Open Access. Powered by Scholars. Published by Universities.®
Oceanography and Atmospheric Sciences and Meteorology Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Atmospheric Sciences (137)
- Meteorology (129)
- Engineering (60)
- Environmental Sciences (54)
- Oceanography (39)
-
- Physics (38)
- Electrical and Computer Engineering (35)
- Earth Sciences (32)
- Climate (23)
- Signal Processing (19)
- Life Sciences (18)
- Computer Sciences (13)
- Civil and Environmental Engineering (11)
- Optics (11)
- Atomic, Molecular and Optical Physics (10)
- Electromagnetics and Photonics (10)
- Statistics and Probability (10)
- Plasma and Beam Physics (8)
- Marine Biology (6)
- Natural Resources and Conservation (6)
- Operations Research, Systems Engineering and Industrial Engineering (6)
- Engineering Physics (5)
- Environmental Monitoring (5)
- Natural Resources Management and Policy (5)
- Water Resource Management (5)
- Applied Statistics (4)
- Electrical and Electronics (4)
- Environmental Health and Protection (4)
- Institution
- Keyword
-
- Weather forecasting (25)
- Atmospheric turbulence (14)
- Ionosphere (14)
- Lightning (11)
- #climate (9)
-
- Meteorology (9)
- #afcec (8)
- Adaptive optics (8)
- Algorithms (7)
- Climate change (7)
- Meteorology in aeronautics (7)
- Thunderstorms (7)
- Gulf of Mexico (6)
- Turbulence (6)
- GIS (5)
- Global Positioning System (5)
- Refractive index (5)
- Remote sensing (5)
- Clouds (4)
- Computerized simulation (4)
- GPS radio occultation (4)
- Ionospheric models (4)
- Long-range weather forecasting (4)
- Machine learning (4)
- Meteorological data (4)
- Numerical weather forecasting (4)
- Phytoplankton (4)
- Satellite meteorology (4)
- Solar flares (4)
- Space weather (4)
- Publication Year
Articles 211 - 240 of 368
Full-Text Articles in Oceanography and Atmospheric Sciences and Meteorology
Validation Of The Air Force Weather Agency Ensemble Prediction Systems, William B. Clements
Validation Of The Air Force Weather Agency Ensemble Prediction Systems, William B. Clements
Theses and Dissertations
Air Force Weather Agency's (AFWA) Ensemble Prediction Systems (EPS), Global Ensemble Prediction System (GEPS), 20km Mesoscale Ensemble Prediction System (MEPS20) and 4km Mesoscale Prediction System (MEPS4), were evaluated from April to October 2013 for 10 locations around the world to determine how accurately forecast probabilities for wind and precipitation thresholds and lightning occurrence match observed frequencies using Aerodrome Routine Meteorological Reports (METARs) and Aerodrome Special Meteorological Reports (SPECIs). Reliability diagrams were created for each forecast hour detailing the Brier skill score (BSS) to depict EPS performance compared to climatology for each site and score composition through reliability, resolution and uncertainty. …
Enhancing Ground Based Telescope Performance With Image Processing, John C. Zingarelli
Enhancing Ground Based Telescope Performance With Image Processing, John C. Zingarelli
Theses and Dissertations
The Space Surveillance Telescope (SST) is a Defense Advanced Research Projects Agency (DARPA) program designed to detect objects in space like Near Earth Asteroids (NEAs) and space debris in the Geosynchronous Earth Orbit (GEO) belt. Binary hypothesis tests (BHTs) have historically been used to facilitate the detection of new objects in space. In this dissertation, a multi-hypothesis test (MHT) detection strategy is introduced to improve the detection performance of the SST. In this context, the MHT determines if an unresolvable point source is in the center, corner or side of a pixel in contrast to a BHT, which only tests …
Improving Multiple Surface Range Estimation Of A 3-Dimensional Flash Ladar In The Presence Of Atmospheric Turbulence, Brian J. Neff
Improving Multiple Surface Range Estimation Of A 3-Dimensional Flash Ladar In The Presence Of Atmospheric Turbulence, Brian J. Neff
Theses and Dissertations
Laser Radar sensors can be designed to provide two-dimensional and three-dimensional (3-D) images of a scene from a single laser pulse. Currently, there are various data recording and presentation techniques being developed for 3-D sensors. While the technology is still being proven, many applications are being explored and suggested. As technological advancements are coupled with enhanced signal processing algorithms, it is possible that this technology will present exciting new military capabilities for sensor users. The goal of this work is to develop an algorithm to enhance the utility of 3-D Laser Radar sensors through accurate ranging to multiple surfaces per …
Investigation Of Diode Pumped Alkali Laser Atmospheric Transmission Using Tunable Diode Laser Absorption Spectroscopy, Christopher A. Rice
Investigation Of Diode Pumped Alkali Laser Atmospheric Transmission Using Tunable Diode Laser Absorption Spectroscopy, Christopher A. Rice
Theses and Dissertations
