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At least 1,207 records · Page 67
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NASA NTRS1985

A numerical study of diffusive shock acceleration of cosmic rays in supernova shocks

The evolution of the energy spectrum of cosmic rays accelerated by the first order Fermi mechanism, by a supernova remnant shock wave, including adiabatic deceleration effects behind the front, is carried out by means of a time-dependent numerical code. The calculations apply to the adiabatic stage (or Sedov stage) of the supernova explosion, and the energetic particle spectrum is calculated in the test particle limit (i.e., the back reaction of the cosmic rays on the flow is not included). The particles are injected mono-energetically at the shock. The radial distribution, The radial distribution, and the spectrum of the accelerated and decelerated particles is shown.

Ko, C. M.↗
NASA NTRS1985

Do supernovae of type 1 paly a role in cosmic-ray production?

A model of cosmic-ray origin is suggested which aims to account for some salient features of the composition. Relative to solar abundances, the Galactic cosmic rays (GCR) are deficient in hydrogen and helim (H and He) by an order of magnitude when the two compositions are normalized at iron. Our conjectural model implicates supernovae of Type I (SN-I) as sources of some of the GCR. SN-I occur approximately as often as SN-II, through their genesis is thought to be different. Recent studies of nucleosynthesis in SN-I based on accreting white dwarfs, find that the elements from Si to Fe are produced copiously. On the other hand, SN-I are virtually devoid of hydrogen, and upper limits deduced for He are low. If SN-I contribute significantly to the pool of GCR by injecting energetic particles into the interstellar medium (ISM), then this could explain why the resulting GCR is relatively deficient in H and He. A test of the model is proposed, and difficulties are discussed.

Shapiro, M. M.↗
NASA NTRS1985

Neutron-rich nuclei in cosmic rays and Wolf-Rayet stars

Wolf-Rayet stars figure prominently in astrophysical research. As a bonus, they seem to offer, in the recent past, an interesting connection between classical astronomy and high energy astrophysics due to their unusual composition and their huge mechanical power. The material flowing from WC stars (carbon-rich WR stars) contains gas which has been processed through core-helium burning, i.e., considerably enriched into 12C,16O, 22Ne, and 25,26Mg. This composition is reminiscent of the cosmic ray source anomalies. Encouraging agreement is obtained with observation in the mass range 12 A 26 assuming acceleration of wind particles at the shock that delineates the WR cavity, and adequate dilution with normal cosmic rays, but silicon poses.

Prantzos, N.↗
NASA NTRS1985

Exact solutions for sporadic acceleration of cosmic rays

The steady state spectra of cosmic rays which are subject to a sporadic acceleration process, wherein the gain in energy in each encounter is a finite fraction of the particle energy are discussed. They are derived from a mathematical model which includes the possibility of energy dependent leakage of cosmic rays from the galaxy. Comparison with observations allows limits to be placed on the frequency and efficiency of such encounters.

Cowsik, R.↗
NASA NTRS1985

An experiment to measure the energy spectrum of cosmic ray antiprotons from 100 to 1000 MeV

Production models were developed and the confirmation of each one had significant astrophysical impact. These include radical modifications of propagation models, cosmic ray antiprotons injection from neighboring domains of antimatter, p production by evaporating primordial black holes, and cosmic ray p's as annihilation products of supersymmetry particles that might make up the dark dynamical mass of the Galaxy. It is that p's originating from supersymmetric parents might have distinct spectral features that would survive solar modulation; in one model, higgsino annihilation proceeds through the bb quark-antiquark channel, producing a spectral bump at approx. 0.3 GeV in the p spectrum.

Salamon, M. H.↗
NASA NTRS1985

The development of a high energy cosmic ray detector for Spacelab-2

A large cosmic ray detector aimed at measurements of the energy spectra and of the elemental abundances of cosmic ray nuclei at very high energies, up to several TeV/nucleon was constructed. The instrument is an electronic counter telescope with a geometric factor of 5 sq ster. It accomplishes measurements of the particle energies through the use of gas Cerenkov counters and of transition radiation detectors. The solutions of a number of technological problems that are encountered when developing such instrumentation for Shuttle missions are discussed.

Lheureux, J.↗
NASA NTRS1985

Cherenkov-dE/dx-range measurements on cosmic ray iron group nuclei

A balloon experiment which combined a large area plastic detector unit with electronic dE/dx-C data is presented. The correlation of the electronic data with the range data of the plastic detector stack was achieved by rotating plastic detector disks which provided in this way the passive plastic detector with an incorporated time determination. The constant flux of cosmic ray particles with charge Z greater than two was used to gauge the time resolving system. Stopping cosmic ray iron group nuclei in the energy range 400 to 700 MeV/nuc are identified using their electronic scintillator and Cherenkov signals and their etch conelengths and range data. The precise knowledge of the particle's trajectory proposes refined pathlength corrections to the electronic data.

Sermund, G.↗
NASA NTRS1985

Nineteenth International Cosmic Ray Conference. SH Sessions, Volume 5

Papers submitted for presentation at the 19th International Cosmic Ray Conference are compiled. This volume contains papers addressing cosmic ray gradients in the heliosphere; siderial, diurnal, and long term modulations; geomagnetic and atmospheric effects; cosmogenic nuclides; solar neutrinos; and detection techniques.

