IONOSPHERIC DISTURBANCES - Storming Media

Measurement of the Characteristics of TIDs Using Small and Regional Networks of GPS Receivers during the Campaign of 17-30 July of 2008

Jan 2012

15 pages

Authors: Cesar E Valladares; Matthew A Hei; BOSTON COLL CHESTNUT HILL MA INST FOR SCIENTIFIC RESEARCH

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This scientific report presents the results of a dedicated experiment that was conducted within the framework of the Low-latitude ionospheric Sensor Network (LISN) observatory to measure the characteristics of medium-scale (hundreds of km) Traveling Ionospheric Disturbances (TIDs) as they transit through the low-latitude ionosphere. A small array of 3 GPS receivers separated by 4-5 km placed in a triangular configuration was installed near Huancayo in Peru possessing several characteristics of ...

Study of Equatorial Ionospheric Irregularities with ROCSAT-1/IPEI Data for Assessment of Impacts on Communication/Navigation System (IV)

01-Sep-2008

24 pages

Authors: Chao-Han Liu; S -Y Su; NATIONAL CENTRAL UNIV CHUNG-LI (TAIWAN) INST OF SPACE SCIENCE

(1) Study the Cause of Seasonal/Longitudinal(s/l) Variations of Equatorial Irregularity Occurrences: The examination of global monthly occurrence pattern of density irregularities indicates that a smooth and slow variation in the occurrence pattern exists from one longitude sector to the next. Such variation should be related to the smooth and slow variations of the magnetic declination as well as the longitudinal variation of the geographic location of the dip equator for ...

LEO Orbit Surface Charging and Its Relationship to Environment, Vehicle Geometry, and Ionospheric Conditions

05-Jun-2008

13 pages

Authors: Joseph F Fennell; Phillip C Anderson; AEROSPACE CORP EL SEGUNDO CA SPACE SCIENCES LAB

Ungrounded surface materials on the exterior of low-to-medium altitude and medium-to-high inclination satellites can become charged in the auroral electron environment at high latitudes. The orientation of such surfaces will present different aspects relative to the satellite sun line and the satellite velocity vector. Such surfaces can be both in shadow and in the satellite wake at the same time, which enhances the chances of charging in the dusk to ...

Material Identification Algorithm

SEP 2007

14 pages

Authors: Elizabeth Bleszynski; Marek Bleszynski; Thomas Jaroszewicz; MONOPOLE RESEARCH THOUSAND OAKS CA

We developed numerical techniques for simulating radar returns from large realistic scenes composed of uneven ground, trees, and reflecting objects. The simulation includes effects of ionospheric dispersion on the radar pulses. We developed an integral-equation code and performed numerical simulation of radiation for small-loop large-current antennas, with loops radiating in open space or partly shielded by enclosures of various material properties. The code implements regularization methods for handling of subwavelength ...

Influence of Different Solar Drivers on the Winds in the Middle Atmosphere and on Geomagnetic Disturbances

18-May-2007

27 pages

Authors: Katya Y Georgieva; BULGARIAN ACADEMY OF SCIENCES SOFIA

This report results from a contract tasking Bulgarian Academy of Sciences as follows: The grantee will investigate the effects of various solar drivers on the dynamics of the stratosphere and on the geomagnetic disturbances to the earth. To accomplish this, the grantee will create a database of all registered coronal mass ejections, magnetic clouds, solar flares, and high speed solar streams; neutral wind measurements at different atmospheric levels in the ...

Frequency Dependent Quality of HF-Communication Channels Estimated by Superresolution Direction Finding

01-Oct-2006

16 pages

Authors: Stefan Hawlitschka; FGAN-FKIE WACHTBERG (GERMANY)

A Space Based Radar Antenna Concept to Counter Camouflage and Concealment

07 SEP 2006

36 pages

Authors: Phillip Howard; Mike Notter; C. D. Hall; Sergio Pellegrino; EADS ASTRIUM LTD PORTSMOUTH (UNITED KINGDOM)

This paper presents a novel concept for a low-mass 50m^2 deployable P-Band dual polarisation antenna, noting that P-Band observations can penetrate dense forests and possibly penetrate the earth to support searches for tunnels and caves. P-Band is important because existing optical or radar instruments cannot penetrate the forest canopy or the earth's surface in order to monitor suspicious activities. Existing space based Synthetic Aperture Radar (SAR) systems operate at a ...

