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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 397 records · Page 22
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NASA NTRS1981

Nitric oxide delta band emission in the earth's atmosphere - Comparison of a measurement and a theory

Attention is given to the altitude dependent emission rate in the delta-bands of nitric oxide as measured in the earth's atmosphere at night by a scanning ultraviolet spectrometer. It is noted that the reaction responsible is the two-body association of nitrogen and oxygen atoms. The measurements show a vertical intensity beneath the layer for the delta-band system of 19 R. The horizontal emission rate is found to increase from 70 R at 117 km to 140 R at 150 km. The data are analyzed with a one-dimensional, time-dependent, vertical-transport model of odd nitrogen photochemistry. The calculated and measured intensities agree so long as the quenching of N(2D) by atomic oxygen is near 5 x 10 to the -13 cu cm/sec.

Rusch, D. W.↗
NASA NTRS1981

Comets and the origin of life; Proceedings of the Fifth College Park Colloquium on Chemical Evolution, University of Maryland, College Park, MD, October 29-31, 1980

Papers are presented concerning the characteristics of comets and their possible role in the origin of life. Specific topics include the characteristics, origin and structure of the cometary nucleus, cometary chemical abundances, the nature of interplanetary dust and its entry into terrestrial planet atmospheres, and the mechanism of ray closure in comet tails. Attention is also given to chemically evolved interstellar dust as a source of prebiotic material, the relation of comets to paleoatmospheric photochemistry, comets as a vehicle for panspermia, limits to life posed by extreme environments, and the status of cometary space missions as of 1980.

Ponnamperuma, C.↗
NASA NTRS1981

Photolysis of CH4-NH3 mixtures and PH3 as models for the photochemical transformations on the primitive earth and Jupiter

Methane, ammonia and phosphine are some of the possible constituents of the atmospheres of the Jovian planets and their satellites. Photolysis of NH3 in the presence of CH4 at 185 nm in the temperature range of 25 C to -100 C results in the decomposition of CH4. The reaction is inhibited by added H2 or SF6. These findings are consistent with the reaction of hot hydrogen atoms with CH4 to give the CH3 radical. P2H4 is the initial product formed by the photolysis of PH3 at 206 nm. Kinetic studies established that it is the intermediate in the formation of P4 from PH3. The potential significance of these reactions to the atmospheric photochemistry of the Jovian planets and moons is discussed.

Ferris, J. P.↗
NASA NTRS1981

The atmosphere and ionosphere of Jupiter

The thermal structure of the upper atmosphere of Jupiter, the composition of the atmosphere and the strength of mechanical mixing, and sources and sinks of ionization in the Jupiter ionosphere are described from Voyager UV spectrometer, radio, IR, and imaging data. A topside ionospheric temperature of 1300 K was observed, along with an energy equilibrium between the plasma and neutral gas in the upper atmosphere. A composite thermal structure is provided, noting a close similarity to earth conditions at upper levels, and enhanced thermal behavior has been detected between the times of solar minimum and maximum activity. Ammonia photochemistry is examined, and measured concentrations of H2, CH4, C2H6, and C2H2 as a function of height are outlined. Eddy diffusion coefficient calculations are carried out, yielding a highest Ly-alpha intensity of 100 million sq cm/sec. The increased exospheric temperature between 1973 and 1980 is stressed to have no known satisfactory explanation.

Atreya, S. K.↗
NASA NTRS1982

The evolution of solar ultraviolet luminosity

Astronomical observations of stars analogous to the sun are used to construct a tentative account of the evolution of solar UV luminosity. Evidence exists that the young sun was a much more powerful source of energetic particles and radiation than it is today, and while on the main sequence, solar activity has declined as an inverse power law of age as a consequence of angular momentum loss to the solar wind. Observations of pre-main sequence stars indicate that before the sun reached the main sequence, it may have emitted as much as ten thousand times the amount of ultraviolet radiation that it does today. The impact of the results on knowledge of photochemistry and escape of constituents of primordial planetary atmospheres is discussed.

