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Results for “IONOSPHERIC PROPAGATION”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Rocket observations of the precipitation of electrons by ground VLF transmitters

Recent results obtained with electric and magnetic receivers aboard a NASA sounding rocket launched on July 31, 1987 are presented which relate multiple electron spectral peaks observed in the bounce loss cone fluxes to the resonant interaction of electrons with VLF waves from ground transmitters. The correlation of transmitter signals passing through the ionosphere with the precipitated electrons was investigated. The analysis of these in situ wave and particle data addresses the propagation of waves through the ionosphere, and, through an application of the resonant theory, enables an estimation of the cold plasma density in the interaction region.

Arnoldy, Roger L.↗
DOE OSTI2026

Los Alamos Portable Pulser (LAPP) Marx Bank and Digitizer System Characterization

Over the duration of June 22 nd to July 15 th , I interned at Los Alamos National Laboratory within ISR-2 on the Los Alamos Portable Pulser (LAPP) Program. This program concerns a radar dish used for characterizing signal propagation through earth’s ionosphere. The bulk of my internship consisted of characterizing the delay of a Marx Bank Generator and writing hardware-interface C/C++ code for the pulse-recording Digitizer System.

47 OTHER INSTRUMENTATION↗
NASA NTRS1974

Wave propagation and earth satellite radio emission studies

Radio propagation studies of the ionosphere using satellite radio beacons are described. The ionosphere is known as a dispersive, inhomogeneous, irregular and sometimes even nonlinear medium. After traversing through the ionosphere the radio signal bears signatures of these characteristics. A study of these signatures will be helpful in two areas: (1) It will assist in learning the behavior of the medium, in this case the ionosphere. (2) It will provide information of the kind of signal characteristics and statistics to be expected for communication and navigational satellite systems that use the similar geometry.

Yeh, K. C.↗
NASA NTRS1975

Theoretical and experimental studies of space-related plasma wave propagation and resonance phenomena

A ten year summary was given of university research on the nature and characteristics of space related plasma resonance phenomena, whistler propagation in laboratory plasmas, and theoretical and experimental studies of plasma wave propagation. Data are also given on long delayed echoes, low frequency instabilities, ionospheric heating, and backscatter, and pulse propagation. A list is included of all conference papers, publications, and reports resulting from the study.

Crawford, F. W.↗
NASA NTRS1977

Altimeter error sources at the 10-cm performance level

Error sources affecting the calibration and operational use of a 10 cm altimeter are examined to determine the magnitudes of current errors and the investigations necessary to reduce them to acceptable bounds. Errors considered include those affecting operational data pre-processing, and those affecting altitude bias determination, with error budgets developed for both. The most significant error sources affecting pre-processing are bias calibration, propagation corrections for the ionosphere, and measurement noise. No ionospheric models are currently validated at the required 10-25% accuracy level. The optimum smoothing to reduce the effects of measurement noise is investigated and found to be on the order of one second, based on the TASC model of geoid undulations. The 10 cm calibrations are found to be feasible only through the use of altimeter passes that are very high elevation for a tracking station which tracks very close to the time of altimeter track, such as a high elevation pass across the island of Bermuda. By far the largest error source, based on the current state-of-the-art, is the location of the island tracking station relative to mean sea level in the surrounding ocean areas.

Martin, C. F.↗
NASA NTRS1979

Solar-terrestrial Predictions Proceedings. Volume 1: Prediction Group Reports

The current practice in solar terrestrial predictions is reviewed with emphasis of prediction, warning, and monitoring services. Topics covered include: ionosphere-reflected HF radio propagation; radiation hazards for manned space flights and high altitude and high latitude aircraft flights; and geomagnetic activity.

Donnelly, R. F.↗
NASA NTRS1983

Atmospheric storm explanation of saturnian electrostatic discharges

Saturn electrostatic discharges (SED) monitored by the Voyager 1 were investigated to determine the source of the phenomena. Consideration has been given to two sources: the atmosphere at equatorial latitudes, where the cloud-top wind velocities correspond to the Saturn 10 hr 10 min rotation period; and the rings at 1.8 Saturn radius. The data were analyzed in terms of time and frequency, revealing a time-varying frequency, few detectable discharges outside of a low threshold, and the appearances and disappearances of the SED with no correlation with frequency. The periodicity of the SED episodes indicated that the source was occulted between revolutions, which ruled out the ring source. The SED signals were only detected on the dayside, suggesting the signals propagated through the dayside ionosphere. Diurnal variations in the ion densities could prohibit the signals from escaping on the nightside, a factor supported by detection of low frequency SED only during close passage of the Voyager. Ray tracing experiments have demonstrated that storm sources have emissions observable with the storm on the limb at the observed 30-40 MHz interval.