Jones, F. C.↗
NASA NTRS1985

Influence of the neutral sheet on the Swinson's type north-south anisotropy of cosmic rays

The relations between the north-south anisotropy of cosmic rays and/or nucleonic intensity variation and the latitudinal angular distance (lambda) of the Earth from the neutral sheet is examined using the data in the period from Apr. 1976 to Aug. 1977 at the solar minimum. It is found that the nucleonic intensity variation of the cosmic rays has no correlation with sin lambda in this period as shown in a correlation diagram; but the amplitude of the north-south anisotropy is fairly correlated with sin lambda as shown in another diagram.

Munakata, Y.↗
NASA NTRS1985

Characteristics of cosmic ray pole-equator anisotropy derived from spherical harmonic analysis of neutron monitor data

The spherical harmonic analysis of cosmic ray neutron data from the worldwide network neutron monitor stations during the years, 1966 to 1969 was carried out. The second zonal harmonic component obtained from the analysis corresponds to the Pole-Equator anisotropy of the cosmic ray neutron intensity. Such an anisotropy makes a semiannual variation. In addition to this, it is shown that the Pole-Equator anisotropy makes a variation depending on the interplanetary magnetic field (IMF) sector polarities around the passages of the IMF sector boundary. A mechanism to interpret these results is also discussed.

Takahashi, H.↗
NASA NTRS1985

First zonal harmonic component of cosmic ray neutron intensity

Cosmic ray neutron data from the cosmic ray stations from the worldwide network in 1966, 1967 and 1969 are analyzed by means of the three dimensional analysis method by Nagashima. The variations of the north-south anisotropy, which is the first zonal harmonic component obtained from the analysis are studied. The result obtained confirms earlier findings. Relationship of the anisotropy to the interplanetary magnetic field sector polarity is also studied.

Takahashi, H.↗
NASA NTRS1985

The corotating variation of the north-south anisotropy of cosmic rays

Correlation analysis on the relation of the north-south (N-S) anisotropy of cosmic rays, observed by the Nagoya multidirectional meson telescope, with the interplanetary magnetic field (IMP) as well the solar wind velocity within solar Carrington rotation for the period 1971 to 1976 is discussed. It is found that the N-S anisotropy of cosmic rays correlates quite well with the Bx component of the IMF. The correlation coefficient is nearly equal to 0.8.

Xue, S.↗
NASA NTRS1985

A study of periodicities and recurrences in solar activity and cosmic ray modulation

The 154d periodicity was found in the cosmic ray intensity (RE) vs Flares, and some other peaks of coherency in the RC vs aa sub I, that when interpreted as aliased values, might correspond to recurring interplanetary magnetic field structures and solar wind streams. It cannot be excluded, however, that some of the correspondence with aa are of terrestrial origin. This study cannot be considered exhaustive due to the fact that other solar variables, such as polar hole size, are possibly correlated to cosmic ray intensities. However, the number of observations is small so that the interpretation of the results is very difficult.

Attolini, M. R.↗
NASA NTRS1985

Dynamics of two-year cosmic ray variations inferred from the data of spacecraft and stratospheric measurements and from the neutron monitor data in 1959-1981

The two year cosmic ray variations are studied using the spacecraft measurements of 1967 to 1976, the sonde measurements at high latitudes in the stratosphere (Murmansk, Mirny), and the neutron monitor data of 1959 to 1981. The two year variations are most pronounced from 1967 to 1975. An anticorrelation is observed between the two year variations in cosmic rays and in geomagnetic activity.

Charakhchyan, T. N.↗
NASA NTRS1985

Long-term modulation of galactic cosmic rays in high-energy region

The results of continuous registration of the cosmic ray muon intensity on the ground and underground at 7, 20 and 60 m w.e. depths in Yakutsk for 1957 to 1983 are presented. In years of the solar activity maximum in cosmic ray density were found two minima or two-stepped decrease. The second intensity minimum appears to be not the result of the inversion of the general magnetic field of the Sun but caused by the increase of the solar wind speed.

Krivoshapkin, P. A.↗
NASA NTRS1985

Solar tri-diurnal variation of cosmic rays in a wide range of rigidity

Solar tri-diurnal variations of cosmic rays have been analyzed in a wide range of rigidity, using data from neutron monitors, and the surface and underground muon telescopes for the period 1978-1983. The rigidity spectrum of the anisotropy in space is assumed to be of power-exponential type as (P/gamma P sub o) to the gamma exp (gamma-P/P sub o). By means of the best-fit method between the observed and the expected variations, it is obtained that the spectrum has a peak at P (=gamma P sub o) approx = 90 GV, where gamma=approx 3.0 and P sub o approx. 30 GV. The phase in space of the tri-diurnal variation is also obtained as 7.0 hr (15 hr and 23 hr LT), which is quite different from that of approx. 1 hr. arising from the axisymmetric distribution of cosmic rays with respect to the IMF.

Mori, S.↗