Considerations affecting the estimation of cosmic-ray age

1968 ◽  
Vol 46 (10) ◽  
pp. S561-S568 ◽  
Author(s):  
M. M. Shapiro ◽  
R. Silberberg
Keyword(s):  
Cosmic Rays ◽  
Cross Sections ◽  
Galactic Disk ◽  
Principal Component ◽  
Cosmic Ray ◽  
Light Nuclei ◽  
The Galaxy ◽  
Primary Cosmic Radiation ◽  
Order Of Magnitude ◽  
Medium Nuclei

Previous investigations by Daniel and Durgaprasad on the ratios Be/B and Be/Li in the primary cosmic radiation exploited the decay of 10Be produced in space to deduce a confinement time for cosmic rays in the galaxy. They concluded that this "age" T is at least 50 million years, and thence inferred that the cosmic-ray nuclei are trapped in a volume much larger than that of the galactic disk. These conclusions depended upon the values of fragmentation cross sections available in 1962 to Badhwar, Daniel, and Vijayalakshmi. Recent values of the Orsay group, however, reduce the calculated rates of 10Be and 9Be production by an order of magnitude; and an analysis based upon the latest cross sections leads to the following conclusions: (1) The possibility that cosmic rays are mainly confined to the disk of the galaxy and that T ≈ 106 years is not excluded. (2) The fragmentation parameter for medium nuclei [Formula: see text] into light nuclei [Formula: see text] is revised from 0.48 (the value of Badhwar et al.) to 0.34. (3) The mean path-length of 2.5 ± 0.5 g/cm2 of Badhwar et al. is revised to 4 ± 1 g/cm2. (4) 7Be now appears to be the principal component of cosmic-ray beryllium (about 70 or 80%, depending upon the cosmic-ray lifetime).

Cosmic-ray nuclei up to 10 10 eV/u in the galaxy

1975 ◽  
Vol 277 (1270) ◽  
pp. 319-348 ◽  
Keyword(s):  
Cosmic Rays ◽  
Solar System ◽  
Cross Sections ◽  
Cosmic Ray ◽  
Interstellar Space ◽  
Heavy Nuclei ◽  
Hydrogen Atoms ◽  
Interstellar Gas ◽  
The Galaxy ◽  
Ionization Cross Sections

O f the nuclear cosmic rays arriving in the vicinity of Earth from interstellar space, more than 90% have energies less than 1010 eV /u.f Some effects of their modulation (including deceleration) in the Solar System are briefly discussed. The origin of particles at energies < 107 eV/u is still obscure. They could be due to stellar explosions or to solar emissions, or perhaps to interaction of interstellar gas with the solar wind. Between 108 and 1010 eV/u, the composition appears constant to ca. 30% within the statistics of available data. Cosmic rays traverse a mean path length of 6 g/cm 2 in a medium assumed to contain nine hydrogen atoms for each helium atom. Spallation reactions occurring in this medium result in enhancement of many cosmic-ray elements that are more scarce in the general abundances by several orders of magnitude. Cosmic-ray dwell time in the Galaxy seems to be < 107 years. The source composition of cosmic rays has been derived for elements with atomic numbers 1 ≤ Z ≤ 26. A comparison with abundances in the Solar System implies that the latter is richer in hydrogen and helium by a factor of ca. 20, in N and O by ca. 5, and in C by a factor of ca.2. Possible interpretations invoke (a) nucleosynthesis of cosmic rays in certain sources, e.g. supernovae, or (b) models of selective injection that depend, e.g. on ionization potentials or ionization cross sections. Calculated isotopic abundances of arriving cosmic rays are compared with the observed values now becoming available, and found to be in general agreement. Recent progress in probing the composition and spectrum of ultra-heavy nuclei is outlined.

scholarly journals Particle acceleration in the superwinds of starburst galaxies

2018 ◽  
Vol 616 ◽  
pp. A57 ◽  
Author(s):  
G. E. Romero ◽  
A. L. Müller ◽  
M. Roth
Keyword(s):  
Cosmic Rays ◽  
Galactic Disk ◽  
Cosmic Ray ◽  
High Energy ◽  
Shock Acceleration ◽  
Spectral Energy ◽  
Starburst Galaxy ◽  
Diffusive Shock Acceleration ◽  
Mass Load ◽  
The Galaxy