Quasi-Analytic Model of OTHR Clutter from Equatorial Bubbles in the Ionosphere

27 FEB 2006

61 pages

Authors: Paul A. Bernhardt; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV

Ground clutter for the over-the-horizon radar (OTHR) sky wave becomes Doppler shifted because of the ionosphere through which the radio rays are propagating changes. One source of these changes is ionospheric bubbles, which rise vertically through a horizontally stratified plasma near the equator. The rising plume structures are formed when gravity, neutral winds, or external electric fields act on the F-region plasma. The effect of these ionospheric disturbances can be ...

Optical Imaging Provides a Clear Picture of Ionospheric Disturbances

15 AUG 2005

9 pages

Authors: R. Esposito; T. Pedersen; AIR FORCE RESEARCH LAB HANSCOM AFB MA

During daylight hours, ultraviolet light from the sun ionizes the neutral gas of the earth's upper atmosphere (70-1500 km altitude), creating a partially ionized plasma. This plasma then gradually decays throughout the night. The atmospheric region associated with this phenomenon is called the ionosphere, and this zone is of great practical importance to the Department of Defense and civilian industries because of its effect on radio waves. Depending on the ...

Ionospheric Modification at Twice the Electron Cyclotron Frequency

01 APR 2005

Authors: F. T. Djuth; T. R. Pedersen; E. A. Gerken; P. A. Bernhardt; C. A. Selcher; W. A. Bristow; M. J. Kosch; AIR FORCE RESEARCH LAB HANSCOM AFB MA

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In 2004, a new transmission band was added to the HAARP high- frequency ionospheric modification facility that encompasses the second electron cyclotron harmonic at altitudes between ^220 and 330 km. Initial observations indicate that greatly enhanced airglow occurs whenever the transmission frequency approximately matches the second electron cyclotron harmonic at the height of the upper hybrid resonance. This is the reverse of what happens at higher electron cyclotron harmonics. The ...

The 1859 Solar-Terrestrial Disturbance and the Current Limits of Extreme Space Weather Activity

08 OCT 2004

17 pages

Authors: E. W. Cliver; L. Svalgaard; AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE WEATHER CENTER OF EXCELLENCE

It is generally appreciated that the September 1859 solar-terrestrial disturbance, the first recognized space weather event, was exceptionally large. How large and how exceptional? To answer these questions, we compiled rank order lists of the various measures of solar-induced disturbance for events from 1859 to the present. The parameters considered included: magnetic crochet amplitude, solar energetic proton fluence (McCracken et al., 2001a), Sun-Earth disturbance transit time, geomagnetic storm intensity, and ...

Estimating the Amplitude Scintillation Index From Sparsely Sampled Phase Screen Data

01 SEP 2004

18 pages

Authors: T. L. Beach; T. R. Pedersen; M. J. Strks; S.-y Su; AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE

Phase screen techniques are commonly used to model scintillation of radio signals passing through a disturbed ionosphere, but observational phase or in situ density from both archival and real-time sources is often sampled at rates well below the resolution desired. Previous phase screen resolution criteria do not address the computation of the amplitude scintillation index (S4), which is widely used in scintillation monitoring systems, for practical applications that rely on ...

Space Systems Environmental Interaction Studies

30 AUG 2001

Authors: M. A. Morgan; Alan C. Huber; David J. Sperry; Alan N. Donkin Jr.; Scott J. Moran; AMPTEK INC BEDFORD MA

This report describes the objectives and summarizes the outcome, of the work performed under this contract. In addition, and this constitutes the major portion of the report, a comprehensive summary of all the important design elements for the anticipated DIDM-3 instrument is presented herein. As the final effort of the contract, all of the various facets to designing and building a Digital Ion Drift Meter for inclusion in the Communication/Navigation ...

A Comparison of GPS Performance in a Scintillation Environment at Ascension Island

SEP 2000

9 pages

Authors: K. M. Groves; S. Basu; J. M. Quinn; T. R. Pedersen; K. Falinski; A. Brown; R. Silva; P. Ning; AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE

Post-sunset disturbances in the equatorial ionosphere routinely cause rapid phase and amplitude fluctuations (i.e., scintillation) of radio waves propagating through the disturbed regions. The intensity of scintillations is positively correlated with the solar cycle and the associated signal fades will often exceed 20 dB at L-band frequencies during solar maximum. The effect of such an environment on the performance of GPS navigation systems is poorly understood. In March 2000 AFRL ...

