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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Updated Computational Model of Cosmic Rays Near Earth

An updated computational model of the galactic-cosmic-ray (GCR) environment in the vicinity of the Earth, Earth s Moon, and Mars has been developed, and updated software has been developed to implement the updated model. This model accounts for solar modulation of the cosmic-ray contribution for each element from hydrogen through iron by computationally propagating the local interplanetary spectrum of each element through the heliosphere. The propagation is effected by solving the Fokker-Planck diffusion, convection, energy-loss boundary-value problem. The Advanced Composition Explorer NASA satellite has provided new data on GCR energy spectra. These new data were used to update the original model and greatly improve the accuracy of prediction of interplanetary GCR.

ONeill, Patrick M.↗
NASA NTRS1984

Isotopic composition of primary cosmic rays H-Fe for ISEE-C

The high energy cosmic ray instrument built for the International Sun-Earth Explorer is described. Some aspects of that system are critically renewed so that the experience gained in the design, construction and operation of this experiment can serve as a guide in designing future cosmic ray particle identification systems.

Heckman, H. H.↗
NASA NTRS1973

Isotopic composition of heavy cosmic rays

The mean isotopic composition was measured of even-charge cosmic ray elements with 14 equal to or less than 26 near 0.8 GeV/N using a balloon-borne ionization-chamber/Cerenkov-counter detector system. The experimental method makes use of the geomagnetic field as a magnetic spectrometer. Results indicate that the most abundant isotopes at the cosmic ray source are Si-28, S-32, and Ca-40, like the solar system; but Fe-54, unlike the solar system.

Maehl, R. C.↗
NASA NTRS1973

Variations of three-dimensional anisotropy of cosmic rays during Forbush decreases.

Variations of three-dimensional anisotropy of cosmic rays during Forbush decreases are examined by a spherical harmonic method and by constructing successive isointensity contour maps in the solar ecliptic coordinate system. The east-west and north-south anisotropies are studied statistically and for several individual events; the data are based on cosmic ray records from about 24 stations for the 3-year period from 1966 to 1968. For the individual events, the high anisotropies of about 4% are examined in terms of the convective, diffusive and density gradient components of the differential streaming as well as the interplanetary magnetic field and solar wind. In each case, vector gradients are derived that lead to the observed anisotropies, and the magnitude of these gradients is typically 10-20 times that of the quiet time interplanetary gradient.

Yoshida, S.↗
NASA NTRS1993

Time-dependent modulation of galactic cosmic rays by merged interaction regions

Models that solve the one-dimensional, solar modulation equation have reproduced the 11-year galactic cosmic ray using functional representations of global merged interaction regions (MIRs). This study extends those results to the solution of the modulation equation with explicit time dependence. The magnetometers on Voyagers 1 and 2 provide local magnetic field intensities at regular intervals, from which one calculates the ratio of the field intensity to the average local field. These ratios in turn are inverted to form diffusion coefficients. Strung together in radius and time, these coefficents then fall and rise with the strength of the interplanetary magnetic field, becoming representations of MIRs. These diffusion coefficients, calculated locally, propagate unchanged from approx. 10 AU to the outer boundary (120 AU). Inside 10 AU, all parameters, including the diffusion coefficient are assumed constant in time and space. The model reproduces the time-intensity profiles of Voyager 2 and Pioneer 10. Radial gradient data from 1982-1990 between Pioneer 10 and Voyager 2 are about the same magnitude as those calculated in the model. It is also shows agreement in rough magnitude with the radial gradient between Pioneer 10 and 1 AU. When coupled with enhanced, time-dependent solar wind speed at the probe's high latitude, as measured by independent observers, the model also follows Voyager 1's time-intensity profile reasonably well, providing a natural source the model also follows Voyager 1's time-intensity profile reasonably well, providing a natural source for the observed negative latitudinal gradients. The model exhibits the 11-year cyclical cosmic ray intensity behavior at all radii, including 1 AU, not just at the location of the spacecraft where the magnetic fields are measured. In addition, the model's point of cosmic ray maximum correctly travels at the solar wind speed, illustrating the well-known propagation of modulation. Finally, at least in the inner heliosphere this model accounts for the delay experienced by lower-rigidity protons in reaching their time-intensity peak. The actual delays in this model, however, are somewhat smaller than the data. In the outer heliosphere the models sees no delays, and the data are ambiguous as to their existence. It appears that strong magnetic field compression regions (merged interaction regions) that are 3-4 times the average field strength can, at least in a helioequatorial band, disrupt effects, such as drifts, that could dominate in quieter magnetic fields. The question remains: Is the heliosphere ever quiet enough to allow such effects to be unambiguously measured, at least in the midlatitudes?

