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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Experimental investigations of low-energy (4 to 40 eV) collisions of O(-)(P2) ions and O(P3) atoms with surfaces

Using a newly-developed, magnetically confined source, low-energy, ground state oxygen negative ions and neutral atoms are generated. The energy range is variable, and atom and neutrals have been generated at energies varying from 2 eV to 40 eV and higher. It was found that the interaction of these low-energy species with a solid magnesium fluoride target leads to optical emissions in the (at least) visible and infrared regions of the spectrum. Researchers describe y details of the photodetachment source, and present spectra of the neutral and ion glows in the wavelength range 250 to 850 nm (for O(-)) and 600 to 850 nm (for O), and discuss the variability of the emissions for incident energies between 4 and 40 eV.

Chutjian, A.↗
NASA NTRS1990

Experimental investigations of low-energy (4-40 eV) collisions of O-(2P) ions and O(3P) atoms with surfaces

Using a newly-developed, magnetically confined source, low-energy, ground state oxygen negative ions and neutral atoms are generated. The energy range is variable, and atom and neutrals have been generated at energies varying from 2 eV to 40 eV and higher. It was found that the interaction of these low-energy species with a solid magnesium fluoride target leads to optical emissions in the (at least) visible and infrared regions of the spectrum. Researchers describe y details of the photodetachment source, and present spectra of the neutral and ion glows in the wavelength range 250 to 850 nm (for O/-/) and 600 to 850 nm (for O), and discuss the variability of the emissions for incident energies between 4 and 40 eV.

Orient, O. J.↗
NASA NTRS1995

Ponderomotive effects on distributions of O(+) ions in the auroral zone

Test particle calculations are used to compute the effects of gravity and ponderomotive acceleration by shear Alfven wave oscillations on the distribution function of O(+) ions along auroral field lines, assuming an ionospheric Maxwellian source of the ions at 2000 km altitude with approximately 0.5 eV of thermal energy in the parallel component of velocity. The electric field model corresponds to a standing wave oscillation with a frequency approximately 1 Hz in the azimuthal direction superimposed on the background dipole field, in which the wave amplitude is either increasing or decreasing in time. The electric field is taken to be primarily in the perpendicular direction. The time varying wave produces broad distributions with widths of 2 to 10 times the initial 0.5-eV thermal energy of the Maxwellian source, and the density and flux of upward going O(+) ions at one Earth radius are both enhanced in this model. The oxygen ion distribution functions at 1 R(sub E) altitude resulting from interaction with waves whose amplitudes are increasing in time have a more gradual lower energy cutoff than do the distribution functions resulting from decaying waves. The high-energy part of the distribution functions in growing waves reflects the temperature of the Maxwellian source, while the high-energy part of the distributions resulting from decaying waves steepens with time, independent of the source temperature.

Witt, E.↗
NASA NTRS1994

Origin of the O(+) pick-up ions in the hehiosphere

The main sources for the ions in the interplanetary medium are the solar wind and the interstellar gas intruding into the heliosphere. Other sources, i.e. comets and planets can, however, contribute significantly locally. We present approximate expressions for deriving fluxes of pick-up ions originating from local neutral gas sources. Since the Io-torus is thought to be a relatively strong emitter of fast atoms, particular O and S, we used the O(+) data obtained by SWICS-Ulysses as a function of distance from Jupiter, both in and out-off the ecliptic plane in order to recognize a possible contribution of the Ionian source to the measured O(+). We find that - except for a very limited zone near the Jovian magnetosphere - the contribution of the Io-torus to the O(+) fluxes is minor, thus confirming our previous results on the pick-up H(+), He(+), N(+), O(+), and Ne(+) fluxes of interstellar origin.

