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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 649 records · Page 36
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NASA NTRS1972

A Multi-ring Ionospheric Plasma Probe

An ionospheric plasma probe was constructed which consists of a long cylinder with the end facing the flow closed by an end plate made up of multiple annular rings and a center disk. A theoretical argument is given which yields the plasma potential and electron temperature in terms of known plasma parameters and the currents to the various rings of the end plate. This probe was successfully operated in an ionospheric flow simulation facility and the resulting plasma potential is in excellent agreement with the traditional Langmuir analysis (1.22 volts).

Sheldon, J. W.↗
NASA NTRS1972

An experimental investigation of the power spectrum of phase modulation induced on a satellite radio signal by the ionosphere

The power spectrum of phase modulation imposed upon satellite radio signals by the inhomogeneous F-region of the ionosphere (100 - 500 km) was studied. Tapes of the S-66 Beacon B Satellite recorded during the period 1964 - 1966 were processed to yield or record the frequency of modulation induced on the signals by ionospheric dispersion. This modulation is produced from the sweeping across the receiving station as the satellite transits of the two dimensional spatial phase pattern are produced on the ground. From this a power spectrum of structure sizes comprising the diffracting mechanism was determined using digital techniques. Fresnel oscillations were observed and analyzed along with some comments on the statistical stationarity of the shape of the power spectrum observed.

Moser, D. T.↗
NASA NTRS1973

The midlatitude ionospheric response to fluctuations in solar activity under low geomagnetic activity conditions

The ionospheric response, which is the sensitivity and delay of the electron content to the 270 day fluctuations of solar radiation has been theoretically analyzed. In the context of the present work the sensitivity is defined as the magnitude of the electron content fluctuation for a given change in solar flux, and the delay is defined as the timeshift of the response of the electron content to fluctuations in solar flux. Both the model in which the action of neutral winds on the F-2 layer is disregarded and that in which the wind effect is included as part of a positive feedback mechanism, are studied. It is shown that the neutral winds play a dominant role in the mentioned ionospheric response. The computed delays decrease with increasing solar activity in both models.

Bendito, J. L.↗
NASA NTRS1972

Isis 1 observations of the high-latitude ionosphere during a geomagnetic storm.

The Isis 1 satellite has made measurements of several ionospheric and related parameters, and the results of the various measurements have been compared in detail for two north transpolar passes during the geomagnetic storm of February 3, 1969. Simultaneous measurements were made of local electron and ion densities and temperatures, electron density between the satellite and the peak of the F layer, radio noise, and particle fluxes over a wide energy range extending down to 10 eV. Several features of the ionosphere (in particular, enhancements of radio noise, scale height, and plasma temperatures) appear to be due to soft-particle (100 eV to 1 keV) precipitation, which is related to magnetospheric structure as delineated by the observation of more energetic particles. The magnetosheath particles precipitating on the dayside of the polar cap are particularly effective.

Whitteker, J. H.↗
NASA NTRS1973

A modified Monte Carlo model for the ionospheric heating rates.

A Monte Carlo method is adopted as a basis for the derivation of the photoelectron-heat input into the ionospheric plasma. Since a great number of Monte Carlo runs are required normally for the computation of the heating rates, this approach is modified in an attempt to minimize the computation time. The heat-input distributions are computed for arbitrarily small source elements that are spaced apart at distances corresponding to the photoelectron dissipation range. By means of a nonlinear interpolation procedure their individual heating-rate distributions are utilized to produce synthetic ones that fill the gaps between the Monte Carlo generated distributions. By varying these gaps and the corresponding number of Monte Carlo runs the accuracy of the results is tested to verify the validity of this procedure. It is concluded that this model can reduce the computation time by as much as an order of magnitude, thus improving the feasibility of including Monte Carlo calculations in self-consistent ionosphere models.

Mayr, H. G.↗
NASA NTRS1973

Can the ionosphere regulate magnetospheric convection.

A simple model is outlined that relates the dayside magnetopause displacement to the currents feeding the polar cap ionosphere, from which the ionospheric electric field and the flux return rate may be estimated as a function of magnetopause displacement. Then, flux conservation arguments make possible an estimate of the time scale on which convection increases.