The Effect of Electric Field Structure on Joule Heating

31 MAY 2000

18 pages

Authors: D. N. Walker; W. E. Amatucci; G. Ganguli; NAVAL RESEARCH LAB WASHINGTON DC

We have recently performed a detailed characterization of ion Joule heating perpendicular to an axial magnetic field in the laboratory in a simulated ionospheric plasma environment which contains localized electric field structuring. Since Joule heating is often regarded as an important mechanism contributing to energization of outflowing heavy ions observed by higher altitude auroral satellites, this work has particular relevance to space physics issues; and, to our knowledge, has not ...

Development and Validation of a Global Dynamo Model and its Coupling to the CITFM

15 MAY 2000

5 pages

Authors: Robert W. Schunk; SPACE ENVIRONMENT CORP LOGAN UT

This is a summary of the work accomplished under this effort. Develop and validate a global dynamo model and couple it to the Coupled Ionosphere and Thermosphere Forecast Models (CITFM).

Space Environment Network Display (SEND)

JUL 1999

17 pages

Authors: Edward Jaeger; AIR FORCE SPACE BATTLELAB SHRIEVER AFBCO

SEND is an integrated system designed to incorporate information from three separate sensor systems and to create products, which describe two space environment problems: Ultra High Frequency Satellite Communication (UHF SATCOM) outages and High Frequency (HF) communication degradation. The overall objective of the campaign concept was to integrate new and existing space environment sensor data with models to provide graphical, web page space environment displays to ...

Parallel Developments in Theoretical Modeling, Empirical Modeling, and Ionospheric Data Analyses

DEC 1998

47 pages

Authors: Matthew W. Fox; BOSTON UNIV MA CENTER FOR SPACE PHYSICS

In this report, we describe a number of ionospheric studies, involving variously theoretical models, empirical models, and data analyses. All are ultimately geared towards Air Force objectives of monitoring and specification of the ionospheric environment. A new multiple-ion theoretical model has been examined with a view to both describing the morphology of light ionos, and validating the model by comparisons with observational data. Further, a version of the code has ...

Participation in the Spring 1996 MISETA HF

20 FEB 98

46 pages

Authors: Michael C. Kelley; CORNELL UNIV ITHACA NY SCHOOL OF ELECTRICAL ENGINEERING

This report summarizes two quite different research tasks conducted under AFOSR Grant F49620-97-1-0177 (Participation in the Spring 1996 MISETA HF Campaign). The transition occurred part way through the program when the Air Force negotiations broke down with Chile. Although we carried out our component of the project in Peru, it became clear that the Air Force Phillips component would not be forthcoming due to diplomatic ...

Ionospheric Effects on Global Positioning System Receivers

FEB 98

Authors: Mark F. Knight; Anthony Finn; Manuel Cervera; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION CANBERRA (AUSTRALIA)

This report presents the results of a study conducted under tasks ADL 94/373 and ADA 96/005 into the effects of the ionosphere on Global Positioning System (CPS) receivers. The report focuses on the effects of the disturbed ionosphere on GPS as this phenomenon has the capacity to degrade the accuracy and reliability of both civilian and military GPS receivers. The impact of ionospheric disturbances on the susceptibility of GPS in ...

Plasma Waves Observed Inside Plasma Bubbles in the Equatorial F Region

15 JAN 98

11 pages

Authors: H. C. Koons; J. L. Roeder; P. Rodriguez; AEROSPACE CORP EL SEGUNDO CA TECHNOLOGY OPERATIONS

Plasma waves have been detected within and around density depletions in the topside equatorial F region by the electric and magnetic field sensors of the Extremely Low Frequency Wave Analyzer (ELFWA) instrument which is part of the Low Altitude Satellite Studies of Ionospheric Irregularities experiment on the Combined Release and Radiation Effects Satellite. The plasma waves include both electrostatic waves that have a small magnetic field component and electromagnetic waves ...

Theoretical, Diagnostic and Empirical Ionospheric Model Development, and Wave Signatures in Upper Atmosphere Density

JAN 97

65 pages

Authors: Matthew W. Fox; Xiaoqing Pi; Jules Aarons; Jeffrey M. Forbes; BOSTON UNIV MA CENTER FOR SPACE PHYSICS

To provide a better description of the ionospheric environment studies have been undertaken ranging from the expansion of scope of a theoretical ionospheric model, event modeling studies, and studies of new applications-oriented empirical models. The Phillips Laboratory Global Theoretical Ionospheric Model has been rewritten to solve for multiple ion densities, and physical drivers have been updated. A theoretical model has been used to study latitudinal symmetry in equatorial electron densities ...

