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Articles 91 - 120 of 391

Full-Text Articles in Oceanography and Atmospheric Sciences and Meteorology

Optimization Of Spacecraft Formations About Lagrange Points For The Next Generation Space Weather Prediction Mission, Roberto Cuéllar Rangel Jul 2020

Optimization Of Spacecraft Formations About Lagrange Points For The Next Generation Space Weather Prediction Mission, Roberto Cuéllar Rangel

Doctoral Dissertations and Master's Theses

This thesis’s work serves as proof of concept for the Next Generation Space Weather Prediction Mission, a multi-spacecraft mission at various libration points whose objective is to forecast Space Weather hazards with a 12day warning time. This thesis deals with the design and control of orbits of spacecraft formations at different libration points. The systems studied are SunEarth, SunVenus, SunMercury, and SunMars. The orbit design and formation keeping control of the spacecraft are solved simultaneously using an optimization software called DIDO. Initial conditions are obtained through two different strategies. The first one, by placing the spacecraft in a tetrahedral formation …


An Aviation Weather Preflight Decision Support Tool To Improve Ga Pilots' Preflight And Inflight Performance, Jayde M. King Jul 2020

An Aviation Weather Preflight Decision Support Tool To Improve Ga Pilots' Preflight And Inflight Performance, Jayde M. King

Doctoral Dissertations and Master's Theses

Low hour, inexperienced General Aviation (GA) pilots account for the majority of weather-related incidents, which often result in fatalities. Previous research identifies poor preflight planning practices and a lack of aviation weather knowledge as key contributing factors to the high novice private pilot accident and fatality rate. Research invested into resolving these issues often attempt to introduce new inflight weather technology to assist pilots with weather avoidance. However, these interventions usually result in pilots using the information to strategically navigate closer to degraded weather conditions (Beringer & Ball, 2004; Burgess & Thomas, 2004). Therefore, the purpose of this study was …


Evidence For Horizontal Blocking And Reflection Of A Small-Scale Gravity Wave In The Mesosphere, N. R. Criddle, C. Heale, J. Snively, P. -D. Pautet, T. Yuan, Y. Zhao, M. J. Taylor Apr 2020

Evidence For Horizontal Blocking And Reflection Of A Small-Scale Gravity Wave In The Mesosphere, N. R. Criddle, C. Heale, J. Snively, P. -D. Pautet, T. Yuan, Y. Zhao, M. J. Taylor

Publications

The variations of the horizontal phase velocity of an internal gravity wave, generated by wave “blocking” or “reflection” due to an inhomogeneous wind field, have been predicted theoretically and numerically investigated but had yet to be captured experimentally. In this paper, through a collaborative observation campaign using a sodium (Na) Temperature/Wind lidar and a collocated Advanced Mesospheric Temperature Mapper (AMTM) at Utah State University (USU), we report the first potential evidence of such a unique gravity wave process. The study shows that a small-scale wave, captured by the AMTM, with initial observed horizontal phase velocity of 37 ± 5 m/s …


Modeling Of Ionospheric Responses To Atmospheric Acoustic And Gravity Waves Driven By The 2015 Nepal M W 7.8 Gorkha Earthquake, P. A. Inchin, J. B. Snively, M. D. Zettergren, A. Komjathy, O. P. Verkhoglyadova, S. Tulasi Ram Feb 2020

Modeling Of Ionospheric Responses To Atmospheric Acoustic And Gravity Waves Driven By The 2015 Nepal M W 7.8 Gorkha Earthquake, P. A. Inchin, J. B. Snively, M. D. Zettergren, A. Komjathy, O. P. Verkhoglyadova, S. Tulasi Ram

Publications

Near- and far-field ionospheric responses to atmospheric acoustic and gravity waves (AGWs) generated by surface displacements during the 2015 Nepal 7.8 Gorkha earthquake are simulated. Realistic surface displacements driven by the earthquake are calculated in three-dimensional forward seismic waves propagation simulation, based on kinematic slip model. They are used to excite AGWs at ground level in the direct numerical simulation of three-dimensional nonlinear compressible Navier-Stokes equations with neutral atmosphere model, which is coupled with a two-dimensional nonlinear multifluid electrodynamic ionospheric model. The importance of incorporating earthquake rupture kinematics for the simulation of realistic coseismic ionospheric disturbances (CIDs) is demonstrated and …


