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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

The electron heating rate and ion chemistry in the thermosphere above Wallops Island during the solar eclipse of 7 March 1970.

Measurement of the N2 concentration and temperature, the ion composition and concentrations, and the electron temperature up to 290 km about 30 and 5 min before totality during the Mar. 7, 1970, eclipse. The rockets traveled similar trajectories, thus permitting the purely temporal changes between flights to be resolved. The neutral temperature and N2 concentration changed little, but the electron temperature decreased by as much as 20% in the lower F region. The ion concentration decreased by about 30% in the F region and about 50% in the E region, with little change in relative ion composition. The electron cooling rates decreased by a factor of 6 in the lower F region, approximately in proportion to the change in the visible solar disk. A smaller than expected decrease in the cooling rate below 150 km between the two flights indicates a hardening of the solar spectrum and suggests a significant heat contribution from the solar corona near totality. The ion composition measurements were consistent with solutions of the ion continuity equations. A proper fit required a factor-of-three enhancement of the flux below 200 A, an amount also consistent with the electron heat balance analysis. Reactions involving the minor ions N(+) and N2(+) were found to be important for the ion chemistry of the major ions O2(+) and NO(+), especially at the time of eclipse.-

Brace, L. H.↗
NASA NTRS1972

Longitudinal variations of thermospheric composition indicating magnetic control of polar heat input.

Measurement of neutral N2, O, and He densities from Ogo 6 over the south polar region during magnetically quiet periods in late August and early September 1969. It is found that N2 densities, when they are extrapolated to a common altitude, maximize at about 0800 UT near 70 deg invariant latitude. The density of He has a minimum at this time, and the density of O has a slight maximum. It is proposed that these phenomena are the result of cyclic variations in soft electron precipitation, which heats the thermosphere either directly or through enhanced Joule heating. This heat energy would increase the gas temperature, the increase in the gas temperature leading to the N2 increase, and would vary the composition by generation of a wind system.

Hedin, A. E.↗
NASA NTRS1972

Upper atmospheric probing by resonance fluorescence excited by tunable laser radiation.

Consideration of the application of the measurement of resonance fluorescence radiation excited by tunable laser radiation to the detection of atomic, molecular, and ionic species in the upper atmosphere. The species considered are N2, N2(+), NO, NO(+), O2(+), CO, CO(+), CH, Na, K, and Ca. Calculations of the resonance scattering cross sections, photon returns, and signal-to-noise ratios are given for these species for a range of conditions. Based on a probing altitude of 100 km, the detections of N2, NO, CO, CH, O2, and the trace metals appear feasible with state-of-the-art systems and within the concentration range present in the atmosphere.

Saunders, A. R.↗
NASA NTRS1972

Empirical model of global thermospheric temperature and composition based on data from the OGO-6 quadrupole mass spectrometer

An empirical global model for magnetically quiet conditions has been derived from longitudinally averaged N2, O, and He densities by means of an expansion in spherical harmonics. The data were obtained by the OGO-6 neutral mass spectrometer and cover the altitude range 400 to 600 km for the period 27 June 1969 to 13 May 1971. The accuracy of the analytical description is of the order of the experimental error for He and O and about three times experimental error for N2, thus providing a reasonable overall representation of the satellite observations. Two model schemes are used: one representing densities extrapolated to 450 km and one representing densities extrapolated to 120 km with exospheric temperatures inferred from N2 densities. Using the best fit model parameters the global thermospheric structure is presented in the form of a number of contour plots.

Hedin, A. E.↗
NASA NTRS1972

The photolysis of ozone

Ozone was photolyzed at 25 C with steady illumination at several wavelengths from 2288 to 2850 A, at O3 pressures from 0.1 to 2.7 torr, and at absorbed intensities from 0.15 to 65 microns/min. Experiments were done in pure dry O3, and in the presence of He, CO2, N2, H2O, H2, N2O, He-CO2, He-H2O, CO2-H2O, O2-N2O, CO2-O2, and N2O5-O2-CO2 mixtures. The results show that in the absence of added gases or in the presence of He, the quantum yield of O3 consumption is 5.5 independent of conditions, except at pressures below 0.4 torr. In the presence of CO2 or N2, ozone consumption falls toward 4.0. The primary photolytic act produces O(1 D) and siglet O2, presumably O2(1 delta), at all wavelengths below 3000 A. Relative quenching constants O(1 D) removal by various gases were measured at 2288, 2537, and 2800 A. For O3, CO2, and N2, the relative rates are 1.0/0.4 to 0.5/0.08 to 0.11 at all wavelengths. For H2O the constant at 2537 A is 1.5 relative to that for O3. With N2O, a noticeable wavelength effect is observed and the relative rate constants are 1.5, 2 to 3, 4.0 for O3 compared to N2O at 2800, 2537, and 2288 A, respectively.

Lissi, E.↗
NASA NTRS1972

Foreign-gas-broadening effects in the 15-micron CO2 bands.

