نتایج جستجو برای: cosmic rays
تعداد نتایج: 69861 فیلتر نتایج به سال:
It has been suggested that cosmological γ-ray bursts (GRBs) can produce the observed flux and spectrum of cosmic rays at the highest energies. However, recent observations indicate that the redshift distribution of GRBs most likely follows that of the star formation rate in the universe, a rate which was much higher at redshifts 1.5-2 than it is today. Thus, most GRBs are at high redshifts. As ...
We investigate the injection spectrum of ultra-high-energy (> 10 eV) cosmic rays under the hypotheses that (1) these cosmic rays are protons and (2) the sources of these cosmic rays are extra-galactic and are homogeneously distributed in space, although they may have had a different strength in the past; furthermore, we assume that we are not unusually close to any individual source(s). The mos...
It has been suggested that cosmological γ-ray bursts (GRBs) can produce the observed flux and spectrum of cosmic rays at the highest energies. However, recent observations indicate that the redshift distribution of GRBs most likely follows that of the star formation rate in the universe, a rate which was much higher at redshifts 1.5-2 than it is today. Thus, most GRBs are at high redshifts. As ...
EGRET data on the Gamma ray emission from the inner Galaxy have shown a rather flat spectrum. This spectrum extends to about 50 GeV in photon energy. It is usually assumed that these gamma-rays arise from the interactions of cosmic ray nuclei with ambient matter. Cosmic Ray particles have been observed up to 3 10 20 eV, with many arguments suggesting, that up to about 3 10 18 eV they are of Gal...
The global processes that determine cosmic ray modulation are reviewed. The essential elements of the theory which describes cosmic ray behavior in the heliosphere are summarized, and a series of discussions is presented which compare the expectations of this theory with observations of the spatial and temporal behavior of both galactic cosmic rays and the anomalous component; the behavior of c...
NASA's Chandra X-ray Observatory has discovered the first direct evidence for a superfluid, a bizarre, friction-free state of matter, at the core of a neutron star. Superfluids created in laboratories on Earth exhibit remarkable properties, such as the ability to climb upward and escape airtight containers. The finding has important implications for understanding nuclear interactions in matter ...
Assuming that refractory elements in cosmic rays originate in dust grains, we examine the viability of cosmic ray origin models wherein the bulk of present day cosmic rays are accelerated out of fresh supernova ejecta material before it mixes with the average interstellar medium (ISM). We conclude that the fresh ejecta scenarios that have been proposed thus far have serious flaws, and are unabl...
Recent observations on ultra high energy cosmic rays (those cosmic rays with energies greater than ∼ 4× 10 eV) suggest an abundant flux of incoming particles with energies above 1× 10 eV. These observations violate the Greisen-Zatsepin-Kuzmin cutoff. To explain this anomaly we argue that quantum-gravitational effects may be playing a decisive role in the propagation of ultra high energy cosmic ...
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