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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Changes in atmospheric composition inferred from ionospheric production rates

Changes in the total electron content of the ionosphere near sunrise are used to determine the integrated production rate in the ionosphere (Q) from 1965 to 1971 at latitudes of 34S, 20N, and 34N. The observed regular semiannual variation in Q through a range of 1:3:1 is interpreted as an increase in the ratio O/N2 (relative densities) near the equinoxes. It follows that there is a worldwide semiannual variation in atmospheric composition, with the above ratio maximum just after the equinoxes. There is a large seasonal variation in the Northern hemisphere with a maximum in mid-summer. This effect is absent in the Southern hemisphere. At all times except solar maximum in the Northern hemisphere there is a global asymmetry. The ratio O/N2 is about three times as large in the Northern hemisphere. The overall mechanism appears to be N2 absorption.

Titheridge, J. E.↗
NASA NTRS1973

Ionospheric effects on one-way timing signals

A proposed navigation concept requires that a user measure the time-delay that satellite-emitted signals experience in traversing the distance between satellite and user. Simultaneous measurement of the propagation time from four different satellites permits the user to determine his position and clock bias if satellite ephemerides and signal propagation velocity are known. A pulse propagating through the ionosphere is slowed down somewhat, giving an apparent range that is larger than the equivalent free space range. The difference between the apparent range and the true range, or the free space velocity and the true velocity, is the quantity of interest. This quantity is directly proportional to the total electron content along the path of the propagating signal. Thus, if the total electron content is known, or is measured, a perfect correction to ranging could be performed. Faraday polarization measurements are continuously being taken at Fort Monmouth, N. J., using beacon emissions of the ATS-3 (137.35 MHz) satellite. Day-to-day variability of the diurnal variation of total electron content values is present with differences of up to 50% or more not being uncommon. In addition, superposed on the overall diurnal variation are smaller scale variations of approximately 5 to 10% of the total content which are attributed to ionospheric density irregularities.

Soicher, H.↗
NASA NTRS1975

Composition measurements of the topside ionosphere using a magnetic mass spectrometer, ion mass spectrometer on ISIS-2 spacecraft

The ion mass spectrometer (IMS) on the ISIS-II satellite is described; it measures the composition and distribution of positive ions in the earth's ionosphere in the mass range of 1 to 64 atomic mass units. Significant data were received which show a wide variation in ion composition at night near the equator and in the daytime poleward of the plasmapause. It was found that these data enable further study of the polar wind and that the experiment produced timely data during the August, 1972 magnetic storm to show the development of a unique ionosphere above the plasmapause during the period of the storm. The scientific objectives and results of the experiment, the technical description of the instrument, a bibliography with sample papers attached, and a summary of recommendations for further study are presented.

Hoffman, J. H.↗
NASA NTRS1975

Kinetic description of ionospheric dynamics in the three-fluid approximation

Conservation equations are developed in the three-fluid approximation for general application problems of ionospheric dynamics in the altitude region 90 km to 800 km for all geographic locations. These equations are applied to a detailed study of auroral E region neutral winds and their relationship to ionospheric plasma motions.

Comfort, R. H.↗
NASA NTRS1974

A global model of the earth's ionosphere for use in space applications

A general expression is derived for the F layer electron density profile as a function of latitude and longitude for that part of the earth which is in direct sunlight including dawn and dusk. Furthermore, the derived model is extended to encompass the night-time ionosphere. The expressions allow determination by standard means of the range correction for arbitrary ray path directions. It is also shown that the naive application of the Chapman ionospheric model entails range correction errors which for low elevation angles (less than 20 deg) and large solar zenith angles (40 deg) cannot be tolerated. Numerical calculations are displayed showing the dependence of the range correction on the pertinent parameters.

Von Roos, O. H.↗
NASA NTRS1975

Propagation predictions and studies using a ray tracing program combined with a theoretical ionospheric model

Radio wave propagation predictions are described in which modern comprehensive theoretical ionospheric models are coupled with ray-tracing programs. In the computer code described, a network of electron density and collision frequency parameters along a band about the great circle path is calculated by specifying the transmitter and receiver geographic coordinates, time, the day number, and the 2800-MHz solar flux. The ray paths are calculated on specifying the frequency, mode, range of elevation angles, and range of azimuth angles from the great circle direction. The current program uses a combination of the Penn State MKI E and F region models and the Mitra-Rowe D and E region model. Application of the technique to the prediction of satellite to ground propagation and calculation of oblique incidence propagation paths and absorption are described. The implications of the study to the development of the next generation of ionospheric models are discussed.

