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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Artificially created holes in the ionosphere

The artificial creation of ionospheric holes by the release of highly reactive molecules into the F region is investigated. Through ion-atom interchange or charge transfer reactions, H2 or H2O reacts with O(+) to form OH(+) or H2O(+), respectively, which subsequently dissociatively recombines with electrons at a very rapid rate. The diffusion of H2 is also modified by chemical loss to the ambient atomic oxygen atmosphere. The limited spatial and temporal extent of the hole-making process allows several approximations to be made which permit three-dimensional analytic solutions of the continuity equations for the released particles, the O(+) and e(-) densities, and the intermediary molecular ions. A versatile formalism is developed whereby the hole-making capability of virtually any spatial-temporal configuration of released particles can be determined by convolving a set of destruction operators which can be viewed as Green's functions for the problem. As a specific application of the techniques developed, the modification of a winter nighttime ionosphere is described by simulating the release of 1000 kg of water vapor near a height of 300 km.

Mendillo, M.↗
NASA NTRS1978

A comprehensive model of the Venus ionosphere

Coupled time-dependent continuity-momentum and energy balance equations for the Venus ionosphere were simultaneously solved for CO2(+), O2(+), O(+), He(+), and H(+) densities and electron and ion temperatures for an altitude range of 120-500 km. Values of the solar zenith angle varied from 0 deg (subsolar point) to 90 deg (terminator). The calculations include the horizontal bulk transport of ions by neutral winds but not the horizontal diffusion. The two-stream photoelectron transport method was used to find the heating rates for the ambient electrons. Different boundary conditions were considered, and a nightside ionosphere was calculated. The results of these model calculations are in good agreement with measurements in the region of maximum electron density. Characteristics of topside and nightside densities and temperatures are discussed.

Chen, R. H.↗
NASA NTRS1978

The calculated and observed ionospheric properties during Atmospheric Explorer-C satellite crossings over Millstone Hill

Results are presented for calculated and observed incoherent scatter radar data on ionospheric and atmospheric properties during the crossings of the Atmospheric Explorer-C satellite over the Millstone Hill, Massachusetts incoherent scatter radar station. The incoherent scatter radar measured electron density vertical profiles and electron and ion temperatures. These values yielded the exospheric temperature and the vertical distribution of neutral gas temperature. The satellite measured electron and ion temperatures and densities, neutral gas composition, and photoelectron spectra. Measurements were also made of solar UV and EUV fluxes, the vertical profile of the NO number density, and the vertical profile of the 6300 A airglow-volume emission rate. The results are compared to those of a time-dependent coupled model of the ionospheric E- and F-regions. Good agreement is found between satellite results, incoherent scatter radar measurements, and model calculations. Along the orbital path satellite measurements show significant latitudinal gradients in the measured properties.

Roble, R. G.↗
NASA NTRS1978

Effect of diffusion-thermal processes on the high-latitude topside ionosphere

The extent to which diffusion-thermal heat flow affects H(+) temperatures in the high-latitude topside ionosphere is studied. Such a heat flow occurs whenever there are H(+)-O(+) relative drifts. From our study we have found that at high-latitudes, where H(+) flows up and out of the topside ionosphere, diffusion-thermal heat flow acts to reduce H(+) temperatures by 500-600 K at altitudes above about 900 km.

Schunk, R. W.↗
NASA NTRS1978

Currents and electric fields in the ionosphere due to field-aligned auroral currents

Birkeland (1908, 1913) did a detailed analysis of the upper atmospheric current system in the high-latitude region, and suggested that field-aligned currents flowing into and out of the auroral ionosphere were the driving mechanism for this current system. In the present paper, static electric field and current patterns due to the field-aligned Birkeland currents are examined, using a model in which currents approximating those reported by Iijima and Potemra (1976) are used as input to a global model of the ionospheric conductivities, in which interhemispheric coupling along field lines is included. The model reproduces the main features of the high-latitude current and voltage system and the penetration of these currents within the plasmasphere.