The effects of N2, O2, Ar, and He on the absorption of radiation by the 15-micron perpendicular CO2 bands are reported. The investigation was carried out at medium resolution and at gas pressures less than 1 atm. The results of the study are presented in the form of a band-averaged broadening coefficient for N2, band-averaged broadening factors for O2, Ar, and He, and wavelength dependent broadening coefficients for N2, O2, Ar, and He. Comparisons are made with other experimental and theoretical results. In addition transmittances were calculated for homogeneous paths using some of the molecular parameters determined in the study and compared with measured transmittances.

Reichle, H. G., Jr.↗
NASA NTRS1972

Diatomic gasdynamic lasers.

Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant overpopulations of upper vibrational states. When mixtures of CO and N2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N2 expansions. The resulting CO-N2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO2 lasers.

Mckenzie, R. L.↗
NASA NTRS1973

Diurnal and semidiurnal nitrogen density and temperature variations from thermosphere probe measurements.

Amplitudes and phases for the diurnal and semidiurnal variations of thermospheric molecular nitrogen density and temperature are determined from data obtained by six rocket-launched thermosphere probes. The semidiurnal tide is significant for the lower thermosphere variations, where it could dominate in the N2 density at 140 km and in the temperature for altitudes between 170 and 200 km. At exospheric heights, the magnitudes of the semidiurnal modes in density and temperature are significantly smaller than those of the diurnal mode. The temperature phase is height-dependent in both diurnal and semidiurnal components below 200 km, thus contributing to phase differences between N2 density and temperature in both modes. No significant phase differences are apparent between N2 density and thermospheric temperature above 250 km.

Newton, G. P.↗
NASA NTRS1974

CO2 photodissociation and vibrational excitation in the planetary atmospheres

The principal subjects of investigation were the determination of the CO2 photodissociation quantum yields at the wavelengths from 1200 A to 1500 A, and the efficiency of electronic-to-vibrational energy transfer in the systems 0(1D) + CO, N2, CO2 yields 0(3P) + CO N2, CO2 vibrational energies. Measurements on the photodissociation quantum yield of CO2 in the 1200-1500 A region show that it is wavelength dependent, and for the six atomic line sources used, the quantum yield varied from 0.2 to 0.8. The data appear to fit the interpretation of stable CO2 bound states mixed with repulsive or predissociating states, since the low quantum yields coincide with the maximum structure in the CO2 absorption spectrum. The first reliable measurements were made on the efficiency of electronic-to-vibrational energy transfer in the systems 0(1D)-CO and 0(1D)-N2, using a uv resonance fluorescence technique. The 0(1D)-CO2 interaction was investigated by infrared techniques.

Slanger, T. G.↗
NASA NTRS1974

Argon: A thermometer of the upper atmosphere

The exospheric temperatures are derived from Ar, N2, O and He measurements obtained from the Aeros-1 NATE experiment. It is shown that the temperatures derived from Ar and N2 are very close to each other and show very similar seasonal, latitudinal and the day to night variations both under quiet and the geomagnetically disturbed conditions. The temperatures derived from O and He do not usually follow this pattern because of their large variabilities in the lower thermosphere. The differences in the inferred temperatures from these gases are particularly noticeable when the neutral composition data between 220-250 km are used. In this altitude region Ar appears to have some advantage over N2 for the purpose of deriving neutral temperature.

Chandra, S.↗
NASA NTRS1973

Theoretical models for electron energy relaxation in the lower ionosphere

Elastic collisions and rotation inelastic collisions involving quadrupole molecular transitions are important in energy relaxation of electrons in molecular gases. It has been customary in studying the cooling of electrons in a plasma heated by high-frequency waves to characterize this relaxation by the ionospheric G factor. The G factor is first defined in a fundamental way by use of kinetic theory. Then present models for theoretical cross sections for electron collision with O2 and N2 are used to derive expressions for the G factor in the lower ionosphere. Two models are considered: one uses Gerjuoy-Stein models for both N2 and O2; the other uses a Gerjuoy-Stein model for N2 and a Geltman-Takayanaki model for O2. Neither O2 model has been definitely established experimentally. It is found that temperature dependence of G is critically dependent on the O2 model.

Hagenbuch, K. M.↗
NASA NTRS1974

Pulse-modulated dual-gas control subsystem for space cabin atmosphere

An atmosphere control subsystem (ACS) was developed for use in a closed manned cabin, such as the Space Shuttle Orbiter. This subsystem uses the Perkin Elmer mass spectrometer for continuous measurement of major atmospheric constituents (H2, H2O, N2, O2, and CO2). The O2 and N2 analog signals are used as inputs to the controller, which produces a pulse-frequency-modulated output to operate the N2 gas admission solenoid valve and an on-off signal to operate the O2 valve. The proportional controller characteristic results in improved control accuracy as compared with previously used on-off controllers having significant dead-band. A 60-day evaluation test was performed on the ACS during which operation was measured at various values of control setpoint and simulated cabin leakage.