Context. Starbursts are galaxies undergoing massive episodes of star formation. The combined effect of stellar winds from hot stars and supernova explosions creates a high-temperature cavity in the nuclear region of these objects. The very hot gas expands adiabatically and escapes from the galaxy creating a superwind which sweeps matter from the galactic disk. The superwind region in the halo is filled with a multi-phase gas with hot, warm, cool, and relativistic components. Aims. The shocks associated with the superwind of starbursts and the turbulent gas region of the bubble inflated by them might accelerate cosmic rays up to high energies. In this work we calculate the cosmic ray production associated with the superwind using parameters that correspond to the nearby southern starburst galaxy NGC 253, which has been suggested as a potential accelerator of ultra-high-energy cosmic rays. Methods. We evaluate the efficiency of both diffusive shock acceleration (DSA) and stochastic diffusive acceleration (SDA) in the superwind of NGC 253. We estimate the distribution of both hadrons and leptons and calculate the corresponding spectral energy distributions of photons. The electromagnetic radiation can help to discriminate between the different scenarios analyzed. Results. We find that the strong mass load of the superwind, recently determined through ALMA observations, strongly attenuates the efficiency of DSA in NGC 253, whereas SDA is constrained by the age of the starburst. Conclusions. We conclude that NGC 253 and similar starbursts can only accelerate iron nuclei beyond ~1018 eV under very special conditions. If the central region of the galaxy harbors a starved supermassive black hole of ~106 M⊙, as suggested by some recent observations, a contribution in the range 1018−1019 eV can be present for accretion rates ṁ ~ 10−3 in Eddington units. Shock energies of the order of 100 EeV might only be possible if very strong magnetic field amplification occurs close to the superwind.

scholarly journals The composition of galactic cosmic rays

1968 ◽  
Vol 46 (10) ◽  
pp. S544-S547 ◽  
Author(s):  
D. V. Reames ◽  
C. E. Fichtel
Keyword(s):  
Cosmic Rays ◽  
Cross Sections ◽  
Length Distribution ◽  
Cosmic Ray ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Interstellar Space ◽  
Fermi Acceleration ◽  
Fixed Amount ◽  
The Galaxy

Recent measurements of low-energy galactic cosmic rays obtained on sounding rockets and satellites exhibit a composition different from that obtained for intermediate and high-energy radiation obtained at balloon altitudes. In particular the ratio of light to medium nuclei is observed to be 0.2–0.3 in the 50–100 MeV/nucleon interval as compared with values near 0.5 in the 200–500 MeV/nucleon region. Lower values of the ratios C/O, N/O, F/O, and odd-Z/even-Z are also found. In the light of these new measurements and of new measurements on the fragmentation cross sections for cosmic-ray nuclei in interstellar space, an attempt has been made to calculate the composition expected if similar source spectra are assumed. It is found that neither passage through a fixed amount of material nor an equilibrium condition (exponential path-length distribution) is adequate to explain the observed features. The effects of including other mechanisms such as rigidity-dependent escape from the galaxy and Fermi acceleration in interstellar space are evaluated.

scholarly journals PRECISE COSMIC RAYS MEASUREMENTS WITH PAMELA

2013 ◽  
Vol 53 (A) ◽  
pp. 712-717
Author(s):  
A. Bruno ◽  
O. Adriani ◽  
G. C. Barbarino ◽  
G. A. Bazilevskaya ◽  
R. Bellotti ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Secondary Production ◽  
Cosmic Ray ◽  
Light Nuclei ◽  
Energy Spectra ◽  
Wide Energy Range ◽  
Pamela Experiment ◽  
Production Models ◽  
The Galaxy ◽  
Wide Energy

The PAMELA experiment was launched on board the Resurs-DK1 satellite on June 15th 2006. The apparatus was designed to conduct precision studies of charged cosmic radiation over a wide energy range, from tens of MeV up to several hundred GeV, with unprecedented statistics. In five years of continuous data taking in space, PAMELA accurately measured the energy spectra of cosmic ray antiprotons and positrons, as well as protons, electrons and light nuclei, sometimes providing data in unexplored energetic regions. These important results have shed new light in several astrophysical fields like: an indirect search for Dark Matter, a search for cosmological antimatter (anti-Helium), and the validation of acceleration, transport and secondary production models of cosmic rays in the Galaxy. Some of the most important items of Solar and Magnetospheric physics were also investigated. Here we present the most recent results obtained by the PAMELA experiment.