Recovering From Industrial Overshoot: Thermal Removal Of Atmospheric Co2, Ted Von Hippel, Sandra Boetcher, Matthew Traum, Farshid Azadian Ph.D., William Mackunis Jan 2020

Recovering From Industrial Overshoot: Thermal Removal Of Atmospheric Co2, Ted Von Hippel, Sandra Boetcher, Matthew Traum, Farshid Azadian Ph.D., William Mackunis

Sustainability Conference

Humanity will soon overshoot a safe level of atmospheric CO2, if it hasn't done so already. Countries, industries, and the global economy need to dramatically and quickly alter their behavior and technology to avoid this dangerous overshoot, yet this appears unlikely. Direct Air Capture of CO2 represents an insurance policy for society - a way of removing excess atmospheric CO2. I will present an approach to this problem based on thermal physics that cools cubic kilometers of air to extract CO2 as it sublimates. I propose a combination of an efficient heat exchanger, radiative cooling, and refrigeration, all at industrial …


Assessing If Motivation Impacts General Aviation Pilots’ Persistence In Varying Weather Conditions, Sabrina Woods Jan 2020

Assessing If Motivation Impacts General Aviation Pilots’ Persistence In Varying Weather Conditions, Sabrina Woods

Doctoral Dissertations and Master's Theses

Continued flight under visual flight rules into instrument meteorological conditions is the predominant cause for fatal accidents by percentage, for general aviation aircraft operations. It is possible that a pilot’s motivation or reason for flying will override other safer, more logical courses of action when a hazard presents itself. The decision appears to stem from a willingness to persist in a course of action despite factors that indicate an alternate and safer course is warranted. This research addresses what is currently presumed about the decision to continue flying under visual flight rules into instrument conditions and marries those ideas with …


Development Of A Sensor Suite For Atmospheric Boundary Layer Measurement With A Small Multirotor Unmanned Aerial System, Kevin A. Adkins, Christopher J. Swinford, Peter D. Wambolt, Gordon Bease Jan 2020

Development Of A Sensor Suite For Atmospheric Boundary Layer Measurement With A Small Multirotor Unmanned Aerial System, Kevin A. Adkins, Christopher J. Swinford, Peter D. Wambolt, Gordon Bease

International Journal of Aviation, Aeronautics, and Aerospace

Small unmanned aerial systems (sUAS) are increasingly being used to conduct atmospheric research. Because of the dynamic nature and inhomogeneity of the atmospheric boundary layer (ABL), the ability of instrumented sUAS to make on-demand 3-dimensional high-resolution spatial measurements of atmospheric parameters makes them particularly suited to ABL investigations. Both fixed-wing and multirotor sUAS have been used for ABL investigations. Most investigations to date have included in-situ measurement of thermodynamic quantities such as temperature, pressure and humidity. When wind has been measured, a variety of strategies have been used. Two of the most popular techniques have been deducing wind from inertial …


A Proposed Taxonomy For General Aviation Pilot Weather Education And Training, John M. Lanicci, Thomas A. Guinn, Jayde M. King, Beth Blickensderfer, Robert Thomas, Yolanda Ortiz Jan 2020

A Proposed Taxonomy For General Aviation Pilot Weather Education And Training, John M. Lanicci, Thomas A. Guinn, Jayde M. King, Beth Blickensderfer, Robert Thomas, Yolanda Ortiz

Journal of Aviation/Aerospace Education & Research

As General Aviation (GA) safety continues to remain a focus of the aviation community, GA pilot weather education and training continues to be an active area of interest within the research community. This study introduces a taxonomy for organizing GA pilot weather education and training materials that was originally conceived as part of the FAA’s Weather Technology In the Cockpit research program. The taxonomy is built upon three main knowledge categories, or tiers:1) Weather Phenomena (which includes hazards); 2) Weather Hazard Products; and 3) Weather Hazard Product Sources and their Application. The concept behind the categorization is to link knowledge …


Atmospheric And Ionospheric Responses To Acoustic And Gravity Waves Driven By Earthquakes And Tsunamis, Pavel A. Inchin Jan 2020

