Physics Commons^™

Changes In Thermospheric Temperature Induced By High-Speed Solar Wind Streams, Larry Gardner, Jan Josef Sojka, Robert W. Schunk, Rod Heelis

All Physics Faculty Publications

During high-speed stream (HSS) events the solar wind speed increases, and the cross polar cap potential increases, leading to increased Joule heating at high latitudes. The heat input at high latitudes heats the polar regions, which then conducts to lower latitudes, producing global heating. The heating occurs during the risetime of the cross polar cap potential and throughout the period of high cross polar cap potential as seen in our simulation. These simulations are performed using the Utah State University global thermosphere model driven by Joule heating rates that are consistent with electric fields observed by DMSP-15 observations of HSS …

First Temperature Observations With The Usu Very Large Rayleigh Lidar: An Examination Of Mesopause Temperatures, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham, Lance W. Petersen, Matthew T. Emerick

Posters

As the impetus for extended observational measurements throughout the middle atmosphere has increased1 , the limits of previous instrumentation need to be pushed. The Rayleigh lidar group at the Atmospheric Lidar Observatory (ALO) at Utah State University has pushed such limits on existing Rayleigh scatter lidar technology and, through major upgrades to the previous lidar system, has been able to gather temperature measurements in the upper mesosphere and lower thermosphere from approximately 70P109 km. A data campaign with the new system was conducted around the annual temperature minimum, centered on late June 2012, in this region. The temperatures from this …

Multiple Peaks In Saber Mesospheric Oh Emission Altitude Profiles, Jordan Rozum, Gene A. Ware, Doran J. Baker, Martin G. Wlynczak, James M. Russell

Browse All Undergraduate research

No abstract provided.

Defect-Driven Dynamic Model Of Electrostatic Discharge And Endurance Time Measurements Of Polymeric Spacecraft Materials, Charles Sim, Alec Sim, Jr Dennison, Matthew Stormo

Posters

Charge buildup on insulating materials in the space environment can produce long exposure to electric fields, which can lead to Electrostatic Discharge (ESD). Charge buildup is the leading cause of spacecraft failure due to space environment interactions. ESD can be thought of as the point at which the buildup of charge in localized defects, found in polymeric insulating materials, leads to a catastrophic change in electrical conductivity, which can cause the materials to structurally breakdown. Defects produced by radiation, or prolonged exposure to electric fields, significantly alter the endurance time, the time it takes to produce enough defects to generate …

Defect-Driven Dynamic Model Of Electrostatic Discharge And Endurance Time Measurements Of Polymeric Spacecraft Materials, Alec Sim, John R. Dennison, Matthew Stormo

All Physics Faculty Presentations

Charge buildup on insulating materials in the space environment can produce long exposure to electric fields, which can lead to Electrostatic Discharge (ESD). Charge buildup is the leading cause of spacecraft failure due to space environment interactions. ESD can be thought of as the point at which the buildup of charge in localized defects, found in polymeric insulating materials, leads to a catastrophic change in electrical conductivity, which can cause the materials to structurally breakdown. Defects produced by radiation, or prolonged exposure to electric fields, significantly alter the endurance time, the time it takes to produce enough defects to generate …

Viscous And Induced Current Heating In Plasma Focus Plasmoids, Ahmad Talaei, Eric Lerner

Graduate Student Presentations

Recently, Abolhasani et al, proposed that the high ion energies observed in plasmoids formed in the plasma focus could be explained by viscous heating. We here elaborate this proposal, demonstrating that during plasmoid formation, ion motion along magnetic field lines can be rapidly converted, at least in part, to thermal energy through viscous diffusion. This effect is strongly enhanced by higher-z ions. We compare the theoretical predictions with the recent observation by Lerner et al, of trapped ion energies of 160 keV. In addition, we propose a second source of heating. The mildly relativistic electron beam emitted by the plasmoid, …

Space Impact Ejecta Model Of Micrometeoroid Collision On Misse-6, Kelby T. Peterson, Jr Dennison

Presentations

The Utah State University SUSpECS project was a unique student experiment that allowed for pre- and post-flight analysis of various materials used in space-component design. Approximately 180 material samples were flown on MISSE-6 and spent 18 months suspended off the side of the International Space Station, which were returned in pristine condition. This presentation focuses on the most intriguing sample, a thin film of polyethylene terephthalate (PET) Mylar^TM coated with Vapor Deposited Aluminum (VDA). Samples that were part of the Materials International Space Station Experiment (MISSE) experienced diverse effects whilst exposed to the space environment. This sample in particular, …

Space Impact Ejecta Model Of Micrometeoroid Collision On Misse-6, Kelby T. Peterson, Jr Dennison

Presentations

No abstract provided.