Zahnle, K. J.↗
NASA NTRS1982

Methane and nonmethane hydrocarbon concentrations in the Atlantic marine boundary layer

The reactions of reduced tropospheric trace gases with hydroxyl radicals are thought to play a significant role in global tropospheric photochemistry. Since tropospheric methane and nonmethane hydrocarbon (NMHC) concentrations will affect the tropospheric hydroxyl radical concentrations, accurate measurements of tropospheric CH4 and NMHC concentrations are necessary. Such measurements were, therefore, included in the first leg (from Hamburg, West Germany to Montevideo, Uruguay) of the 1980-1981 Antarctic Expedition. On the basis of the obtained data, a pronounced gradient between northern and southern hemispheric methane concentrations was observed in the marine boundary layer in the region of the intertropical convergence zone. Methane concentrations gradually decreased from about 1.70 ppmv at 40 deg N latitude to about 1.68 ppmv at 14 deg N latitude, then dropped sharply between 14 deg N and 10 deg N latitude to about 1.61 ppmv. NMHC data are also discussed.

Cofer, W. R., III↗
NASA NTRS1982

PAN and the NOx budget of the troposphere

The present investigation has the objective to examine the interaction of NOx with the nonmethane hydrocarbons (NMHCs) photochemistry. Attention is given to the influence of temperature, transport, and hydrocarbon radical reactions on the profiles of peroxyacylnitrates (PANs) and NO2. A lumped NMHC chemical reaction scheme was used in a one-dimensional photochemical model of the global troposphere. Model calculations were performed with various temperature profiles and the corresponding solar zenith angles to examine seasonal variations in the profiles of PAN and NOx. A study of the effects of changing temperature and solar zenith angle on the profiles of PAN and NOx showed that the amount of NO2 tied up in PAN increased as temperature decreased.

Brewer, D. A.↗
NASA NTRS1981

Quadrennial International Ozone Symposium, Boulder, CO, August 4-9, 1980, Proceedings. Volumes 1 & 2

Recent developments in observational techniques are examined, taking into account a review of some unresolved problems in the measurement/estimation of total ozone and the vertical ozone profile, the sensitivity of Dobson total ozone estimations to wavelength band calibration uncertainties, errors in Dobson total measurements arising from aerosol attenuation, and optical stop and focussing effects in the Dobson instrument. Other subjects considered are related to total ozone observations, tropospheric ozone, upper air ozone observations, observations of trace gases in the atmosphere, ozone photochemistry and directly related photochemical models, the interaction of ozone and atmospheric circulation, ozone effects on climate, and solar activity and ozone variations. Programs and recommendations involving ozone theory and observations are also discussed, giving attention to current problems of ozone chemistry, the upper atmosphere research satellite program, a French contribution to ozone related studies, and ozone and the middle atmosphere program.

London, J.↗
NASA NTRS1981

The validation of LIMS ozone profiles using correlative rocket, ECC, and Dobson data sets

The Limb Infrared Monitor of the Stratosphere (LIMS) experiment is a limb scanning infrared sounder designed to measure vertical temperature profiles and the concentrations of key chemical compounds which are important in the stratospheric ozone-nitrogen photochemistry. Preliminary ozone profiles are being intercompared with correlative rocket and balloonsonde ozone data sets as part of the Nimbus 7 LIMS data validation activity. The LIMS ozone retrievals extend from the lower mesosphere to the tropopause (or cloud-top altitudes). In this paper, preliminary statistics of comparisons of ECC (electrochemical concentration cell) ozonesonde and rocket ozone profiles with LIMS ozone profiles are presented. ECC ozonesonde data taken at times of LIMS overpasses are also used to extend the LIMS retrieval down to ground level. Each combined profile is then integrated to obtain total column ozone. These integrated results are compared to Dobson data obtained at approximately the same time and location.

