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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Cosmic ray studies with a gas Cherenkov counter in association with an ionization spectrometer

The results from a balloon-borne gas Cherenkov counter (threshold 16.5 GeV/nucleon) and an ionization spectrometer are presented. The gas Cherenkov counter provides an absolute energy distribution for the response of the calorimeter for 5 or = Z 26 nuclei of cosmic rays. The contribution of scintillation to the gas Cherenkov pulse height was obtained by independently selecting particles below the gas Cherenkov threshold using the ionization spectrometer. Energy spectra were derived by minimizing the chi squared between Monte Carlo simulted data and flight data. Best fit power laws, dN/dE = AE-gamma, were determined for C, N, O, Ne, Mg, and Si. The power laws, all consistent with E (-2.7) are not good fits to the data. A better fit is obtained using the spectrum derived from the spectrometer. The data from the ionization calorimeter and the gas Cherenkov are thus completely self-consistent.

Balasubrahmanyan, V. K.↗
NASA NTRS1979

On the inference of properties of Saturn's Ring E from energetic charged particle observations

The paper demonstrates that information about Saturn's Ring E particle size is potentially obtainable from observations of Saturnian trapped radiation. It is shown that observations of the radial dependence of the intensities, energy spectra, electron-to-proton intensity ratio, and pitch angle distributions of energetic charged particles trapped outside of Ring A can potentially provide information (1) on the existence of Ring E, (2) on the effective size of the particulate matter therein, and (3) on the magnitude of the radial diffusion coefficient for energetic particles. A parametric study of these possibilities is specialized to the characteristics of the University of Iowa detectors on Pioneer 11 which was scheduled to make a close encounter with Saturn in 1979.

Thomsen, M. F.↗
NASA NTRS1980

Energetic particle penetrations into the inner magnetosphere

The nose structures observed on 90-deg pitch angle ion spectrograms characteristic of energetic particle injection into the ring current region of the inner magnetosphere in the afternoon to midnight sector are examined in detail on the basis of Explorer 45 data. A statistical analysis of the time dependence of nose structures yields a highest probability of occurrence at around 2000 MLT, and most events are found to occur on successive passes. The appearance of nose events is also related to an enhancement or change in configuration of the geoelectric field which alters magnetospheric convection patterns to drive an ion front close to the earth, where it can be observed by Explorer 45. The observed characteristics of nose structures are interpreted in terms of adiabatic charged particle motions in the magnetosphere in a Volland-Stern convection electric field model, which is also applied to explain the energy spectra and dispersion in penetration distances of electrons and ions observed in the postmidnight to morning sectors.

Ejiri, M.↗
NASA NTRS1980

Impulsive 2-10 keV solar electron events not associated with flares

Data from the ISEE 3 satellite reveal a class of impulsive solar electron events with no measurable increase in flux above 10-20 keV. The flux histories and angular distributions indicate that the electrons propagate through interplanetary space with little or no scattering. The smooth extension of the power-law energy spectra down to the limit of the observations at 2 keV indicates that the electrons are accelerated at altitudes greater than 0.5 solar radii in the solar corona. Although these events occur more frequently than any other type of impulsive solar particle event observed, no correlation is found with flares or flare-related activity. However, there is a close correlation with low-frequency type III radio bursts.

Potter, D. W.↗
NASA NTRS1980

Energetic particles in solar flares

The various manifestations of energetic particles in solar flares are examined, and possible mechanisms for the acceleration of these particles are considered. Hard X-ray observations and possible mechanisms for the production of the dominant form of solar energetic particles, electrons with energies between 10 and 100 keV, are discussed, with consideration of thin-target models, thick-target models and thick-target models with reverse currents, and first-phase acceleration mechanisms for energetic electrons emitting impulsive microwave and fast-drift Type III radio bursts as well as impulsive hard X rays, which are detected themselves 20 min after the flare at 1 AU are considered. Radio evidence on the number, energy and pitch-angle distributions of energetic particles produced during solar flares is summarized, and observations at 1 AU of proton and electron energy spectra, the proton/electron ratio and energetic particle events rich in He-3 from solar flares are discussed. Finally, consideration is given to gamma-ray evidence of nuclear reactions in flares and white-light flares

Ramaty, R.↗
NASA NTRS1980

Cosmic ray studies with a gas Cerenkov counter in association with an ionization spectrometer

The results from a balloon-borne gas Cerenkov counter (threshold 16.5 GeV/nuc) and an ionization spectrometer are presented. The gas Cerenkov counter provides an absolute energy calibration for the response of the calorimeter for the Z range of 5-26 nuclei of cosmic rays. The contribution of scintillation to the gas Cerenkov pulse height has been obtained by independently selecting particles below the gas Cerenkov threshold using the ionization spectrometer. Energy spectra were derived by minimizing the chi-squared between a Monte Carlo simulated data and flight data. Best fit power laws were determined for C, N, O, Ne, Mg, and Si. The power laws, all consistent with E exp-2.7, are not good fits to the data. A better fit is obtained using the spectrum derived from the spectrometer.

