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At least 955 records · Page 53
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NASA NTRS1985

Anisotropy of cosmic rays above 10(14) eV

A survey is made of the anisotropy of cosmic rays at energies above 10 to the 14th power eV. It is concluded that cosmic gamma-rays may have an effect in the range 10 to the 14 power - 10 to the 16th power eV, above which protons dominate. Evidence is presented for an excess in the general direction of the Galactic plane which grows with increasing energy until about 10 to the 19th power eV, indicating a Galactic origin for these particles. At higher energies an Extragalactic origin is indicated.

Wdowczyk, J.↗
NASA NTRS1985

Interpretation of cosmic-ray anisotropy below 10(14) eV

It is found that the measured data on the degree of anisotropy of cosmic rays are consistent with our proposed nonuniform galactic disk model. Moreover, it is pointed out that the abrupt increase of the anisotropy of cosmic rays beyond 10 to the 14th power eV should imply a change of their mass composition.

Tan, L. C.↗
NASA NTRS1985

Observed antiprotons and energy dependent confinement of cosmic rays: A conflict?

In the frame work of energy dependent confinement for cosmic rays, the energy spectrum inside the source is flatter than that observed. Antiproton observation suggests large amount of matter is being traversed by cosmic rays in some sources. As a result, secondary particles are produced in abundance. Their spectra was calculated and it is shown that the energy dependent confinement model is in conflict with some observations.

Stephens, S. A.↗
NASA NTRS1985

Galactic cosmic ray antiprotons and supersymmetry

The physics of the annihilation of photinos is considered as a function of mass in detail, in order to obtain the energy spectra of the cosmic ray antiprotons produced under the assumption that photinos make up the missing mass in the galactic halo. The modulated spectrum is at 1 a.w. with the cosmic ray antiprotons data. A very intriguing fit is obtained to all of the present antiprotons up to 13.4 GeV data for similar to 15 GeV. A cutoff is predicted in the antiprotons spectrum at E = photino mass above which only a small flux from secondary production should remain.

Stecker, F. W.↗
NASA NTRS1985

Halo of NGC 4631 and models of cosmic-ray transport

The halo of edge on spiral galaxy of NGC 4631 is studied from 327 MHz to 10700 MHz to delineate the models of cosmic ray transport. Preliminary studies show that the spectral steepening as a function of height above the plane can be understood in terms of the simplest cosmic ray transport models, viz., simple isotropic diffusion in an infinite medium.

Cowsik, R.↗
NASA NTRS1985

Ninteenth International Cosmic Ray Conference. SH Sessions, Volume 4

Papers submitted for presentation at the 19th International Cosmic Ray Conference are compiled. This volume covers solar and heliospheric phenomena, specifically, particle acceleration; cosmic ray compsotion, spectra, and anisotropy; propagation of solar and interplanetary energetic particles; solar-cycle modulation; and propagation of galactic particles in the heliosphere.

Jones, F. C.↗
NASA NTRS1985

Diffusion-convection function of cosmic rays

The fundamental properties and some numerical results of the solution of the diffusion equation of an impulsive cosmic-ray point source in an uniform, unbounded and spherically symmetrical moving medium is presented. The diffusion-convection(D-C) function is an elementary composite function of the solution of the D-C equation for the particles injected impulsively from a diffusive point source into the medium. It is the analytic solution derived by the dimensional method for the propagation equation of solar cosmic rays in the heliosphere, i.e. the interplanetary space. Because of the introduction of convection effect of solar wind, a nonhomogeneous term appears in the propagation equation, it is difficult to express its solution in terms of the ordinary special functions. The research made so far has led to a solution containing only the first order approximation of the convection effect.

Zhang, G.↗
NASA NTRS1985

Evidence for regions of negligible cosmic-ray modulation in the inner heliosphere ( 10 AU)

Gold and Venkatesan report observations of periods during 1974-1976 when extended regions of heliolongitude that emitted lower than average solar wind velocities at 1 AU also exhibited higher than average cosmic ray intensities as measured by the E 35 MeV CPME anti-coincidence scintillator (28 sq cm omnidirectional geometric factor) on IMP-8. Their observations reproduced by a simple model, based on the observed steady solar wind structure, wherein there is little modulation of cosmic rays in the inner heliosphere until they reach the shocked plasma beyond the stream interactions in the outer heliosphere (similar to 5 to 10 AU). Beyond the interaction boundary, the intensity exhibits a constant radial gradient (similar to 2%/AU). The model also offers an explanation for the irregular behavior of the rotation averaged radial gradients observed by inside 10 AU, as well as the significant, but often ephemeral, latitude gradients observed by Voyagers 1 and 2 and IMP-8.

Roelof, E. C.↗
NASA NTRS1985

Differential measurement of cosmic-ray gradient with respect to interplanetary current sheet

Simultaneous magnetic field and charged particle measurements from the Voyager spacecraft at heliographic latitude separations from 10 deg. to 21 deg. are used to determine the latitude gradient of the galactic cosmic ray flux with respect to the interplanetary current sheet. By comparing the ratio of cosmic ray flux at Voyager 1 to that a Voyager 2 during periods when both spacecraft are first nort and then south of the interplanetary current sheet, we find an estimate of the latitudinal gradient with respect to the current sheet of approximately -0.15 + or 0.05% deg under restricted interplanetary conditions.

