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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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NASA NTRS1972

The stable auroral red arc of October 31 - November 1, 1968 and its interaction with the neutral atmosphere

Satellite observations of electron temperature and the topside electron density structure are used to calculate the red arc according to the thermal conduction model. In this model, energy from the magnetosphere flows in the electron gas along geomagnetic field lines into the ionosphere. This energy heats the ambient F-region electrons sufficiently to excite the oxygen atoms to the O I(1D) level by collisional impact giving rise to the 6300 A emission characteristic of the arc. For the 31 October/1 November 1968 red arc, the calculated emission rate, geographical position, and horizontal extent of the red arc are in agreement with the photometric data obtained by airglow observatories. Almost all of the energy conducted into the red arc is ultimately transferred to the neutral gas through elastic and inelastic collisions. This energy drives a large thermal cell and the circulation extends the influence of the arc thousands of kilometers beyond the region of direct heat input. The calculated neutral gas temperature response to electron heating within the arc is small.

Roble, R. G.↗
NASA NTRS1972

N2 positive and N2/+/ band systems and the energy spectra of auroral electrons.

Use of the relative emission rates of the auroral N2 positive and N2(+) band systems to limit the permissible range of differential electron fluxes in auroras, due to remarkable differences in electron excitation functions for the two kinds of systems. Use of recently measured electron cross sections and many observational data from ground based and rocket studies shows that the results are consistent with spectra equivalent to a power law E to the minus 1.4 power for primaries and secondaries combined. The unified primary spectra of Rees (1969) and secondary spectra of Rees et al. (1969) fail seriously to predict the optical ratios. It is shown that Rees' primary spectrum is deficient in slow primaries, owing to the use of defective Monte Carlo results of Maeda (1965). Doubt is thereby cast on the validity of experimental results for the differential spectrum below 50 eV reported by Feldman et al. (1971) because of the rapid decrease in flux with energy shown by those measurements.

Shemansky, D. E.↗
NASA NTRS1973

PPUAS--photopeak unfolding and self-shielding program

Computer code was developed to determine radioactive emission rates of nuclear fuels. Code is basically written for two different source geometries; however, unfolding routine can be executed for other source geometries.

Taherzadeh, M.↗
NASA NTRS1972

The IR emission spectrum of N2 excited under auroral conditions.

Recently determined experimental and theoretical cross sections for electron impact excitation of six triplet states of N2 (A, B, W, C, E, D) have been utilized to predict the absolute IR volume emission rates from N2 under nighttime auroral conditions. Secondary electron fluxes appropriate to an IBC II normal aurora were used in the calculations. The cascade contributions coupling the various electronic states were included as well as the most important quenching processes. The results indicate that the B yields reversibly A and W yields reversibly B cascade processes, which are important in the population of the A, B, and W states, produce appreciable radiation in the 1- to 5-micron wavelength region.

Cartwright, D. C.↗
NASA NTRS1973

Comet Bennett 1970 II.

The model for dust comets, formulated by Finson and Probstein, which had previously been tested only on Comet Arend-Roland 1957 III, has been successfully applied to three calibrated photographic plates of Comet Bennett. The size distribution, emission rate, and initial velocities of dust particles emitted from the comet's nucleus are given.

Sekanina, Z.↗
NASA NTRS1973

Photodissociation continuums of N2 and O2.

Dissociation continuum cross sections for N2 and O2 have been determined from previously measured total absorption and ionization cross sections. Several dissociation continuums were found for each molecule. Some of these continuums were attributed to specific dissociation products in which the dissociation products are in excited states. The upper-atmosphere emission rates resulting from these photodissociative excitation processes have been calculated for the N I 10,400-A and O I 1356-A lines. The results indicate, particularly for the oxygen line, that these photodissociative processes may be important in the dayglow.

Cook, G. R.↗
NASA NTRS1973

Predawn enhancement of 6300-A emission observed near the plasmapause from the Isis-2 spacecraft.

Data from several Isis-2 spacecraft passes are described in which the 6300-A atomic oxygen red line photometer mapped intensity steps resembling the predawn enhancement. Comparison with the electron density measured at the spacecraft indicates a plasmapause influence on the 6300-A emission rate, in that the intensity varies roughly inversely with the electron density at 1400 km. A simple calculation demonstrates the idea that field line opacity differences for photoelectrons are significant across the plasmapause. The measured electron temperatures are inadequate to account for the 6300-A excitation, thus confirming that it must arise from another mechanism.

Shepherd, G. G.↗
NASA NTRS1974

Jet engine exhaust emissions of high altitude commercial aircraft projected to 1990

Projected minimum levels of engine exhaust emissions that may be practicably achievable for future commercial aircraft operating at high-altitude cruise conditions are presented. The forecasts are based on:(1) current knowledge of emission characteristics of combustors and augmentors; (2) the status of combustion research in emission reduction technology; and (3) predictable trends in combustion systems and operating conditions as required for projected engine designs that are candidates for advanced subsonic or supersonic commercial aircraft fueled by either JP fuel, liquefied natural gas, or hydrogen. Results are presented for cruise conditions in terms of both an emission index (g constituent/kg fuel) and an emission rate (g constituent/hr).

