نتایج جستجو برای: cosmic ray nucleus
تعداد نتایج: 432120 فیلتر نتایج به سال:
Context. Low-energy cosmic rays are a fundamental source of ionization for molecular clouds, influencing their chemical, thermal and dynamical evolution. Aims. The purpose of this work is to explore the possibility that a low-energy component of cosmic-rays, not directly measurable from the Earth, can account for the discrepancy between the ionization rate measured in diffuse and dense interste...
Radio relics in galaxy clusters are extended synchrotron sources produced by cosmic-ray electrons the microgauss magnetic field. Many found cluster periphery and have a cluster-centric, narrow arc-like shape, which suggests that accelerated or reaccelerated merger shock fronts propagating outward intracluster plasma. In X-ray, some do exhibit such shocks at location of relic, but many not. We e...
We present a time-dependent cosmic-ray modified shock model for which the calculated Hα emissivity profile agrees well with the Hα flux increase ahead of the Balmer-dominated shock at knot g in Tycho’s supernova remnant, observed by Lee et al. (2007). The backreaction of the cosmic ray component on the thermal component is treated in the two-fluid approximation, and we include thermal particle ...
Aims. The capability of radio antenna arrays to measure cosmic ray air showers with very large zenith angles is explored. This is important, since a possible neutrino detection has to fulfill two requirements. First: antennas should be able to detect very inclined cosmic ray air showers, and second: it should be possible to estimate the distance to the shower maximum, since neutrinos are most l...
We use the high energy predictions of a QCD-inspired parameterization of all accelerator data on forward proton-proton and antiproton-proton scattering amplitudes, along with Glauber theory, to predict proton–air cross sections at energies near √ s ≈ 30 TeV. The parameterization of the proton-proton cross section incorporates analyticity and unitarity, and demands that the asymptotic proton is ...
[1] Galactic cosmic ray electrons and nuclei respond differently to solar modulation, with the differences directly related to the reversals of the solar magnetic field, which occur every 11 years. If the large-scale heliospheric magnetic field has certain types of structures, the charge sign of cosmic ray particles can affect their propagation. Careful study of the behavior of cosmic ray posit...
Supernova remnants are likely to be the accelerators of the galactic cosmic rays. Assuming the correctness of this hypothesis, we develop a method to extract the parent cosmic ray spectrum from the VHE gamma ray flux emitted by supernova remnants (and other gamma transparent sources). We illustrate the use of this technique by applying it to the young SNR RX J1713.7-3946 which has been observed...
Supernova remnants have long been regarded as sources of the Galactic cosmic rays up to petaelectronvolts, but convincing evidence is still lacking. In this work we explore the common origin of the subtle features of the cosmic ray spectra, such as the knee of cosmic ray spectra and the excesses of electron/positron fluxes recently observed by ATIC, H.E.S.S., Fermi-LAT and PAMELA. Numerical cal...
In this review it will be attempted to briefly cover some of the recent developments in the observation of photons and neutrinos to constrain models on the origin and acceleration of cosmic rays. It appears that EGRET on board of CGRO provides most valuable new data in that context. Data from high energy airshower arrays and Tscherenkov telescopes add to the picture although not yet strong enou...
In 1990’s Very High Energy Gamma-ray Astrophysics has dramatically advanced due to the Imaging Air Čerenkov Telescopes(IACTs). After the first detection of TeV gamma-ray emission from the Crab nebula in 1989, several type of TeV gamma-ray sources, Active Galactic Nuclei(AGN), young pulsar, and SuperNova Remnant(SNR), have been detected. In those discoveries, recent detections of both synchrotro...
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