scholarly journals The Origin and Dynamical Effects of the Magnetic Fields and Cosmic Rays in the Disk of the Galaxy

1970 ◽  
Vol 39 ◽  
pp. 168-183
Author(s):  
E. N. Parker
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Magnetic Fields ◽  
Dynamical Behavior ◽  
Cosmic Ray ◽  
Interested Reader ◽  
Written Text ◽  
The Galaxy ◽  
Basic Ideas ◽  
The Magnetic Field

The topic of this presentation is the origin and dynamical behavior of the magnetic field and cosmic-ray gas in the disk of the Galaxy. In the space available I can do no more than mention the ideas that have been developed, with but little explanation and discussion. To make up for this inadequacy I have tried to give a complete list of references in the written text, so that the interested reader can pursue the points in depth (in particular see the review articles Parker, 1968a, 1969a, 1970). My purpose here is twofold, to outline for you the calculations and ideas that have developed thus far, and to indicate the uncertainties that remain. The basic ideas are sound, I think, but, when we come to the details, there are so many theoretical alternatives that need yet to be explored and so much that is not yet made clear by observations.

Influence of supernovae, gamma-ray bursts, solar flares, and cosmic rays on the terrestrial environment

2008 ◽  
Author(s):  
Arnon Dar
Keyword(s):  
Solar Activity ◽  
Cosmic Rays ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
Gamma Ray Bursts ◽  
The Sun ◽  
Terrestrial Environment ◽  
The Earth ◽  
The Galaxy ◽  
Threat To Life

Changes in the solar neighbourhood due to the motion of the sun in the Galaxy, solar evolution, and Galactic stellar evolution influence the terrestrial environment and expose life on the Earth to cosmic hazards. Such cosmic hazards include impact of near-Earth objects (NEOs), global climatic changes due to variations in solar activity and exposure of the Earth to very large fluxes of radiations and cosmic rays from Galactic supernova (SN) explosions and gamma-ray bursts (GRBs). Such cosmic hazards are of low probability, but their influence on the terrestrial environment and their catastrophic consequences, as evident from geological records, justify their detailed study, and the development of rational strategies, which may minimize their threat to life and to the survival of the human race on this planet. In this chapter I shall concentrate on threats to life from increased levels of radiation and cosmic ray (CR) flux that reach the atmosphere as a result of (1) changes in solar luminosity, (2) changes in the solar environment owing to the motion of the sun around the Galactic centre and in particular, owing to its passage through the spiral arms of the Galaxy, (3) the oscillatory displacement of the solar system perpendicular to the Galactic plane, (4) solar activity, (5) Galactic SN explosions, (6) GRBs, and (7) cosmic ray bursts (CRBs). The credibility of various cosmic threats will be tested by examining whether such events could have caused some of the major mass extinctions that took place on planet Earth and were documented relatively well in the geological records of the past 500 million years (Myr). A credible claim of a global threat to life from a change in global irradiation must first demonstrate that the anticipated change is larger than the periodical changes in irradiation caused by the motions of the Earth, to which terrestrial life has adjusted itself. Most of the energy of the sun is radiated in the visible range. The atmosphere is highly transparent to this visible light but is very opaque to almost all other bands of the electromagnetic spectrum except radio waves, whose production by the sun is rather small.

scholarly journals Observation of Properties of Primary and Secondary Cosmic Rays by the Alpha Magnetic Spectrometer on the International Space Station

2019 ◽  
Vol 208 ◽  
pp. 13002
Author(s):  
Alberto Oliva
Keyword(s):  
Cosmic Rays ◽  
International Space Station ◽  
Spectral Index ◽  
Space Station ◽  
Cosmic Ray ◽  
Magnetic Spectrometer ◽  
Light Nuclei ◽  
International Space ◽  
Rigidity Dependence ◽  
Alpha Magnetic Spectrometer