Lee, M. K.↗
NASA NTRS1975

The atmosphere and ionosphere of Io

Models for Jupiter's innermost Galilean satellite's atmosphere, ionosphere, and sodium airglow are developed on the basis of recent observational data. The sodium emission detected by Brown (1973) is seen to require a collisional excitation process in Io's atmosphere, while the extended sodium emission measured by Trafton et al. (1974) may require scattering of the planetary radiation by an extended sodium cloud. The sodium is presumably present in bound form on Io's surface, and may be released by a sputtering mechanism proposed by Matson et al. (1974). The ionosphere detected by a radio occultation experiment on Pioneer 10 could be attributed to photoionization of atmospheric sodium, provided Io's atmosphere could sustain significant upward motions during daytime and downward motions during nighttime. The incomplete hydrogen torus observed by Judge and Carlson (1974) in the vicinity of Io appears to require a large supply of hydrogen from the satellite's atmosphere. Implications of the hydrogen torus for the energy and mass balance of Jupiter's magnetosphere are discussed.

Mcelroy, M. B.↗
NASA NTRS1975

The ionosphere and atmosphere of Io

A neon atmosphere and ionosphere is proposed for Io, based on Pioneer 10 observations of the peak electron number density, height of the peak above the surface, and the topside plasma scale height. Calculations of mass, momentum and energy equations for a neon atmosphere yield results that are in reasonable agreement with the observations. A nitrogen atmosphere and a neon-argon-helium atmosphere are also considered. Calculations of the electron number density of a neon ionosphere also yield reasonable agreement with observations. It is noted that Io has about the same mass and radius as the moon, and that Apollo mass spectrometer measurements indicated an abundance of neon in the lunar atmosphere. The presence of other elements, such as hydrogen, helium, and sodium, in Io's atmosphere is also discussed.

Whitten, R. C.↗
NASA NTRS1975

Effect of small ionospheric irregularities on radio wave absorption

The ionospheric absorption of a radio wave caused by small-scale irregularities with a gaussian autocorrelation function is calculated for various values of the linear scale height, the radio frequency, the scale size of the irregularities, and the mean-square fractional electron density fluctuations. The absorption is due to scattering of the radio wave into plasma oscillations by the irregularities. It is concluded that the absorption due to such irregularities with a mean-square fractional electron density deviation greater than about 0.000001 exceeds the normal collisional height-integrated absorption. Absorption of this type could play a significant part in heating experiments or in an ionosphere containing naturally occurring irregularities.

Chen, H. C.↗
NASA NTRS1975

A model of the Venus ionosphere

Results of model calculations of the Venus ionosphere from 120 to 300 km are presented. The chemical scheme and reaction rates used are the same as given by Kumar and Hunten (1974) except that the electron temperature dependence of the dissociative recombination rates is taken into account. Calculations are made for low and high atomic oxygen models in which the O/CO2 ratios are 0.4% and 4% respectively at 140 km, and the results agree well in shape and magnitude with the Mariner 5 and 10 occultation results in the chemically controlled region. Reasonable agreement is obtained at higher altitudes if diffusive equilibrium and high vertical flow velocities (10 km/s) are assumed as upper boundaries for the Mariner 5 and 10 conditions respectively, although solar wind-ionosphere interactions are considered to be the controlling mechanism for the Mariner 10 results.

Nagy, A. F.↗
NASA NTRS1975

Ionospheric effects of X-ray source Scorpius XR-1

A simple two-ion model was employed to evaluate the ionospheric effects of various nocturnal ionization sources. The model was used to calculate the decay of the electron number density at 90 km with and without illumination by Scorpius XR-1 X rays. Reflection parameters for the determination of the effect of cosmic x-ray sources on radio wave propagation were also obtained. The results obtained in the investigation do not support the proposal made by Anathakrishnan and Ramanathan (1969) that the X-ray source in Scorpius XR-1 affects the nighttime lower ionosphere of the earth.

Poppoff, I. G.↗
NASA NTRS1975

Ionosphere-magnetosphere coupling. II - Electric fields

An attempt is made to fit individual observations and theories into the broader network of magnetosphere-ionosphere-atmosphere couplings as they affect the general behavior of quasi-static electric fields in the magnetosphere and ionosphere. Particular attention is given to high-latitude processes, however, mid-latitude penetration of electric fields of magnetospheric origin during disturbed periods is discussed.

