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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Auroral heating and the composition of the neutral atmosphere.

Heating of the neutral atmosphere by auroral particle fluxes and by orthogonal electric fields is responsible for large changes in the thermospheric composition that have been observed by satellite mass spectrometers. Vertical winds of a few meters per second are produced in the region subject to auroral heating; this vertical upwelling drives circulation cells that extend the effects of heating in the auroral region on a global scale. Our analysis focuses on the initial phase of a magnetic storm within the auroral region.

Hays, P. B.↗
NASA NTRS1978

Diffusion model for the upper atmosphere of Venus

On the basis of a linear theory it is shown that wind-induced diffusion associated with large-scale circulation in the Venus atmosphere leads to nighttime bulges in O, He, and H. The effect on He is very large with a 243-day rotation period of the atmosphere, yielding an upper limit for the maximum/minimum diurnal density ratio of approximately 1000. This ratio is much smaller for H (max/min of about 4) due to the greater importance of exospheric flow, which acts (as for He) as a damping mechanism. For the faster rotation period of 4 days consistent with the motions of the cloud tops, the diurnal variation of O is significantly reduced, contributing to an increase by a factor of two in the horizontal wind velocity. The same effect significantly reduces the He variations to an increase by a factor of 7 from day to night. The results suggest that composition and wind measurements provide valuable information on the rotation rate of the Cytherean thermosphere.

Mayr, H. G.↗
NASA NTRS1992

An investigation of the solar cycle response of odd-nitrogen in the thermosphere

This annual report covers the first year of funding for the study of the solar cycle variations of odd-nitrogen (N((sup 2)D), N((sup 4)S), NO) in the Earth's thermosphere. The study uses the extensive data base generated by the Atmosphere Explorer (AE) satellites, and the Solar Mesosphere Explorer Satellite. The AE data are being used, for the first time, to define the solar variability effect on the odd-nitrogen species through analysis of the emissions at 520 nano-m from N((sup 2)D) and the emission from O(+)((sup 2)P). Additional AE neutral and ion density data are used to help define and quantify the physical processes controlling the variations. The results from the airglow study will be used in the next two years of this study to explain the solar cycle changes in NO measured by the Solar Mesosphere Explorer.

Rusch, David W.↗
NASA NTRS1983

The dynamic response of the high-latitude thermosphere and geostrophic adjustment

The theory of geostrophic adjustment in which the adjustment process is critically dependent on the ratio of the scale size of the forcing to the Rossby radius of deformation, is applied to the qualitative explanation of certain features of the response of the high latitude thermosphere to inputs of energy and momentum. When the ratio is small, large wind speeds are efficiently generated by a momentum source, and when small, changes in the mass field associated with a heat source are more effectively produced. The Rossby radius variation with height explains the qualitatively different responses of the high latitude E and F regions during disturbed geomagnetic conditions as shown by both observations and numerical models. The present analytic solutions are in good agreement with model results concerning energy apportionment between divergent and rotational components of the wind field as a function of wavenumber.

Larsen, M. F.↗
NASA NTRS2019

ALMA Spectral Imaging of Titan Contemporaneous with Cassini's Grand Finale

The Cassini mission performed 127 targeted ybys of Titan during its 13 yr mission to Saturn, culminating in the Grand Finale between 2017 April and September. Here we demonstrate the use of the Atacama Large Millimeter/ submillimeter Array (ALMA) to continue Cassini's legacy for chemical and climatological studies of Titan's atmosphere. Whole-hemisphere, interferometric spectral maps of HCN, HNC, HC3N, CH3CN, C2H3CN, C2H5CN,and C3H8 were obtained using ALMA in 2017 May at moderate (0 2, or 1300 km) spatial resolution, revealing the effects of seasonally variable chemistry and dynamics on the distribution of each species. The ALMA submillimeter observations of HCN and HC3N are consistent with Cassini infrared data on these species, obtained in the same month. Chemical/dynamical lifetimes of a few years are inferred for C2H3CN and C2H5CN, in reasonably close agreement with the latest chemical models incorporating the sticking of C2H5CN to stratospheric aerosol particles. ALMA radial limb ux proles provide column density information as a function of altitude, revealing maximum abundances in the thermosphere (above 600 km) for HCN, HNC, HC3N, and C2H5CN. This constitutes the rst detailed measurement of the spatial distribution of HNC, which is found to be conned predominantly to altitudes above 730 ± 60 km. The HNC emission map shows an east-west hemisphericasymmetry of 13% ± 3%. These results are consistent with very rapid production (and loss) of HNC in Titan's uppermost atmosphere, making this molecule an effective probe of short-timescale (diurnal) ionospheric processes.