Auroral and Midlatitude Radar Studies: Radar Methods for Improved Diagnostics of the HF-Modified and Natural Ionospheres

MAR 96

71 pages

Authors: Frank T. Djuth; John H. Elder; Kenneth L. Williams; GEOSPACE RESEARCH INC EL SEGUNDO CA

This research program addresses fundamental issues related to the interaction of a high-power, high- frequency (3 - 10 MHz) radio wave with the ionosphere. Data acquired with incoherent scatter radars and a modest (50 kW) VHF radar were examined. The reported observations were made with the Arecibo HF modification facility in Puerto Rico and the Tromsoe 'superheater' located in Norway. Particular attention is paid to the excitation of Langmuir and ...

Proceedings of Air Force Office of Scientific Research and Phillips Laboratory Workshop on Sprites and Blue Jets Held in Phillips Laboratory, Geophysics Directorate, Hanscom AFB, MA on 18-19 October 1995.

30 JAN 1996

410 pages

Authors: L. S. Jeong; PHILLIPS LAB HANSCOM AFB MA

This report contains the viewgraphs presented at the AFOSR-PL workshop on Sprites and Blue Jets held at the Phillips Laboratory, Geophysics Directorate, Hanscom AFB, MA, 18-19 October 1995. (MM)

Environmental Factors in Electronic Warfare Related to Aerospace Systems (Les Facteurs d'Environnement en Guerre Electronique Relatifs aux Systemes Aerospatiaux)

JAN 96

Authors: ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT NEUILLY-SUR-SEINE (FRAN CE)

This publication reports the unclassified papers presented at a specialists' meeting held by the Sensor and Propagation Panel at its Spring 1995 meeting. The topics covered included: Survey of threat and EW scenarios for aerospace systems; Relevant environmental effects with respect to aerospace systems in the applicable portions in the entire spectrum from optical/infrared frequencies to the ELF range; Environmental control (including artificial modification of propagation media); Aerospace system aspects; ...

Electromagnetic Measurements of the Ionosphere at the Ionospheric Station of Rome

JAN 96

1 pages

Authors: ISTITUTO NAZIONALE DI GEOFISICA ROME (ITALY)

Physics of the Ionosphere for OTH Operation; Chapter 3, OTH Handbook

09 NOV 95

104 pages

Authors: B. S. Dandekar; J. Buchau; J. A. Whalen; P. Fougere; PHILLIPS LAB HANSCOM AFB MA

The purpose of this report is to familiarize the Environmental Assessment radar operators with (a) the complex ionospheric phenomena that vary with location (geography), time of the day, and season and (b) with the phenomena of solar origin that affect the environment surrounding the earth. The first section describes the basic features of the ionosphere, which are an integral part of the radar system, the mirror which enables the operation ...

Proceedings of ION GPS-95, the International Technical Meeting of the Satellite Division of the Institute of Navigation (8th) Held at Palm Springs, California on 12-15 September 1995. Part 1

15 SEP 95

1040 pages

Authors: INSTITUTE OF NAVIGATION WASHINGTON DC

This conference presented current and future commercial and military uses and technology of Global Positioning Systems (GPS) and Differential Global Positioning Systems (DGPS). Test results of new methods and equipment were detailed. A Russian system, Global Navigation Satellite System (GLONASS), was discussed in several of the conference sessions. Topics included the following: (1) Air traffic control; (2) Airborne instrumentation applications; (3) Phase ambiguity resolution; (4) Attitude determination; (5) Spacecraft orbits; ...

Proceedings of ION GPS-95, the International Technical Meeting of the Satellite Division of the Institute of Navigation (8th) Held at Palm Springs, California on 12-15 September 1995. Part 2

15 SEP 95

959 pages

Authors: INSTITUTE OF NAVIGATION WASHINGTON DC

Analysis of N(2D) and N(2P) Emissions Observed During an Artificial Auroral Experiment

JUL 95

21 pages

Authors: James W. Duff; Fritz Bien; SPECTRAL SCIENCES INC BURLINGTON MA

The EXCEDE III rocketborne electron beam experiment was successfully launched from White Sands Missile Range on April 27, 1990. An 18 A, 2.4 keV electron beam was pulsed along the Earth's magnetic field lines over an altitude range of 60 to 115 km. Measurements were made of 5200 A N(2D), 3466 A N(2P), as well as the 3914 A (0,0) and 5228 A (0,3) N2+ first negative band emissions, between ...

