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At least 361 records · Page 20
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NASA NTRS1982

Cosmic ray antimatter and baryon symmetric cosmology

The relative merits and difficulties of the primary and secondary origin hypotheses for the observed cosmic-ray antiprotons, including the new low-energy measurement of Buffington, et al. We conclude that the cosmic-ray antiproton data may be evidence for antimatter galaxies and baryon symmetric cosmology. The present bar P data are consistent with a primary extragalactic component having /p=/equiv 1+/- 3.2/0.7x10 = to the -4 independent of energy. We propose that the primary extragalactic cosmic ray antiprotons are most likely from active galaxies and that expected disintegration of bar alpha/alpha ban alpha/alpha. We further predict a value for ban alpha/alpha =/equiv 10 to the -5, within range of future cosmic ray detectors.

Stecker, F. W.↗
NASA NTRS1984

Elemental advances of ultraheavy cosmic rays

The elemental composition of the cosmic-ray source is different from that which has been generally taken as the composition of the solar system. No general enrichment of products of either r-process or s-process nucleosynthesis accounts for the differences over the entire range of ultraheavy (Z 30) elements; specific determination of nucleosynthetic contributions to the differences depends upon an understanding of the nature of any acceleration fractionation. Comparison between the cosmic-ray source abundances and the abundances of C1 and C2 chondritic meteorites suggests that differences between the cosmic-ray source and the standard (C1) solar system may not be due to acceleration fractionation of the cosmic rays, but rather to a fractionation of the C1 abundances with respect to the interstellar abundances.

Source record↗
NASA NTRS1983

Large scale solar modulation of 500 MeV/N galactic cosmic rays seen from 1-30 AU

Using measurements of cosmic rays obtained by Cerenkov counters on Pioneer 10 and Pioneer 11 and neutron monitor data from Earth, the spatial and temperal development of cosmic ray modulation during the last solar maximum were observed. The large-scale features of modulation and recovery are similar at these three sites and thus appear rotationally symmetric near the ecliptic plane. Outward propagating features characterize the radial dependence. The decline of the old cosmic ray cycle is marked by steplike decreases that propagate outward at nearly the solar wind velocity. During the start of the new cosmic ray cycle, recovery occurs first in the inner heliosphere and, after a lag comparable with that of the declining phase, appears later farther out. However, the direction of diffusive propagation is still inward, because the gradient remains positive. Forbush decreases are common at all three sites, and are evidently of great importance in understanding modulation. The largest decrease occurred during a short series of events in the summer of 1982 and had half the amplitude of the eleven year cycle.

Fillius, W.↗
NASA NTRS1983

Solar modulation of galactic cosmic rays. V - Time-dependent modulation

A numerical technique is introduced for the solution of the time-dependent equation for the solar modulation of galactic cosmic rays, in which transport in heliographic latitude is ignored. We illustrate this method with a model for the solar cycle variation in cosmic ray intensity. The variation is assumed to result from changes in the number of enhanced cosmic ray scattering regions, which are produced by flare-generated shock waves in the solar wind. The model can account for the observed solar cycle variation in intensity at different energies as well as the observed spatial gradients. This model also provides a natural explanation for the cosmic ray hysteresis effect.

Perko, J. S.↗
NASA NTRS1984

Integral radial cosmic ray gradients in the solar system from 1972 to 1982

The cosmic-ray telescope data on IMP 8, Voyagers 1 and 2, and Pioneer 10 have been used to determine the integral radial cosmic-ray intensity gradients for energies greater than 60 MeV per nucleon. When the 26 day average counting rates are time-shifted for the effects of the outward propagation speed of the solar modulation, the average integral radial gradients (Gr) are 3.0 + or - 0.35 (percent/AU) from 1975 to 1982. Gr is independent to the first order of the cosmic-ray intensity and radial heliocentric distance out to about 30 AU. After the large transient variations in the cosmic-ray intensity in mid-1982, the integral gradients returned to their original values.

Lockwood, J. A.↗
NASA NTRS1984

Radial gradient of cosmic ray intensity from a comparative study of data from Voyager 1 and 2 and IMP 8

The IMP 8 satellite and Voyager 1 and 2 space probes obtained cosmic ray measurements during the late 1977 to mid-1982 period. Comparisons of 27-day averages of the data show that a positive radial intensity gradient existed on the average during this period, and that the cosmic ray intensity decrease toward solar maximum in 1980-1981 proceeds in a stepwise fashion. The cosmic ray minimum reached in late 1980/early 1981 appears almost simultaneously at 1 AU and at 10 AU, with and without propagation time delay effects, between IMP 8 and the Voyager spacecraft. These data are generally consistent with a heliolatitudinal gradient of 0 + or - 1 percent/deg. Attention is given to the implications of these results in the overall context of cosmic ray modulation theory.