Geiss, J.↗
NASA NTRS1993

Experimental investigation of possible geomagnetic feedback from energetic (0.1 to 16 keV) terrestrial O(+) ions in the magnetotail current sheet

Data from energetic ion mass spectrometers on the International Sun Earth Explorer 1 (ISEE 1) and AMPTE/CCE spacecraft are combined with geomagnetic and solar indices to investigate, in a statistical fashion, whether energized O(+) ions of terrestrial origin constitute a source of feedback which triggers or amplifies geomagnetic magnetotail current sheet. The ISSE 1 data (0.1-16 keV/e) provide in situ observations of the O(+) solar cycle 21, as well as inner magnetosphere data from same period. The CCE data (0.1-17 keV/e), taken during the subsequent solar minimum, all within 9 R(sub E), provide a reference for long-term variations in the magnetosphere O(+) content. Statistical correlations between the ion data and the indices, and between different indices, all point in the same direction: there is probably no feedback specific to the O(+) ions, in spite of the fact that they often contribute most of the ion mass density in the tail current sheet.

Lennartsson, O. W.↗
NASA NTRS1987

Observations of spatial distribution of energetic O(3+), O(4+), and O(5+) ions in the magnetosphere

L profiles of ions with intermediate charge states (O(5+), O(4+), and O(3+) are presented and compared with those of O(+), O(2+), and O(6+) ions in order to determine their possible sources of origin. The L profiles exhibit broad maxima located at L = 6-7 for O(3+) and O(4+) and L = 7-8 for O(5+) ions during periods of low to medium geomagnetic activity. With increasing Kp, the flux versus L distributions extend further earthward and the maxima move to slightly lower L values. While the flux decrease earthward of the maximum is very steep, the gradual decrease outward of the maximum becomes flatter with increasing charge state. These results suggest that O(3+), O(4+), and O(5+) ions are produced predominantly by charge exchange processes, and that the O(4+) and O(5+) ions are produced from the solar wind-originating O(6+).

Kremser, G.↗
NASA NTRS1980

A laboratory study on the dissociative recombination of vibrationally excited O2/+/ions

The dissociative recombination of vibrationally excited O2(+) ions is studied in light of the possible importance of this reaction in upper atmospheric chemistry. A plasma spectroscopy experiment was performed in a microwave cavity filled by an argon-oxygen mixture, with O(1S) production monitored by measurements of the 5577-A afterglow, the O2(+) density and the electron concentration. Plasma and optical data reveal the predominant afterglow ions to be Ar2(+) and O2(+), with an effective O(1S) dissociative recombination coefficient of 2.1 x 10 to the -8th cu cm/sec, corresponding to a quantum yield of 10%. Experiments with an argon-krypton-oxygen mixture reveal that vibrationally excited O2(+) ions are the chief source of the O(1S) atoms, with a specific recombination coefficient for the dissociation of O2(+)(2 pi g) into O(1S) and O(1D) of 4.2 x 10 to the -9th cu cm/sec. A comparison of the laboratory results with Atmospheric Explorer data on the 5577-A airglow implies that O2(+) ions in the sunlit ionosphere are vibrationally excited to the same degree as in the laboratory, with the vibrational relaxation of these ions much slower than dissociative recombination. Results also predict a dawn-twilight asymmetry in the effective O(1S) yield due to the normal variation of electron content.

Zipf, E. C.↗
NASA NTRS1987

Thermal ion complexities observed within the Spacelab 2 bay

Examples of prominent thermal ion composition variations characteristic of the Shuttle environment as observed from within the open cargo bay on the Spacelab 2 mission are discussed. Although the prominent ionization source is the inflow of the ambient plasma, water ions of Shuttle origin were present throughout the mission, and there was evidence for a local source of molecular ions NO(+) and/or O(2+) which also exist in the ionosphere. Bursts in the fluxes of these contaminant species were frequently observed coincident with thruster firings, while O(+) depletions or enhancements could occur depending on the scattering geometry. These effects bring into question whether reliable ambient thermal ion measurements can be made from the vicinity of such vehicles. The presence of significant inflows of contaminant ions into the bay within the Shuttle wake also indicates that Shuttle emissions play a significant role in the evolution of its wake structure.