Cordiner, M. A.↗
NASA NTRS1986

Observations of vertical winds and the origin of thermospheric gravity waves launched by auroral substorms and westward travelling surges

Several sequences of observations of strong vertical winds in the upper thermosphere are discussed, in conjunction with models of the generation of such winds. In the auroral oval, the strongest upward winds are observed in or close to regions of intense auroral precipitation and strong ionospheric currents. The strongest winds, of the order of 100 to 200 m/sec are usually upward, and are both localized and of relatively short duration (10 to 20 min). In regions adjacent to those displaying strong upward winds, and following periods of upward winds, downward winds of rather lower magnitude (40 to about 80 m/sec) may be observed. Strong and rapid changes of horizontal winds are correlated with these rapid vertical wind variations. Considered from a large scale viewpoint, this class of strongly time dependent winds propagate globally, and may be considered to be gravity waves launched from an auroral source. During periods of very disturbed geomagnetic activity, there may be regions within and close to the auroral oval where systematic vertical winds of the order of 50 m/sec will occur for periods of several hours. Such persistent winds are part of a very strong large scale horizontal wind circulation set up in the polar regions during a major geomagnetic disturbance. This second class of strong horizontal and vertical winds corresponds more to a standing wave than to a gravity wave, and it is not as effective as the first class in generating large scale propagating gravity waves and correlated horizontal and vertical oscillations. A third class of significant (10 to 30 m/sec) vertical winds can be associated with systematic features of the average geomagnetic energy and momentum input to the polar thermosphere, and appear in statistical studies of the average vertical wind as a function of Universal Time at a given location.

Rees, D.↗
NASA NTRS1989

Environmental definition of the earth's neutral atmosphere

Although number densities are low at altitudes where spacecraft typically operate, high orbital speeds result in incident fluxes and collisional energies large enough to interact with and degrade material surfaces. Global thermospheric models, when combined with orbital mechanics models, may be used to predict atomic oxygen fluence, or total integrated flux incidence on spacecraft sentences. Fluence predictions, when used with STS materials reactivity measurements, provide reliable estimates of the oxidative effects on spacecraft surfaces.

Visentine, James T.↗
NASA NTRS1989

Modeled F region response to auroral dynamics based upon Dynamics Explorer auroral observations

Auroral images from the Dynamics Explorer 1 (DE 1) scanning auroral imager have been combined with in situ auroral precipitation data from the DE 2 low-altitude plasma instrument, to form a time-dependent global auroral energy flux model. This model has both good time (12 min) and spatial (100 km) resolution compared to that currently available for global-scale ionospheric and thermospheric modeling. The development and comparison of this model with others are discussed. Data from an aurorally active period, November 25, 1981, are presented and used as a case study for this model. Using a global ionospheric model, the effect of the DE auroral model is contrasted with that of a conventional empirical auroral energy flux model. Major differences in the modeled F region ionosphere are predicted from this comparative study.

Sojka, J. J.↗
NASA NTRS1994

A Space and Atmospheric Visualization Science System

SAVS (a Space and Atmospheric Visualization Science system) is an integrated system with user-friendly functionality that employs a 'push-button' software environment that mimics the logical scientific processes in data acquisition, reduction, analysis, and visualization. All of this is accomplished without requiring a detailed understanding of the methods, networks, and modules that link the tools and effectively execute the functions. This report describes SAVS and its components, followed by several applications based on generic research interests in interplanetary and magnetospheric physics (IMP/ISTP), active experiments in space (CRRES), and mission planning focused on the earth's thermospheric, ionospheric, and mesospheric domains (TIMED). The final chapters provide a user-oriented description of interface functionalities, hands-on operations, and customized modules, with details of the primary modules presented in the appendices. The overall intent of the report is to reflect the accomplishments of the three-year development effort and to introduce potential users to the power and utility of the integrated data acquisition, analysis, and visualization system.