A field deployable, tunable diode laser absorption spectroscopy (TDLAS) device fiber coupled to a pair of 12.5" Ritchey-Chretien telescopes was used to study atmospheric propagation for open path lengths of 100 m to 1,000 m to estimate atmospheric transmission at key High Energy Laser (HEL) wavelengths. The potassium (K) version of the Diode Pumped Alkali Laser (DPAL) operates in between two of the sharp oxygen rotational features in the PP and the PQ branches. Initial experiments were performed in the vicinity of molecular oxygen X3Σ-g to b1Σ+g electronic transition lines near the potassium emission line at 770 nm. More than …
Implementation Of Branch-Point-Tolerant Wavefront Reconstructor For Strong Turbulence Compensation, Michael J. Steinbock
Implementation Of Branch-Point-Tolerant Wavefront Reconstructor For Strong Turbulence Compensation, Michael J. Steinbock
Theses and Dissertations
Branch points arise in optical transmissions due to strong atmospheric turbulence, long propagation paths, or a combination of both. Unfortunately, these conditions are very often present in desired operational scenarios for laser weapon systems, optical communication, and covert imaging, which suffer greatly when traditional adaptive optics systems either cannot sense branch points or implement non-optimal methods for sensing and correcting branch points. Previous research by Pellizzari presented a thorough analysis of various novel branch point tolerant reconstructors in the absence of noise. In this research a realistic model of the Air Force Institute of Technology's adaptive optics system is developed …
Ladar Performance Simulations With A High Spectral Resolution Atmospheric Transmittance And Radiance Model- Leedr, Benjamin D. Roth
Ladar Performance Simulations With A High Spectral Resolution Atmospheric Transmittance And Radiance Model- Leedr, Benjamin D. Roth
Theses and Dissertations
In this study of atmospheric effects on Geiger Mode laser ranging and detection (LADAR), the parameter space is explored primarily using the Air Force Institute of Technology Center for Directed Energy's (AFIT/CDE) Laser Environmental Effects Definition and Reference (LEEDR) code. The LADAR system is assessed at operationally representative wavelengths of 1.064, 1.56 and 2.039 μm with several up and down looking engagement geometries at locations worldwide. Results computed with LEEDR are compared to standard atmosphere and Fast Atmospheric Signature Code (FASCODE) assessments. Results show significant climate dependence, but large variances between climatological and standard atmosphere assessments. An overall average absolute …
Turbulence Measurement In The Atmospheric Boundary Layer Using Cellular Telephone Signals, Lee R. Burchett
Turbulence Measurement In The Atmospheric Boundary Layer Using Cellular Telephone Signals, Lee R. Burchett
Theses and Dissertations
This thesis investigated a new method for measuring the intensity of turbulence in the planetary boundary layer that shows a high correlation with measurements from weather radar. The method takes measurements of cell phone signal strength and uses scintillation in the signal to estimate the strength of local turbulence. Using cell phone signals provides unique measurement advantages: it is a passive measurement method, it is not strongly affected by precipitation, and one device can potentially measure several paths at once. The measurements were taken using an Android® cell phone running a custom built application. The strength of turbulence was quantified …
Effect Of Storm Enhanced Densities On Geo-Location Accuracy Over Conus, Lindon H. Steadman
Effect Of Storm Enhanced Densities On Geo-Location Accuracy Over Conus, Lindon H. Steadman
Theses and Dissertations
Storm enhanced densities (SEDs) are ionospheric plasma enhancements that disrupt radio communications in the near-Earth space environment, degrading the Global Positioning System (GPS) and other key technologies. Accurate GPS/total electron content (TEC) correction maps produced by ionosphere models can mitigate degradations from SEDs. An artificial SED was created and ingested via slant TEC measurements into the Global Assimilation of Ionospheric Measurements Gauss-Markov Kalman Filter Model to determine how many ground GPS receivers are needed to produce reliable GPS/TEC correction maps over the continental United States during geomagnetic storming. It was found that 110 well-positioned GPS receivers produced the best overall …
Verification Of Global Assimilation Of Ionospheric Measurements Gauss Markov (Gaim-Gm) Model Forecast Accuracy, Paul H. Domm
Verification Of Global Assimilation Of Ionospheric Measurements Gauss Markov (Gaim-Gm) Model Forecast Accuracy, Paul H. Domm
Theses and Dissertations