The Alpha Magnetic Spectrometer (AMS-02) is a wide acceptance high-energy physics experiment installed on the International Space Station in May 2011 and operating continuously since then. With a collection rate of approximately 1.7 × 1010 events/year, and the combined identification capabilities of 5 independent detectors, AMS-02 is able to precisely separate cosmic rays light nuclei (1 ≤ Z ≤ 8). Knowledge of the precise rigidity dependence of the light nuclei fluxes is important in understanding the origin, acceleration, and propagation of cosmic rays. AMS-02 collaboration has recently released the precise measurements of the fluxes of light nuclei as a function of rigidity (momentum/charge) in the range between 2 GV and 3 TV. Based on the observed spectral behaviour, the light nuclei can be separated in three distinct families: primaries (hydrogen, helium, carbon, and oxygen), secondaries (lithium, beryllium, and boron), and mixed (nitrogen). Spectral indices of all light nuclei fluxes progressively harden above 100 GV. Primary cosmic ray fluxes have an identical hardening above 60 GV, of about γ = 0.12 ± 0.04. While helium, carbon and oxygen have identical spectral index magnitude, the hydrogen spectral index shows a different magnitude, i.e. the primary-to-primary H/He ratio is well described by a single power law above 45 GV with index -0.077 ± 0.007. Secondary cosmic ray fluxes have identical rigidity dependence above 30 GV. Secondary cosmic rays all harden more than primary species, and together all secondary-to-primary ratios show a hardening difference of 0.13 ± 0.03. Remarkably, the nitrogen flux is well described over the entire rigidity range by the sum of the primary flux equal to 9% of the oxygen flux and the secondary flux equal to 62% of the boron flux.

scholarly journals Composition and Galactic Confinement of Cosmic Rays

1971 ◽  
Vol 2 ◽  
pp. 740-756
Author(s):  
Maurice M. Shapiro
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Interstellar Space ◽  
Heavy Nuclei ◽  
High Energy Astrophysics ◽  
Transit Times ◽  
The Galaxy ◽  
Path Lengths

The ‘Galactic’ cosmic rays impinging on the Earth come from afar over tortuous paths, traveling for millions of years. These particles are the only known samples of matter that reach us from regions of space beyond the solar system. Their chemical and isotopic composition and their energy spectra provide clues to the nature of cosmic-ray sources, the properties of interstellar space, and the dynamics of the Galaxy. Various processes in high-energy astrophysics could be illuminated by a more complete understanding of the arriving cosmic rays, including the electrons and gamma rays.En route, some of theprimordialcosmic-ray nuclei have been transformed by collision with interstellar matter, and the composition is substantially modified by these collisions. A dramatic consequence of the transformations is the presence in the arriving ‘beam’ of considerable fluxes of purely secondary elements (Li, Be, B), i.e., species that are, in all probability, essentially absent at the sources. We shall here discuss mainly the composition of the arriving ‘heavy’ nuclei -those heavier than helium - and what they teach us about thesourcecomposition, the galactic confinement of the particles, their path lengths, and their transit times.

scholarly journals Radio haloes around galaxies and in clusters

1978 ◽  
Vol 79 ◽  
pp. 161-163
Author(s):  
V. L. Ginzburg
Keyword(s):  
Cosmic Rays ◽  
Radio Emission ◽  
Cosmic Ray ◽  
Relativistic Electrons ◽  
Radio Halo ◽  
Normal Galaxies ◽  
Extended Region ◽  
The Galaxy ◽  
Nuclear Component ◽  
Galactic Sources

The question of whether or not our and other normal galaxies have some sort of halo - an extended region containing, in particular, cosmic rays - has been discussed for no less than 25 years. Such a “cosmic ray halo” (CRH) appears as a radio-halo, although the absence of the latter is not evidence against the presence of CRH. the point is that the relativistic electrons responsible for the radio emission from the radio-halo undergo synchrotron and Compton losses which are practically absent in the case of the cosmic-ray proton-nuclear component. Possibly because the discussion concerning the existence of the radio-halo in the Galaxy has lasted for years it has acquired a particular character. the latter is clearly reflected in the report by Baldwin (1976) who emphasized that: ȜIn this discussion so far I have avoided the use of the phrase Ȝradio-haloȝ. It arouses antagonism in otherwise placid astronomers and many sought to deny its existence …ȝ Such a situation evidently reflects the difficulties that arise in detecting the radio-halo of our own Galaxy when account is taken of other confusing galactic sources as well as of the metagalactic background.

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