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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 469 records · Page 26
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NASA NTRS1980

Carbon, nitrogen and oxygen isotopes in the low energy galactic cosmic rays

The isotopes of C, N, and O in the galactic cosmic rays were measured in the 45-106 Mev/nucleon range with data collected during 1973-77 by the cosmic-ray telescope onboard the IMP-7 spacecraft. The ratios of (N-15)/N, (C-13)/C, and ((O-18)/O agreed with previous measurements. Cosmic ray propagation and solar modulation indicate that the measured N isotopic ratio is in agreement with a source ratio of (N-14)/O = 0.03, which is much lower than the solar system abundance ratio.

Guzik, T. G.↗
NASA NTRS1985

Solar cycle variations of the anomalous cosmic ray component

The intensity of the anomalous cosmic ray component, consisting of He, N, O, and Ne, has long been known to be especially sensitive to the effects of solar modulation. Following its discovery in 1972, this component dominated the quiet-time flux of cosmic ray nuclei below approximately 30 MeV/nucleon during the 1972 to 1978 solar minimum, but then became essentially unobservable at 1 AU with the approach of solar maximum conditions. One recent theoretical model predicts substantial differences in the intensity of the anomalous fluxes from one solar minimum period to the next because of the reversal of the solar magnetic field. Using data from the Caltech experiments on IMP-8 and ICE (ISEE-3), the intensity of anomalous O and He at 1 AU during the years 1972 to 1985 is reported. We hope to determine whether the anomalous fluxes will return to their 1972 to 1978 levels, as predicted by spherically symmetric modulation models, or whether they will fail to return to 1 AU, as suggested by modulation models in which gradient and curvature drifts dominate.

Mewaldt, R. A.↗
NASA NTRS1985

Distributed reacceleration of cosmic rays

A model is developed in which cosmic rays, in addition to their initial acceleration by a strong shock, are continuously reaccelerated while propagating through the Galaxy. The equations describing this acceleration scheme are solved analytically and numerically. Solutions for the spectra of primary and secondary cosmic rays are given in a closed analytic form, allowing a rapid search in parameter space for viable propagation models with distributed reeacceleration included. The observed boron-to-carbon ratio can be reproduced by the reacceleration theory over a range of escape parameters, some of them quite different from the standard leaky-box model. It is also shown that even a very modest amount of reacceleration by strong shocks causes the boron-to-carbon ratio to level off at sufficiently high energies.

Wandel, Amri↗
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 NTRS1980

The high energy cosmic ray detector for Spacelab II

A large cosmic ray detector to be flown on Spacelab II is presently under construction at the University of Chicago. The instrument, with a geometric factor of 5 sq m-ster, is designed to measure the elemental composition and the energy spectra of individual cosmic ray nuclei (Li to Fe) from 50 GeV/nucleon to several TeV/nucleon. Plastic scintillators are used for charge determination, and gas Cerenkov and transition radiation detectors for energy measurements. The instrument and its functions are described, and several test results that are important for an optimum design are discussed.

Lamport, J. E.↗
NASA NTRS1982

Development of the cosmic ray techniques

It has been found that most advances of cosmic-ray physics have been directly related to the development of observational techniques. The history of observational techniques is discussed, taking into account ionization chambers, refinements applied to ionization chambers to make them suitable for an effective use in the study of cosmic radiation, the Wulf-type electrometer, the electrometer designed by Millikan and Neher, the Geiger-Mueller counter, the experiment of Bothe and Kolhoerster, the coincidence circuit, and a cosmic-ray 'telescope'. Attention is given to a magnetic lens for cosmic rays, a triangular arrangement of Geiger-Mueller counters used to demonstrate the production of a secondary radiation, a stereoscopic cloud-chamber photograph of showers, the cloud-chamber picture which provided the first evidence of the positive electron, and arrangements for studying photon components, mu-mesons, and air showers.