GAIM-GM is an operational Kalman filter data assimilation model of the ionosphere that can assimilate data from GPS total electron content (TEC), ionosonde electron density profiles, and satellite based in situ electron densities. The Air Force Weather Agency (AFWA) uses GAIM-GM to specify and forecast the ionosphere. An in depth investigation into the accuracy of these forecasts has not been completed. GAIM-GM output obtained from four cases run from combinations of geomagnetic and solar activity was used to determine GAIM-GM forecast accuracy. Forecast accuracy was determined through the use of a skill score as well as other statistical tools to …
Assessment Of The Effects Of Plasma Bubbles On Gaim-Gm, Kenneth R. Fenton
Assessment Of The Effects Of Plasma Bubbles On Gaim-Gm, Kenneth R. Fenton
Theses and Dissertations
Plasma bubbles are regions of depleted plasma density generated in the post-sunset equatorial region of the ionosphere. Bubbles significantly affect total electron count (TEC) and consequently alter communication and navigation capabilities. Here, the Global Assimilation of Ionospheric Measurements Gauss-Markov (GAIM-GM) model is studied in order to assess its capability to accurately model equatorial plasma bubbles. GAIM-GM uses the Ionospheric Forecast Model (IFM) as a background state modified through the application of a Kalman Filter to incorporate ionospheric observations such as Global Positioning System (GPS) total electron content (TEC) values. GPS TEC values representative of plasma bubble conditions are modeled and …
Hyperspectral-Based Adaptive Matched Filter Detector Error As A Function Of Atmospheric Profile Estimation, Allan W. Yarbrough
Hyperspectral-Based Adaptive Matched Filter Detector Error As A Function Of Atmospheric Profile Estimation, Allan W. Yarbrough
Theses and Dissertations
Hyperspectral imagery is collected as radiance data. This data is a function of multiple variables: the radiation profile of the light source, the reflectance of the target, and the absorption and scattering profile of the medium through which the radiation travels as it reflects off the target and reaches the imager. Accurate target detection requires that the collected image matches as closely as possible the known "true" target in the classification database. Therefore, the effect of the radiation source and the atmosphere must be removed before detection is attempted. While the spectrum of solar light is relatively stable, the effect …
Analysis Of Plasma Bubble Signatures In The Ionosphere, Omar A. Nava
Analysis Of Plasma Bubble Signatures In The Ionosphere, Omar A. Nava
Theses and Dissertations
Plasma bubbles are large scale structures of depleted plasma density in Earth's ionosphere that disrupt radio and satellite communications, to include global navigation satellite systems. This study used the Ionospheric Forecast Model (IFM) to analyze affected look angles and total electron content (TEC) differences due to plasma bubbles of various sizes for 27 geophysical conditions consisting of different seasons and levels of solar and geomagnetic activity at 421 GPS ground stations worldwide. Overall, different geographic locations and plasma bubble configurations produced different affected look angle profiles. Bigger plasma bubbles, larger density depletion factors, higher levels of solar activity and the …
Passive Ranging Of Dynamic Rocket Plumes Using Infrared And Visible Oxygen Attenuation, Robert Anthony Vincent
Passive Ranging Of Dynamic Rocket Plumes Using Infrared And Visible Oxygen Attenuation, Robert Anthony Vincent
Theses and Dissertations
Atmospheric oxygen absorption bands in observed spectra of boost phase missiles can be used to accurately estimate range from sensor to target. This work compares two oxygen absorption bands in the near-infrared (NIR) and visible (Vis) spectrum, centered at 762nm and 690 nm, to passively determine range. Spectra were observed from static tests of both surface-to-air missile simulators at 405m range and a full-scale solid rocket motor at 900m range. The NIR O2 band provided range estimates accurate to within 3% for both tests, while the Vis O2 band had range errors of 77% and 15 %, respectively. …
Determining The Index Of Refraction Of An Unknown Object Using Passive Polarimetric Imagery Degraded By Atmospheric Turbulence, Milo W. Hyde Iv
Determining The Index Of Refraction Of An Unknown Object Using Passive Polarimetric Imagery Degraded By Atmospheric Turbulence, Milo W. Hyde Iv
Theses and Dissertations
In this research, an algorithm is developed to estimate the index of refraction of an unknown object using passive polarimetric images degraded by atmospheric turbulence. The algorithm uses a variant of the maximum-likelihood blind-deconvolution algorithm developed by LeMaster and Cain to recover the true object (i.e., the first Stokes parameter), the degree of linear polarization, and the polarimetric-image point spread functions. Nonlinear least squares is then used to find the value of the complex index of refraction which best fits the theoretical degree of linear polarization, derived using a polarimetric bidirectional reflectance distribution function, to the turbulence-corrected degree of linear …