Szuszczewicz, E. P.↗
NASA NTRS1992

ARCLITE: the Arctic Lidar Technology Facility at Sondre Stromfjord, Greenland

SRI International is presently developing an Arctic lidar (ARCLITE) facility at the incoherent-scatter radar site in Sondre Stromfjord, Greenland (67.0 degrees N, 209.2 degrees W). The project, funded by NSF through the CEDAR (Coupling Energetics and Dynamics of Atmospheric Regions) initiative, is to perform high-altitude molecular/aerosol backscatter measurements in the Arctic covering the stratosphere/mesosphere region during nighttime and daytime conditions. The lidar system employs an injection seeded, high-energy GCR-5 Spectra Physics Nd:YAG laser for primary operation at 532 nm (550 mJ per pulse at 30 Hz). The receiver system is designed around a 36-inch Cassegrainian telescope of astronomical quality with receiver components and photon-counting electronics for day and night operations. The Rayleigh backscatter measurements will conduct investigations concerning long-term studies of the basic density and temperature structure of the Arctic stratosphere/mesosphere region; effects of stratospheric warming on the structure of the stratosphere/mesosphere region; occurrence and properties of polar stratospheric clouds; occurrence of noctilucent clouds and their properties at high latitudes; and dynamic and thermodynamic coupling between the stratosphere/mesosphere region and the lower thermosphere.

Thayer, J. P.↗
NASA NTRS2022

Determining Latitudinal Extent of Energetic Electron Precipitation Using MEPED On-Board NOAA/POES

Energetic Electron Precipitation (EEP) from the plasma sheet and the radiation belts ionizes the polar lower thermosphere and mesosphere. EEP increases the production of NO x and HO x , which will catalytically destroy ozone, an important element of atmospheric dynamics. Therefore, measurement of the latitudinal extent of the precipitation boundaries is important in quantifying the atmospheric effects of the Sun-Earth interaction. This study uses measurements by the Medium Energy Proton Electron Detector (MEPED) of six NOAA/POES and EUMETSAT/METOP satellites from 2004 to 2014 to determine the latitudinal boundaries of EEP and their variability with geomagnetic activity and solar wind drivers. Variation of the boundaries for different electron energies and Magnetic Local Time (MLT) is studied. Regression analyses are applied to determine the best predictor variable based on solar wind parameters and geomagnetic indices. The highest correlation was found for the pressure-corrected Dst index when applying a linear regression model. A model of the equatorward EEP boundary is developed separately for three different energy channels, >43, >114, and >292 keV, and for 3 hour MLT sectors. For >43 keV EEP, 80% of the equatorward boundaries predicted by the model are within ±2.2° cgmlat. The model exhibits a solar cycle bias where it systematically exaggerates the equatorward movement of the EEP region during solar minimum. The highest accuracy of the model is found in periods dominated by corotating interaction regions/high speed solar wind streams. The result will be a key element for constructing a model of EEP variability to be applied in atmosphere climate models.

E. M. Babu↗
NASA NTRS1988

A simple model describing the nonlinear dynamics of the dusk/dawn asymmetry in the high-latitude thermospheric flow

A simple nonlinear, axisymmetric, shallow-water numerical model has been used to study the asymmetry in the neutral flow between the dusk and dawn sides of the auroral oval. The results indicate that the Coriolis force and the curvature terms are nearly in balance on the evening side and require only a small pressure gradient to effect adjustment. The result is smaller neutral velocities near dawn and larger velocities near dusk than would be the case for a linearized treatment. A consequence is that more gravity wave energy is produced on the morning side than on the evening side.

Gundlach, J. P.↗
NASA NTRS1989

The response of thermospheric nitric oxide to an auroral storm. II - Auroral latitudes

NOAA 6 and 7 particle measurements are used, in conjunction with a statistical model of the auroral particle precipitation, to study the response of auroral NO to the auroral storm of September 19, 1984. The results of a time-dependent photochemical calculation show that particle precipitation can more effectively produce NO than can Joule heating, in contrast to nonauroral latitudes where heating is important. Both the model and the NO data show NO increases as a result of the storm; however, the absolute magnitude of the NO in the model, as well as the amplitude of the increase, significantly exceeded what was observed. Two possible explanations for the this discrepancy are proposed.