Atmospheric And Ionospheric Responses To Acoustic And Gravity Waves Driven By Earthquakes And Tsunamis, Pavel A. Inchin

Doctoral Dissertations and Master's Theses

Natural hazards (NHs) are causes for significant concern due to their potentially catastrophic impacts on society. The study of their effects on the upper atmosphere can provide significant insight into the coupled nature of geophysical processes, and drives important applications for radio communication and navigation, leading potentially to the development of NH early-warning systems. Although general concepts underlying their coupling mechanisms are well understood, recent computational capabilities, supported by high temporal and spatial density of observations, have reached the level where such processes can be modeled with unprecedented realism for detailed case studies. The studies provided in this thesis are …


An Analysis Of The Atmospheric Propagation Of Underground-Explosion-Generated Infrasonic Waves Based On The Equations Of Fluid Dynamics: Ground Recordings, Roberto Sabatini, Jonathan B. Snively, Michael P. Hickey, J. L. Garrison Dec 2019

An Analysis Of The Atmospheric Propagation Of Underground-Explosion-Generated Infrasonic Waves Based On The Equations Of Fluid Dynamics: Ground Recordings, Roberto Sabatini, Jonathan B. Snively, Michael P. Hickey, J. L. Garrison

Publications

An investigation on the propagation of underground-explosion-generated infrasonic waves is carried out via numerical simulations of the equations of fluid dynamics. More specifically, the continuity, momentum, and energy conservation equations are solved along with the Herzfeld-Rice equations in order to take into account the effects of vibrational relaxation phenomena. The radiation of acoustic energy by the ground motion caused by underground explosions is initiated by enforcing the equality, at ground level, between the component of the air velocity normal to the Earth's surface and the normal velocity of the ground layer. The velocity of the ground layer is defined semi-empirically …


Steve And The Picket Fence: Evidence Of Feedback-Unstable Magnetosphere-Ionosphere Interaction, Evgeny Mishin, Anatoly Streltsov Dec 2019

Steve And The Picket Fence: Evidence Of Feedback-Unstable Magnetosphere-Ionosphere Interaction, Evgeny Mishin, Anatoly Streltsov

Publications

This paper aims to extend the understanding of Strong Thermal Emission VelocityEnhancement (STEVE) and the Picket Fence related to strong subauroral ion drifts (SAID). Wenumerically demonstrated that precipitating energetic electrons are critical for the structuring of the PicketFence. It is created by feedback-unstable magnetosphere-ionosphere interactions driven by the SAIDelectric field when the Hall conductance created by energetic (≥1 keV) electrons exceeds the Pedersenconductance. We show that thermal excitation of the red-line emission in STEVE is inhibited by inelasticcollisions with molecular nitrogen. Suprathermal (≤500 eV) electrons coming from the turbulentplasmasphere appear to be the major source. We also show that the …


Determination Of Global Mean Eddy Diffusive Transport In The Mesosphere And Lower Thermosphere From Atomic Oxygen And Carbon Dioxide Climatologies, G. R. Swenson, C. C. J. H. Salinas, F. Vargas, Y. Zhu, M. Kaufmann, M. Jones Jr., A. Liu, Et Al. Dec 2019

Determination Of Global Mean Eddy Diffusive Transport In The Mesosphere And Lower Thermosphere From Atomic Oxygen And Carbon Dioxide Climatologies, G. R. Swenson, C. C. J. H. Salinas, F. Vargas, Y. Zhu, M. Kaufmann, M. Jones Jr., A. Liu, Et Al.

Publications

Quantifying the eddy diffusion coefficient profile in the mesosphere and lower thermosphere (MLT) is critical to the constituent density distributions in the upper mesosphere and thermosphere. Previous work by Swenson et al. (2018, https://doi.org/10.1016/j.jastp.2018.05.014) estimated the global mean eddy diffusion (kzz) values in the upper mesosphere using atomic oxygen (O), derived from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) hydroxyl (OH). In this study, vertical eddy diffusive transport velocities of O were determined from continuity of mass in the mesopause region (80–97 km), primarily via the HOx chemistry. Global average constituent climatology from previously deduced SABER ozone (O3) …