Balasubrahmanyan, V. K.↗
NASA NTRS1980

Initial assessment of the effects of energetic ion injections in the magnetosphere due to the transport of satellite power system components from low earth orbit to geosynchronous earth orbit

Potentially serious environmental effects exist when cargo orbital transfer vehicle (COTV) ion propulsion is used on the scale proposed in the preliminary definition studies of the Satellite Power System. These effects of the large scale injections of ion propulsion exhaust in the plasmasphere and in the outer magnetosphere were shown to be highly model dependent with major differences existing in the predicted effects of two models, the ion cloud model and the ion sheath model. The expected total number density deposition of the propellant Ar(+) in the plasmasphere, the energy spectra of the deposited Ar(+) and time dependent behavior of the Ar(+) injected into the plasmasphere by a fleet of COTV vehicles differ drastically between the two models. The ion sheath model was demonstrated to be applicable to the proposed Ar(+) beam physics if the beam was divergent and turbulent whereas the ion cloud model was not a realistic approximation for such a beam because the "frozen-field" assumption on which it is based is not valid.

Curtis, S. A.↗
NASA NTRS1981

Elemental composition of solar energetic particles

The Low Energy Telescopes on the Voyager spacecraft are used to measure the elemental composition (2 or = Z or = 28) and energy spectra (5 to 15 MeV/nucleon) of solar energetic particles (SEPs) in seven large flare events. Four flare events are selected which have SEP abundance ratios approximately independent of energy/nucleon. The abundances for these events are compared from flare to flare and are compared to solar abundances from other sources: spectroscopy of the photosphere and corona, and solar wind measurements. The four flare average SEP composition is significantly different from the solar composition determined by photospheric spectroscopy. The average SEP composition is in agreement with solar wind abundance results and with a number of recent coronal abundance measurements. The evidence for a common depletion of oxygen in SEPs, the corona and the solar wind relative to the photosphere suggest that the SEPs originate in the corona and that both the SEPs and solar wind sample a coronal composition which is significantly and persistently different from that of the photosphere.

Cook, W. R., III↗
NASA NTRS1981

Rocket experiments

Payloads designed to study the ionization and the ionizing sources (energetic particles) during periods of auroral activity are described. These include a probe experiment to measure the variation in electron concentration, to measure electron temperature, and to measure the vehicle potential; a propagation experiment to obtain the electron concentration and the electron collision frequency; and an energetic particle experiment to measure particle energy spectra.

Source record↗
NASA NTRS1980

Search for characteristic features of low-energy quiet-time H, He and heavy nuclei fluxes, 1973-1977

Results of a survey of the 0.5-10 MeV/nucleon fluxes of H, He and heavier ions during interplanetary 'quiet-times' over the period 1973-1977 using the ULET telescope on IMP-8 are reported. It is found that in this energy range no characteristic flux level, or, e.g., proton/alpha ratio emerges during quiet periods in any year, thus precluding systematic long-term studies of the time behavior of the quiet-time component at these energies. Spectra for a uniquely quiet period in May 1977 and a less restrictively chosen set of quiet periods in 1976-1977 are presented and compared with previous results.

Mason, G. M.↗
NASA NTRS1980

Numerical models of solar modulation of galactic cosmic rays, including drifts

Numerical solutions are presented of the steady-state modulation of galactic cosmic rays for a realistic two-dimensional model which includes drifts. Calculations of energy spectra and the spatial density variation of protons are shown for a model that incorporates the solar-minimum magnetic field and nominal interplanetary propagation parameters. The calculated values are relatively insensitive to the assumed size of the modulating region and to the magnitude of the particle diffusion coefficient. The solutions show a broad interior 'plateau' in which radial gradients are small. A simple model that neglects diffusion but includes drifts and adiabatic cooling accounts for these results. It is concluded that in this model and the range of parameters, diffusion plays a role secondary to that of drifts and adiabatic cooling.