Coroniti, F. V.↗
NASA NTRS1973

On the extent of the Martian ionosphere.

The boundary of the Martian ionosphere just above the photochemical layer, where solar-wind induced convection becomes important, is estimated. The Martian ionosphere is expected to terminate at an altitude of approximately 300 km.

Bauer, S. J.↗
NASA NTRS1973

Equatorial airglow and the ionospheric geomagnetic anomaly.

Ogo 4 observations of the O I (6300-A) emissions have revealed a global pattern hitherto undetected from the ground-based observations. It is seen that the postsunset emission of O I (6300 A) in October 1967 is very asymmetrical with respect to the geomagnetic equator in certain longitude regions and shows poor correlation with the electron density measured simultaneously from the same spacecraft. This asymmetry is less marked in the UV airglow, O I (1356 A), which appears to vary as the square of the maximum electron density in the F region. The horizon scan data of the 6300-A airglow reveal that the latitudinal asymmetry is associated with asymmetry in the height of the O I (6300-A) emission and hence with the altitude of the F2 peak. From the correlative studies of the airglow and the ionospheric measurements the mechanisms of the UV and the 6300 A emissions are discussed in terms of the processes involving radiative and dissociative recombination. Theoretical expressions are developed which relate the airglow data to the ionospheric parameters.

Chandra, S.↗
NASA NTRS1973

Investigation of mid-latitude ionospheric currents by combined rocket techniques.

A comprehensive range of neutral atmospheric and simultaneous ionospheric structure measurements were obtained from a Skylark rocket launched at Woomera during evening twilight on a quiet magnetic day. Above 150 km, good agreement was found between the results obtained from three different methods of electric field measurement despite the low field strength (about 1.5 mV/m). In the immediate vicinity of an intense sporadic E layer, the probe measurements indicated large excursions of the electrostatic field amounting to 6.5 mV/m at 105.3 km and 2.7 mV/m at 104.8 km. The calculated ionospheric current system in the vicinity of the rocket trajectory was of similar magnitude to that indicated by local ground-based magnetometers, but was diametrically opposed in direction.

Rees, D.↗
NASA NTRS1973

The slab thickness of the mid-latitude ionosphere.

The thickness of the peak of the ionosphere depends primarily on the temperature T sub n of the neutral gas, and corresponds approximately to an alpha-Chapman layer at a temperature of 0.87T sub n. The overall slab thickness, as given by Faraday rotation measurements, is then tau = 0.22T sub n + 7 km. Expansion of the topside ionosphere, and changes in the E- and F1-regions increase tau by about 20 km during the day in summer. Near solar minimum, tau is increased by a lowering of the O(+)/H(+) transition height; if the neutral temperature T sub n is estimated, this height can be obtained from observed values of tau. Hourly values of slab thickness were determined over a period of 6 yr at 34 and 42 S. Near solar maximum the nighttime values were about 260 km in all seasons. The corresponding neutral temperatures agree with satellite drag values; they show a semiannual variation of 14% and a seasonal change of 5%. Daytime values of tau were about 230 km in winter and 320 km in summer, implying a seasonal change of 30% in T sub n.

Titheridge, J. E.↗
NASA NTRS1973

Investigation of the D and E regions of the ionosphere

Details of an experimental program that investigates the ionosphere using sounding rockets are presented. The investigation is part of a continuing program to gather data on the D and E regions of the ionosphere during periods of recurring natural phenomena that influence these regions. To achieve these ends, four vehicles were launched during the eclipse of the sun on March 7, 1970. Other vehicles totalling 10 in all were launched to investigate transient phenomena such as the sporadic E layer.

Kelly, R. N.↗
NASA NTRS1973

Investigations of the ionospheric using radio signals from artificial satellites

The occurrence and characteristics of ionospheric irregularities in medium latitudes and in polar regions were measured using radio signals from artificial satellites. Ionospheric changes during quiet and disturbed conditions were also measured. Electron density, elevation angle, and amplitude and frequency of these high frequency signals were determined as well as the direction of their arrival.