A Numerical Investigation On The Variation Of Sodium Ion And Observed Thermospheric Sodium Layer At Cerro Pachón, Chile During Equinox, Xuguang Cai, Tao Yuan, J. Vincent Eccles, N. M. Pedatella, Xiaoqi Xi, Chao Ban, Alan Z. Liu Dec 2019

A Numerical Investigation On The Variation Of Sodium Ion And Observed Thermospheric Sodium Layer At Cerro Pachón, Chile During Equinox, Xuguang Cai, Tao Yuan, J. Vincent Eccles, N. M. Pedatella, Xiaoqi Xi, Chao Ban, Alan Z. Liu

Publications

The extension of the neutral sodium (Na) layer into the thermosphere (up to 170 km) has recently been observed at low and high latitudes using a Na lidar. However, the geophysical mechanisms and implications of its formation are currently unknown. In this study, we conduct an advanced two‐dimensional numerical simulation of the Na and Na+ variations in the E and F regions at low latitudes. The numerical simulations are used to investigate the contributions of the electromagnetic force, neutral wind, diffusion, and gravity. The simulations lead to three major findings. First, Na+ in the subtropical region of the geomagnetic equator …


Multilayer Observations And Modeling Of Thunderstorm-Generated Gravity Waves Over The Midwestern United States, C. J. Heale, J. B. Snively, A. N. Bhatt, L. Hoffmann, C. C. Stephan Dec 2019

Multilayer Observations And Modeling Of Thunderstorm-Generated Gravity Waves Over The Midwestern United States, C. J. Heale, J. B. Snively, A. N. Bhatt, L. Hoffmann, C. C. Stephan

Publications

We present multilayer observations and numerical simulations of gravity waves (GWs) generated by a series of Mesoscale Convective Systems over the midwestern United States. Strong semiconcentric GWs were observed and modeled, which couple from their tropospheric sources to the thermosphere, displaying strong nonlinearity indicated by instability, breaking, and formation of turbulent vortices. GWs in the stratosphere display a large range of horizontal scales from 34–400 km; however, the smaller wavelength waves break rapidly in the mesosphere and lower thermosphere. Larger-scale (≥150 km) waves dominate in the thermosphere and display northwestward propagation at 200–300 km altitude, opposing the mean winds. Despite …


Fuel Shortages During Hurricanes: Epidemiological Modeling And Optimal Control, Sabique Ul Islam Dec 2019

Fuel Shortages During Hurricanes: Epidemiological Modeling And Optimal Control, Sabique Ul Islam

Doctoral Dissertations and Master's Theses

Hurricanes are powerful agents of destruction with significant socioeconomic impacts. A persistent problem due to the large-scale evacuations during hurricanes in the southeastern United States is the fuel shortages during the evacuation. Fuel shortages often lead to stranded vehicles and exacerbate the evacuation efforts. Computational models can aid in emergency preparedness and help mitigate the impacts of hurricanes. In this thesis, the hurricane fuel shortages are modeled using the Susceptible-Infected-Recovered (SIR) epidemic model. Crowd-sourced data corresponding to Hurricane Irma and Florence are utilized to parametrize the model. An estimation technique based on Unscented Kalman filter (UKF) is employed to evaluate …


How Airport Construction Will Evolve With The Increased Effects Of Climate Change, Xavier M. Ashley Nov 2019

How Airport Construction Will Evolve With The Increased Effects Of Climate Change, Xavier M. Ashley

Beyond: Undergraduate Research Journal

This report addressed the effects rising global temperatures resulting from climate change have had on flight operations in their entirety. The research objective was to discover what methods could enhance climate adaptation in airport construction, as higher mean-surface temperatures have an increasingly negative effect on aircraft performance. The findings would primarily be of interest to the Federal Aviation Administration (FAA) Primary Office presiding over the planning and development of airports. Overall, the report provided a comprehensive analysis of global warming’s effects on aviation, including the implications of degraded aircraft performance and sea-level rise for coastal airports. Additionally, it examined comparative …


Design And Performance Of A Communications System For A Low-Cost High Altitude Balloon Platform For Troposphere And Stratosphere Research, Noemí Miguélez Gómez Nov 2019

Design And Performance Of A Communications System For A Low-Cost High Altitude Balloon Platform For Troposphere And Stratosphere Research, Noemí Miguélez Gómez

Doctoral Dissertations and Master's Theses

AFOSR Multidisciplinary University Research Initiative (MURI), "Integrated Measurement and Modeling Characterization of Stratospheric Turbulence", is a 5-year effort to resolve significant operational issues concerning hypersonic vehicle aerothermodynamics, boundary layer stability, and aero-optical propagation. In situ turbulence measurements along with modeling will quantify spatiotemporal statistics and the dependence of stratospheric turbulence on underlying meteorology to a degree not previously possible. Data from high altitude balloons sampling up to kHz is required to characterize turbulence to the inner-scale, or smaller, over paltitudes from 20 km to 35+ km.