Grebowsky, J. M.↗
NASA NTRS1994

Experimental investigation of possible geomagnetic feedback from energetic (0.1 to 16 keV) terrestrial O(+) ions in the magnetotail current sheet

Data from energetic ion mass spectrometers on the ISEE 1 and AMPTE/CCE spacecraft are combined with geomagnetic and solar indices to investigate, in a statistical fashion, whether energized O(+) ions of terrestrial origin constitute a source of feedback which triggers or amplifies geomagnetic activity as has been suggested in the literature, by contributing a destabilizing mass increase in the magnetotail current sheet. The ISEE 1 data (0.1-16 keV/e) provide in situ observations of the O(+) concentration in the central plasma sheet, inside of 23 R(sub E), during the rising and maximum phases of solar cycle 21, as well as inner magnetosphere data from same period. The CCE data (0.1-17 keV/e) taken during the subsequent solar minimum all within 9 R(sub E). provide a reference for long-term variations in the magnetosphere O(+) content. Statistical correlations between the ion data and the indices, and between different indices. all point in the same direction: there is probably no feedback specific to the O(+) ions, in spite of the fact that they often contribute most of the ion mass density in the tail current sheet.

Lennartsson, O. W.↗
NASA NTRS1979

The photochemistry of N/+/ ions

The photochemistry of N(+) ions in the daytime thermosphere is studied using the data base of the Atmosphere Explorer C Satellite. The reaction O(+) + N(2D) yields O + N(+) is considered a major source of N(+) ions at altitudes between 250 and 500 km. At altitudes below 300 km, N(+) is removed by reactions with O2, but at higher altitudes the reactions of N(+) with O and with H are the most important loss mechanisms. The empirical rate coefficients for reactions N(+) + O yields N and O(+) and N(+) + H yields N + H(+) are derived.

Constantinides, E. R.↗
NASA NTRS1982

The dynamic response of the thermosphere to the energy influx resulting from energetic O/+/ ions

Precipitating fluxes of energetic O(+) ions during magnetic storms constitute a significant source of energy to the nightside thermosphere at altitudes above 200 km. The resulting perturbations of temperature and winds in the thermosphere due to energetic O(+) precipitation are examined by computing the heating rate profile from such a precipitation event and using this as input to the NCAR thermospheric general circulation model. The results of a time dependent calculation show that heating due to energetic O(+) ion precipitation produces a significant perturbation to the thermospheric structure above about 300 km. Energetic O(+) precipitation events should produce considerable variability in the upper thermosphere during geomagnetic storms.

Torr, M. R.↗
NASA NTRS1994

Energy transfer between energetic ring current H(+) and O(+) by electromagnetic ion cyclotron waves

Electromagnetic ion cyclotron (EMIC) waves in the frequency range below the helium gyrofrequency can be excited in the equatorial region of the outer magnetosphere by cyclotron resonant instability with anisotropic ring current H(+) ions. As the unducted waves propagate to higher latitudes, the wave normal should become highly inclined to the ambient magnetic field. Under such conditions, wave energy can be absorbed by cyclotron resonant interactions with ambient O(+), leading to ion heating perpendicular to the ambient magnetic field. Resonant wave absorption peaks in the vicinity of the bi-ion frequency and the second harmonic of the O(+) gyrofrequrency. This absorption should mainly occur at latitudes between 10 deg and 30 deg along auroral field lines (L is greater than or equal to 7) in the postnoon sector. The concomitant ion heating perpendicular to the ambient magnetic field can contribute to the isotropization and geomagnetic trapping of collapsed O(+) ion conics (or beams) that originate from a low-altitude ionospheric source region. During geomagnetic storms when the O(+) content of the magnetosphere is significantly enhanced, the absorption of EMIC waves should become more efficient, and it may contribute to the observed acceleration of O(+) ions of ionospheric origin up to ring current energies.

