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The Pierre Auger Observatory

Description: The Pierre Auger Observatory is an international collaboration for the detailed study of the highest energy cosmic rays. It will operate at two similar sites, one in the northern hemisphere and one in the southern hemisphere. The Observatory is designed to collect a statistically significant data set of events with energies greater than 10{sup 19} eV and with equal exposures for the northern and southern skies.
Date: March 1, 1997
Creator: Hojvat, C.
Partner: UNT Libraries Government Documents Department

Non-LTE astrophysics and the origin of high-energy cosmic rays

Description: The most startling aspects of the universe are the departures from the nonuniform, nonthermodynamic equilibrium state. Mass concentrations and high energy electromagnetic quanta and particles are the primary examples. Of these various departures the extremum of nonexplained phenomena is still the acceleration of cosmic rays. The usual explanations involving multiple mechanisms contributing to various regions of the spectrum is suggested as most unlikely. In particular, the suggestion of the acceleration of the very highest energy cosmic rays in distant active galactic nuclei is shown to be untenable because of photon particle interactions.
Date: January 1, 1982
Creator: Colgate, S.A.
Partner: UNT Libraries Government Documents Department

Nuclear fragmentation cross sections for NASA database development

Description: Heavy ions with energies of hundreds to thousands of MeV/nucleon are present in the Galactic Cosmic Rays and will be a source of risk to astronaut health when long-duration crewed missions are undertaken. Nuclear interactions of these GCR ions in shielding materials must be accurately modeled by transport codes in order to estimate the dose and dose equivalent at points inside a spacecraft. Uncertainties in the nuclear fragmentation cross sections are propagated into these estimates, and the overall uncertainties increase as shielding depth increases. A program of fragmentation cross section measurements has therefore been undertaken to reduce these uncertainties, using GCR-like ion species and energies in particle accelerators in the United States, at the Brookhaven National Laboratory's Alternating Gradient Synchrotron (AGS) and in Japan at the National Institute of Radiological Science's Heavy Ion Medical Accelerator in Chiba (HIMAC). An extensive set of data has been obtained with beams ranging from helium to iron and including most of the species that are prominent in the GCR.
Date: August 24, 2001
Creator: Zeitlin, Cary J.; Heilbronn, Lawrence H.; Miller, Jack; Fukumura, Akifumi; Iwata, Yoshi; Murakami, Takeshi et al.
Partner: UNT Libraries Government Documents Department

Ames collaborative study of cosmic-ray neutrons. II. Low- and mid-latitude flights. [Preliminary results]

Description: The continuing progress of the Ames Collaborative Study of Cosmic Ray Neutrons is described. Data obtained aboard flights from Hawaii at altitudes of 41,000 and 45,000 feet, and in the range of geomagnetic latitude 17/sup 0/N less than or equal to lambda less than or equal to 21/sup 0/N are reported. Preliminary estimates of neutron spectra were made.
Date: March 1, 1978
Creator: Stephens, L.D.; McCaslin, J.B.; Smith, A.R.; Thomas, R.H.; Hewitt, J.E. & Hughes, L.
Partner: UNT Libraries Government Documents Department

Review of cosmic background radiation spectrum measurements: limits on distortions, energy release, and cosmological processes

Description: This paper reviews the three major cosmic microwave background radiation (CMBR) spectrum measurement programs conducted and published since the last (XVII) IAU General Assembly. The results are consistent with a Planckian spectrum with temperature 2.72 +- 0.03 K spanning a wavelength range of 0.1 to 12 cm. Limits on possible distortions and implications are outlined. Ongoing and future measurements are discussed.
Date: January 1, 1986
Creator: Smoot, G.F.
Partner: UNT Libraries Government Documents Department

Radioactive isotopes on the Moon

Description: A limited review of experiments and studies of radioactivity and isotope ratios in lunar materials is given. Observations made on the first few millimeters of the surface where the effects of solar flare particles are important, some measurements on individual rocks, and some studies of radioactivities produced deep in the lunar soil by galactic cosmic rays, are among the experiments discussed. (GHT)
Date: January 1, 1975
Creator: Davis, R. Jr.
Partner: UNT Libraries Government Documents Department

The history of gamma-ray burst observations

Description: Cosmic gamma-ray bursts have been observed for 1-1/2 decades since their fortuitous discovery by nuclear test detection instruments flown on the Vela satellites. Although the volume and detail of data available through these observations has considerably refined our knowledge of the characteristics of these events, there is no confident identification of source objects or reliable model of the processes involved. The observations do suggest, however, that the bursts originate at neutron stars (probably highly-magnetized neutron stars). 17 refs., 16 figs.
Date: January 1, 1988
Creator: Klebesadel, R.W.
Partner: UNT Libraries Government Documents Department