This thesis presents the development of a standard balloon bus, based on reliable COTS …


Comparison Between Fluid Simulation With Test Particles And 1 Hybrid Simulation For The Kelvin-Helmholtz Instability, Xuanye Ma, Katariina Nykyri, Brandon L. Burkholder, Rachel C. Rice, Peter A. Delamere, Bishwa Neupane Aug 2019

Comparison Between Fluid Simulation With Test Particles And 1 Hybrid Simulation For The Kelvin-Helmholtz Instability, Xuanye Ma, Katariina Nykyri, Brandon L. Burkholder, Rachel C. Rice, Peter A. Delamere, Bishwa Neupane

Publications

A quantitative investigation of plasma transport rate via the Kelvin‐Helmholtz (KH) instability can improve our understanding of solar‐wind‐magnetosphere coupling processes. Simulation studies provide a broad range of transport rates by using different measurements based on different initial conditions and under different plasma descriptions, which makes cross literature comparison difficult. In this study, the KH instability under similar initial and boundary conditions (i.e., applicable to the Earth's magnetopause environment) is simulated by Hall magnetohydrodynamics with test particles and hybrid simulations. Both simulations give similar particle mixing rates. However, plasma is mainly transported through a few big magnetic islands caused by KH‐driven …


Non-Linear Magnetosphere-Ionosphere Interactions At High Latitudes, Beket Tulegenov Aug 2019

Non-Linear Magnetosphere-Ionosphere Interactions At High Latitudes, Beket Tulegenov

Doctoral Dissertations and Master's Theses

Non-linear, 3D electromagnetic coupling between the ionosphere and magnetosphere is investigated in this dissertation. The study is based on a non-linear, 3D, reduced magnetohydrodynamic model describing interaction between dispersive Alfven waves and the nightside high-latitude ionosphere. Results are presented from a numerical study of small-scale, intense magnetic field-aligned currents observed in the vicinity of the discrete auroral arc by the Magnetosphere-Ionosphere Coupling in the Alfven Resonator (MICA) sounding rocket launched from Poker Flat, Alaska, on 19 February 2012. The goal of the MICA project was to investigate the hypothesis that such currents can be produced inside the ionospheric Alfven resonator …


Aviation Weather Products In General Aviation : Interpretability And Usability Research Trends, Jacqueline Mcsorley, Jayde King, Beth Blickensderfer Jul 2019

Aviation Weather Products In General Aviation : Interpretability And Usability Research Trends, Jacqueline Mcsorley, Jayde King, Beth Blickensderfer

General Aviation Weather Display Interpretation

  • Introduction
  • Current Study
  • Trends
  • Summary
  • Conclusion


Parameterizing Wave‐Driven Vertical Constituent Transport In The Upper Atmosphere, Alan Z. Liu, Chester S. Gardner, Yafang Guo Jun 2019

Parameterizing Wave‐Driven Vertical Constituent Transport In The Upper Atmosphere, Alan Z. Liu, Chester S. Gardner, Yafang Guo

Publications

Dissipating waves contribute to vertical mixing of the atmosphere, alter molecular and eddy diffusion, and induce chemical transport of reactive species. These processes induce strong vertical transport of atmospheric constituents in regions where wave dissipation is significant. The effective wave diffusivity is proportional to the Stokes drift velocity imparted by the spectrum of vertically propagating waves, which is related to the vertical heat and wave energy fluxes. Because the heat flux cannot be derived from wave parameterization schemes employed in most atmospheric models, wave‐driven constituent transport has not been fully incorporated. However, we show in this paper that wave diffusivity …


