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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Relative abundances of positrons and antiprotons in the primary cosmic ray flux

Observations on the ratio of positrons to the electron-positron sum made in the 5 to 50 GeV range by Buffington et al. (1974) are used to put an upper limit on the ratio of antiprotons to protons at various energies. The calculation of the latter ratio is based on detailed measurements of the cross section of antiproton production up to intersecting storage ring energies.

Badhwar, G. D.↗
NASA NTRS1975

The relative abundances of galactic cosmic ray Be-7, Be-9, and Be-10

The isotopic composition of galactic cosmic ray Be near 100 MeV/nucleon was measured in interplanetary space with high-resolution solid-state telescopes on the IMP-7 and IMP-8 satellites during 1973-1974. These two independent measurements yield Be-10/Be ratios above 10%. Taken together with the galactic propagation model described in the text, these results show that the cosmic ray 'clock' lifetime (most probable value of roughly 20 million years) is significantly greater than that deduced for a nominal interstellar gas density of about 1 to 3 atoms/cu cm.

Garcia-Munoz, M.↗
NASA NTRS1978

Relative abundance of antiprotons and antihelium in the primary cosmic radiation

The paper reports measurement of the antiproton-to-proton and antihelium-to-helium ratios in the 4-100 GeV/c range. A superconducting magnet spectrophotometer obtained the data during a balloon flight in May 1976. The upper limit value for the antiproton ratio is 0.0005 in the 4.2-12.5 GeV/c range. This value is only slightly higher than the expected value for a leaky box-model and nearly equal to the value expected in the Peter-Westergard model. It is suggested that this upper limit value rules out the closed galaxy model. Upper limit values for the antihelium ratio are 0.000058 in the 4-10 GeV/c range; less than 0.0001 in the 4-33 GeV/c range; and less than 0.01 in the 33-100 GeV/c range. The interpretation of the raw data is explained.

Badhwar, G. D.↗
NASA NTRS1983

The relative abundance of 3He(++) in the solar wind

Continuous measurements of solar wind 3He(++) and 4He(++) were made covering a full range of solar wind conditions. The average flux ratio derived from these data is 2310 + or - 50, in excellent agreement with the Apollo foil measurements. A probable correlation between average flux ratio and solar activity was found; however, an examination of the data during periods of 3He(++)-rich solar flares shows no detectable increase in 3He(++) in the solar wind.

Coplan, M. A.↗
NASA NTRS1983

A measurement of the energy spectra and relative abundance of the cosmic-ray H and He isotopes over a broad energy range

The measurements reported of these isotopes were made using two sets of detectors during the same minimum modulation period in 1977. One measurement was made with a balloon-borne telescope, the other with telescopes on the Voyager spacecraft. It is noted that together they provide the widest energy range yet available for studying these isotopes: 14-150 MeV per nucleon for H2 and 10-290 MeV per nucleon for He-3. The simultaneous helium isotope observations are used to give a mutually consistent picture of galactic propagation and solar modulation. The data define the form of the interstellar H-1 and He-4 spectra, an interstellar matter path length for both H-1 and He-4, and a total residual modulation for He-4. The H-2 observations suggest a picture that is very similar for the galactic propagation of H-1 and He-4.

Webber, W. R.↗
NASA NTRS1984

Relative abundance of the helium isotopes He-3 and He-4 in the cosmic radiation

The geomagnetic field near the equator is used to measure the He-3/He-4 abundance ratio near 6 GeV/nucleon. This ratio is found to be 0.24 + or - 0.05, under the assumption that the helium rigidity spectrum has the form dI/dR = about R exp(-2.65). If all He-3 is of secondary origin, this implies an interstellar mean escape-path length of about 15 g/sq cm, a value considerably larger than that determined from observations of heavier elements but compatible with measurements of the helium isotopic ratio at lower energies.

Jordan, S. P.↗
NASA NTRS1991

Relative abundances in the low-metallicity dwarf irregular galaxy UGC 4483

UGC 4483 is a dwarf irregular galaxy in the M 81 group. Narrow-band optical imaging has revealed an H II region in UGC 4483 with an H-alpha flux of about 2 x 10 to the -13th erg/sq cm per A per s. Optical, UV and NIR spectroscopy of this H II region yield He, C, N, O, Ne, and S abundances for the ISM in this galaxy. With an oxygen abundance of 0.000021 12 + log(O/H) = 7.3, this galaxy is among the most metal-poor dwarf irregulars known to date. A comparison of the S/O abundance ratio in this galaxy with that in I Zw 18 supports the claim by Garnett (1990) that the S/O ratio is consistent with the solar ratio for low-metallicity dwarf irregulars. The C/O ratio in UGC 4483 is lower than that derived for I Zw 18 and, therefore, more in line with the trend seen in higher metallicity H II regions. The derived helium abundance is He/H = 0.075, which converts to a He mass fraction of 0.23, consistent with earlier determinations of the primordial He abundance.

