 2:0.7:2.5. The ratio (Li, Be, B): (C, N, 0) = 0 26 + 004. The abundance of the Fe-Ni group relative to C and 0 is nearly equal to its abundance at high energies. For nuclei 5 <Z < 14 the differential energy spectra are remarkably independent of energy below 300 MeV/nucleon. It is shown that the spectra for these nuclei, when extrapolated to the nearby interstellar medium, must be continuously rising toward the lowest observed energies ( 20 MeV/nucleon) with greater negative slopes than for the He spectrum. Experimental evidence for the galactic origin of these nuclei is presented. The bearing of this experiment on the origin and propagation of cosmic-ray nuclei is discussed, and it is pointed out that some assumptions commonly accepted are no longer tenable. Two specific alternatives are considered. It appears that energy degradation by ionization loss alone may not account for the results It is suggested that the rate of particle acceleration for a wide range of Z competes effectively with the rate of ionization loss at these low energies. Alternatively, a discrete, and possibly nearby, source in the Galaxy could account for these low-energy measurements. Since the technique of using solid-state devices for measuring multiply charged nuclei is novel, a description of the instrument and the methods for analyzing the data are given. Publication: The Astrophysical Journal Pub Date: October 1966 DOI: 10.1086/148859 Bibcode: 1966ApJ...146...51C full text sources ADS |

Age of Cosmic Ray Nuclei and Their Propagation in Space

Information on the origin, age and propagation of cosmic ray nuclei can be obtained from a detailed study of the intensities of Li, Be, and B nuclei in the primary radiation observed in the vicinity of the earth. While at any given energy, the absolute total flux of these nuclei, (Li+Be+B), at the top of the atmosphere will depend almost exclusively on the amount of matter traversed by the radiation, their relative intensities will depend on the extent to which the long lived Be10 isotopes, produced in spallation reactions in space, have decayed during the life time (or age T) of the cosmic rays. In the present work the dependence of the ratio of the flux of Be nuclei to that of B nuclei on the age of the cosmic rays has been taken advantage of to set a reasonable lower limit to the age of the cosmic ray nuclei; from an experiment performed with nuclei having a geomagnetic cutoff rigidity corresponding to 7.5 GeV/n it is found that T \gtrsim5 ×107 years. This result is then used together with the total amount of matter traversed by cosmic ray nuclei (2.5 g/cm2), obtained from other experiments, to deduce the average gas density of regions traversed by the cosmic rays as \lesssim 0.03 hydrogen atoms/cm3. This very low value of the average density suggests that cosmic ray nuclei are not confined to the disc or spiral arms of our galaxy but reside for the major fraction of their life time in regions of much lower density such as the intergalactic space and the halo of our galaxy, if it exists.