Venkatesan, D.↗
NASA NTRS1985

Long term variability of the cosmic ray intensity

In a previous paper Bhat, et al., assess the evidence for the continuing acceleration of cosmic rays in the Loop I supernova remnant. The enhanced gamma-ray emission is found consistent with the Blandford and Cowie model for particle acceleration at the remnant shock wave. The contributions of other supernovae remnants to the galactic cosmic ray energy density are now considered, paying anisotropy of cosmic rays accelerated by local supernovae ( 100 pc). The results are compared with geophysical data on the fluctuations in the cosmic ray intensity over the previous one billion years.

Bhat, C. L.↗
NASA NTRS1985

A model for the proton spectrum and cosmic ray anisotropy

The problem of the origin of the cosmic rays is still uncertain. As a theory, it should explain the support of particles and energy, the mechanism of acceleration and propagation as well as some important features obtained directly from cosmic ray experiments, such as the power spectrum and the knee. There are two kinds of models for interpreting the knee of the cosmic ray spectrum. One is the leaky box model. Another model suggests that the cut-off rigidity of the main sources causes the knee. The present paper studies the spectrum and the anisotropy of cosmic rays in an isotropic diffuse model with explosive discrete sources in an infinite galaxy.

Xu, C.↗
NASA NTRS1985

Difference between even and odd 11-year cycles in cosmic ray intensity

Cosmic ray data for the period 1946-1984 are used to determine the run of the cosmic ray intensity over three complete solar cycles. The analysis shows a tendency towards a regular alternation of cosmic ray intensity cycles with double and single maxima. Whereas a saddle-like shape is characteristic of even cycles, odd cycles are characterized by a peak-like shape. The importance of this behavior is discussed in terms of different processes influencing cosmic ray transport in the heliosphere.

Otaola, J. A.↗
NASA NTRS1985

Elemental technetium as a cosmic-ray clock

Several radioactive isotopes have been proposed as clocks for the study of the mean cosmic ray confinement time, T sub e. Measurements of Be-10 and Al-26 give a value for T sub e of about 10 Myr when one uses a leaky box cosmic ray propagation model. It is important to obtain additional measurements of T sub e from other radioactive isotopes in order to check whether the confinement is the same throughout the periodic table. The possible use of Tc (Z = 43) as a cosmic clock is investigated. Since all isotopes of Tc are radioactive, one might be able to group these isotopes and use the elemental abundance as a whole. The results of the calculations are somewhat inconclusive for two reasons. First, the beta + decay half lives of two of the Tc isotopes relevant to our calculation are not known. Second, the dependence of the Tc abundance on the mean confinement time is rather weak when one considers the number of events expected in 4 trays of plastic track detectors. However, a future, finite measurement of the Beta + half lives and the possible use of the entire collecting area of the HNC to detect Tc nuclei could make the use of Tc as a cosmic ray clock more attractive.

Drach, J.↗
NASA NTRS1985

Cosmic ray secondary nuclei and the structure of the galaxy

The consequencies of diffusive acceleration of cosmic rays in supernova shocks propagation through an inhomogeneous interstellar medium are explored. The acceleration takes place in the hot, tenuous, intercloud gas, while nuclear collisions, leading to the production of cosmic ray secondaries, predominantly occur in those regions where the supernova shocks collide with interstellar clouds. A simple model is used to calculate the interaction of a (cosmic ray + gas) shock with a cloud, and thus determine the gross topology. Extending this to the whole system, using mean cloud sizes and space densities, allows us to calculate the secondary/primary cosmic ray abundance ratios for light and heavy nuclei.

Morfill, G. E.↗
NASA NTRS1985

Propagation of cosmic rays and new evidence for distributed acceleration

The origin and propagation of cosmic rays in terms of conventional and supplementary newer assumptions were explored. Cosmic rays are considered to be accelerated by supernoava shock waves and to traverse clouds in the source region. After rigidity-dependent escape from these clouds into interstellar space, cosmic rays are further accelerated by the weakened shocks of old supernova remnants and then pass through additional material. The distributed acceleration hypothesis is discussed with emphasis on recent data on the abundances of cosmic-ray isotopes of N above 1 GeV/u and of He near 6 GeV/u.