Remsberg, E. E.↗
NASA NTRS1981

The seasonal variations of ozone and temperature in the middle and the upper stratosphere

The seasonal variations in ozone and temperature inferred from the Nimbus-4 BUV (Backscatter Ultraviolet Spectrometer) and the SCR (Selective Chopper Radiometer) experiments are compared with predictions based on a simplified radiative photochemical model. It is shown that the observations, in agreement with the model calculations, show a systematic phase shift from a summer maximum at 10 mb to a winter maximum at 1 mb with equinoctial maxima at intermediate heights. In contrast, the temperature between these pressure levels shows no appreciable phase shift and the summer maximum prevails at all heights. The observed phase differences in ozone and temperature are shown to be a manifestation of the radiative feedback on the photochemistry of the upper stratosphere.

Chandra, S.↗
NASA NTRS1982

Chemistry and evolution of Titan's atmosphere

The chemistry and evolution of Titan's atmosphere are reviewed, in light of the scientific findings from the Voyager mission. It is argued that the present N2 atmosphere may be Titan's initial atmosphere, rather than one photochemically derived from an original NH3 atmosphere. The escape rate of hydrogen from Titan is controlled by photochemical production from hydrocarbons. CH4 is irreversibly converted to less hydrogen-rich hydrocarbons, which over geologic time accumulate on the surface to a layer thickness of about 0.5 km. Magnetospheric electrons interacting with Titan's exosphere may dissociate enough N2 into hot, escaping N atoms to remove about 0.2 of Titan's present atmosphere over geologic time. The energy dissipation of magnetospheric electrons exceeds solar EUV energy deposition in Titan's atmosphere by an order of magnitude, and is the principal driver of nitrogen photochemistry. The environmental conditions in Titan's upper atmosphere are favorable to building up complex molecules, particularly in the north polar cap region.

Strobel, D. F.↗
NASA NTRS1982

The Venus environment; Proceedings of the International Conference, Palo Alto, CA, November 1-6, 1981

Attention is given to noble gases in planetary atmospheres, the photochemistry of the stratosphere of Venus, the chemistry of metastable species in the Venusian ionosphere, the Venus ionosphere at grazing incidence of solar radiation, disappearing ionospheres on the nightside of Venus, and the observed composition of the ionosphere of Venus. Other investigations considered are concerned with the predicted electrical conductivity between 0 and 80 km in the Venusian atmosphere, sulfuric acid vapor and other cloud-related gases in the Venus atmosphere, the composition and vertical structure of the lower cloud deck on Venus, amorphous sulfur as the ultraviolet absorber on Venus, and polarization studies of the Venus UV contrasts. A description is provided of topics related to temporal variability of ultraviolet cloud features in the Venus stratosphere, zonal mean circulation at the cloud level on Venus, the influence of thermospheric winds on exospheric hydrogen on Venus, and an analysis of Venus gravity data.

Source record↗
NASA NTRS1982

The satellite power system - Assessment of the environmental impact on middle atmosphere composition and on climate

Numerical models were developed to calculate the total deposition of watervapor, hydrogen, CO2, CO, SO2, and NO in the middle atmosphere from operation of heavy lift launch vehicles (HLLV) used to build a satellite solar power system (SPS). The effects of the contaminants were examined for their effects on the upper atmosphere. One- and two-dimensional models were formulated for the photochemistry of the upper atmosphere and for rocket plumes and reentry. An SPS scenario of 400 launches per year for 10 yr was considered. The build-up of the contaminants in the atmosphere was projected to have no significant effects, even at the launch latitude. Neither would there by any dangerous ozone depletion. It was found that H, OH, and HO2 species would double in the thermosphere. No measurable changes in climate were foreseen.