Realistic Vertical Atmospheric Profiles And Effects From Limited Surface Observations, Dane P. Ranney
Realistic Vertical Atmospheric Profiles And Effects From Limited Surface Observations, Dane P. Ranney
Theses and Dissertations
The ability to accurately describe the atmospheric conditions around us is not only important to the Air Force, but to anyone involved in signal propagation. The programs currently utilized to describe the atmosphere take into account a variety of measures. The LEEDR (Laser Environmental Effects Definition and Reference) program in particular, allows the user to select a location, aerosol and molecular effects model, numerous cloud and precipitation events, as well as other features. Even with the control that the user has, the output that the program provides can vary from actual conditions on a day to day basis. This is …
Evaluation Of Interplanetary Magnetic Field Tracing Models Using Impulsive Seps, Brian P. Elliott
Evaluation Of Interplanetary Magnetic Field Tracing Models Using Impulsive Seps, Brian P. Elliott
Theses and Dissertations
Current Interplanetary Magnetic Field (IMF) models are evaluated in this study to determine which model(s) perform an accurate representation of this magnetic structure. These IMF models include the Parker Spiral model, the Potential Field Source Surface (PFSS) model, the Wang-Sheeley-Arge (WSA) model and the ENLIL model. Impulsive Solar Energetic Particles (SEPs) are used as tracers to determine the magnetic structure of the IMF and provide source locations for model comparisons. Each individual model is analyzed, compared to the identified solar source region and a longitude/latitude offset of these traces assigned. The model connection of the PFSS and Parker models is …
Passive Ranging Using Infra-Red Atmospheric Attenuation, Douglas J. Macdonald
Passive Ranging Using Infra-Red Atmospheric Attenuation, Douglas J. Macdonald
Theses and Dissertations
Methods of estimating range to an emissive target based on the depth of an atmospheric absorption band are demonstrated. The present work uses measurements of the CO2 absorption band centered at 2.0 µm where signal-to-background ratios are maximum for many applications. Model results, based on high-resolution transmission molecular absorption (HITRAN) database cross sections, are used to predict range accuracy at ranges of up to 50 km and are compared with short range (<5km) experimental results. The spectra of 23 high explosive events were used to validate the model. Using the assumption of a blackbody spectrum, extracted ranges consistently underestimated the true range by approximately 13%. By incorporating the stoichiometry of the fireball from previous research and using particulate contribution as a parameter, the error for the range estimates could be reduced to 3%.
Experimental Validation Techniques For The Heleeos Off-Axis Laser Propagation Model, John D. Haiducek
Experimental Validation Techniques For The Heleeos Off-Axis Laser Propagation Model, John D. Haiducek
Theses and Dissertations
The High Energy Laser End-to-End Operational Simulation (HELEEOS) off-axis scattering algorithm is designed to predict the irradiance that will be detected at a given off-axis location due to atmospheric scattering of a high-energy laser. The HELEEOS system models the propagation of the laser through the atmosphere, accounting for such effects as turbulence, thermal blooming, and atmospheric absorption. The HELEEOS off-axis scattering algorithm uses the scattering phase functions of the Mie scattering models to predict the amount of radiation that will be scattered toward a particular observation location from each point along the beam path, and the total irradiance that will …
Application Of Satellite-Derived Wind Profiles To Joint Precision Airdrop System (Jpads) Operations, David C. Meier
Application Of Satellite-Derived Wind Profiles To Joint Precision Airdrop System (Jpads) Operations, David C. Meier
Theses and Dissertations
The Joint Precision Airdrop System has revolutionized military airdrop capability, allowing accurate delivery of equipment and supplies to smaller drop zones, from higher altitudes than was previously possible. This capability depends on accurate wind data which is currently provided by a combination of high-resolution forecast models and GPS dropsondes released in the vicinity of the dropzone shortly before the airdrop. This research develops a windprofiling algorithm to derive the needed wind data from passive IR satellite soundings, eliminating the requirement for a hazardous dropsonde pass near the drop zone, or allowing the dropsonde to be dropped farther from the dropzone. …
Operations-Focused Optimized Theater Weather Sensing Strategies Using Preemptive Binary Integer Programming, Andrew J. Geyer
