Cosmic Ray Origin and Propagation Model (original) (raw)

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Cosmic Rays from Supernova Remnants: A Brief Description of the Shock Acceleration of Gas and Dust

The Advanced Composition Explorer Mission, 1998

We summarize our model of galactic cosmic-ray (GCR) origin and acceleration, wherein a mixture of interstellar and/or circumstellar gas and dust is accelerated by a supernova remnant (SNR) blast wave. A detailed analysis of observed GCR abundances , combined with the knowledge that many refractory elements known to be locked in grains in the interstellar medium (ISM) are abundant in cosmic rays, has lead us to revive an old suggestion (Epstein, 1980) that charged dust grains can be shock accelerated. Here, we outline results (presented more completely in Ellison et al., 1997) from a nonlinear shock model which includes (i) the direct acceleration of interstellar gas-phase ions, (ii) a simplified model for the direct acceleration of weakly charged grains to ∼100 keV amu −1 energies, simultaneously with the acceleration of the gas ions, (iii) the energy losses of grains colliding with the ambient gas, (iv) the sputtering of grains, and (v) the simultaneous acceleration of the sputtered ions to TeV energies. We show that the model produces GCR source abundance enhancements of the volatile, gas-phase elements, which are an increasing function of mass, as well as a net, mass independent, enhancement of the refractory, grain elements over protons, consistent with cosmic-ray observations. The GCR 22 Ne and C excesses may also be accounted for in terms of the acceleration of 22 Ne-C-enriched pre-SN Wolf-Rayet star wind material surrounding the most massive supernovae. The O excess seen in cosmic rays probably cannot be interpreted in terms of W-R star nucleosynthesis, but is easily accounted for in our model since 15 to 20% of O is trapped in grain cores and this O will be preferentially accelerated. We have expanded the parameter range explored in to lower shock speeds and higher maximum cosmic-ray energies and find similar fits to the H/He ratio and the cosmic-ray source spectra.

Galactic Cosmic Rays from Supernova Remnants. II. Shock Acceleration of Gas and Dust

The Astrophysical Journal, 1997

We show that the Galactic Cosmic Ray source (GCRS) composition is best described in terms of (i) a general enhancement of the refractory elements relative to the volatile ones, and (ii) among the volatile elements, an enhancement of the heavier elements relative to the lighter ones; this mass dependence most likely reflects a mass-to-charge (A/Q) dependence of the acceleration efficiency; among the refractory elements, there is no such enhancement of heavier species, or only a much weaker one. We regard as coincidental the similarity between the GCRS composition and that of the solar corona, which is biased according to first ionization potential. In a companion paper, this GCRS composition is interpreted in terms of an acceleration by supernova shock waves of interstellar and/or circumstellar (e.g., 22 Ne-rich Wolf-Rayet wind) gas-phase and especially dust material.

Cosmic-ray composition and its relation to shock acceleration by supernova remnants

An overview is given on the present status of the understanding of the origin of galactic cosmic rays. Recent measurements of charged cosmic rays and photons are reviewed. Their impact on the contemporary knowledge about the sources and acceleration mechanisms of cosmic rays and their propagation through the Galaxy is discussed. Possible reasons for the knee in the energy spectrum and scenarios for the end of the galactic cosmic-ray component are described.

The contribution of supernova remnants to the galactic cosmic ray spectrum

Astroparticle Physics, 2010

The supernova paradigm for the origin of galactic cosmic rays has been deeply affected by the development of the non-linear theory of particle acceleration at shock waves. Here we discuss the implications of applying such theory to the calculation of the spectrum of cosmic rays at Earth as accelerated in supernova remnants and propagating in the Galaxy. The spectrum is calculated taking into account the dynamical reaction of the accelerated particles on the shock, the generation of magnetic turbulence which enhances the scattering near the shock, and the dynamical reaction of the amplified field on the plasma. Most important, the spectrum of cosmic rays at Earth is calculated taking into account the flux of particles escaping from upstream during the Sedov-Taylor phase and the adiabatically decompressed particles confined in the expanding shell and escaping at later times. We show how the spectrum obtained in this way is well described by a power law in momentum with spectral index close to -4, despite the concave shape of the instantaneous spectra of accelerated particles. On the other hand we also show how the shape of the spectrum is sensible to details of the acceleration process and environment which are and will probably remain very poorly known.