Siskind, D. E.↗
NASA NTRS1995

Thermospheric nitric oxide from the ATLAS 1 and Spacelab 1 missions

Spectral and spatial images obtained with the Imaging Spectrometric Observatory on the ATLAS 1 and Spacelab 1 missions are used to study the ultraviolet emissions of nitric oxide in the thermosphere. By synthetically fitting the measured NO gamma bands, intensities are derived as a function of altitude and latitude. We find that the NO concentrations inferred from the ATLAS 1 measurements are higher than predicted by our thermospheric airglow model and tend to lie to the high side of a number of earlier measurements. By comparison with synthetic spectral fits, the shape of the NO gamma bands is used to derive temperature as a function of altitude. Using the simultaneous spectral and spatial imaging capability of the instrument, we present the first simultaneously acquired altitude images of NO gamma band temperature and intensity in the thermosphere. The lower thermospheric temperature images show structure as a function of altitude. The spatial imaging technique appears to be a viable means of obtaining temperatures in the middle and lower thermosphere, provided that good information is also obtained at the higher altitudes, as the contribution of the overlying, hotter NO is nonnegligible. By fitting both self-absorbed and nonabsorbed bands of the NO gamma system, we show that the self absorption effects are observable up to 200 km, although small above 150 km. The spectral resolution of the instrument (1.6 A) allows separation of the N(+)(S-5) doublet, and we show the contribution of this feature to the combination of the NO gamma (1, 0) band and the N(+)(S-5) doublet as a function of altitude (less than 10% below 200 km). Spectral images including the NO delta bands support previous findings that the fluorescence efficiency is much higher than that determined from laboratory measurements. The Spacelab 1 data indicate the presence of a significant population of hot NO in the vehicle environment of that early shuttle mission.

Torr, Marsha R.↗
NASA NTRS1997

The First National Student Conference: NASA University Research Centers at Minority Institutions

The conference includes contributions from 13 minority universities with NASA University Research Centers. Topics discussed include: leadership, survival strategies, life support systems, food systems, simulated hypergravity, chromium diffusion doping, radiation effects on dc-dc converters, metal oxide glasses, crystal growth of Bil3, science and communication on wheels, semiconductor thin films, numerical solution of random algebraic equations, fuzzy logic control, spatial resolution of satellite images, programming language development, nitric oxide in the thermosphere and mesosphere, high performance polyimides, crossover control in genetic algorithms, hyperthermal ion scattering, etc.

Daso, Endwell O.↗
NASA NTRS1977

Departures from hydrostatic equilibrium in the global distribution of thermospheric argon

This report describes the application of a three-dimensional two-component model to the distribution of argon in the upper atmosphere of the earth. The Cira (1972) model is used to specify the background gas density and the temperature as functions of altitude, latitude, local time, and day of the year. Emphasis is placed on examining the effects of departures from hydrostatic equilibrium on the argon density distribution. Such effects are found to be significant, producing a strong summer argon bulge. Comparisons of the model results with observational data are discussed.

Straus, J. M.↗
NASA NTRS1973

Differential equation of exospheric lateral transport and its application to terrestrial hydrogen

The differential equation description of exospheric lateral transport of Hodges and Johnson is reformulated to extend its utility to light gases. Accuracy of the revised equation is established by applying it to terrestrial hydrogen. The resulting global distributions for several static exobase models are shown to be essentially the same as those that have been computed by Quessette using an integral equation approach. The present theory is subsequently used to elucidate the effects of nonzero lateral flow, exobase rotation, and diurnal tidal winds on the hydrogen distribution. Finally it is shown that the differential equation of exospheric transport is analogous to a diffusion equation. Hence it is practical to consider exospheric transport as a continuation of thermospheric diffusion, a concept that alleviates the need for an artificial exobase dividing thermosphere and exosphere.

Hodges, R. R., Jr.↗
NASA NTRS1974

Hydrogen in the upper atmosphere

Theoretical altitude distributions are examined, taking into account D and E region density distributions, relations between escape and exospheric density distributions, and aspects of thermospheric distributions and changes with exospheric temperature. Theoretical diurnal variations are considered along with ion-neutral interactions, radiative transfer theory, optical observations, nonoptical observations, aspects regarding the altitude profile of deuterium, the ionization of the night time D and E regions, and the effect of hydrogen loss on oxygen evolution. Questions concerning the presence of H and D around other planets are also investigated, giving particular attention to Venus, Mars, and Jupiter.

Tinsley, B. A.↗