High-Frequency Pulsed-Electro-Acoustic (Pea) Measurements For Mapping Charge Distribution, Kristina Sorensen, Lee H. Pearson, Jr Dennison, Timothy E. Doyle, Kent D. Hartley

Browse All Undergraduate research

No abstract provided.

Histological Analysis Of Biological Tissues Using High-Frequency Ultrasound, Kristina Sorensen, Tim Doyle, B. D. Borget, M. Cervantes, H, A. Chappell, B. J. Curtis, M. A. Grover, J. E. Roring, J. E. Stiles, L. A. Thompson

Browse All Undergraduate research

No abstract provided.

Modeling Spiral Galaxy Luminosity Profiles, Jordan Rozum, Matt Garlock, Shane L. Larson, Bradley W. Carroll

Browse All Undergraduate research

The distribution of spiral and bar galaxy inclination an- gles is expected to be uniform. However, analysis of sev- eral major galaxy catalogs shows this is not the case; galaxies oriented near edge-on are significantly more common in these catalogs. In an attempt to explain this discrepancy, we have developed a galaxy simulation code to compute the appearance of a spiral type galaxy as a function of its morphological parameters. We examine the dependence of observed brightness upon inclination angle by using smooth luminous mass density and in- terstellar medium (ISM) density distributions. The lu- minous mass component is integrated …

Muon Contribution To Cathodoluminescence Tests?, Justin Dekany, Allen Anderson, Jr Dennison

Posters

Tests of composites incorporating highly disordered insulating materials that were bombarded with low-flux keV electron beams exhibited three distinct forms of light emission: short-duration (<<1 s), high intensity luminous electrostatic discharges between the insulator and ground--termed “arcs”; intermediate-duration (10-100 s), intense surface emissions—termed “flares”; and lower intensity, continuous surface cathodoluminescent “glow”. During long-duration experiments at temperatures <150 K, relatively intense flare events occurred at rates of ~2 per min. Rapid increase in photon emission and electron displacement current were observed, with long exponential decay times >1 min. We propose that the source of the flares is the interactions of high energy muons—of cosmic ray origin—with the highly-charged insulating components of the composite materials, which trigger avalanche electrostatic discharge and subsequent recharging along with concomitant light emission. We review evidence from the insulator conductivity at low temperatures, the rates and magnitude of surface charging, the flare frequency, and the magnitude and time-dependence of currents and light emission with regard to this …

Muon Contribution To Cathodoluminescence Tests?, Justin Dekany, Allen Andersen, Jr Dennison

Presentations

Tests of composites incorporating highly disordered insulating materials that were bombarded with low-flux keV electron beams exhibited three distinct forms of light emission: short-duration (<<1 s), high intensity luminous electrostatic discharges between the insulator and ground--termed “arcs”; intermediate-duration (10-100 s), intense surface emissions—termed “flares”; and lower intensity, continuous surface cathodoluminescent “glow”. During long-duration experiments at temperatures <150 K, relatively intense flare events occurred at rates of ~2 per min. Rapid increase in photon emission and electron displacement current were observed, with long exponential decay times >1 min. We propose that the source of the flares is the interactions of high energy muons—of cosmic ray origin—with the highly-charged insulating components of the composite materials, which trigger avalanche electrostatic discharge and subsequent recharging along with concomitant light emission. We review evidence from the insulator conductivity at low temperatures, the rates and magnitude of surface charging, the flare frequency, and the magnitude and time-dependence of currents and light emission with regard to this …

Extending The Band Model Of Disordered Sio2 Through Cathodoluminescence Studies, Amberly Evans, Gregory Wilson, Jr Dennison, Justin Dekany

Presentations

Optical coatings of disordered thin film SiO₂/SiO_x dielectric samples on reflective metal substrates exhibited electron-induced luminescence (cathodoluminescence) under electron beam irradiation in an ultrahigh vacuum chamber at the USU facilities,. These experiments provided measurements of the absolute radiance and emission spectra as functions of incident electron energy, flux and power over a range of sample temperatures (300 K to 40 K). Early results from these experiments have led to a preliminary model of the band structure of highly disordered trapped states within the band gap of SiO₂. We now extend this model to further describe …

Power And Charge Deposition In Multilayer Dielectrics From Monoenergetic Electron Bombardment, Gregory Wilson, Amberly Evans, Justin Dekany, Jr Dennison