Whitten, R. C.↗
NASA NTRS1982

A study of mesospheric rocket contrails and clouds produced by liquid-fueled rockets

Changes in the atmospheric composition, particularly through the condensation of rocket vehicle exhaust, caused by the flights of 400 heavy lift launch vehicles (HLLV) to carry crews and materials into space to build a satellite solar power system (SPS) were examined. Attention was given to the formation of mesospheric contrails and clouds. A one-dimensional model was used to formulate the photochemistry and vertical transport of water vapor, its nucleation into an ice cloud, and the microphysical development of the cloud. Considering one HLLV launch per day for a decade, it is projected that the upper atmosphere water vapor concentration would be increased by 10-20%, thereby augmenting the size and opacity of natural noctilucent clouds by 50%. No climatological consequences are foreseen from the clouds, although spectacular noctiluminescent cloud displays are thought to be possible.

Turco, R. P.↗
NASA NTRS1982

The atmospheres of Io and other satellites

Voyager measurements of gaseous SO2 in a hot spot region and of ions of sulfur, oxygen, and SO2(+) in the plasma torus, combined with the groundbased measurements of SO2 frost on the surface, indicate that SO2 is perhaps the dominant constituent of Io's atmosphere. Indeed the ionosphere of Io can be sustained by a pure SO2 atmosphere in thermal equilibrium with the surface. Upper limits on common volatiles H2O, CO2, NH3, and CH4 and exceedingly small, although S2 and Ar may still be present. Photochemistry of SO2 could lead to O2 as the major gas on the night side. Reasonable processes for loss to the torus include thermal escape, sputtering, and sweep-up of ions. The symmetry of the sodium cloud between eastern and western elongation is difficult to reconcile with any substantial, diurnally varying atmosphere. Europa, Ganymede, and Callisto may have oxygen atmospheres resulting from photolysis of water vapor. A pressure of approximately 10 to the -6th microbar is predicted, consistent with the Voyager upper limit for Ganymede. A much higher pressure might be present if the water vapor pressure is increased by a low albedo (Callisto) or sputtering (Europa).

Kumar, S.↗
NASA NTRS1982

Atmosphere explorer and the IMS

The Atmosphere Explorer (AE) program provided assistance to participants in the International Magnetosphere Study (IMS). The AE program, which began about 1970 employed three spacecraft in three complementary orbits. The program initiated a concept of a common data base, which is, a data base shared by all the participating investigators, to facilitate the correlation of the measured parameters. The immediate goal of the AE program has been study of the thermosphere, giving particular attention to photochemistry. Three satellites, AE-C, D, and E, were launched into orbits of 68 deg, 90 deg, and 19 deg inclination respectively in December 1973, October 1975, and November 1975. An instrument complement description is provided, and the AE data base is discussed.

Spencer, N. W.↗
NASA NTRS1982

Fluorescence yields from photodissociation of OCS at 1060-1240 A

The cross sections for the production of fluorescence (3000-8000 A) from excited photofragments of OCS were determined in order to gain a better understanding of the role of carbonyl sulfide in interstellar photochemistry. Synchrotron radiation was used as the light source for the measurements in the 1060-1240 A region, as it is suitable for measuring the absorption cross section in the structured region. It was found that the quantum yields for the production of various CO triplet states are less than 1.5% at the observed excitation photon wavelengths.

Lee, L. C.↗
NASA NTRS1983

A mechanistic model of Eulerian, Lagrangian mean, and Lagrangian ozone transport by steady planetary waves

Ozone transport is calculated for steady, dissipative planetary waves using the Eulerian, Lagrangian mean, and residual circulation. A Lagrangian model of parcel dynamics is used to interpret planetary wave-photochemistry interaction. In chemically active regions the mean field ozone changes are found to be significant only where there are large gradients in chemical sources and sinks along parcel trajectories. The largest changes in the mean field are found in the lower stratosphere and are due to the Lagrangian mean advection. When the Lagrangian mean advection is approximated by the residual circulation, errors in the transport velocities as large as 30 pct may occur.

Rood, R. B.↗