Silberberg, R.↗
NASA NTRS1985

Relativistic transport theory for cosmic-rays

Various aspects of the transport of cosmic-rays in a relativistically moving magnetized plasma supporting a spectrum of hydromagnetic waves that scatter the cosmic-rays are presented. A local Lorentz frame moving with the waves or turbulence scattering the cosmic-rays is used to specify the individual particle momentum. The comoving frame is in general a noninertial frame in which the observer's volume element is expanding and shearing, geometric energy change terms appear in the cosmic-ray transport equation which consist of the relativistic generalization of the adiabatic deceleration term and a further term involving the acceleration vector of the scatterers. A relativistic version of the pitch angle evolution equation, including the effects of adiabatic focussing, pitch angle scattering, and energy changes is presented.

Webb, G. M.↗
NASA NTRS1985

Variations of the cosmic ray general component in Antarctica

A cosmic ray variations, zonal cosmic ray modulation, was found in the lower atmosphere from the sonde measurement results. The variations give rise to anomalies in the latitude distributions of the cosmic ray charged component and the anomalous north-south asymmetry. To find the nature of the variations, the cosmic ray general component was measured with the same detectors as in the sonde measurements gas discharge counters and the counter telescopes with 7-mm Al filters detecting the electrons of energy above 200 keV and 5 MeV. The measurement data obtained in Antarctica in the years 1978 to 1983 are presented and discussed.

Charakhchyan, T. N.↗
NASA NTRS1985

Magnetic fluctuation and cosmic ray diurnal variations

A unified theory of cosmic ray diurnal variations has been proposed in which the first 3 harmonics of the cosmic ray daily variation all results from a single anisotropy produced by the combined effects of adiabatic focusing and anisotropic pitch angle scattering. The theoretical description of steady state cosmic ray anisotropies are simplified and improved. Preliminary results of a study of correlations between cosmic ray diurnal variations and the fluctuation characteristics of the interplanetary magnetic field are presented and discussed in light of the theory.

Bieber, J. W.↗
NASA NTRS1985

Study of cosmic ray scintillations from 5-minute data of the scintillations telescope Izmran and world-wide network stations

During cosmic ray propagation in interplanetary space there appear characteristic cosmic-ray intensity scintillations which are due to charged particle scattering on random inhomogeneities of the interplanetary magnetic field. The power spectra of cosmic ray scintillations on the Earth during some intervals from 1977 to 1982 (for quiet periods, for solar flares and Forbush decreases due to power shock waves) have been calculated from five-minute, one and two-hour values of the cosmic-ray intensity measured by the scintillator supertelescope IZMIRAN. The spectra were estimated by the methods of spectral analysis and by autoregressive methods which mutually control each other and make it possible not only to analyze scintillation powers at distinguished frequencies, but also to determine the behavior of spectrum slopes in some frequency ranges.

Gulinsky, O. V.↗
NASA NTRS1985

Cosmic-ray exposure records and origins of meteorites

The cosmic-ray records of meteorites are used to infer much about their origins and recent histories. The methods used to interpret meteorites' cosmic-ray records, especially identifying simple or complex exposure histories, often are inadequate. Spallogenic radionuclides, stable nuclides, and measurements of products that have location-sensitive production rates, such as the tracks of heavy cosmic-ray nuclei or neutron-capture nuclides, are very useful in accurately determining a meteorite's history. Samples from different, known locations of a meteorite help in studying the cosmic-ray record. Such extensive sets of meteorite measuremetns, plus theoretical modeling of complex histories, improves the ability to predict the production of cosmogenic nuclides in meteorites, to distinguish simple and complex exposure histories, and to better determine exposure ages.

Reedy, R. C.↗
NASA NTRS1985

Solar cosmic ray bursts and solar neutrino fluxes

The neutrino flux detected in the C1-Ar experiment seems to respond to the powerful solar cosmic ray bursts. The ground-based detectors, the balloons and the satellites detect about 50% of the bursts of soalr cosmic ray generated on the Sun's visible side. As a rule, such bursts originate from the Western side of the visible solar disk. Since the solar cosmic ray bursts are in opposite phase withthe 11-year galactic cosmic ray cycle which also seems to be reflected by neutrino experiment. The neutrino generation in the bursts will flatten the possible 11-year behavior of the AR-37 production rate, Q, in the Cl-Ar experiment. The detection of solar-flare-generated gamma-quanta with energies above tens of Mev is indicative of the generation of high-energy particles which in turn may produce neutrinos. Thus, the increased Q during the runs, when the flare-generated high energy gamma-quanta have been registered, may be regarded as additional evidence for neutrino geneation in the solar flare processes.

Basilevakaya, G. A.↗