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  • Artikel: DFG Deutsche Nationallizenzen  (14)
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  • Artikel: DFG Deutsche Nationallizenzen  (14)
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  • 1
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] A significant fraction of the energy density of the interstellar medium is in the form of high-energy charged particles (cosmic rays). The origin of these particles remains uncertain. Although it is generally accepted that the only sources capable of supplying the energy required to accelerate ...
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 115 (1985), S. 31-37 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A hypothesis is suggested that the observed excess atE≥300 keV in the spectrum of Cyg X-1 has a nonthermal origin and is associated with the development of a relativistic electromagnetic cascade, initiated by accelerated particles in the accretion plasma, surrounding a black hole.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 115 (1985), S. 201-225 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The possibility of relativistic electron-photon shower formation in compact X-ray sources is discussed and the results of Monte-Carlo calculations are reported.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 66 (1979), S. 497-502 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An analysis of the experimental data on nuclear gamma-ray lines from Cen A reveals essential energetic difficulties, associated with the usual interpretation of these lines as a result of interactions of subcosmic rays with interstellar gas; since the necessary instantaneous energy loss rate of the cosmic rays should reach tremendous values of about 1048–1049 ergs s−1. These difficulties are eliminated if the gamma rays are produced in the relativistic non-isothermal plasma near a compact source of activity — such as a massive black hole or a magnetoid (spinar).
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 79 (1981), S. 321-336 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The problem of single Compton scattering is considered and the resulting spectrum, angular distribution and polarization of scattered photons in a general case are obtained. The inverse Compton scattering (ICS) for arbitrary energies of electronsE and photons ω0 is investigated in detail. In the case of isotropically-distributed initial photons and relativistic electrons, a strong rise of the scattered spectrum near the upper edge takes place, starting from the values of the characteristic parameterb≡4Eω 0≳10 (in units of mc2=1). The energy-loss rate of relativistic electrons due to ICS is calculated. It is shown that the relativistic electrons of the energiesE≳100 MeV, when scattering on the X-rays with ω0~10KeV, transmit the dominant part of their energy to the photons which fall after scattering into the energy range of the electrons (≳100 MeV). The radiation spectrum of ICS, as well as the energy-losses of relativistic electrons distributed by power-lawE −α, are calculated. The radiation spectrum reveals the power-law behaviour with the different indices in two limits: the dependence ω−(αα1)/2 at ωω0≪1 gradually changes to ω−(α+1) ln (ωω0) law for ωω0≫1.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 93 (1983), S. 229-245 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The annihilation spectrum of isotropically distributed monoenergetic electrons and positrons is analysed. For the annihilation spectrum of Maxwellian electron-positron plasma the convenient analytical expressions in the case of relativistic as well as nonrelativistic temperatures are obtained. A comparison of our results with those based on up-to-date numerical investigations is carried out.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 180 (1991), S. 305-320 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Very high and ultra-high-energy gamma-ray fluxes expected from giant molecular clouds, and the prospects of detection of these fluxes by means of air Cherenkov telescopes and EAS arrays of new generation are discussed.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 167 (1990), S. 93-110 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The formation of the ‘bump’ and the ‘black-body cutoff’ in the cosmic-ray (CR) spectrum arising from the π-meson photoproduction reaction in collisions of UHE CR protons with the microwave background radiation (MBR) is studied. A kinetic equation which describes CR proton propagation in the MBR with account of the catastrophic nature of the π-meson photoproduction process is derived. The equilibrium CR proton spectrum obtained from the solution of the stationary kinetic equation is in general agreement with the spectrum obtained under assumption of the continuous energy loss approximation. However, the spectra from point sources noticeably differ from those obtained in the continuous loss approximation. Both, the equilibrium and the point source spectra are modified when taking into account the possible deviation of the MBR spectrum from the Planckian one in the Wien region. Thus, for the recently measured MBR spectrum, which reveals an essential ‘excess’ in the submillimeter region, the ‘black-body cutoff’ and the preceding ‘bump’ shift towards lower energies.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 167 (1990), S. 111-124 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The possible contribution of gamma-rays predicted within the universal cosmic-ray (CR) hypothesis to the energy range of CR spectrum above ‘black-body cutoff’ is calculated. These gamma-rays arise from the relativistic electromagnetic cascade generated in the field of microwave background radiation (MBR). The ultra-high energy photons and electrons that initiate the cascade are produced at the decay of π-mesons created in interactions of photons with the MBR. Simple analytic expression for cascade gamma-ray spectrum is obtained from the solution of kinetic equations for electrons and photons as well as for protons propagating in the MBR field. It is shown that at certain values of magnetic field and radio-wave density in the intergalactic space te flux of cascade gamma-rays may at least partly mask the ‘black-body cutoff’ in the CR spectrum.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Space science reviews 49 (1989), S. 55-60 
    ISSN: 1572-9672
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Model-independent requirements for the positron source in the galactic centre are formulated. From the known physical processes of positron production the most probable seems to be the e + − e − pair production as a result of photon-photon collisions. When certain conditions are satisfied, the efficiency of positron creation due to this mechanism can reach values ≥ 10%, which is comparable with the observed ratio of the annihilation line photon luminosity to the continuum one at E γ 〉 511 keV. Such a situation can be realized: (i) in a thermal pair-dominated mildly relativistic plasma, and (ii) on the development of a nonthermal electromagnetic cascade, initiated by relativistic particles in the field of ambient X-rays. Future gamma-ray observations at ultrahigh energies can be crucial to the choice of the model.
    Materialart: Digitale Medien
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