Gamma-rays from cosmic-ray irradiated molecular clouds

1981 ◽  
Vol 301 (1462) ◽  
pp. 533-535 ◽  
Keyword(s):  
Monte Carlo ◽  
Cosmic Rays ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Cosmic Ray ◽  
Monte Carlo Analysis ◽  
The Galaxy

An examination is made of the contribution to the number of apparently discrete sources of y-rays from cosmic rays interacting with molecular clouds in the Galaxy. Attention is directed to specific nearby clouds and to clouds in general, the latter by a Monte-Carlo analysis.

scholarly journals Gamma Rays from Cosmic Rays

1981 ◽  
Vol 94 ◽  
pp. 309-319 ◽  
Author(s):  
A. W. Wolfendale
Keyword(s):  
Cosmic Rays ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity ◽  
Cosmic Ray Interactions ◽  
The Galaxy ◽  
Γ Rays ◽  
Γ Ray

It is shown that there is evidence favouring molecular clouds being sources of γ-rays, the fluxes being consistent with expectation for ambient cosmic rays interacting with the gas in the clouds for the clouds considered. An estimate is made of the fraction of the apparently diffuse γ-ray flux which comes from cosmic ray interactions in the I.S.M. as distinct from unresolved discrete sources. Finally, an examination is made of the possibility of gradients of cosmic ray intensity in the Galaxy.

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.

scholarly journals High energy cosmic ray interactions and UHECR composition problem

2019 ◽  
Vol 210 ◽  
pp. 02001
Author(s):  
Sergey Ostapchenko
Keyword(s):  
Experimental Data ◽  
Monte Carlo ◽  
Cosmic Rays ◽  
Cosmic Ray ◽  
High Energy ◽  
Ultra High Energy ◽  
Hadronic Interactions ◽  
High Energy Cosmic Rays ◽  
Cosmic Ray Interactions ◽  
Composition Problem

The differences between contemporary Monte Carlo generators of high energy hadronic interactions are discussed and their impact on the interpretation of experimental data on ultra-high energy cosmic rays (UHECRs) is studied. Key directions for further model improvements are outlined. The prospect for a coherent interpretation of the data in terms of the UHECR composition is investigated.

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 Molecular Clouds and Star Formation at Large R

1991 ◽  
Vol 144 ◽  
pp. 121-130
Author(s):  
J. Brand ◽  
J.G.A. Wouterloot
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Density Wave ◽  
Cosmic Ray ◽  
Volume Density ◽  
Kinetic Temperature ◽  
Galactocentric Distance ◽  
The Galaxy ◽  
The Mean ◽  
Cosmic Ray Flux

In the outer Galaxy (defined here as those parts of our system with galactocentric radii R>R0) the HI gas density (Wouterloot et al., 1990), the cosmic ray flux (Bloemen et al, 1984) and the metallicity (Shaver et al., 1983) are lower than in the inner parts. Also, the effect of a spiral density wave is much reduced in the outer parts of the Galaxy due to corotation. This changing environment might be expected to have its influence on the formation of molecular clouds and on star formation within them. In fact, some differences with respect to the inner Galaxy have been found: the ratio of HI to H2 surface density is increasing from about 5 near the Sun to about 100 at R≈20kpc (Wouterloot et al., 1990). Because of the “flaring” of the gaseous disk, the scale height of both the atomic and the molecular gas increases by about a factor of 3 between R0 and 2R0 (Wouterloot et al., 1990), so the mean volume density of both constituents decreases even more rapidly than their surface densities. The size of HII regions decreases significantly with increasing galactocentric distance (Fich and Blitz, 1984), probably due to the fact that outer Galaxy clouds are less massive (see section 3.3), and therefore form fewer O-type stars than their inner Galaxy counter parts. There are indications that the cloud kinetic temperature is lower by a few degrees (Mead and Kutner, 1988), although it is not clear to what extent this is caused by beam dilution.

scholarly journals Could bow-shaped magnetic morphologies surround filamentary molecular clouds?