Rossi, B.↗
NASA NTRS1980

Super-alfvenic propagation of cosmic rays: The role of streaming modes

Numerous cosmic ray propagation and acceleration problems require knowledge of the propagation speed of relativistic particles through an ambient plasma. Previous calculations indicated that self-generated turbulence scatters relativistic particles and reduces their bulk streaming velocity to the Alfven speed. This result was incorporated into all currently prominent theories of cosmic ray acceleration and propagation. It is demonstrated that super-Alfvenic propagation is indeed possible for a wide range of physical parameters. This fact dramatically affects the predictions of these models.

Morrison, P. J.↗
NASA NTRS1986

Predicting the Cosmic-Ray Environment Near Earth

Package of computer programs developed to predict cosmic-ray environment for spacecraft in orbit near Earth. Single cosmic-ray particle deposits enough electrical charge on sensitive area of individual circuit to change bit state. Single-event upsets may not cause permanent damage but upset functioning devices. Used to predict upset rate for space mission. Also calculates time-average cosmic-ray environment for multiple circular orbits, fragments of trajectories, and isolated points. Package written in HPL for interactive execution and implemented on HP 9825B desktop computer.

Edmonds, L.↗
NASA NTRS2013

All-Particle Cosmic Ray Energy Spectrum Measured with 26 Icetop Stations

We report on a measurement of the cosmic ray energy spectrum with the IceTop air shower array, thesurface component of the IceCube Neutrino Observatory at the South Pole. The data used in this analysiswere taken between June and October, 2007, with 26 surface stations operational at that time, corresponding to about one third of the final array. The fiducial area used in this analysis was 0.122 square kilometers.The analysis investigated the energy spectrum from 1 to 100 PeV measured for three different zenithangle ranges between 0 and 46. Because of the isotropy of cosmic rays in this energy range the spectrafrom all zenith angle intervals have to agree. The cosmic-ray energy spectrum was determined under differentassumptions on the primary mass composition. Good agreement of spectra in the three zenithangle ranges was found for the assumption of pure proton and a simple two-component model. Forzenith angles theta less than 30 deg., where the mass dependence is smallest, the knee in the cosmic ray energy spectrumwas observed at about 4 PeV, with a spectral index above the knee of about -3.1. Moreover, an indicationof a flattening of the spectrum above 22 PeV was observed.

icetop↗
NASA NTRS1983

Studies of low energy cosmic rays - The anomalous component

Data from the cosmic ray subsystem on the Voyager spacecraft is used to measure the spectra of He, C, N, O, and Ne with about 4-124 MeV/nuc (for O) near 1 AU. By subtracting both a low-energy solar/interplanetary component and the high-energy galactic component the energy spectra of the anomalous cosmic-ray species He, N, O, and Ne have been determined. It is suggested that the shapes of these spectra carry information about the charge state of the particles and the rigidity dependence of the diffusion coefficient. For similar power-law source spectra at the boundary of the modulation region, the location of features in the energy spectra indicates that the anomalous particles are singly ionized.

Webber, W. R.↗
NASA NTRS1981

The charge and isotopic composition of Z equals 7-16 cosmic ray nuclei at their source

Using the combined data from our 1976 and 1977 balloon flights, the charge and isotopic composition of Z equals 7-16 cosmic ray nuclei have been determined. A low abundance of both N and Ne in the cosmic ray source relative to solar cosmic rays is observed. However, the cosmic ray source ratio, Ne-22/Ne is 2.75 plus or minus 0.42 times the solar ratio. A possible enhancement of the Mg-26/Mg ratio, which is 1.29 plus or minus 0.14 times the solar ratio is also observed.

Webber, W. R.↗
NASA NTRS2002

CEM2k and LAQGSM Codes as Event-Generators for Space Radiation Shield and Cosmic Rays Propagation Applications