Effects Of The Hall Conductivity In Ionospheric Heating Experiments, B. Tulegenov, A. V. Streltsov May 2019

Effects Of The Hall Conductivity In Ionospheric Heating Experiments, B. Tulegenov, A. V. Streltsov

Publications

We investigate the role of Hall conductivity in ionospheric heating experiments. Ionosphericheating by powerful X-mode waves changes the Hall and Pedersen conductances in theEandDregions,which lead to the generation of ultra-low frequency (ULF)/extremely-low frequency/very low frequencywaves, when the electric field exists in the ionosphere. The importance of the Hall currents in themagnetosphere-ionosphere interactions, carried by ULF waves and field-aligned currents, has beenconsistently overlooked in studies devoted tothe active experiments. Simulations of the three-dimensionaltwo-fluid magnetohydrodynamic (MHD) model, presented in this paper, demonstrate that the Hallconductivity changes (1) the growth rate and the amplitude of ULF waves generated by the heating and (2)the …


Exploring Perceived Usability And Interpretability Of Aviation Weather Products Among Ga Pilots, Jackie Mcsorley, Jayde King, Beth Blickensderfer May 2019

Exploring Perceived Usability And Interpretability Of Aviation Weather Products Among Ga Pilots, Jackie Mcsorley, Jayde King, Beth Blickensderfer

General Aviation Weather Display Interpretation

  • Introduction
  • Results
  • Discussion
  • Current Investigations


On The Long Lasting “C‐Type” Structures In The Sodium Lidargram: The Lifetime Of Kelvin‐Helmholtz Billows In The Mesosphere And Lower Thermosphere Region, S. Mondal, S. Sarkhel, Jay Agarwal, D. Chakrabarty, R. Sekar, Tao Yuan, Alan Z. Liu, Et Al. Apr 2019

On The Long Lasting “C‐Type” Structures In The Sodium Lidargram: The Lifetime Of Kelvin‐Helmholtz Billows In The Mesosphere And Lower Thermosphere Region, S. Mondal, S. Sarkhel, Jay Agarwal, D. Chakrabarty, R. Sekar, Tao Yuan, Alan Z. Liu, Et Al.

Publications

In order to understand the characteristics of long‐lasting “C‐type” structure in the Sodium (Na) lidargram, six cases from different observational locations have been analyzed. The Na lidargram, collected from low‐, middle‐, and high‐latitude sites, show long lifetime of the C‐type structures which is believed to be the manifestation of Kelvin‐Helmholtz (KH) billows in the Mesosphere and Lower Thermosphere (MLT) region. In order to explore the characteristics of the long‐lasting C‐type structures, the altitude profile of square of Brunt‐Väisälä frequency in the MLT region has been derived using the temperature profile collected from the Na lidar instruments and the SABER instrument …


Induced Magnetic Dipole On Jupiter’S Moon Europa, Luke Francis, Michele Zanolin Apr 2019

Induced Magnetic Dipole On Jupiter’S Moon Europa, Luke Francis, Michele Zanolin

Student Works

Physics can have some of the most unique and extraordinary applications of basic principles applied on a larger scale. This paper will explore the properties of induced magnetic dipoles and will examine this phenomenon directly from Jupiter's moon, Europa. These properties will be used to determine if there is liquid water beneath its icy surface and how this conclusion was verified. This will be accomplished using the concepts of magnetic dipoles and induced currents. Recent missions have also revealed estimates of the depth of Europa's subsurface ocean. There have been many measurements taken of Europa's magnetic field, and they are …


Artificial Aurora Produced By Haarp, B. Tulegenov, A. V. Streltsov, E. Kendall, M. Mccarrick, I. Galkin Apr 2019

Artificial Aurora Produced By Haarp, B. Tulegenov, A. V. Streltsov, E. Kendall, M. Mccarrick, I. Galkin

Publications

We present results from the ionospheric heating experiment conducted at the HighFrequency Active Auroral Research Program (HAARP) facility, Alaska, on 12 March 2013. During theexperiment, HAARP transmitted in the direction of the magnetic zenith X-mode 4.57-MHz wave. Thetransmitted power was modulated with the frequency of 0.9 mHz, and it was pointed on a 20-km spot at thealtitude of 120 km. The heating (1) generates disturbances in the magnetic field detected with the fluxgatemagnetometer on the ground and (2) produces bright luminous spots in the ionosphere, observed with theHAARP telescope. Numerical simulations of the 3-D reduced magnetohydrodynamic (MHD) model revealthat these …


