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Jones, F. C.

Publications and source records attributed to Jones, F. C..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Propagation of Light Elements in the Galaxy

The origin and evolution of isotopes of the lightest elements d, He-3, Li, Be, and B in the universe is a key problem in such fields as astrophysics of CR, Galactic evolution, non-thermal nucleosynthesis, and cosmological studies. One of the major sources of these species is spallation by CR nuclei in the interstellar medium. On the other hand, it is the Boron/Carbon ratio in CR and Be-10 abundance which are used to fix the propagation parameters and thus spallation rate. We study production and Galactic propagation of these species using the numerical propagation code GALPROP and updated production cross sections.

Moskalenko, I. V.↗
NASA NTRS2003

GALPROP: New Developments in CR Propagation Code

The numerical Galactic CR propagation code GALPROP has been shown to reproduce simultaneously observational data of many kinds related to CR origin and propagation. It has been validated on direct measurements of nuclei, antiprotons, electrons, positrons as well as on astronomical measurements of gamma rays and synchrotron radiation. Such data provide many independent constraints on model parameters while revealing some contradictions in the conventional view of Galactic CR propagation. Using a new version of GALPROP we study new effects such as processes of wave-particle interactions in the interstellar medium. We also report about other developments in the CR propagation code.

Moskalenko, I. V.↗
NASA NTRS2002

Propagation of Secondary Antiprotons and Cosmic Rays in the Galaxy

Recent more accurate antiproton data obtained by the BESS team during the last solar minimum pose a challenge to conventional propagation models of cosmic rays. In particular, the diffusive reacceleration model, which matches well key secondary/primary isotope ratios in cosmic rays, fails to reproduce the secondary antiproton spectrum. Tuning both secondary/primary isotope ratios and antiprotons is possible, but requires artificial breaks in the diffusion coefficient and the injection spectrum of primaries. We will discuss some possibilities to overcome these difficulties in the propagation models. We will present new results of our calculation of CR propagation in the Galaxy using the GALPROP code.

Moskalenko, I. V.↗
NASA NTRS2002

Propagation Model for Cosmic Ray Species in the Galaxy

During the last decade there have been a number of space and balloon experiments with improved sensivity and statistics, which impose stricter constraints on cosmic ray propagation models. Propagation is the main issue in the interpretation of such data as antiproton and positron fluxes in cosmic rays, and diffuse gamma-ray emission. We develop a new propagation model that reproduces measurements of secondary antiprotons as well as primary and secondary nuclei. We will present results of our calculation of CR propagation in the Galaxy for this model using the GALPROP code.

White, Nicholas E.↗
NASA NTRS2001

K-Capture Cosmic Ray Secondaries and Reacceleration

We have investigated the effect of reacceleration on interstellar flux of K-capture secondaries V-49 and Cr-51. Several isotopic ratios for these two isotopes are calculated using the galactic diffusion model with and without distributed reacceleration. It is found that the statistical accuracy of the ACE experiment on itself is high enough to see a signature of reacceleration. However, the uncertainties in nuclear production cross sections are probably too large to conclude that reacceleration process took place.

Jones, F. C.↗
NASA NTRS1995

Monte Carlo simulations of particle acceleration at oblique shocks: Including cross-field diffusion

The Monte Carlo technique of simulating diffusive particle acceleration at shocks has made spectral predictions that compare extremely well with particle distributions observed at the quasi-parallel region of the earth's bow shock. The current extension of this work to compare simulation predictions with particle spectra at oblique interplanetary shocks has required the inclusion of significant cross-field diffusion (strong scattering) in the simulation technique, since oblique shocks are intrinsically inefficient in the limit of weak scattering. In this paper, we present results from the method we have developed for the inclusion of cross-field diffusion in our simulations, namely model predictions of particle spectra downstream of oblique subluminal shocks. While the high-energy spectral index is independent of the shock obliquity and the strength of the scattering, the latter is observed to profoundly influence the efficiency of injection of cosmic rays into the acceleration process.

Baring, M. G.↗
NASA NTRS1994

A program to measure new energetic particle nuclear interaction cross sections

The Transport Collaboration, consisting of researchers from institutions in France, Germany, Italy, and the USA, has established a program to make new measurements of nuclear interaction cross sections for heavy projectiles (Z greater than or equal to 2) in targets of liquid H2, He and heavier materials. Such cross sections directly affect calculations of galactic and solar cosmic ray transport through matter and are needed for accurate radiation hazard assessment. To date, the collaboration has obtained data using the Lawrence Berkeley Laboratory Bevalac HISS facility with 20 projectiles from He-4 to Ni-58 in the energy range 393-910 MeV/nucleon. Preliminary results from the analysis of these data are presented here and compared to other measurements and to cross section prediction formulae.