Kaiser, M. L.↗
NASA NTRS1989

Calculating the electromagnetic field on the earth due to an electrodynamic tethered system in the ionosphere

A method is presented for calculating the electromagnetic wave field on the earth's surface associated with the operation of an electrodynamic tethered satellite system of constant or slowly varying current in the upper ionosphere. The wave field at the ionospheric boundary and on the earth's surface is obtained by numerical integration. The results suggest that the ionospheric waves do not propagate into the atmosphere and that the image of the Alfven wings from a steady-current tether should be greatly broadened on the earth's surface.

Estes, Robert D.↗
NASA NTRS1988

Faraday polarization fluctuations of satellite beacon signals

The anisotropic effects of random density irregularities in causing Faraday polarization fluctuations of VHF radio signals are examined, taking both rod-like and sheet-like irregularities into consideration. It is found that the variance of Faraday polarization fluctuations depends on the ratio of perpendicular to parallel correlation lengths. The anisotropic effect of rod-like ionospheric irregularities are shown to be most appreciable for longitudinal propagation. The anisotropic effect of sheet-like ionospheric irregularities, however, is not strongly dependent on the radio propagation angle. During transionospheric propagation at large angles with respect to the geomagnetic field, sheet-like irregularities may cause greater Faraday polarization fluctuations than rod-like irregularities.

Lee, M. C.↗
NASA NTRS1995

Lightning driven EMP in the upper atmosphere

Large lightning discharges can drive electromagnetic pulses (EMP) that cause breakdown of the neutral atmosphere between 80 and 95 km leading to order of magnitude increases in the plasma density. The increase in the plasma density leads to increased reflection and absorption, and limits the pulse strength that propagates higher into the ionosphere.

Rowland, H. L.↗
NASA NTRS2000

Ionospheric specification algorithms for precise GPS-based aircraft navigation

We present a technique for converting real-time total electron content (TEC) measurements into gridded vertical delay corrections at the GPS L***sub***1 frequency, which will be broadcast to users every 5 min via geosynchronous satellite. Users will convert these delays to slant corrections for their own particular lines of sight to GPS satellites. To preserve user safety, estimates of the error in the user delay corrections will also be broadcast.

Global↗
NASA NTRS2014

Ionospheric Delay Compensation Using a Scale Factor Based on an Altitude of a Receiver

In one embodiment, a method for ionospheric delay compensation is provided. The method includes determining an ionospheric delay based on a signal having propagated from the navigation satellite to a location below the ionosphere. A scale factor can be applied to the ionospheric delay, wherein the scale factor corresponds to a ratio of an ionospheric delay in the vertical direction based on an altitude of the satellite navigation system receiver. Compensation can be applied based on the ionospheric delay.

Zhao, Hui↗
NASA NTRS1995

Plasma wave evidence for lightning on Venus

Plasma wave data from the Pioneer Venus Orbiter provide the largest body of data cited as evidence for lightning on Venus. These data are also the most controversial, mainly because of the ambiguity in mode identification due to limited spectral information. We review some of the more recent studies of the plasma wave data at Venus, and we demonstrate that the characteristics of the 100 Hz waves are consistent with whistler-mode waves propagating vertically from below the ionosphere. We further show that in situ instabilities are too weak to generate whistler-mode waves, mainly because the thermal pressure is comparable with the magnetic field pressure in the ionosphere of Venus. The lower hybrid drift instability has also been suggested as an alternative source for the 100 Hz waves. However, the wave properties are more consistent with whistler-mode propagation; the lower hybrid dirft instability requires very short gradient scale lengths to overcome damping due to collisions. We also note that an apparent association between Langmuir probe anomalies and 100 Hz waves is much lower than previously reported, once we apply a consistent intensity threshold for identifying wave bursts. The lightning hyposthesis remains the most probable explanation of the plasma waves detected at low altitudes in the nightside ionosphere of Venus.

Strangeway, Robert J.↗
NASA NTRS1985

A theoretical model of artificial spread F echoes

A theoretical model is developed for artificial spread F echoes elicited by irradiating the ionospheric F region with signals from ground-based HF transmitters. Account is taken of the irregularity polarizations, scale length and the magnetic dip angle of the echo. Ray tracing equations are defined for wave propagation in a horizontally stratified ionosphere which has been bathed with HF signals and therefore contains wavelike structures. Irregularities polarized within the meridian plane are found to cause the spread F echoes, while perpendicularly polarized irregularities do not. A magnetic dip angle of 5 deg must be exceeded for the spread F to become strong. The irregularities need scale lengths exceeding 100 m. Modes of operation are identified for inducing the required spread F echoes using ground-based radiotelescopes.

Kuo, S. P.↗