Titheridge, J. E.↗
NASA NTRS1973

Behavior of thermal plasma in the ionosphere and magnetosphere

Models of ion flow in the topside ionosphere were developed. These models took both H(+) and O(+) into account and permitted various parameter studies to be made affecting H(+) escape in polar winds. Extensive computer programs were written to display the measured electron density profiles in ways useful to geophysical analysis. The relationship between the location of the plasmapause as it is found in the equatorial plane and the location of the ionospheric trough was also investigated.

Banks, P. M.↗
NASA NTRS1974

Observations of enhanced ion line frequency spectrum during Arecibo ionospheric modification experiment

The Arecibo 430 MHz incoherent scatter radar (ISR) was used to monitor the effects of modifying the ionosphere by a high power HF transmitter feeding the 305 m reflector antenna. When in the ordinary magnetoionic mode parametric instabilities develop in the ionosphere near the reflection level. Manifestations of these instabilities are the strong enhancement of Langmuir oscillations in the direction of the ISR beam at a wavelength of 35 cm and the simultaneous much weaker enhancement of ion oscillations in that direction. The spectral analysis of the enhanced peak with a height resolution of 2.4 km shows that the ionic mode enhancement most often has a double humped frequency spectrum corresponding to up- and down-going ion acoustic waves. The shape of the frequency spectrum is interpreted in terms of a stable oscillation which is driven by a secondary electrostatic field caused by nonlinear interaction of Langmuir waves within a cone centered on the magnetic field and by the scattering of the pump field on stable Langmuir waves travelling along the direction of the ISR.

Hagfors, T.↗
NASA NTRS1974

Investigations of the ionosphere by space techniques

Much of the impetus to ionosphere research since the International Geophysical Year has come from new types of measurement using space vehicles. The key developments are outlined, together with the contributions that they have made to the understanding of the ionosphere.

Bowhill, S. A.↗
NASA NTRS1973

A catalog of ionospheric F region irregularity behavior based on Ogo 6 retarding potential analyzer data

Review of in situ data obtained with the aid of the retarding potential analyzer on board Ogo 6 which reveal the nature of ionospheric irregularities in the total ion concentration above 400 km. Except for the high-latitude regions, the ionosphere is usually observed to be very smooth in the daytime, but considerable structure is observed at night, particularly near the equator and at Atlantic longitudes. Although most of the irregularities observed appear to be stochastic in nature, many nearly monochromatic waveforms are observed near the equator. The topics discussed include the midlatitude scintillation boundary, large-amplitude equatorial irregularities, the fluctuation spectrum of typical F-region irregularities, the lower edge of the equatorial F region, sinusoidal waveforms, ground glass irregularities, breaking wave irregularities, and regions of smooth and irregular ionization inside the polar cap.

Mcclure, J. P.↗
NASA NTRS1973

Theoretical models for electron energy relaxation in the lower ionosphere

Elastic collisions and rotation inelastic collisions involving quadrupole molecular transitions are important in energy relaxation of electrons in molecular gases. It has been customary in studying the cooling of electrons in a plasma heated by high-frequency waves to characterize this relaxation by the ionospheric G factor. The G factor is first defined in a fundamental way by use of kinetic theory. Then present models for theoretical cross sections for electron collision with O2 and N2 are used to derive expressions for the G factor in the lower ionosphere. Two models are considered: one uses Gerjuoy-Stein models for both N2 and O2; the other uses a Gerjuoy-Stein model for N2 and a Geltman-Takayanaki model for O2. Neither O2 model has been definitely established experimentally. It is found that temperature dependence of G is critically dependent on the O2 model.

Hagenbuch, K. M.↗
NASA NTRS1973

Jovian ionospheric models

This paper reports results obtained on ionosphere formation in the Jovian upper atmosphere with special reference to some of the recently available reaction rates, and to recent models of the Jovian neutral atmosphere based on the possibility of a warmer mesopause. In the older models of the Jovian ionosphere, the major ions were H+ which were lost only by pure radiative recombination. This led to high electron densities and practically no diurnal change. In contrast, recent models have relatively much smaller electron densities, especially in lower regions, and may be susceptible to significant diurnal variation.

Capone, L. A.↗