Guzik, T. G.↗
NASA NTRS1986

Phase propagation of the solar modulation of galactic cosmic rays

The phase of the 11-yr galactic cosmic ray variation, due to a varying rate of emission of long-lived, propagating regions of enhanced scattering, travels faster than the scattering regions themselves. The radial speed of the 11-yr phase in the quasi-steady force field approximation is exactly twice the speed of the individual episodic decreases. A time-dependent numerical solution for 1-GeV protons at 1 and 30 AU gives a phase speed which is 1.85 times the propagation speed of the individual decreases.

Forman, M. A.↗
NASA NTRS1986

Nineteenth International Cosmic Ray Conference. Conference Papers: Invited Rapporteur, Highlight, Miscellaneous, Volume 9

Invited talks, rapporteur talks, and highlight talks are included. Topics of the invited and highlight talks include astrophysical jets, gamma-ray line astronomy, cosmic rays and gamma rays in astrophysics, the early universe, elementary particle physics, solar flares and acceleration of energetic particles, cosmogenic nuclei, extragalactic astronomy, composition of solar flare particles, very high energy gamma ray sources, gamma-ray bursts, shock acceleration in the solar wind, cosmic rays in deep underground detectors, spectrum of cosmic rays at 10 to the 19th power eV, and nucleus-nucleus interactions.

Jones, F. C.↗
NASA NTRS1985

Ninteenth International Cosmic Ray Conference. OG Sessions, Volume 2

Contributed papers addressing cosmic ray origin and galactic phenomena are compiled. Topic areas include the composition, spectra, and anisotropy of cosmic ray nuclei with energies and 1 TeV, isotopes, antiprotons and related subjects, and electrons, positrons, and measurements of synchrotron radiation.

Jones, F. C.↗
NASA NTRS1985

Ninteenth International Cosmic Ray Conference. SH Sessions, Volume 4

Papers submitted for presentation at the 19th International Cosmic Ray Conference are compiled. This volume covers solar and heliospheric phenomena, specifically, particle acceleration; cosmic ray compsotion, spectra, and anisotropy; propagation of solar and interplanetary energetic particles; solar-cycle modulation; and propagation of galactic particles in the heliosphere.

Jones, F. C.↗
NASA NTRS1985

Propagation of the phase of solar modulation

The phase of the 11 year galactic cosmic ray variation, due to a varying rate of emission of long lived propagating regions of enhanced scattering, travels faster than the scattering regions themselves. The radial speed of the 11 year phase in the quasi-steady, force field approximation is exactly twice the speed of the individual, episodic decreases. A time dependent, numerical solution for 1 GeV protons at 1 and 30 Au gives a phase speed which is 1.85 times the propagation speed of the individual decreases.

Forman, M. A.↗
NASA NTRS1985

Nineteenth International Cosmic Ray Conference. SH Sessions, Volume 5

Papers submitted for presentation at the 19th International Cosmic Ray Conference are compiled. This volume contains papers addressing cosmic ray gradients in the heliosphere; siderial, diurnal, and long term modulations; geomagnetic and atmospheric effects; cosmogenic nuclides; solar neutrinos; and detection techniques.

Jones, F. C.↗
NASA NTRS1985

Nineteenth International Cosmic Ray Conference. HE Sessions, Volume 6

Papers contributed to the 19th International Cosmic Ray Conference which address high energy interactions and related phenomena are compiled. Particular topic areas include cross sections; particle production; nuclei and nuclear matter; nucleus-nucleus collisions; gamma ray and hadron spectra; C-jets, a-jets, and super families; and emulsion chamber simulations.

Jones, F. C.↗
NASA NTRS1985

Nineteenth International Cosmic Ray Conference. HE Sessions, Volume 8

Papers submitted for presentation at the 19th International Cosmic Ray Conference are compiled. The present volume contains papers addressing high energy interactions and related phenomena. Specific topic areas include muons, neutrinos, magnetic monopoles, nucleon decay, searches for new particles, and acoustic and thermoluminescence detection techniques.

Jones, F. C.↗