Nisbet, J. S.↗
NASA NTRS1978

Ionospheric and magnetospheric 'plasmapauses'

The locations of Explorer 45 plasmapause crossings are studied as a likely indicator of ionospheric and magnetospheric trough locations. Attention is given to vertical flows of H(+) ions in the light ion trough, as detected by the magnetic ion mass spectrometer aboard Isis 2 (which was operating in conjunction with Explorer 45 during August 1972). The possibility of an equatorial plasmapause is discussed, whose field lines map into the ionosphere at latitudes poleward of the H(+) density decrease, probably due to the refilling of magnetic flux tubes in the outer plasmasphere.

Grebowsky, J. M.↗
NASA NTRS1978

Theory of short-scale field-aligned density striations due to ionospheric heating

The theoretical saturation spectrum of parametrically excited Langmuir waves in a locally uniform ionosphere is shown by the present calculations to produce, by ohmic dissipation, short-scale field-aligned density striations. The spectrum of the calculated striations is not inconsistent with observations of field-aligned scatter of VHF and UHF waves in ionospheric modification experiments if local increases of the pump field due to focusing are invoked.

Lee, M.-C.↗
NASA NTRS1978

Rocket observations of electron-density irregularities in the equatorial ionosphere below 200 km

Nike Apache rockets carring instrumentation to measure electron density and its fine structure in the equatorial ionosphere were launched from Chilca, Peru in May and June 1975. The fine structure experiment and the data reduction system are described. Results obtained from this system are presented and compared with those obtained by VHF radar and from other rocket studies. A description of the equatorial ionosphere and its features is also presented.

Klaus, D. E.↗
NASA NTRS1979

Changes in the terrestrial atmosphere-ionosphere-magnetosphere system due to ion propulsion for solar power satellite placement

Preliminary estimates of the effects massive Ar(+) injections on the ionosphere-plasmasphere system with specific emphasis on potential communications disruptions are given. The effects stem from direct Ar(+) precipitation into the atmosphere and from Ar(+) beam induced precipitation of MeV radiation belt protons. These injections result from the construction of Solar Power Satellites using earth-based materials in which sections of a satellite must be lifted from low earth to geosynchronous orbit by means of ion propulsion based on the relatively abundant terrestrial atmospheric component, Ar. The total amount of Ar(+) injected in transporting the components for each Solar Power Satellite is comparable to the total ion content of the ionosphere-plasmasphere system while the total energy injected is larger than that of this system. It is suggested that such effects may be largely eliminated by using lunar-based rather than earth-based satellite construction materials.

Curtis, S. A.↗
NASA NTRS1978

Operational physical models of the ionosphere

Global models of the neutral constituents are considered relevant to ion density models and improved knowledge of the ion chemistry. Information provided on the pressure gradients that control the wind system and the electric field systems due to balloon, satellite, and incoherent scatter measurements is discussed along with the implication of these results to the development of global ionospheric models. The current state of knowledge of the factors controlling the large day to day variations in the ionosphere and possible approaches for operational models are reviewed.

Nisbet, J. S.↗
NASA NTRS1978

Investigation of electrical currents in the auroral ionosphere

Two papers are presented on the investigation of electrical currents in the auroral ionosphere: (1) The Relationship Between Field-Aligned Current Carried by Suprathermal Electrons, and the Auroral Arc; and (2) Ionospheric Electrical Currents in the Late Evening Plasma Flow Reversal. In the first paper (1), data from four auroral sounding rockets, which directly measured field-aligned currents with partical detectors, are presented. In the second paper (2), data are presented for an instrumented sounding rocket that was launched from Andoya, Norway in January 1977, in the late evening auroral oval.

Arnoldy, R. L.↗
NASA NTRS1979

Electric generators in the magnetosphere-ionosphere system

The nature and cause of electric fields in the coupled magnetosphere-ionosphere system and their effects in the middle atmosphere are discussed. Electric fields induced by the solar wind are reported. The equivalence between forces and electric currents and also between current closure and stress balance is described. The motions of the magnetospheric and ionospheric fluids and the electric fields of interest were determined by the balance of these forces, or equivalently by the closure of the currents. The physical nature of stresses and currents was examined.