Jackson, J. K.↗
NASA NTRS1976

A study of a sector spectrophotometer and auroral O+(2P-2D) emissions

The metastable O+(2P-2D) auroral emission was investigated. The neighboring OH contaminants and low intensity levels of the emission itself necessitated the evolution of an instrument capable of separating the emission from the contaminants and having a high sensitivity in the wavelength region of interest. A new type of scanning photometer was developed and its properties are discussed. The theoretical aspects of auroral electron interaction with atomic oxygen and the resultant O+(2P-2D) emissions were examined in conjunction with N2(+)1NEG emissions. Ground based measurements of O+(2P-2D) auroral emission intensities were made using the spatial scanning photometer (sector spectrophotometer). Simultaneous measurements of N2(+)1NEG sub 1,0 emission intensity were made in the same field of view using a tilting photometer. Time histories of the ratio of these two emissions made in the magnetic zenith during auroral breakup periods are given. Theories of I sub 7319/I sub 4278 of previous investigators were presented. A rocket measurement of N2(+)1NEG sub 0,0 and O+(2P-2D) emission in aurora was examined in detail and was found to agree with the ground based measurements. Theoretical examination resulted in the deduction of the electron impact efficiency generating O+(2P) and also suggests a large source of O+(2P) at low altitude. A possible source is charge exchange of N+(1S) with OI(3P).

Swenson, G. R.↗
NASA NTRS1976

Composition waves in the thermosphere

Neutral-composition waves excited by auroral heat sources are investigated. For horizontal wavelengths of the order of 1000 km, it is concluded that diffusion processes (1) play a significant role such that deviations from diffusive equilibrium prevail for He throughout the thermosphere; (2) produce phase differences of about 220 deg (or -140 deg) between He and N2, and (3) account for He amplitudes comparable to those of N2. These results basically explain recent AE-C satellite measurements which have revealed an anticorrelation between the heavier and lighter constituents of the thermosphere. The calculations also indicate that temperature and N2 concentration are generally out of phase by about 100 deg.

Mayr, H. G.↗
NASA NTRS1976

High resolution daytime photoelectron energy spectra from AE-E

The daytime photoelectron energy spectrum has been measured at altitudes above 154 km by the photoelectron-spectrometer experiment on the Atmosphere Explorer-E satellite. Below 200 km, well-resolved peaks are observed in the spectrum corresponding to production of O(+) and N2(+) in various electronic states from photoionization of N2 and O by solar He II (304A) radiation. Vibration-rotation excitation of N2 by inelastic electron scattering is observed at 2.5 eV. The features due to nitrogen disappear from the spectrum at altitudes above 200 km.

Doering, J. P.↗
NASA NTRS1976

Effects of electric fields and other processes upon the nighttime high-latitude F layer

The dynamics of the nighttime high-latitude F region is studied with special emphasis on the formation of the electron-density trough region which lies equatorward of the auroral oval. It is found that the absence of photoionization together with ordinary ionic recombination and slow plasma convection velocity can give a deep trough over a period of many hours. However, the normal global pattern of electric fields has regions of plasma convection sufficiently rapid to affect the rate of O(+) + N2 reactions and to speed the rate of ionospheric decay. In addition, the escape of thermal plasma via the polar winds as well as N2 vibrational excitation and enhanced N2 densities act to deplete the ionosphere. In combination, these destructive processes can readily account for the great variety of troughs found by experimentation. Thus, it appears that there is no single cause for the observed troughs, but that at various times, different processes act together to create density depressions of substantial magnitude.

Schunk, R. W.↗
NASA NTRS1976

Isotopic composition of nitrogen - Implications for the past history of Mars' atmosphere

Models are presented for the past history of nitrogen on Mars, based on Viking measurements showing that the atmosphere is enriched in N-15. The enrichment is attributed to selective escape, with fast atoms formed in the exosphere by electron impact dissociation of N2 and by dissociative recombination of N2(+). The initial partial pressure of N2 should have been at least as large as several millibars and could have been as large as 30 millibars if surface processes were to represent an important sink for atmospheric HNO2 and HNO3.

Mcelroy, M. B.↗
NASA NTRS1976

OGO-4 observations of the ultraviolet auroral spectrum

Auroral ultraviolet spectra in the range from 1200 to 3200 A have been obtained by the spectrometer on board the OGO-4 satellite. Emissions of N2, H, O, and N are readily identified. Atomic and molecular intensities are deduced from the comparison with a synthetic spectrum and compare reasonably well with some previous measurements and calculations. A feature at 2150 A is assigned to the (1-0) NO gamma band. Taking into consideration the various excitation mechanisms of NO(A2 Sigma), it is proposed that energy transfer from N2 metastable molecules to oxygen accounts for the excitation of the NO gamma bands. In particular, it is suggested that the resonant reaction between O2 and highly metastable N2 molecules may be a major source of NO(A2 Sigma).

Gerard, J.-C.↗