Perko, J. S.↗
NASA NTRS1975

On the origin of cosmic rays

Using Recent surveys of molecular clouds and gamma rays in the galaxy, it is possible to determine the distribution of 1 to 10 GeV cosmic-ray nucleons in the galaxy. This distribution appears to be identical to the supernova remnant distribution to within experimental error and provides strong support for the hypothesis that supernovae produce most of the observed cosmic rays. This distribution resembles that of OB associations of average age approximately 30 million years suggesting that cosmic rays are produced by population objects about 30 million years after their birth.

Stecker, F. W.↗
NASA NTRS1976

Photonuclear interactions of ultrahigh energy cosmic rays and their astrophysical consequences

Results are presented for detailed Monte Carlo calculations of the interaction histories of ultrahigh-energy cosmic-ray nuclei with intergalactic radiation fields, using improved estimates of these fields and empirical determinations of photonuclear cross sections, including multinuclear disintegrations for nuclei up to Fe-56. Intergalactic and galactic energy-loss rates and nucleon-loss rates for nuclei up to Fe-56 are also given. Astrophysical implications are discussed in terms of expected features in the cosmic-ray spectrum between 10 to the 18th and 10 to the 21st power eV for the universal and supercluster origin hypotheses. The results of these calculations indicate that ultrahigh-energy cosmic rays cannot be universal in origin regardless of whether they are protons or nuclei. Both the supercluster and galactic origin hypotheses, however, are possible regardless of nuclear composition.

Puget, J. L.↗
NASA NTRS1975

Observations of nitrogen and oxygen isotopes in the low energy cosmic rays

The isotopic composition of low-energy nitrogen and oxygen cosmic rays was measured with an electron/isotope spectrometer aboard the IMP-7 satellite to determine the possible source of the particles. Instrument calibration showed the standard range-energy tables to be inadequate to calculate the isotope response, and corrections were obtained. The low-energy nitrogen and oxygen cosmic rays were found to be primarily 14N and 16O. Upper limits were obtained for the abundances of the other stable nitrogen and oxygen isotopes. The nitrogen composition differs from higher energy measurements which indicate that 15N, which is thought to be secondary, is the dominant isotope.

Vidor, S. B.↗
NASA NTRS1985

On the importance of interstellar helium for the propagation of heavy cosmic rays

The influence of interstellar He on the fragmentation of heavy cosmic rays in the interstellar medium (ISM) has long been a controversial subject. While H-induced cross section data are now avialable over broad mass and energy ranges, little data for He-induced fragmentation exists. With the recent reports of accurate measurements of the secondary/primary ratios in cosmic rays and of H-induced cross sections the problem of including interstellar He in propagation calculations becomes even more critical. As is argued the escape lengths lambda e deduced from the B/C+) and Sc-Cr/Fe ratios cannot be reconciled within the frame of a simple leaky box model assuming the ISM composed of pure H. It is quite remarkable that the discrepancy is especially large in the GeV region where (1) secondary/primary ratios measured by several groups agree fairly well and (2) fragmentation cross sections have been recently measured with good accuracy.

Ferrando, P.↗
DOE OSTI2012

SimProp: a simulation code for ultra high energy cosmic ray propagation

A new Monte Carlo simulation code for the propagation of Ultra High Energy Cosmic Rays is presented. The results of this simulation scheme are tested by comparison with results of another Monte Carlo computation as well as with the results obtained by directly solving the kinetic equation for the propagation of Ultra High Energy Cosmic Rays. A short comparison with the latest flux published by the Pierre Auger collaboration is also presented.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