2019 ◽  
Vol 632 ◽  
pp. A68 ◽  
Author(s):  
M. Tahani ◽  
R. Plume ◽  
J. C. Brown ◽  
J. D. Soler ◽  
J. Kainulainen
Keyword(s):  
Magnetic Field ◽  
Monte Carlo ◽  
Magnetic Fields ◽  
Faraday Rotation ◽  
Molecular Clouds ◽  
Monte Carlo Analysis ◽  
Line Of Sight ◽  
Field Reversal ◽  
Filamentary Structure ◽  
Western Side

Context. A new method based on Faraday rotation measurements recently found the line-of-sight component of magnetic fields in Orion-A and showed that their direction changes from the eastern side of this filamentary structure to its western side. Three possible magnetic field morphologies that can explain this reversal across the Orion-A region are toroidal, helical, and bow-shaped morphologies. Aims. In this paper, we constructed simple models to represent these three morphologies and compared them with the available observational data to find the most probable morphology(ies). Methods. We compared the observations with the models and used probability values and a Monte Carlo analysis to determine the most likely magnetic field morphology among these three morphologies. Results. We found that the bow morphology had the highest probability values, and that our Monte-Carlo analysis suggested that the bow morphology was more likely. Conclusions. We suggest that the bow morphology is the most likely and the most natural of the three morphologies that could explain a magnetic field reversal across the Orion-A filamentary structure (i.e., bow, helical and toroidal morphologies).

scholarly journals What do Gamma Rays tell us about the ISM?: New Insight from the Compton Observatory

1996 ◽  
Vol 169 ◽  
pp. 437-446 ◽  
Author(s):  
Hans Bloemen
Keyword(s):  
Interstellar Medium ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Line Emission ◽  
Cosmic Ray ◽  
Gamma Ray Astronomy ◽  
Early Results ◽  
The Galaxy ◽  
Γ Ray ◽  
Insight Into

Gamma-ray astronomy has become a rich field of research and matured significantly since the launch of NASA's Compton Gamma Ray Observatory in April 1991. Studies of the diffuse γ-ray emission of the Galaxy can now be performed in far more detail and extended into the MeV regime, including both continuum and line emission. These studies provide unique insight into various aspects of the interstellar medium, in particular of the cosmic-ray component. This paper gives a brief review on the diffuse Galactic γ-ray emission and summarizes early results and prospects from the Compton Observatory.

scholarly journals Interaction between molecular clouds and MeV–TeV cosmic-ray protons escaped from supernova remnants

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Ken Makino ◽  
Yutaka Fujita ◽  
Kumiko K Nobukawa ◽  
Hironori Matsumoto ◽  
Yutaka Ohira
Keyword(s):  
Gamma Rays ◽  
Molecular Clouds ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
Iron Line ◽  
X Ray ◽  
Line Intensities ◽  
Neutral Gas ◽  
Additional Support

Abstract Recent discovery of the X-ray neutral iron line (Fe  i Kα at 6.40 keV) around several supernova remnants (SNRs) show that MeV cosmic-ray (CR) protons are distributed around the SNRs and are interacting with neutral gas there. We propose that these MeV CRs are the ones that have been accelerated at the SNRs together with GeV–TeV CRs. In our analytical model, the MeV CRs are still confined in the SNR when the SNR collides with molecular clouds. After the collision, the MeV CRs leak into the clouds and produce the neutral iron line emissions. On the other hand, GeV–TeV CRs had already escaped from the SNRs and emitted gamma-rays through interaction with molecular clouds surrounding the SNRs. We apply this model to the SNRs W 28 and W 44 and show that it can reproduce the observations of the iron line intensities and the gamma-ray spectra. This could be additional support of the hadronic scenario for the gamma-ray emissions from these SNRs.

scholarly journals THE MYSTERIOUS ULTRAHIGH ENERGY COSMIC RAY CLUSTERING

2001 ◽  
Vol 16 (31) ◽  
pp. 2033-2045 ◽  
Author(s):  
LUIS A. ANCHORDOQUI ◽  
HAIM GOLDBERG ◽  
STEPHEN REUCROFT ◽  
JOHN SWAIN ◽  
GUSTAVO E. ROMERO ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Cosmic Rays ◽  
Cosmic Ray ◽  
Ultrahigh Energy ◽  
Arrival Direction ◽  
Ultrahigh Energy Cosmic Rays ◽  
Chance Probability

We examine the correlation between compact radio quasars (redshifts in the range z=0.3–2.2) and the arrival direction of ultrahigh energy cosmic rays forming clusters. Our Monte Carlo simulation reveals a statistically significant correlation on the AGASA sample: the chance probability of this effect being less than 1%. The implications of this result on the origin of ultrahigh energy cosmic rays are discussed.

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.

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