Akinson, G.↗
NASA NTRS1979

Rocket radio measurement of electron density in the nighttime ionosphere

One experimental technique based on the Faraday rotation effect of radio waves is presented for measuring electron density in the nighttime ionosphere at midlatitudes. High frequency linearly-polarized radio signals were transmitted to a linearly-polarized receiving system located in a spinning rocket moving through the ionosphere. Faraday rotation was observed in the reference plane of the rocket as a change in frequency of the detected receiver output. The frequency change was measured and the information was used to obtain electron density data. System performance was evaluated and some sources of error were identified. The data obtained was useful in calibrating a Langmuir probe experiment for electron density values of 100/cu cm and greater. Data from two rocket flights are presented to illustrate the experiment.

Gilchrist, B. E.↗
NASA NTRS1979

Ionospheric research

Projects currently in progress on ionospheric research are described. General topics discussed include: planetary atmospheres, the ionosphere and its region, and mass spectroscopy.

Source record↗
NASA NTRS1978

Effect of anomalous transport coefficients on the thermal structure of the storm time auroral ionosphere

By analyzing an observed storm time auroral electron temperature profile it is shown that anomalous transport effects strongly influence the thermal structure of the disturbed auroral ionosphere. Such anomalous transport effects are a consequence of plasma turbulence, the existence of which has been established by a large number of observations in the auroral ionosphere. The electron and composite ion energy equations are solved with anomalous electron thermal conductivity and parallel electrical resistivity coefficients. The solutions are parameterized with respect to a phenomenological altitude-dependent anomaly coefficient A and are compared with an observed storm time electron temperature profile above Chatanika. The calculated temperature profile for the classical case (A = 1) disagrees considerably with the measured profile over most of the altitude range up to 450 km. It is shown that an anomaly coefficient with a sharp peak of the order of 10,000 centered around the F2 peak is consistent with observations.

Fontheim, E. G.↗
NASA NTRS1978

A case study of the aurora, high-latitude ionosphere, and particle precipitation during near-steady state conditions

An Isis 2 pass studied in related experiments was singled out for a detailed examination of the particle fluxes, optical emissions, and ionospheric parameters observed during a quiescent period (late recovery) between two substorms. Since both long-duration measurements (aircraft) and transient snapshot (spacecraft) data are available, space and time effects can, on a macroscopic level, be separated. The latitudinal morphology observed by the satellite is found to be basically spatial in nature. It is suggested that the observed particle fluxes can be explained in terms of precipitation from the quiet time plasma sheet without intervening acceleration. The agreement of the observed optical emissions and ionospheric parameters with the electron fluxes is discussed.

Winningham, J. D.↗
NASA NTRS1979

Ionosphere of Venus - First observations of the effects of dynamics on the dayside ion composition

Data obtained by Bennett radio-frequency ion mass spectrometers indicate that the ionosphere envelope, dominated above 200 km by O(+), responds dramatically to variations in the solar wind pressure. The pressure compresses the thermal ion distributions from heights as great as 1800 km inward to 280 km. At the thermal ion boundary, or ionopause, the ambient ions are swept away by the solar wind, while at higher altitudes energetic ion currents are detected. Within the ionosphere, ion convection stimulated by the solar wind interaction causes pass-to-pass differences in the ion scale heights.

Taylor, H. A., Jr.↗
NASA NTRS1979

Electron temperatures and densities in the Venus ionosphere - Pioneer Venus orbiter electron temperature probe results

The Pioneer Venus orbiter electron temperature probe was used to obtain altitude profiles of electron temperature and density in the ionosphere of Venus. Elevated temperatures at times of low solar wind flux might indicate support for a certain model. According to this model, less than 5% of the solar wind energy is deposited at the ionopause and is conducted downward through an unmagnetized ionosphere to the region below 200 km where electron cooling to the neutral atmosphere proceeds rapidly. The patterns of electron temperatures and densities at higher solar wind fluxes are considered, the variability of the ionopause height in the late afternoon is noted, and the role of an induced magnetic barrier in the neighborhood of the ionopause is discussed.

Brace, L. H.↗