Characterization of Propagation and Communication Properties of the Natural and Artificially Disturbed Ionosphere

MAY 95

28 pages

Authors: Bobo W. Reinisch; Gary S. Sales; Ronald Brent; Jens Ostergaard; Yuming Huang; MASSACHUSETTS UNIV LOWELL CENTER FOR ATMOSPHERIC RESEARCH

This basic research project, conducted during the period starting 12 September 1990 and ending 12 December 1994, studied the effects of natural and artificial ionospheric disturbances on HF and VHF propagation and communication. This project was reasonably divided into two parts where each stood by itself; VHF meteor scatter investigation and HF ionospheric modification studies. In addition to these two studies, a third study was later added to the project ...

Mode Conversion in an Oxygen-Hydrogen Plasma

22 MAR 95

74 pages

Authors: Jay R. Johnson; Tom Chang; G. B. Crew; MASSACHUSETTS INST OF TECH CAMBRIDGE CENTER FOR SPACE RESEARCH

The complications of mode conversion which occur near a minority resonance are studied in the context of electromagnetic ion cyclotron heating of a minority oxygen population in the magnetosphere. This problem is investigated using several different approaches. A perturbation approach demonstrates that the coupling results from non parallel propagation. The phase integral approach involves analytic continuation of (WKB) solutions and involves a discontinuity in the Poynting flux corresponding to energy ...

Environmental Conditions Responsible for Solar Activity

28 FEB 95

18 pages

Authors: Peter A. Sturrock; STANFORD UNIV CA CENTER FOR SPACE SCIENCE AND ASTROPHYSICS

Solar coronal activity is of concern to the Air Force primarily because of the terrestrial effects of coronal mass ejections and solar flares. Coronal mass ejections can lead to geomagnetic disturbances that in turn cause magnetospheric substorms. This geomagnetic activity disturbs the ionosphere, especially in the polar regions, interfering with radio propagation. Ionizing radiation (UV and X-ray) and particle events from solar flares can also lead to ionospheric disturbances. Furthermore, ...

CRRES Observations of Particle Flux Dropout Events

15 NOV 94

18 pages

Authors: Joseph F. Fennell; James L. Roeder; H. Spence; H. Singer; A. Korth; AEROSPACE CORP EL SEGUNDO CA TECHNOLOGY OPERATIONS

The complete disappearance of energetic electrons was observed by CRRES in the near geosynchronous region in 7.5% of the orbits examined. These total flux dropouts were defined by the fluxes rapidly dropping to levels below the sensitivity of the MEA energetic electron spectrometer on the CRRES satellite. They were separated into those that were only energetic electron dropouts and those that were associated with energetic ion and plasma dropouts. Approximately ...

Measurements of Ionospheric Variability

OCT 94

34 pages

Authors: R. A. Sprague; NAVAL COMMAND CONTROL AND OCEAN SURVEILLANCE CENTER RDT AND E DIV SAN DIEGO CA

This document reports on FY 94 progress in the ongoing measurement of ionospheric variability. Two measurement campaigns are described and results-to- date are presented. Comparisons of measured signal power are made to predictions from the PROPHET ionospheric propagation model. Examples of a new variability index for several ionospheric F-region parameters (foF2, MUF(3000), hmF2, and ymF2) are presented.

PLGR Accuracy Evaluation

JUN 94

9 pages

Authors: Daniel C. Oimoen; ARMY TOPOGRAPHIC ENGINEERING CENTER FORT BELVOIR VA

Personnel in the Corps of Engineers are authorized users of Precise Positioning Service (PPS) GPS. The Precise Lightweight GPS Receiver (PLGR) is the Army's authorized GPS receiver (Corps of Engineers personnel can obtain this). The U.S. Army Engineer School requested TEC evaluate the positional accuracies attainable with the PLGR. The evaluation covered four areas: real- time absolute, real-time differential, 'post-processed' absolute, and 'post- processed' differential. This paper discusses the techniques ...

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, June, July, August, September 1992.

02 FEB 1994

Authors: A. D. Bailey; J. M. Quinn; P. M. Bench; W. I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

A representative sampling of meteor scatter propagation performance statistics is presented from the PL/GP High Latitude Meteor Scatter Test Bed. The data address questions of meteor scatter propagation under disturbed ionospheric conditions, as well as normal meteor scatter propagation in the polar region. The time and frequency variations of the propagation transfer function are characterized over the 35 to 147 MHz range, including the availability of useful meteor trails, the ...

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, February, March, April, May 1992.

02 FEB 1994

Authors: A. D. Bailey; J. M. Quinn; P. M. Bench; W. I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, October, November, December 1991, January 1991.

