| Investigations of the Nature and Behavior of Plasma-Density Disturbances That May Impact GPS and Other Transionospheric Systems |
31 OCT 2002 |
33 pages |
| Authors:
Angela M. Andreason; Elizabeth A. Holland; Edward J. Fremouw; Andrew J. Mazzella Jr.; G. S. Rao; NORTHWEST RESEARCH ASSOCIATES INC BELLEVUE WA
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 | This report summarizes research during a contract for investigating (a) natural variations in ionospheric total electron content (TEC) and (b) plasma and electromagnetic effects produced by transmitting high-powered HF waves into the ionosphere. Ongoing efforts to maintain and utilize data from the Air Force Ionospheric Measuring Systems are being conducted. Initial efforts in upgrading these systems for enhanced data collection and reporting capabilities also are being conducted. Preliminary scintillation capabilities ... |
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| Investigations of the Nature and Behavior of Plasma Density Disturbances That May Impact GPS and Other Transionospheric Systems |
26 NOV 2001 |
30 pages |
| Authors:
Edward J. Fremouw; Andrew J. Mazzella Jr.; Guan-Shu Rao; NORTHWEST RESEARCH ASSOCIATES INC BELLEVUE WA
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| This report summarizes research during the fourth year of a contract for investigating (a) natural variations in ionospheric total electron content (TEC) and (b) plasma and electromagnetic effects produced by transmitting high- powered HF waves into the ionosphere. Ongoing efforts to maintain and utilize data from the Air Force Ionospheric Measuring Systems are being conducted. Initial efforts in upgrading these systems for enhanced data collection and reporting capabilities also are ... |
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| Investigations of the Effects of Ionospheric Total Electron Content and Scintillation on Transionospheric Radio Wave Propagation |
26 OCT 1998 |
46 pages |
| Authors:
C. C. Andreasen; Edward J. Fremouw; Elizabeth A. Holland; Andrew J. Mazzella Jr.; Guan-Shu Rao; NORTHWEST RESEARCH ASSOCIATES INC BELLEVUE WA
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| Numerous DoD communication, navigation, and surveillance systems depend upon transionospheric propagation of radio signals between space and the ground. The group delay and phase advance encountered by such signals depend upon the path integral of ionospheric plasma density - the so-called total electron content (TEC). Their phase and intensity also can fluctuate due to refractive/diffractive scatter in plasma-density irregularities - i.e., they can suffer complex-signal scintillation. In this project, Northwest ... |
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| Further Investigations of Ionospheric Total Electron Content and Scintillation Effects on Transionospheric Radiowave Propagation |
12 FEB 1998 |
41 pages |
| Authors:
C. C. Andreasen; Edward J. Fremouw; Andrew J. Mazzella; G. S. Rao; James A. Secan; NORTHWEST RESEARCH ASSOCIATES INC BELLEVUE WA
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| The effects of the ionosphere on numerous communication, navigation, and surveillance systems continue to be of Air Force concern. In this project, Northwest Research Associates (NWRA) is collaborating with researchers from Air Force Research Laboratory at Hanscom AFB and others to address these concerns in three broad areas. In the most advanced effort, operational code for running a gridded version of the WBMOD ionospheric scintillation model, called WBMGRID, with the ... |
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| Observation, Analysis, and Modeling of Ionospheric Total Electron Content (TEC) and Scintillation Effects |
JUL 96 |
64 pages |
| Authors:
C. C. Andreasen; Andrew Mazzella; Edward J. Fremouw; G. S. Rao; Elizabeth Holland; NORTHWEST RESEARCH ASSOCIATES INC BELLEVUE WA
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| Many military systems used for communications, command and control, navigation, tracking, and surveillance depend on reliable and relatively noise free transmission of radiowave signals through the earth's ionosphere. These systems can be affected by both large scale features (> 1,000 km) and small scale structures ( |
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| Analysis of Ionospheric Monitoring System (IMS) Total Electron Content (TEC) Data and Equatorial Phase-Scintillation Data |
01 JUL 95 |
52 pages |
| Authors:
James A. Secan; C. C. Andreasen; Edward J. Fremouw; Elizabeth Holland; Andrew Mazzella; NORTHWEST RESEARCH ASSOCIATES INC BELLEVUE WA
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| Many military systems used for communications, command and control, navigation, tracking, and surveillance depend on reliable and relatively noise- free transmission of radiowave signals through the earth's ionosphere. These systems can be affected by both large-scale features (> 1,000 km) and small- scale structures (> few hundred km) in the ionosphere, often leading to degraded operations. This report documents the results of the first year of a three-year investigation of ... |