Banks, P. M.↗
NASA NTRS1975

Simultaneous measurement of the horizontal components of the earth's electric field in the atmosphere and in the ionosphere

Simultaneous measurements have been made of the ionospheric electric field at altitudes above 100 km (with rockets and radar) and of the atmospheric electric field at an altitude of about 30 km (with balloons). These results show that the horizontal components of the electric field at 30 km were essentially equal to the ionospheric electric field, as has been argued previously on theoretical grounds.

Kelley, M. C.↗
NASA NTRS1975

Mid-latitude VLF emissions observed in the topside ionosphere

Narrow-band VLF emissions observed on different days by Alouette-2 are described. It is found that narrow-band VLF hiss (3.5-7.0 kHz) occurs at midlatitudes (at 54 to 64 deg) in the topside ionosphere during both the geomagnetically disturbed and quiet periods, although the hiss region moves towards the auroral zone during the disturbed period. It is likely that the midlatitude hiss at around 5 kHz is the origin of the narrow-band hiss (5 plus or minus 1 kHz) often observed at ground stations at low latitudes, since no VLF emissions above 2 kHz appear in the auroral zone. The midlatitude VLF hiss observed in the topside ionosphere may be generated by the transverse (electron cyclotron) resonance instability in the magnetosphere.

Ondoh, T.↗
NASA NTRS1975

Analysis of satellite data on energetic particles of ionospheric origin

The morphology was studied of precipitating O(+) and H(+) ions in the energy range 0.7 equal to or less than E equal to or less than 12 keV during the storm-time period from December 16-18, 1971, which encompassed two principal magnetic storms. The results are described with emphasis on the temporal variations of parameters characterizing the intensity, average energy, and spatial location of the zones of precipitation of the two ionic species. One of the principal results was the finding that the intensity of the precipitating O(+) ions was well correlated with the geomagnetic indices which measure the strength of magnetospheric substorm activity and the strength of the storm-time ring current. Since the O(+) ions are almost certainly of ionospheric origin the correlations indicate that a previously unknown strong coupling mechanism existed between the magnetosphere and the ionosphere during the storm period.

Sharp, R. D.↗
NASA NTRS1975

Calculation of conductivities and currents in the ionosphere

Formulas and procedures to calculate ionospheric conductivities are summarized. Ionospheric currents are calculated using a semidiurnal E-region neutral wind model and electric fields from measurements at Millstone Hill. The results agree well with ground based magnetogram records for magnetic quiet days.

Kirchhoff, V. W. J. H.↗
NASA NTRS1976

Solar-wind interaction with planetary ionospheres

Planetary encounters by numerous spacecraft have furnished information concerning the solar wind interaction with the planets Mercury, Venus, Mars, and Jupiter. While direct measurements have indicated a wide range of atmospheric densities and intrinsic magnetic field strengths, the data seem to indicate that the flow pattern around nonmagnetized or weakly magnetized planets with atmospheres optically thick at ionizing wavelengths is basically the same as that around a strongly magnetized planet's magnetosphere, such as the earth's. The planetary ionosphere apparently presents a hard obstacle to the flow, with bow shock formation required in the supersonic, super-Alfvenic flow to slow and direct most of the solar wind plasma around the planetary ionosphere. Various aspects of the interaction are examined in the context of theoretical models in an attempt to explain observed details of the interaction regions of Venus and Mars.

Cloutier, P. A.↗
NASA NTRS1975

Alteration of the ionosphere by man-made waves

In recent years powerful radio wave transmissions beamed at the ionosphere at frequencies somewhat below the penetration frequency of the F2 layer produced the following, mostly unexpected, spectacular effects: (1) artificial spread F seen on ionograms and implying the presence of large scale field-aligned irregularities in the ionospheric plasma density; (2) very strong additional absorption of probing waves reflected by the F2 layer; (3) field-aligned 'on frequency' scattering of UHF waves; (4) scattering of UHF waves by Langmuir waves which are believed to be parametrically excited; (5) the 630 nm airglow is artificially enhanced by a modifying wave of ordinary polarization but it is reduced in intensity by a modifying wave of extraordinary polarization; (6) the shape of the F2 layer is modified. The results of the observations are described and their tentative interpretation in terms of different parametric instabilities is outlined.

Fejer, J. A.↗