Thorne, Richard M.↗
NASA NTRS2001

Ionospheric Flow and Escape of Ions from Titan and Venus

Knowledge gained from measurements and models is used to study the high-speed plasmas interacting with the atmospheres and ionospheres of Titan and Venus. Considering the similarities of the interactions, comparative analysis is used to support the interpretations of observations made at each body. Ionospheric flow inferred to exist by analysis of measurements made from the Pioneer Venus Orbiter supports the interpretation of similar flow in the ionosphere of Titan. The concept that cold ions escape from the ionosphere of Venus is supported by the Voyager I observation that cold ions escape down the magnetic tail of Titan. Pickup O+ ion energy distributions observed at their source in the ionosheath of Venus are shown to be influenced by finite gyroradius effects. The signatures of such effects are expected to be retained as the ions move into the wakes of Titan and Venus.

Hartle, R. E.↗
NASA NTRS1985

Deuterium on Venus - Model comparisons with Pioneer Venus observations of the predawn bulge ionosphere

A self-consistent model of the Venus ionosphere in the predawn bulge region where the mass-two ion density is observed to be maximum was prepared in order to examine the question of mass-two ion identification in detail. The model calculations are compared to the Pioneer Venus observations of ion composition and structure in the 153-250 km altitude range. The observed densities of major ions O2(+) and O(+) are used to constrain the source of ionization. Once the source is determined, the density distribution of D(+) and H2(+) is calculated for various values of D and H2 in the atmosphere. It is found that mass-two ion is clearly due to deuterium and that the H2 contribution to the mass-two ion is small, if present at all.

Kumar, S.↗
NASA NTRS1990

Ion composition in and near the frontside boundary layer

A unique set of magnetopause crossings by the AMPTE/CCE spacecraft from near its 8.8 R(E) apogee is used to identify 13 crossings within the first two years after launch time that contain significant data intervals in the magnetosheath, boundary layer, and nearby outer magnetosphere. It is concluded that shocked solar wind or magnetosheath ions as well as ions from the outer magnetosphere overlap the boundary layer. Low-energy He(2+) as well as high charge state CNO, Si, and Fe group ions clearly overlap the boundary layer from their solar wind source. Similarly, O(+), N(+), O2(+) and NO(+) + O2(+) overlap the boundary layer from their magnetospheric source region. It is found that ion densities in the boundary layer are roughly one half those observed in the respective source regions, and that ion transport across the boundary layer is a one-way process with dawn-dusk asymmetry.

Eastman, T. E.↗
NASA NTRS1973

Daytime ion chemistry of N2+.

Rocket measurements of the emission of the (0, 0) first negative band of N2+ at 3914 A in the day airglow have been made between 120 and 300 km. The solar zenith angle at the time of the flight was 60 deg, and the zenith intensity above 120 km was 1.6 kR averaged over both legs of the flight. The data are compared with a model in which charge exchange of N2 with metastable O+(2D) ions is included as an additional source of N2 ionization. Above 240 km this mechanism is dominant over the photoionization of N2 by solar extreme ultraviolet radiation. The derived N2+ density is consistent with the results of rocket-borne mass spectrometric observations.

Feldman, P. D.↗
NASA NTRS1973

Study of neutral composition of lower thermosphere at Fort Churchill.

On Feb. 4 and 6, 1969, and May 11, 1970, Aerobee rockets carrying neutral mass spectrometers were flown at Fort Churchill, Canada during conditions of low geomagnetic activity. As in earlier flights at White Sands, New Mexico, each rocket carried both 'open' and 'closed' ion source instruments. Vertical profiles of N2, O2, O, Ar, and He were measured. Results obtained were essentially the same as those observed at White Sands except that for the winter flights helium appeared to be in diffusive equilibrium.

Nier, A. O.↗