The origin of galactic cosmic rays

The Astronomy and Astrophysics Review, 2013

One century ago Viktor Hess carried out several balloon flights that led him to conclude that the penetrating radiation responsible for the discharge of electroscopes was of extraterrestrial origin. One century from the discovery of this phenomenon seems to be a good time to stop and think about what we have understood about Cosmic Rays. The aim of this review is to illustrate the ideas that have been and are being explored in order to account for the observable quantities related to cosmic rays and to summarize the numerous new pieces of observation that are becoming available. In fact, despite the possible impression that development in this field is somewhat slow, the rate of new discoveries in the last decade or so has been impressive, and mainly driven by beautiful pieces of observation. At the same time scientists in this field have been able to propose new, fascinating ways to investigate particle acceleration inside the sources, making use of multifrequency observations that range from the radio, to the optical, to X-rays and gamma rays. These ideas can now be confronted with data.

Cosmic Rays Acceleration in Wolf-Rayet Stellar Winds

Romanian Astronomical Journal, 2004

Popescu et al. (2004) gave a model for the observed cosmic rays between 5 * 10^15 and 3 * 10^18 eV. Their source is presumed to be the supernova of stars that explode in their winds. The observed cosmic rays abundance at the source are affected by spallation in the supernova shell, by the difference in ionization degree (being one or two times ionized) at the injection in the supernova shock, the stars with initial masses 15MSun ≤ M ≤ 30MSun having a different contribution to them than the stars with 30MSun ≤ M ≤ 50MSun, this being 2:1 for the elements with Z ≥ 6. Still, the abundances after these corrections are different by a factor , where is the atomic number for the element i. This paper is dedicated to the explanation of this factor and its physical meanings by considering that, prior to the shock injection, the wind particles are radiative accelerated.

Origin of Galactic Cosmic Rays

Nuclear Physics B - Proceedings Supplements, 2013

One century ago Viktor Hess carried out several balloon flights that led him to conclude that the penetrating radiation responsible for the discharge of electroscopes was of extraterrestrial origin. One century from the discovery of this phenomenon seems to be a good time to stop and think about what we have understood about Cosmic Rays. The aim of this review is to illustrate the ideas that have been and are being explored in order to account for the observable quantities related to cosmic rays and to summarize the numerous new pieces of observation that are becoming available. In fact, despite the possible impression that development in this field is somewhat slow, the rate of new discoveries in the last decade or so has been impressive, and mainly driven by beautiful pieces of observation. At the same time scientists in this field have been able to propose new, fascinating ways to investigate particle acceleration inside the sources, making use of multifrequency observations that range from the radio, to the optical, to X-rays and gamma rays. These ideas can now be confronted with data.

Cosmic Rays Radiative Pre-acceleration in Wolf-Rayet Stellar Winds

Publications of the Astronomy Department of the Eötvös University (PADEU), 2005

In the article "Cosmic Rays VIII" of Popescu et al. (2005) we gave an model for the observed cosmic rays between 5 • 10^15 and 3 • 10^18 eV. Their surse is presumed to be supernova of stars that explode in their winds. The observed cosmic abundance at the source are affected by spallation in the supernova shell, by the difference in ionization degree (being one two times ionized) at the injection in the supernova shock, the stars with initial masses 15M⊙ ≤ M ≤ 30M⊙ having a different contribution to them than the stars with 30M⊙ ≤ M ≤ 50M⊙ and this is 2:1 for the elements with Z ≥ 6. Still, the abundances after these corrections are different by a factor Z_{i} /Z_{He} where Z_{i} is the atomic number for the element i and Z_{He} the one for He. This paper is dedicated to the explanation of this factor and its physical meanings.