01 FEB 1994

Authors: A. D. Bailey; J. M. Quinn; P. M. Bench; W. I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, October, November, December 1991, January 1992.

01 FEB 1994

Authors: A. D. Bailey; J. M. Quinn; P. M. Bench; W. I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, June, July, August, September 1991.

01 FEB 1994

Authors: A. D. Bailey; J. M. Quinn; P. M. Bench; W. I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation October, November, December 1991, January 1992

01 FEB 94

269 pages

Authors: Alan D. Bailey; John M. Quinn; Patricia M. Bench; Wayne I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, October, November, December 1990, January 1991.

26 JAN 1994

Authors: A. D. Bailey; J. M. Quinn; P. M. Bench; W. I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, June, July, August, September 1990.

26 JAN 1994

Authors: A. D. Bailey; J. M. Quinn; P. M. Bench; W. I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, February, March, April, and May 1990.

26 JAN 1994

Authors: A. D. Bailey; J. M. Quinn; P. M. Bench; W. I. Klemetti; PHILLIPS LAB HANSCOM AFB MA

A Simulation Study OF HF Direction Finding In The Presence oF F-Region Scattering And Sporadic-E

JAN 94

Authors: R. W. Jenkins; COMMUNICATIONS RESEARCH CENTRE OTTAWA (ONTARIO)

An HF direction finding (DF) system employing sampled-aperture techniques on high-latitude signals is simulated. The propagation is treated as scatter from moving patches of field-aligned F-region irregularities modelled as vertical 'thin-wire' scatterers in a horizontally stratified ionosphere, plus a weak sporadic-E (ES) reflection from a horizontal mirror-like surface. The resultant simulated received signals are analyzed by plane wave fitting and multiple-signal classification (MUSIC) DF algorithms. Simulations of DF operations on ...

Investigations of Joint Seismic and Electromagnetic Methods for Nuclear Test Monitoring

31 DEC 93

78 pages

Authors: Charles B. Archambeau; John B. Davies; Jeffrey L. Orrey; COLORADO UNIV AT BOULDER DEPT OF PHYSICS

This study is designed to develop both linear and non-linear modeling methods for prediction of excitation of atmospheric and seismic disturbances from near surface explosions and earthquake sources in complex media which include strong lateral variability, randomness and non-linear response effects. Comparisons with observations are systematically pursued to evaluate these models and to develop source discrimination methods. In this report we describe examples of non-linear atmospheric excitation by near surface ...

Performance Statistics Bulletin. High Latitude Meteor Scatter Propagation, November, December 1989, and January 1990.

22 NOV 1993

Authors: A. D. Bailey; J. C. Ostergaard; R. M. Burton; C. H. Curtis; W. I. Klemetti; J. E. Rasmussen; PHILLIPS LAB HANSCOM AFB MA

A representative sampling of meteor scatter propagation performance statistics is presented from the PL/GP High Latitude Meteor Scatter Test Bed (HLMSTB). The data address questions of meteor scatter propagation under disturbed ionospheric conditions, as well as normal meteor scatter propagation in the polar region. The time and frequency variations of the propagation transfer function are characterized over the 35 to 147 MHz range, including the availability of useful meteor trails, ...

Morphology and Characteristics of Disturbed HF Skywave Channels

03 SEP 93

15 pages

Authors: Leonard S. Wagner; NAVAL RESEARCH LAB WASHINGTON DC

The normal HF skywave channel is one in which propagation via ionospheric reflection predominates. A disturbed HF skywave channel is defined to be one in which ionospheric scatter plays a significant, often dominant, role in point-to-point radiowave propagation. From a communications perspective, a disturbed channel is one which exhibits reduced signal level in combination with the extensive delay and Doppler spread. Channels which are regularly disturbed include the trans-equatorial, trans-polar ...

Electromagnetic Wave Reflection From Irregular Plasma Layers

31 AUG 93

34 pages

Authors: Dennis Papadopoulos; Ramy Shanny; Robert D. Short; ARCO POWER TECHNOLOGIES INC WASHINGTON DC

The general theory describing reflection of electromagnetic waves from irregular reflectors was formulated by using path integral techniques (Dashen, 1979; Flatte, 1979). The general formulae reproduce the well known reflection coefficients for wave scattering from random rough surfaces derived by using Kirchhoff's theory or perturbation theory (Ogilvie, 1991). The theory was used to determine the degradation of an OTH radar signal scattered from irregular Artificial Ionospheric Mirrors (AIM). The cases ...