Presentations

Power and charge deposition in multilayer dielectrics from electron bombardment is dependent upon the flux and electron range of the electron beam, where the range,--a lso known as the penetration depth—is dependent upon the incident beam energy. Using the Continuous Slow Down Approximation (CSDA), a composite analytical formula has been developed to relate the electron range to the dose rate and subsequently to the deposited power in each subsequent layer. Based on the constituent layer geometry and material , the deposited charge can also be inferred. To validate these models two separate experiments were conducted, one based on the net …

High-Frequency Pulsed-Electro-Acoustic (Pea) Measurements For Mapping Charge Distribution, Kristina Sorensen, Lee H. Pearson, Jr Dennison, Timothy E. Doyle, Kent D. Hartley

Presentations

No abstract provided.

Power And Charge Deposition In Multilayer Dielectrics Undergoing Monoenergetic Electron Bombardment, Gregory Wilson, Jr Dennison, Amberly Evans, Justin Dekany

Presentations

No abstract provided.

Short Period Gravity Waves In The Arctic Atmosphere Over Alaska, Michael Negale, Kim Nielsen, Michael J. Taylor, Britta Irving, Richard Collins

Physics Student Research

The propagation nature and sources of short-period gravity waves have been studied extensively at low and mid-latitudes, while their extent and nature at the polar regions are less known. During the last decade, observations from select sites on the Antarctic continent have revealed a significant presence of these waves over the southern Polar Region as well as shown unexpected dynamical behavior. In contrast, observations over the Arctic region are few and the dynamical behavior is unknown. A recent project was initiated in January 2011 to investigate the presence and dynamics of these waves over interior Alaska. This site provides an …

Space Impact Ejecta Model Of Micrometeoroid Collision On Misse-6, Kelby Peterson, Jr Dennison

Presentations

No abstract provided.

Power And Charge Deposition In Multilayer Dielectrics Undergoing Monoenergetic Electron Bombardment, Gregory Wilson, Jr Dennison, Amberly Evans Jensen, Justin Dekany

Presentations

No abstract provided.

Electrostatic Discharge Properties Of Fused Silica Coatings, Allen Andersen, Charles Sim, Jr Dennison

Graduate Student Posters

The electric field value at which electrostatic discharge (ESD) occurs was studied for thin coatings of fused silica (highly disordered SiO2/SiOx) on conductive substrates, such as those encountered as optical coatings and in Si microfabrication. The electrostatic breakdown field was determined using an increasing voltage, while monitoring the leakage current. A simple parallel-plate capacitor geometry was used, under medium vacuum and at temperatures down to ~150 K using a liquid N2 reservoir. The breakdown field, pre-breakdown arcing and I-V curves for fused silica samples are compared for ~60 nm and ~80 μm thick, room and low temperature, and untreated and …

Velocity Plateaus In Traveling-Wave Electrophoresis, R. Correll, Boyd F. Edwards

All Physics Faculty Publications

One-dimensional models are used to study traveling-wave electrophoresis, a tunable method for separating charged analytes. A traveling-electrode model reveals the mechanism for longitudinal oscillations. A stationary-electrode model explains the origin of mode-locked plateaus in the average velocity, predicts devil's staircases with nested Farey sequences, and reduces to a continuum sinusoidal model in the high electrode-density limit. © 2012 American Physical Society.

Histological Analysis Of Biological Tissues Using High-Frequency Ultrasound, Kristina Sorensen, Timothy Doyle, Brett D. Boret, Monica Cervantes, J. Andrew Chappell, Bradley J. Curtis, Matthew A. Grover, Janeese E. Stiles, Laurel A. Thompson

Browse All Undergraduate research

No abstract provided.

Electron Beam Induced Luminescence Of Sio2 Optical Coatings, John R. Dennison, Amberly Evans, Gregory Wilson, Charles W. Bowers, Robert Meloy

All Physics Faculty Presentations

Optical coatings of disordered thin film SiO2/SiOx dielectric samples on reflective metal substrates exhibited cathodoluminescence under electron beam irradiation. Measurements of the absolute radiance and emission spectra as functions of incident electron energy, flux and power over a range of sample temperatures are reported. Radiance reached a saturation plateau at high incident electron power. Well below saturation radiance scaled with deposited power, that is linearly with incident power for lower-energy non-penetrating electrons and decreasing with increasing energy for penetrating radiation. Four bands were observed in spectral measurements from 300 nm to 1000 nm. Changes in peak intensity and shifts in …

How To Create A Two-Component Spinor, Charles G. Torre

How to... in 10 minutes or less

Let (M, g) be a spacetime, i.e., a 4-dimensional manifold M and Lorentz signature metric g. The key ingredients needed for constructing spinor fields on the spacetime are: a complex vector bundle E -> M ; an orthonormal frame on TM ; and a solder form relating sections of E to sections of TM (and tensor products thereof). We show how to create a two-component spinor field on the Schwarzschild spacetime using the DifferentialGeometry package in Maple. PDF and Maple worksheets can be downloaded from the links below.