Jokipii, J. R.↗
NASA NTRS1980

Temporal variations of the anomalous oxygen /1974-1979/ and disappearance in 1978

The temporal changes in the differential intensity and energy spectra of anomalous oxygen, and in the O/C ratios of the anomalous cosmic ray component during the 1974-79 time period were examined using data from the IMP-8 and ISEE-3 spacecrafts. In addition to the solar modulation of the intensity of anomalous oxygen, the strength of the source of this component varies, and in 1978 the anomalous component disappeared almost completely. The results disagree with the existence of a purely galactic source but are consistent with expectations based on an heliospheric origin hypothesis as formulated by Fisk et al., (1974).

Hovestadt, D.↗
NASA NTRS1980

The modulation of galactic cosmic rays between 1 and 17 AU

The galactic cosmic-ray intensity was at approximately solar minimum levels from early 1972 to December 1977. Beginning in early 1978 and ending in June, steady decreases in the galactic proton and helium intensities were observed at 1 AU by IMP-7 and 8. No significant decrease was observed at Pioneer 10 at 16 AU until the second half of April; this time sudden transitions to new intensity levels were observed for protons and helium at low and high energies. The new intensity levels were maintained through January 1979, both at 1 AU and at Pioneer 10. Differential energy spectra from IMP-8, Pioneer 11 and Pioneer 10 are presented and their changes discussed.

Von Rosenvinge, T. T.↗
NASA NTRS1980

Elemental composition, isotopes, electrons and positrons in cosmic rays

Experimental studies on the composition of cosmic rays are reviewed. Studies of elemental composition and time variation, Fe and near-Fe nuclei, trans-iron, high-energy spectra, antiprotons, isotopes, and electrons and positrons are discussed. Some theoretical studies of electrons are also considered.

Balasubrahmanyan, V. K.↗
NASA NTRS1980

Corotation of Saturn's magnetosphere - Evidence from energetic proton anisotropies

The theory and technique of Northrop and Thomsen (1980) are applied to the observations of energy spectra and directional anisotropies of 0.61- to 3.41 MeV protons in Saturn's magnetosphere. The observations were made by the Goddard Space Flight Center/University of New Hampshire and University of Iowa instruments aboard Pioneer 11 during the Pioneer encounter with Saturn in August-September 1979. Fourier fits to 15-min intervals of data are combined with spectral indices to yield information about the E x B convection velocity and temporal changes in the particle population. There is a fundamental inability to distinguish unambiguously between the two, but if one can be assumed, the other then follows from these calculations. It is found that although these data do not by themselves allow an unambiguous determination of the extent of corotation in Saturn's outer magnetosphere, they are consistent with exact corotation at the nominal rotation period in the presence of significant but not unreasonable temporal variations in the energetic proton population.

Thomsen, M. F.↗
NASA NTRS1981

A nonthermal ion layer with high anisotropies at the plasmasheet boundary during substorm recovery

The energy spectra and anisotropies of protons and alpha particles are investigated at the plasmasheet boundary during the recovery phase of geomagnetic substorms using the Max Planck Institut/University of Maryland sensor system on the ISEE-1 satellite. The observations are found to reveal the presence of a thin nonthermal layer of approximately 60 keV/charge protons and alpha particles at the plasmasheet boundary, the particles streaming highly collimated in earthward direction. It is pointed out that the alpha particle layer is confined within the proton layer. It is thought that the principal features of the layers can be explained in terms of an acceleration model proposed by Speiser (1965) for the environment of a magnetic neutral line.

Moebius, E.↗
NASA NTRS1981

Measurements of bow shock particles far upstream from the earth

Electrons and ions moving upstream frequently appear at distances up to 240 earth radii from earth at times when the direction of the interplanetary magnetic field allows their propagation from the bow shock. Strong asymmetries in the ion angular pitch angle distribution are often observed, a consequence of the sharp gradient in guiding center density and very weak scattering. The gradient is due to the restricted spatial region over which these particles are accelerated. The solar wind electric field acts on these particles and produces striking effects in both the ion angular distributions and the ion energy spectra. The frequent occurrence of these effects implies that the source region of the diffuse ions at the bow shock is not more than a few tens of thousands of km.

Anderson, K. A.↗
NASA NTRS1981

On the acceleration of ions by interplanetary shock waves. 3: High time resolution observations of CIR proton events

Observations within + or - 3 hours of corotating interaction region (CIR) shock waves of proton intensities, pitch angle distribution and crude differential energy spectra of the range of 0.6 E sub p 3.4 MeV are presented. The principle result is the evidence for the persistent flow of particles away from the shock. The observations are found to be in good agreement with the hypothesis of local interplanetary shock acceleration by the shock drift and compression mechanisms. The same set of observations strongly suggest that transit time damping does not play an important role in the acceleration of protons to 1 MeV in the immediate vicinity of CIR shocks.

Pesses, M. E.↗