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| An Investigation of Methods for Improving Models of Ionospheric Plasma- Density Irregularities and Radio-Frequency Scintillation |
01 MAR 93 |
57 pages |
| Authors:
James A. Secan; Robert M. Bussey; Edward J. Fremouw; Lee A. Reinleitner; NORTHWEST RESEARCH ASSOCIATES INC BELLEVUE WA
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| Many modern military systems used for communications, command and control, navigation, and surveillance depend on reliable and relatively noise- free transmission of radiowave signals through the earth's ionosphere. Small- scale irregularities in the ionospheric density can cause severe distortion, known as radiowave scintillation, of both the amplitude and phase of these signals. The WBMOD computer program can be used to estimate these effects on a wide range of systems. The ... |
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| The Polar Bear Ionospheric Experiments. A Pre-Launch Overview |
09 MAY 86 |
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| Authors:
Edward J. Fremouw; PHYSICAL DYNAMICS INC BELLEVUE WA
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 | Polar BEAR (Polar Beacon and Auroral Research) will carry three ionospheric experiments: (1) a beacon functionally identical to that on HiLat, (2) a three-axis vector magnetometer for detecting the satellite's attitude, and (3) an improved imager, the Auroral/Ionospheric Remote Sensor (AIRS). In addition to providing images of the aurora and airglow at four visual and vacuum ultraviolet wavelengths, AIRS will function as an ultraviolet spectrophotometer. Using AIRS in its imaging ... |
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| An Equatorial Scintillation Model |
30 SEP 85 |
75 pages |
| Authors:
Edward J. Fremouw; Robert E. Robins; PHYSICAL DYNAMICS INC BELLEVUE WA
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| Radiowave scintillation in the presence of natural and/or high altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model has been incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction ... |
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| Improvement of the Scintillation-Irregularity Model in WBMOD |
28 FEB 1983 |
99 pages |
| Authors:
James A. Secan; Edward J. Fremouw; PHYSICAL DYNAMICS INC BELLEVUE WA
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| The descriptive model of scintillation-producing irregularities in the F layer contained in Program WBMOD has been improved, along with other aspects of the code. Improvements include use of magnetic local time for modeling high-latitude boundaries, correction of a subtle error in calculating the scan velocity of the radio line of sight, simplification of the orbit calculation, and implementation of an irregularity drift routine based on a recently published model of ... |
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| A Computer Model for High-Latitude Phase Scintillation Based on Wideband Satellite Data from Poker Flat |
28 FEB 1981 |
55 pages |
| Authors:
Edward J. Fremouw; John M. Lansinger; PHYSICAL DYNAMICS INC BELLEVUE WA
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| A mathematical model has been developed for describing plasma-density irregularities responsible for radiowave scintillation produced in the auroral ionosphere, and the model has been committed to an applications-oriented computer code, WBMOD. The model characterizes the three-dimensional configuration, gradient sharpness, and height-integrated strength of irregularities represented by a power-law spatial spectrum as functions of geomagnetic latitude, time of day, sunspot number, and planetary geomagnetic activity index. Program WBMOD permits calculation of ... |
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| Hele-Shaw Cell Experiments for Simulation of Structures in High-Altitude Plasmas |
10 DEC 1980 |
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| Authors:
Edward J. Fremouw; PHYSICAL DYNAMICS INC BELLEVUE WA
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| The magnetohydrodynamic (MHD) equations that describe the motion of a tenuous plasma in a uniform magnetic field are mathematically analogous to the hydrodynamic equations describing two-dimensional flow of an incompressible fluid. As a consequence, one can construct a laboratory analogue of MHD phenomena involved in the structuring of high-altitude plasma clouds on scales that lead to radiowave scintillation. A simple laboratory tool for visualizing the relevant dynamics is the Hele-Shaw ... |
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| Statistical Behavior of Signals from the Wideband Satellite. |
31 DEC 1978 |
59 pages |
| Authors:
Edward J. Fremouw; Deborah A. Miller; PHYSICAL DYNAMICS INC BELLEVUE WA
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| Optical and radio signals that have been scattered by random refractive-index structure must be described statistically in systems-oriented codes and other applications. The general nature of the statistics that would best describe such signals has been an open question for some time, with different models being used close to the medium (log-normal) and far from it (Rician). Signal behavior in the intermediate zone, which is the relevant distance regime for ... |