Grobman, J.↗
NASA NTRS1970

Air pollution from future giant jetports

Because aircraft arrive and depart in a generally upwind direction, the pollutants are deposited in a narrow corridor extending downwind of the airport. Vertical mixing in the turbulent atmosphere will not dilute such a trail, since the pollutants are distributed vertically during the landing and take-off operations. As a consequence, airport pollution may persist twenty to forty miles downwind without much attenuation. Based on this simple meteorological model, calculations of the ambient levels of nitric oxide and particulates to be expected downwind of a giant jetport show them to be about equal to those in present urban environments. These calculations are based on measured emission rates from jet engines and estimates of aircraft performance and traffic for future jetports.

Fay, J. A.↗
NASA NTRS1974

Neutrino emission from plasmons in strong magnetic fields

Neutrino pair emission from stellar interiors is investigated. The paper indicates that the proposed enhanced emission mode is a part of a transverse mode spectrum with a refraction index in the limit of infinity. It is concluded that in an astrophysical sense a very strong magnetic field does not have a significant effect on the emission rate of neutrinos from plasmons.

Chen, H.-H.↗
NASA NTRS1975

Optical properties of mercury ion thruster exhaust plumes Significance for candidate SEP science instruments

Emission from the exhaust plume of a 30 cm mercury ion thruster was measured from 160 to 600 nm as a function of axial and radial distance from the thruster discharge chamber. The spectrally dispersed absolute intensities were used to construct an empirical volume emission rate function. The function was integrated along a typical instrument field of view, and the resulting apparent brightness was compared with instrument sensitivities to evaluate the extent of optical interference. The intensity levels degraded rapidly with distance from the thruster so that optical interference was negligible for fields of view not intercepting the beam axis. The operation of only one instrument, a zodiacal photopolarimeter was considered incompatible with simultaneous thruster operation.

Goldstein, R.↗
NASA NTRS1975

Metastable 2P oxygen ions in the daytime thermosphere

Dayglow radiation at 7319 A has been measured by the visible airglow experiment on Atmosphere Explorer C. The overhead surface brightness measured at 15.4 hours local solar time on January 27, 1974, was 250 plus or minus 10 R. The volume emission rate had a peak value of 20 photons per cu cm per sec at a height of about 210 km. The data show clear evidence of quenching by collisons with thermal electrons at the higher altitudes and with neutral particles at lower altitudes. Quenching by neutral particles occurs at nearly the gas kinetic rate.

Walker, J. C. G.↗
NASA NTRS1975

Remote sensing of the ionospheric F layer by use of O I 6300-A and O I 1356-A observations

The possibility of using airglow techniques for estimating the electron density and height of the F layer is studied on the basis of a simple relationship between the height of the F2 peak and the column emission rates of the O I 6300 A and O I 1356 A lines. The feasibility of this approach is confirmed by a numerical calculation of F2 peak heights and electron densities from simultaneous measurements of O I 6300 A and O I 1356 A obtained with earth-facing photometers carried by the Ogo 4 satellite. Good agreement is established with the F2 peak heights estimates from top-side and bottom-side ionospheric sounding.

Chandra, S.↗
NASA NTRS1975

The Mariner 5 ultraviolet photometer experiment - Analysis of Rayleigh-scattered and 1304-A radiation from Venus

Airglow measurements of the disk of Venus, made by the ultraviolet photometer on Mariner 5 on October 19, 1967, are analyzed to determine the sources of the observed emission. Rayleigh-scattering models for a semi-infinite atmosphere are used to determine the scale height and single-scattering albedo of the scatterer and to determine the 1304-A emission rate. It is found that (1) the scale height of the Rayleigh-scattered radiation is about 4.5 km, (2) the single-scattering albedo near 2000 A is about 0.8, and (3) 500 R of 1304-A radiation is detected at solar zenith angles between 90 and 95 deg.

Anderson, D. E., Jr.↗
NASA NTRS1976

On the nature of the anti-tail of Comet Kohoutek /1973f/. II - Comparison of the working model with ground-based photographic observations

On the basis of photographic observations made at the Cerro Tololo Inter-American Observatory, the radial and transverse brightness profiles and time variations in the surface brightness of the anti-tail of Comet Kohoutek were examined. In the process of photometric reduction one-dimensional radial tracings passing through the comet's nucleus and covering the entire anti-tail were used in the place of the standard two-dimensional scans. Each radial scan was defined by the position angle, and 'noise' variations were interpolated from the known field brightness outside the anti-tail. An analysis of the results provides quantitative support for a previously proposed model (Sekanina, 1974) suggesting that the dust particles in the anti-tail suffered a significant loss in radius due to evaporation near the perihelion passage. Preliminary calculations indicate that only particles initially larger than 100-150 micrometers in diameter survived. The emission rate of dust may be comparable to those derived for Comets Arend-Roland (1957 III) and Bennett (1970 II).

Sekanina, Z.↗
NASA NTRS1976

The O I /5577-A wavelength/ airglow - Observations and excitation mechanisms

Analysis of the O I /5577-A wavelength/ airglow observations conducted on board the Atmosphere Explorer C satellite yields the following results when combined with simultaneous measurements of ion and neutral composition. A volume emission rate profile derived after sunset requires the production of an O(1S) atom in 8% of the O2(+) recombinations. Photoelectric impact on atomic oxygen and the dissociative recombination of O2(+) are important sources of O(1S) in the dayglow; however, the airglow measurements require a large additional production of O(1S) below 200 km in addition to these. The reaction N + O2(+) yielding NO(+) + O(1S) can provide the missing O(1S) source if the rate coefficient is near 2.5 times 10 to the minus 11th cu cm per sec.

Frederick, J. E.↗