Christon, S. P.↗
NASA NTRS1985

Spatial variation of cosmic rays near the heliospheric current sheet

A quantitative comparison between theoretical predictions and observations of the intensity of galactic cosmic rays near the interplanetary current sheet is reported. Comparison of model calculations is made with a statistical analysis of observations of galactic cosmic rays at Earth and the simultaneous position of the current sheet. An ensemble of different current sheet inclinations is used, in order to make the analysis of the computations approximate the method used to analyses the data.

Jokipii, J. R.↗
NASA NTRS1985

Effects of solar magnetic field on cosmic rays

Aspects of the problem of galactic cosmic ray propagation, including inversion of the solar total magnetic field and an analysis of data related to the heliomagnetic cycle are discussed. It is noted that the global structure of the solar magnetic field results in an additional flux of galactic cosmic rays generated by curvature and gradient drifts. An analysis of heliomagnetic cycle data shows that the latitudinal gradient results in a N-S asymmetry, with the amplitude of the effect growing with depth in the atmosphere. The inversion of the solar total magnetic field, drift effects, and other space distributions are found to contribute to a 22-year cycle of solar activity.

Goncher, G. A.↗
NASA NTRS1985

The expected cosmic ray density and stream distributions at the heliolatitudinal asymmetry of solar wind

The results of the spatial distribution of cosmic ray density, gradients, and anisotropy obtained on the basis of the numerical solution of the anisotropic diffusion equation with an account of solar wind velocity change depending on the latitudinal angle theta of the form U=u sub oe sup alpha theta and the diffusion coefficient depending on the spatial coordinates and the particle rigidity are presented. It is shown that the increase of the solar wind velocity and the diffusion coefficient with heliolatitude leads to gradient distributions that are in accord with experimental data observed in space. The results of the energetic spectrum of 11 and 22-year cosmic ray variations obtained with an account of direction of the general magnetic field of the Sun are presented are given.

Alania, M. V.↗
NASA NTRS1985

Spatial distribution of cosmic rays in magnetic cycles of the Sun

The space-time distribution of cosmic ray (CR) density is determined from the solution of the anisotropic diffusion equation. The boundary problem is solved in a quasistationary axisymmetric case, taking into account the delay of cosmic rays relative to the cyclic variations of solar activity. The specificty of the modulation model is the use of the empirical dependence of the free path of particles for scattering on the observed latitudinal distribution of solar activity. Another specific feature of the model is an account of an additional effect due to the drift of charged particles towards the helio-equator plane or backward, depending on the direction of the total magnetic field of the Sun.

Alania, M. V.↗
NASA NTRS1985

The dependence of solar modulation on the sign of the cosmic ray particle charge

The solar modulation of galactic cosmic ray helium and electrons at 1 AU, within the 600-1000 MV magnetic rigidity interval, are compared for the period from 1965 through 1984. The time-intensity variations during the two solar maxima around 1970 and 1981 show that after 1970 the helium intensity recovers earlier than that of the electrons, whereas after 1981 the electron intensity recovers earlier than that of helium. The flux ratio of helium to electrons (He/e) undergoes a major increases during the 1969-1971 period and a major decrease during 1979-83. These experimental results can be interpreted as due to a dependence of the solar modulation of galactic cosmic rays on the sign of the particle charge, possibly as a consequence of drifts due to gradients and curvatures in the interplanetary magnetic field. However, the comparison of the shapes of the intensity-time curves of helium and electrons in the period 1970-1981 does not support a major specific prediction of the drift model.

Garcia-Munoz, M.↗
NASA NTRS1985

An update on the correlation between the cosmic radiation intensity and the geomagnetic AA index

A statistical study between the cosmic ray intensity, as observed by a neutron monitor, and of the geomagnetic aa index, as representative of perturbations in the plasma and interplanetary magnetic field in the heliosphere, has been updated to specifically exclude time periods around the reversal of the solar magnetic field. The results of this study show a strong negative correlation for the period 1960 through 1968 with a correlation coefficient of approximately -0.86. However, there is essentially no correlation between the cosmic ray intensity and the aa index for the period 1972-1979 (i.e. correlation coefficient less than 0.16). These results would appear to support the theory of preferential particle propagation into the heliosphere vis the ecliptic during the period 1960-1968 and via the solar polar regions during 1972-1979.

Shea, M. A.↗
NASA NTRS1985

The cosmic ray composition as viewed from the chemical abundances of the solar system

It is shown that the chemical composition of cosmic rays at their sources for the elements up to the atomic number as 80 is quite similar to that of the carbonaceous chondrites, which have been keeping the properties of the protosolar nebula. In particular, the similarity between these two compositions is significant to the elements classified as refractory and siderphile, in addition to the elements, Ca and Al. These results as cited above suggest that cosmic rays, being currently observed near the Earth, may have been accelerated from the matter with the composition similar to that which is found of these chondrites as Allende.

Sakurai, K.↗
NASA NTRS1985

The effects of newly measured cross sections in hydrogen on the production of secondary nuclei during the propagation of cosmic rays through interstellar H

The cross sections of six important cosmic ray source nuclei in hydrogen at several energies between 300 and 1800 MeV/nuc were measured. Significant differences, sometimes exceeding 50%, exist between these new measurements and the earlier semiempirical predictions, and a new set of semiempirical formulae are being determined that better describe this fragmentation. New cross sections were obtained so that the systematics of their effects on cosmic ray propagation through interstellar hydrogen can be examined.

Webber, W. R.↗