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| Two Fortran Programs for Calculating Global Ionospheric Amplitude and Phase Scintillation. |
APR 1978 |
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| Authors:
Charles L. Rino; Edward J. Fremouw; Anne R. Hessing; V. Elaine Hatfield; STANFORD RESEARCH INST MENLO PARK CALIF
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| This report contains detailed descriptions of the FORTRAN computer codes IONSCNT, which calculates average ionospheric amplitude and phase scintillation conditions on a global basis, and the auxiliary statistics program DIST, which uses the IONSCNT outputs to calculate fading statistics. Operating instructions for the programs together with examples and descriptions of the various outputs are included. The theoretical background and data base for the program development is contained in a separately ... |
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| A Transionospheric Communication Channel Model. |
APR 1978 |
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| Authors:
Edward J. Fremouw; Anne R. Hessing; Charles L. Rino; V. Elaine Hatfield; STANFORD RESEARCH INST MENLO PARK CALIF
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| This report presents the final results of a three-year contract to develop a signal-statistical model of the transionospheric radio communication channel, building on a previously existing model for first-order signal statistics. The objectives of the contract work were as follows: (1) to test and improve the first-order statistical model; (2) to extend the model to second-order statistical quantities in the temporal, spatial, and spectral domains; (3) to free the model ... |
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| A Transionospheric Communication Channel Model |
JUL 1977 |
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| Authors:
Edward J. Fremouw; Anne R. Hessing; Charles L. Rino; V. Elaine Hatfield; STANFORD RESEARCH INST MENLO PARK CALIF
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| This report presents the final results of a three-year contract to develop a signal-statistical model of the transionospheric radio communication channel, building on a previously existing model for first-order signal statistics. The objectives of the contract work were as follow: (1) to test and improve the first-order statistical model; (2) to extend the model to second- order statistical quantities in the temporal, spatial and spectral domains; (3) to free the ... |
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| High-Latitude Auroral-Radar and HF-Doppler Studies of Geoacoustic Phenomena. |
JUL 1971 |
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| Authors:
Edward J. Fremouw; Norman J. F. Chang; STANFORD RESEARCH INST MENLO PARK CALIF
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| The document reports the results of a coordinated program of ionospheric observations pertaining to high-latitude geoacoustics research. The program consisted of two types of measurements, aimed respectively at study of Auroral Infrasonic Waves (AIW's) and Traveling Ionospheric Disturbances (TID's). Understanding these two phenomena is relevant to the problem of detecting and interpreting remote, man-made atmospheric pressure disturbances such as those that result from nuclear detonations. (Author) |
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| RADAR INVESTIGATIONS OF AURORAL INFRASONIC WAVE SOURCES. |
APR 1970 |
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| Authors:
Edward J. Fremouw; STANFORD RESEARCH INST MENLO PARK CALIF
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| A radar investigation of possible sources of auroral infrasonic waves (AIW) has disclosed evidence of a relation between AIW sources and radar aurora in supersonic motion. The study employed pre-existing and specially obtained data from the DASA-SRI auroral radar located near Homer, Alaska. Data from the Homer radar were compared with AIW data obtained during five equinoctial periods at the infrasonics observatory operated by the Geophysical Institute of the University ... |
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| INTERFEROMETER SIGNAL STATISTICS UNDER GENERAL SCATTER CONDITIONS, |
NOV 1966 |
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| Authors:
John M. Lansinger; Edward J. Fremouw; BOEING SCIENTIFIC RESEARCH LABS SEATTLE WASH GEO-ASTRO PHYSICS LAB
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| Analytical and numerical results describing the statistics of scattered signals observed interferometrically are presented. Observable quantities are given in terms of two wavefront parameters which are invariant in post-scattering propagation: the ratio of nonscattered to scattered flux and the wavefront autocorrelation. The analytical result refers to the average output of a phase-switch or coherently detecting phase-sweep interferometer. Numerical results are given for distributions and average characteristics of real amplitude-product and ... |
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