Operations-Focused Optimized Theater Weather Sensing Strategies Using Preemptive Binary Integer Programming, Andrew J. Geyer
Theses and Dissertations
This thesis describes a method that optimally deploys weather sensors of all types in a battlefield environment. Gridded climatology models are used to determine an estimate for the weighted frequency of occurrence of operationally significant inclement weather events. That data is used to formulate a series of preemptive Binary Integer Linear Programs that maximize detection of expected operationally significant inclement weather occurrences within the constraints of feasibility of sensor deployment, sensor operational lifespan and the sensor’s ability to detect the operationally significant inclement weather elements. The preemptive Binary Integer Linear Programs are combined into a single objective function that maintains …
Assessment Of Weather Sensitivities And Air Force Weather (Afw) Support To Tactical Lasers In The Lower Troposphere, Francesco J. Echeverria
Assessment Of Weather Sensitivities And Air Force Weather (Afw) Support To Tactical Lasers In The Lower Troposphere, Francesco J. Echeverria
Theses and Dissertations
ATL scientists need to develop a full understanding of the interaction effects between a high-energy laser beam and the atmosphere through which it propagates. Achieving this understanding is important for many reasons. In particular, the high cost of DE weapons systems makes each propagation event expensive. Having an understanding of the atmosphere in which a high-energy laser propagates will increase efficiency and effectiveness of the ATL weapon system, which in turn will decrease cost of operation. A tool that allows for the ATL war-fighter to determine the atmospheric effects on laser propagation currently does not exist. This study creates a …
A Computational Tool For Evaluating Thz Imaging Performance In Brownout Conditions At Land Sites Throughout The World, Seth L. Marek
A Computational Tool For Evaluating Thz Imaging Performance In Brownout Conditions At Land Sites Throughout The World, Seth L. Marek
Theses and Dissertations
This study quantifies terahertz (THz) or sub-millimeter imaging performance during simulated rotary-wing brownout or whiteout environments based on geographic location and recent/current atmospheric weather conditions. The atmospheric conditions are defined through the Air Force Institute of Technology Center for Directed Energy (AFIT/CDE) Laser Environmental Effects Definition and Reference or LEEDR model. This model enables the creation of vertical profiles of temperature, pressure, water vapor content, optical turbulence, and atmospheric particulates and hydrometeors as they relate to line-by-line layer extinction coefficient magnitude at wavelengths from the UV to the RF. Optical properties and realistic particle size distributions for the brownout and …
Demonstration And Verification Of A Broad Spectrum Anomalous Dispersion Effects Tool For Index Of Refraction And Optical Turbulence Calculations, J. Jean Cohen
Theses and Dissertations
An atmospheric optical turbulence strength model with a broad wavelength range of 355nm (ultraviolet) to 8.6m (radio frequencies) has been created at AFIT and implemented into the High Energy Laser End-to-End Operational Simulation tool (HELEEOS). This modeling and simulation tool is a first principles atmospheric propagation and characterization model. Within HELEEOS lies the High-Resolution Transmission Molecular Absorption (HITRAN) database, containing 1,734,469 spectral lines for 37 different molecules as of version 12.0 (2004). HITRAN affords HELEEOS incredible accuracy for electromagnetic (EM) propagation prediction. A full understanding of optical turbulence is needed to successfully predict EM radiation propagation, particularly within the application …
Closed-Loop Adaptive Optics Control In Strong Atmospheric Turbulence, Todd M. Venema
Closed-Loop Adaptive Optics Control In Strong Atmospheric Turbulence, Todd M. Venema
Theses and Dissertations
A self-referencing interferometer based closed-loop adaptive optics controller is developed which is designed to operate effectively under strong turbulence conditions. The aberrated optical field is modeled stochastically and then estimates of the state of the system are developed using a steady-state, fixed-gain Kalman filter. The phase of the optical field is considered the state of the system which is wrapped in a limited range of (-π, π]. This phase is unwrapped through the use of a least-squares reconstructor which has been modified to work effectively in the presence of branch points associated with strong turbulence. The conjugate of the optical …
Ionospheric Response To Solar Flares Using An Improved Version Of Sami2, Joseph P. Reich Iii
Ionospheric Response To Solar Flares Using An Improved Version Of Sami2, Joseph P. Reich Iii