Electron Induced Charging And Arcing Of Multilayered Dielectric Materials, John R. Dennison, Gregory Wilson, Amberly Evans

All Physics Faculty Presentations

Measurements of the charge distribution in electron-bombarded, thin-film, multilayered dielectric samples showed that charging of multilayered materials evolves with time and is highly dependent on incident energy; this is driven by electron penetration depth, electron emission and material conductivity. Based on the net surface potential’s dependence on beam current, electron range, electron emission and conductivity, measurements of the surface potential, displacement current and beam energy allow the charge distribution to be inferred. To take these measurements, a thin-film disordered SiO2 structure with a conductive middle layer was charged using 200 eV and 5 keV electron beams with regular 15 s …

Cedar Electrodynamics Thermosphere Ionosphere (Eti) Challenge For Systematic Assessment Of Ionosphere/Thermosphere Models: Electron Density, Neutral Density, Nmf2, And Hmf2 Using Space Based Observations, J. S. Shim, M. Kuznetsova, L. Rastätter, D. Bilitza, L. Butala, M. Emery, B. Foster, T. J. Fuller-Rowell, J. Huba, A. J. Mannucci, X. Pi, A. Ridley, Ludger Scherliess, Jan Josef Sojka, P. Stephens, D. C. Thompson, D. Weimer, Lie Zhu, E. Sutton

All Physics Faculty Publications

In an effort to quantitatively assess the current capabilities of Ionosphere/Thermosphere (IT) models, an IT model validation study using metrics was performed. This study is a main part of the CEDAR Electrodynamics Thermosphere Ionosphere (ETI) Challenge, which was initiated at the CEDAR workshop in 2009 to better comprehend strengths and weaknesses of models in predicting the IT system, and to trace improvements in ionospheric/thermospheric specification and forecast. For the challenge, two strong geomagnetic storms, four moderate storms, and three quiet time intervals were selected. For the selected events, we obtained four scores (i.e., RMS error, prediction efficiency, ratio of the …

Electron Beam Induced Luminescence Of Sio2 Optical Coatings, John R. Dennison, Amberly Evans, Gregory Wilson, Charles W. Bowers, Robert Meloy

All Physics Faculty Publications

Optical coatings of disordered thin film SiO2/SiOx dielectric samples on reflective metal substrates exhibited cathodoluminescence under electron beam irradiation. Measurements of the absolute radiance and emission spectra as functions of incident electron energy, flux and power over a range of sample temperatures are reported. Radiance reached a saturation plateau at high incident electron power. Well below saturation radiance scaled with deposited power, that is linearly with incident power for lower-energy non-penetrating electrons and decreasing with increasing energy for penetrating radiation. Four bands were observed in spectral measurements from 300 nm to 1000 nm. Changes in peak intensity and shifts in …

An Embedded-Atom-Method Model For Alkali-Metal Vibrations, D. Mark Riffe, Richard B. Wilson

All Physics Faculty Publications

We present an embedded-atom-method (EAM) model that accurately describes vibrational dynamics in the alkali metals Li, Na, K, Rb, and Cs. Bulk dispersion curves, frequency-moment Debye temperatures, and temperature-dependent entropy Debye temperatures are all in excellent agreement with experimental results. The model is also well suited for studying surface vibrational dynamics in these materials, as illustrated by calculations for the Na(110) surface.

A Homogeneous Solution Of The Einstein-Maxwell Equations, Charles G. Torre

Research Vignettes

We exhibit and analyze a homogeneous spacetime whose source is a pure radiation electromagnetic field [1]. It was previously believed that this spacetime is the sole example of a homogeneous pure radiation solution of the Einstein equations which admits no electromagnetic field (see [2] and references therein). Here we correct this error in the literature by explicitly displaying the electromagnetic source. This result implies that all homogeneous pure radiation spacetimes satisfy the Einstein-Maxwell equations.

PDF and Maple worksheets can be downloaded from the links below.