Skillman, Evan D.↗
NASA NTRS1991

Relative abundances in the lower solar transition region

Properties of the lower solar transition region as determined from UV spectral lines recorded by the Naval Research Laboratory HRTS are investigated. The spectra were obtained from a rocket flight in July 1975. Variations of intensity ratios of strong lines of C IV, Si IV, C II, Si III, and O IV over the entire field of view of the HRTS instrument, which extends from disk center to the solar limb are discussed. The largest apparent abundance variations appear to be in the active regions surrounding a sunspot. The C/Si ratio is lower in the active regions than anywhere else in the instrument field of view, implying a lower C/Si abundance ratio in the active regions. There is a possible correlation of line intensity variation in the active region with Doppler shift of the lines; the explanation for this is unclear. The magnitude and reality of intensity ratio variations of all observed solar features are discussed, and monotonic center-to-limb intensity ratio variations due to the opacity of some of the spectral lines are measured.

Doschek, G. A.↗
NASA NTRS1992

The relative abundance of ethane to acetylene in the Jovian stratosphere

The inclusion of the results of laboratory kinetics studies on the reaction of C2H3 and H2 to yield C2H4, which is suggestive of an efficient chemical mechanism for the hydrogenation of C2H2 to C2H6, can be included in a comprehensive model of the Jupiter atmosphere hydrocarbon photochemistry to explain the observed altitude variation of the C2H6/C2H2 ratio. The sensitivity of these results to uncertainties in key low-temperature rate constants is demonstrated. These key reaction-rate constants decrease with falling temperature.

Allen, Mark↗
NASA NTRS1992

Solar wind iron and oxygen charge states and relative abundances measured by SWICS on Ulysses

We present the results of a survey of iron and oxygen charge state distributions as detected by the Solar Wind Ion Composition Spectrometer on the Ulysses spacecraft. The results are categorized in terms of the ionization temperature determined every approximately 13 minute instrument cycle from the O(+7) to O(+6) ratio. Our preliminary Fe/O abundance ratio is 0.12 averaged over this 3 month survey. The Fe charge state distributions accumulated during times of high oxygen ionization temperatures are clearly nonisothermal.

Ipavich, F. M.↗
NASA NTRS1995

Relative Abundance of Ices in the Disks of T Tauri Stars

Very little work has been carried out to determine whether or not large organic molecules similar to those observed on the surfaces of minor solar system bodies also reside in the mantles of icy grains located in dense molecular clouds or in the local environments of protostars and PNIS stars. Ten years ago Lacy et al. first identified a broad absorption band near 4.62 micron, the C equivalent N stretch fundamental, in the spectra of two embedded protostars, W33A and NGC 7538 IRS 9. The only follow-up observational work to this study is that done by us under the sponsorship of Origins of Solar Systems under this grant.

Weintraub, David A.↗
NASA NTRS2007

Relative Abundances of Cosmic Ray Nuclei B-C-N-O in the Energy Region from 10 GeV/n to 300 GeV/n. Results from the Science Flight of the ATIC

The ATIC balloon-borne experiment measures the energy spectra of elements from H to Fe in primary cosmic rays from about 100 GeV to 100 TeV. ATIC is comprised of a fully active bismuth germanate calorimeter, a carbon target with embedded scintillator hodoscopes, and a silicon matrix that is used as a main charge detector. The silicon matrix produces good charge resolution for the protons and helium but only a partial resolution for heavier nuclei. In the present paper a charge resolution of ATIC device was essentially improved and backgrounds were reduced in the region from Be to Si by means of the upper layer of the scintillator hodoscope that was used as an additional charge detector together with the silicon matrix. The flux ratios of nuclei B/C, O/C, N/C in the energy region from about 10 GeV/nucleon to 300 GeV/nucleon that were obtained from new high-resolution and high-quality charge spectra of nuclei are presented. The results are compared with existing theoretical predictions.

Panov, A. D.↗
NASA NTRS1974

Interstellar lines in the ultraviolet spectrum of delta Scorpii

Results of a study of the interstellar resonance lines of the cosmologically most abundant elements with the aid of a spectrograph sensitive in the range from 1150 to 1700 A. These lines were analyzed by curve-of-growth techniques to yield column densities from which abundances relative to atomic hydrogen were determined. With the exception of silicon, the relative abundances of the detected species for which column densities could be determined are less by a factor of 1.8 to 8.6 than the relative solar abundances. Silicon, on the other hand, is slightly overabundant by a factor of 1.6.

Smith, A. M.↗