Theses and Dissertations
Solar flares release energy, primarily at X-ray and EUV wavelengths, which is then absorbed mainly in Earth's ionosphere. This non-uniform absorption of energy alters the ionosphere's structure and can change the propagation of electromagnetic waves causing errors in GPS navigation, false radar echoes, and loss of High Frequency (HF) radio communications. Accurately modeling the ionospheric response to flares is the first step in predicting, and then mitigating, their effects. Accurately modeling these effects requires solar irradiance at a high cadence, to capture the flare, which may only last minutes, as well as treatment of the effects of photoelectrons. Sami2 is …
Limitations Of Segmented Wavefront Control Devices In Emulating Optical Turbulence, Michael D. Plourde
Limitations Of Segmented Wavefront Control Devices In Emulating Optical Turbulence, Michael D. Plourde
Theses and Dissertations
Using a device to act as a surrogate for atmospheric turbulence in a laboratory is necessary to build and test optical systems for imaging, lidar, laser weapons, and laser communications. Liquid-crystal spatial light modulators (LC SLMs) and segmented micro-electro-mechanical-system (MEMS) deformable mirrors (DMs) are commonly used devices for altering wavefronts in order to simulate a portion of atmospheric turbulence. The best location of these devices was theoretically analyzed to obtain the broadest possible range of atmospheric conditions. It was found that two phase screens should be placed at the beginning of the optical path to achieve maximum turbulence strength for …
Modeling Study Of 2006 Central Florida Wildfires Using Fire Area Simulator, Danielle Denise Carpenter
Modeling Study Of 2006 Central Florida Wildfires Using Fire Area Simulator, Danielle Denise Carpenter
Theses and Dissertations
“Fire weather” addresses fire behavior in specified fuels under various weather conditions. In a wildland context, the term “fuel” describes any organic matter, live or dead, that will ignite and bum in a fire. Fuels vary in species, location, and abundance, and may lie in a substrate, surface layer, and/or canopy. Fuel moisture varies to maintain equilibrium with the atmosphere. Fire propagation is the progressive movement of fire in space and time. Advancements of fire from one discrete fuel element to the next is a process that involves heat production, heat transfer, and heat absorption, and is dependent on fuel …
Holes: Ionospheric Scintillation, Gps And Imputation, Robert A. Steenburgh
Holes: Ionospheric Scintillation, Gps And Imputation, Robert A. Steenburgh
Theses and Dissertations
Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within ± 20 degrees of the geomagnetic equator. This belt also hosted roughly half of the completed U.S. military operations in the last decade. The authors examined scintillation data from Ascension Island, United Kingdom, and Ancon, Peru, in the Atlantic longitudinal sector as well as data from Parepare, Indonesia, and Marak Parak, Malaysia, in the Pacific longitudinal sector. From these data, they calculate percent probability of occurrence …
Anisotropy In The South Atlantic Anomaly, Shaun M. Easley
Anisotropy In The South Atlantic Anomaly, Shaun M. Easley
Theses and Dissertations
From June 2000 through July 2006, the TSX-5 satellite measured proton fluxes in the Earth’s magnetosphere using its CEASE instrument. A review of the satellite data by scientists at AFRL/VSBX revealed an unanticipated, recurring bi-modal structure in histograms of the proton counts. This research identified the bi-modal behavior as anisotropic in nature, and the result of two separate processes. At low altitudes the anisotropy was well described by the classic “East-West Effect.” Comparisons of the satellite data to simple analytical models are presented. At high altitudes, the anisotropy was the result of the detector measuring protons at different pitch angles …
Assessment Of The Impact Of Various Ionospheric Models On High Frequency Signal Raytracing, Joshua T. Werner
Assessment Of The Impact Of Various Ionospheric Models On High Frequency Signal Raytracing, Joshua T. Werner
Theses and Dissertations
An assessment of the impact of various ionospheric models on high-frequency (HF) signal raytracing is presented. Ionospheric refraction can strongly affect the propagation of HF signals. Consequently, Department of Defense missions such as over-the-horizon RADAR, HF communications, and geo-location all depend on an accurate specification of the ionosphere. Five case studies explore ionospheric conditions ranging from quiet conditions to solar flares and geomagnetic storms. It is shown that an E layer by itself can increase an HF signal’s ground range by over 100 km, stressing the importance of accurately specifying the lower ionosphere. It is also shown that the GPSII …