Gravity Wave Ducting Observed In The Mesosphere Over Jicamarca, Peru, Gerald A. Lehmacher, Christopher J. Heale, Jonathan B. Snively, Erhan Kudeki, Pablo M. Reyes, Kiwook Lee Apr 2019

Gravity Wave Ducting Observed In The Mesosphere Over Jicamarca, Peru, Gerald A. Lehmacher, Christopher J. Heale, Jonathan B. Snively, Erhan Kudeki, Pablo M. Reyes, Kiwook Lee

Publications

Short-period gravity waves are ubiquitous in the mesosphere, but the vertical structures of their perturbations are difficult to observe. The Jicamarca 50-MHz very high frequency radar allows observations of winds and turbulent scatter with high temporal and vertical resolution. We present a case of a quasi-monochromatic gravity wave with period 520 (±40) s that is likely ducted below a southward wind jet between 68 and 74 km. Above this layer of evanescence, a northward wind enables it to emerge into a more stable layer, where it is refracted to a short vertical wavelength of 2.2 (±0.2) km; data show evidence …


Numerical Modeling Of The Propagation Of Infrasonic Acoustic Waves Through The Turbulent Field Generated By The Breaking Of Mountain Gravity Waves, Michael P. Hickey, Jonathan Snively, C Bailly, J. L. Garrison Apr 2019

Numerical Modeling Of The Propagation Of Infrasonic Acoustic Waves Through The Turbulent Field Generated By The Breaking Of Mountain Gravity Waves, Michael P. Hickey, Jonathan Snively, C Bailly, J. L. Garrison

Publications

The nonlinear propagation of low-frequency acoustic waves through the turbulent fluctuations induced by breaking mountain gravity waves is investigated via 2-D numerical simulations of the Navier-Stokes equations, to understand the effects of atmospheric dynamics on ground-based infrasound measurements. Emphasis is placed on acoustic signals of frequency around 0.1 Hz, traveling through tens-of-kilometers-scale gravity waves and subkilometer-scale turbulence. The sensitivity of the infrasonic phases to small-scale fluctuations is found to depend on the altitudes through which they are refracted toward the Earth. For the considered cases, the dynamics in the stratosphere impact the refracting acoustic waves to a greater extent than …


Comparison Of Terrain Effects In Divergent Versus Non-Divergent Barotropic Models, Tyler E. Green, Thomas A. Guinn Apr 2019

Comparison Of Terrain Effects In Divergent Versus Non-Divergent Barotropic Models, Tyler E. Green, Thomas A. Guinn

Beyond: Undergraduate Research Journal

The effects of including terrain in divergent and non-divergent, single-level barotropic models are examined in detail using a global spectral model. The non-divergent model solves the barotropic vorticity equation, while the divergent model solves the shallow water equations. In both models, the impact of terrain is evaluated by examining the evolution of the predicted heights of a pressure surface. Four simulations with initially zonal flow were run for each model using a two-dimensional Gaussian mountain shape for terrain, with two different mean fluid depths of 5,000 m and 7,500 m, and two different peak mountain heights of 2,000 m and …


Planar Ion Probe For Low-Latitude Ionosphere/Thermosphere Enhancements In Density Cubesat Mission, Liam Owen Gunter Apr 2019

Planar Ion Probe For Low-Latitude Ionosphere/Thermosphere Enhancements In Density Cubesat Mission, Liam Owen Gunter

Doctoral Dissertations and Master's Theses

One of the crucial measurements for characterizing any space weather event is absolute plasma density and plasma density fluctuations, both spatially and temporally. Langmuir probes are the oldest and most proven instruments for these in-situ measurements. This thesis enumerates the development of a miniaturized low-noise Langmuir probe intended for a dual CubeSat mission to study equatorial temperature and wind anomaly in the Earth’s ionosphere.

The Langmuir probe instrument developed is of a planar geometry and fix biased in the ion saturation region, i.e. negative w.r.t. spacecraft chassis. Operating the Langmuir probe in the ion saturation region avoids excessive spacecraft charging …