Space radiation shield applications and studies of cosmic ray propagation in the Galaxy require reliable cross sections to calculate spectra of secondary particles and yields of the isotopes produced in nuclear reactions induced both by particles and nuclei at energies from threshold to hundreds of GeV per nucleon. Since the data often exist in a very limited energy range or sometimes not at all, the only way to obtain an estimate of the production cross sections is to use theoretical models and codes. Recently, we have developed improved versions of the Cascade-Exciton Model (CEM) of nuclear reactions: the codes CEM97 and CEM2k for description of particle-nucleus reactions at energies up to about 5 GeV. In addition, we have developed a LANL version of the Quark-Gluon String Model (LAQGSM) to describe reactions induced both by particles and nuclei at energies up to hundreds of GeVhucleon. We have tested and benchmarked the CEM and LAQGSM codes against a large variety of experimental data and have compared their results with predictions by other currently available models and codes. Our benchmarks show that CEM and LAQGSM codes have predictive powers no worse than other currently used codes and describe many reactions better than other codes; therefore both our codes can be used as reliable event-generators for space radiation shield and cosmic ray propagation applications. The CEM2k code is being incorporated into the transport code MCNPX (and several other transport codes), and we plan to incorporate LAQGSM into MCNPX in the near future. Here, we present the current status of the CEM2k and LAQGSM codes, and show results and applications to studies of cosmic ray propagation in the Galaxy.

Mashnik, S. G.↗
NASA NTRS1974

Cross correlation between cosmic-ray fluctuations and interplanetary magnetic-field fluctuations

Study of the cross-correlation between cosmic-ray intensity fluctuations and the interplanetary magnetic field, using the low-frequency limit of the theory of the interplanetary scintillations of cosmic rays. Cross-spectral analysis of the flux of the Alert neutron monitor and simultaneous values of the interplanetary magnetic field components are presented which support the theory. A model of cosmic-ray fluctuations is described, with effects of gradients and interplanetary sector structure dominating for very low frequencies (less than or about equal to .000005 Hz) and magnetic-field induced interplanetary scintillations of cosmic rays dominating for higher frequencies.

Jokipii, J. R.↗
NASA NTRS1975

Neutron-rich isotopes of cosmic rays with Z between 9 and 16

Data are reported on the isotopic composition of cosmic rays with charges between 9 and 16 at a temperature of 450 MeV per amu. The data show the presence of a considerable neutron-rich component of Mg and Ne, the measured mean masses being 24.3 plus or minus 0.1 and 20.8 plus or minus 0.1, respectively. Coupled with a calculation of the evolution of cosmic-ray isotopic abundances during propagation, these masses indicate that there is probably some neutron-rich material in this charge range at the cosmic-ray source. To explain the Ne mass requires more neutron-rich Ne at the source than is observed in solar-system material. This result is discussed in light of recent theories of nucleosynthesis and cosmic-ray propagation.

Maehl, R. C.↗
NASA NTRS2011

Observation of Anisotropy in the Galactic Cosmic Ray Arrival Directions at 400 TEV With IceCube

In this paper we report the first observation in the Southern hemisphere of an energy dependence in the Galactic cosmic ray anisotropy up to a few hundred TeV. This measurement was performed using cosmic ray induced muons recorded by the partially deployed IceCube observatory between May 2009 and May 2010. The data include a total of 33x l0(epx 9) muon events with a median angular resolution of approx 3 degrees. A sky map of the relative intensity in arrival direction over the Southern celestial sky is presented for cosmic ray median energies of 20 and 400 Te V. The same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV. Instead, the high energy skymap shows a different anisotropy structure including a deficit with a post-trial significance of -6.30 sigma. This anisotropy reveals a new feature of the Galactic cosmic ray distribution, which must be incorporated into theories of the origin and propagation of cosmic rays.

Abbasi, R.↗
NASA NTRS2012

Observation of an Anisotropy in the Galactic Cosmic Ray Arrival Direction at 400 TeV with IceCube

In this paper we report the first observation in the Southern hemisphere of an energy dependence in the Galactic cosmic ray anisotropy up to a few hundred TeV. This measurement was performed using cosmic ray induced muons recorded by the partially deployed IceCube observatory between May 2009 and May 2010. The data include a total of 33 x 10(exp 9) muon events with a median angular resolution of approx. 3 degrees. A sky map of the relative intensity in arrival direction over the Southern celestial sky is presented for cosmic ray median energies of 20 and 400 TeV. The same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV. Instead, the high energy skymap shows a different anisotropy structure including a deficit with a post-trial significance of -6.3 sigma. This anisotropy reveals a new feature of the Galactic cosmic ray distribution, which must be incorporated into theories of the origin and propagation of cosmic rays.

Abbasi, R.↗