Analysis of gamma ray burst spectra with cyclotron lines

Description: Motivated by the recent developments in the cyclotron resonance upscattering of soft photons or CUSP model of Gamma Ray Burst (GRB) continuum spectra, we revisit a select database of GRBs with credible cyclotron absorption features. We measure the break energy of the continuum, the slope below the break and deduce the soft photon energy or the electron beam Lorentz factor cutoff. We study the correlation (or lack of) between various parameters in the context of the CUSP model. One surprise result is that there appears to be marginal correlation between the break energy and the spectral index below the break. 20 refs., 8 figs., 2 tabs.
Date: September 26, 1990
Creator: Kargatis, V. (Rice Univ., Houston, TX (USA). Dept. of Space Physics and Astronomy) & Liang, E.P. (Lawrence Livermore National Lab., CA (USA))
Partner: UNT Libraries Government Documents Department

Measurement of anisotropy in the cosmic background radiation on a large angular scale at 33 GHz

Description: Results of a measurement of anisotropy in the 3 /sup 0/K cosmic background radiation on a large-angular-scale are presented. Observations were carried out with a dual-antenna microwave radiometer operating at 33 GHz (0.89 cm wavelength) flown on board a U-2 aircraft to 20-km altitude. In eleven flights, between December 1976 and May 1978, the radiometer measured differential intensity between pairs of directions distributed over most of the northern celestial hemisphere with an rms sensitivity of +- 46m/sup 0/K/..sqrt..Hz. The measurements show clear evidence of anisotropy that is readily interpreted as due to the motion of the earth relative to the sources of the radiation; the anisotropy is well fit by a cosine distribution of amplitude 3.61 +- 0.54 millireverse arrowreverse arrow-degrees Kelvin (m/sup 0/K), one part in 800 of 3/sup 0/K, implying a velocity of 361 +- 54 km/sec toward the direction 11.23 +- 0.46 hours right ascension, and 19.0 +- 7.5/sup 0/ declination. A simultaneous fit to a combined hypothesis of dipole (cos theta) and quadrupole (cos/sup 2/ theta) angular distributions places a 1 m/sup 0/K limit on the amplitude of most components of quadruple anisotropy with 90% confidence. Additional analysis places a 0.5 m /sup 0/K limit on uncorrelated fluctuations (sky-roughness) in the 3/sup 0/K background on an angular scale of the antenna beam width, about 7/sup 0/. This thesis describes the equipment development through three engineering flights and the data acquisition in eleven additional flights. The astrophysical results are then presented from the statistical analysis of the reduced data.
Date: November 1, 1978
Creator: Gorenstein, M.V.
Partner: UNT Libraries Government Documents Department

Cosmic-ray exposure records and origins of meteorites

Description: The cosmic-ray records of meteorites can be used to infer much about their origins and recent histories. Some meteorites had simple cosmic-ray exposure histories, while others had complex exposure histories with their cosmogenic products made both before and after a collision in space. The methods used to interpret meteorites' cosmic-ray records, especially identifying simple or complex exposure histories, often are inadequate. Besides spallogenic radionuclides and stable nuclides, 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 measurements, plus theoretical modeling of complex histories, will improve our ability to predict the production of cosmogenic nuclides in meteorites, to distinguish simple and complex exposure histories, and to better determine exposure ages.
Date: January 1, 1985
Creator: Reedy, R.C.
Partner: UNT Libraries Government Documents Department

Properties of multiple event gamma ray bursts

Description: We present results from a study of 37 multiple event gamma ray bursts found in the monitoring data of the PVO gamma ray burst detector. We define these bursts as those which have two or more distinct emission events separated by a return to the background intensity. Significant correlation exists between the duration of the first event and the duration of the second event, while some correlation exists between the hardness of the events and only weak correlation exists in the intensity of the events. Although the time profiles of events in a burst may be similar, as measured in the phase portrait, there is no general rule about the degree of similarity of the time profiles. Subdividing the data according to the recurrence time, we find a tendency for the strength of the correlation in the hardness to increase with decreasing separation between the events. 2 refs., 2 figs., 1 tab.
Date: January 1, 1991
Creator: Lochner, J.C.
Partner: UNT Libraries Government Documents Department

Cosmic microwave background: present status and future prospects. [Review]

Description: After a brief review of the origin of the radiation according to the standard model, the status of present measurements of the spectrum and the large-scale isotropy is discussed. Finally, it is indicated what are the prospects for improved measurements in the next decade. 17 references. (JFP)
Date: December 1, 1978
Creator: Muller, R.A.
Partner: UNT Libraries Government Documents Department

Spectrum of the microwave background radiation

Description: A review is given of the present status of measurements of the spectrum of the microwave background. Factors which limit experimental accuracy are discussed with particular reference to high frequency measurements. A selection of the available measurements yields a data set which is reasonably consistent with the blackbody spectrum for a temperature of 2.9 K. A simple statistical analysis suggests either that there are errors in the data set, or that deviations from a blackbody spectrum exist. The difficulties inherent in property averaging the results from different observers are described. Prospects for improved measurements will be summarized.
Date: April 1, 1982
Creator: Richards, P.L.
Partner: UNT Libraries Government Documents Department