MEASUREMENTS OF COSMIC-RAY HYDROGEN AND HELIUM ISOTOPES WITH THE PAMELA EXPERIMENT

The cosmic-ray hydrogen and helium ({sup 1}H, {sup 2}H, {sup 3}He, {sup 4}He) isotopic composition has been measured with the satellite-borne experiment PAMELA, which was launched into low-Earth orbit on board the Resurs-DK1 satellite on 2006 June 15. The rare isotopes {sup 2}H and {sup 3}He in cosmic rays are believed to originate mainly from the interaction of high-energy protons and helium with the galactic interstellar medium. The isotopic composition was measured between 100 and 1100 MeV/n for hydrogen and between 100 and 1400 MeV/n for helium isotopes using two different detector systems over the 23rd solar minimum from 2006 July to 2007 December.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2015

Practical Applications of Cosmic Ray Science: Spacecraft, Aircraft, Ground-Based Computation and Control Systems, Exploration, and Human Health and Safety

In this presentation a review of galactic cosmic ray (GCR) effects on microelectronic systems and human health and safety is given. The methods used to evaluate and mitigate unwanted cosmic ray effects in ground-based, atmospheric flight, and space flight environments are also reviewed. However not all GCR effects are undesirable. We will also briefly review how observation and analysis of GCR interactions with planetary atmospheres and surfaces and reveal important compositional and geophysical data on earth and elsewhere. About 1000 GCR particles enter every square meter of Earth’s upper atmosphere every second, roughly the same number striking every square meter of the International Space Station (ISS) and every other low- Earth orbit spacecraft. GCR particles are high energy ionized atomic nuclei (90% protons, 9% alpha particles, 1% heavier nuclei) traveling very close to the speed of light. The GCR particle flux is even higher in interplanetary space because the geomagnetic field provides some limited magnetic shielding. Collisions of GCR particles with atomic nuclei in planetary atmospheres and/or regolith as well as spacecraft materials produce nuclear reactions and energetic/highly penetrating secondary particle showers. Three twentieth century technology developments have driven an ongoing evolution of basic cosmic ray science into a set of practical engineering tools needed to design, test, and verify the safety and reliability of modern complex technological systems and assess effects on human health and safety effects. The key technology developments are: 1) high altitude commercial and military aircraft; 2) manned and unmanned spacecraft; and 3) increasingly complex and sensitive solid state micro-electronics systems. Space and geophysical exploration needs drove the development of the instruments and analytical tools needed to recover compositional and structural data from GCR induced nuclear reactions and secondary particle showers. Finally, the possible role of GCR secondary particle showers in addressing an important homeland security problem, finding nuclear contraband and weapons, will be briefly reviewed.

Koontz, Steve↗
DOE OSTI2023

Temporal Structures in Positron Spectra and Charge-Sign Effects in Galactic Cosmic Rays

We present the precision measurements of 11 years of daily cosmic positron fluxes in the rigidity range from 1.00 to 41.9 GV based on 3.4 × 10 6 positrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The positron fluxes show distinctly different time variations from the electron fluxes at short and long timescales. A hysteresis between the electron fluxes and the positron fluxes is observed with a significance greater than 5⁢𝜎 at rigidities below 8.5 GV. On the contrary, the positron fluxes and the proton fluxes show similar time variation. Remarkably, we found that positron fluxes are modulated more than proton fluxes with a significance greater than 5⁢𝜎 for rigidities below 7 GV. These continuous daily positron fluxes, together with AMS daily electron, proton, and helium fluxes over an 11-year solar cycle, provide unique input to the understanding of both the charge-sign and mass dependencies of cosmic rays in the heliosphere.

astroparticles↗
NASA NTRS1985

North-south asymmetry in activity on the Sun and cosmic ray density gradients

The marked N-S asymmetry in solar activity (with predominant activity in the Sun's Northern Hemisphere) during the 1960's could certainly account for a S-pointing cosmic ray gradient. It is also clear from the data that the response to this change in solar activity asymmetry, and the related change in the perpendicular cosmic ray density gradient, is different for cosmic ray telescopes in the Earth's Northern and Southern Hemispheres. Northern Hemisphere detectors see a S-pointing gradient in the 60's and a N-pointing gradient after 1971, while Southern Hemisphere telescopes see a S-pointing gradient both before and after the reversal.

Swinson, D. B.↗