On the measurement of cosmogenic nuclides in cometary materials

Description: Determinations of the cosmogenic nuclide concentrations in cometary material will help to define the recent surface history of the comet and its exposure to cosmic rays. In particular, the rates for the removal or mixing of surface material could be studied, and any variations in cosmic-ray intensity implied by the data could be used to infer orbital changes during the last few million years. The measurement of the shorter-lived isotopes poses technical challenges that should be addressed now. The measurement of longer-lived isotopes will be straightforward provided that rates of mass loss are not too high. 46 refs., 2 figs.
Date: January 1, 1989
Creator: Herzog, G.F.; Englert, P.A.J.; Reedy, R.C.; Nishiizumi, K.; Kohl, C.P. & Arnold, J.R.
Partner: UNT Libraries Government Documents Department

Cosmic-ray interactions and dating of meteorite stranding surfaces with cosmogenic nuclides

Description: A wide variety of products from cosmic-ray interactions have been measured in terrestrial or extraterrestrial samples. These ''cosmogenic'' products include radiation damage tracks and rare nuclides that are made by nuclear reactions. They often have been used to determine the fluxes and composition of cosmic-ray particles in the past, but they are usually used to study the history of the ''target'' (such as the time period that it was exposed to cosmic-ray particles). Products made by both the high-energy galactic cosmic rays and energetic particles emitted irregularly from the Sun have been extensively studied. Some of these cosmogenic products, especially nuclides, have been or can be applied to studies of Antarctic meteorite stranding surfaces, the ice surfaces in Antarctica where meteorites have been found. Cosmogenic nuclides studied in samples from Antarctica and reported by others elsewhere in this volume include those in meteorites, especially radionuclides used to determine terrestrial ages, and those made in situ in terrestrial rocks. Cosmogenic nuclides made in the Earth's atmosphere or brought in with cosmic dust have also been studied in polar ice, and it should also be possible to measure nuclides made in situ in ice. As an introduction to cosmogenic nuclides and their applications, cosmic rays and their interactions will be presented below and production systematics of cosmogenic nuclides in these various media will be discussed later. 20 refs., 2 tabs.
Date: January 1, 1988
Creator: Reedy, R.C.
Partner: UNT Libraries Government Documents Department

Photon losses in cosmic ray acceleration in active galactic nuclei

Description: The usual assumption of the acceleration of ultrahigh energy cosmic rays, greater than or equal to 10/sup 18/ eV in quasars, Seyfert galaxies, and other active galactic nuclei is challenged on the basis of the photon interactions with the accelerated nucleons. This is similar to the effect of the black body radiation on particles > 10/sup 20/ eV for times of the age of the universe except that the photon spectrum is harder and the energy density greater by approx. = 10/sup 13/. Hence, a single traversal, radial or circumferential, of radiation whose energy density is no greater than the emitted flux will damp an ultrahigh energy cosmic ray 10/sup 20/ eV by greater than 10/sup 4/ times its energy. Hence, it is unlikely that any reasonable configuration of acceleration can avoid disastrous photon energy loss. A different site for ultrahigh energy cosmic ray acceleration must be found.
Date: January 1, 1984
Creator: Colgate, S. A.
Partner: UNT Libraries Government Documents Department

Spatial evolution of 26-day recurrent galactic cosmic ray decreases: Correlated Ulysses COSPIN/KET and SOHO COSTEP observations

Description: In December 1995 the Ulysses spacecraft was at a radial distance of 3 AU from the Sun and 60{degree} northern heliographic latitude. To that time the Solar and Heliospheric Observatory (SOHO) started its mission. On board of both spacecraft particle sensors are measuring electrons, protons and helium nuclei in the MeV to GeV energy range. In early 1996 the counting rates of several hundred MeV galactic cosmic rays at Ulysses and at SOHO (Earth orbit) were modulated by recurrent cosmic ray decreases (RCRDs). The RCRDs at SOHO were found to be associated with a corotating interaction region (CIRs). A Lomb (spectral) analysis was performed on the galactic cosmic ray flux from February 1996 to June 1996. Surprisingly, the most probable frequency is {approximately} 28 days and not 26 or 27 days, corresponding to one solar rotation. The amplitude of the RCRDs is {approximately} 2.3% on both spacecraft. The variation in the solar wind speed shows the same periodicities and is anticorrelated to the variation in the cosmic ray flux. In contrast to the RCRDs the amplitude found in the solar wind speed is four times larger at WIND (120 km/s) than at Ulysses (32 km/s). The solar wind proton density and magnetic field strength yielded no significant periodicities, neither at Ulysses nor at WIND. Comparing the RCRDs with coronal hole structures observed in the FE XIV line, they found that a single coronal hole close to the heliographic equation can account for the RCRDs observed simultaneously at Ulysses and SOHO. The coronal hole boundaries changed towards lower Carrington longitudes and vanished slowly. The changes of the boundaries during the investigated period could explain a 28 day periodicity.
Date: December 31, 1998
Creator: Heber, B.; Bothmer, V. & Droege, W.
Partner: UNT Libraries Government Documents Department