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Articles 1 - 30 of 35
Full-Text Articles in Physics
Resistivity Of Kapton E At Intermediate Time Scales Following High-Energy Electron Irradiation, S Hart, Jr Dennison, J Brunson, Jodie C. Gillespie
Resistivity Of Kapton E At Intermediate Time Scales Following High-Energy Electron Irradiation, S Hart, Jr Dennison, J Brunson, Jodie C. Gillespie
Presentations
No abstract provided.
Investigating The Photoyield Of Spacecraft Materials, Jennifer Albretsen, Ryan Hoffmann, Jr Dennison
Investigating The Photoyield Of Spacecraft Materials, Jennifer Albretsen, Ryan Hoffmann, Jr Dennison
Presentations
No abstract provided.
Equatorial Ionospheric Electric Fields During The November 2004 Magnetic Storm, Bela G. Fejer, J. W. Jensen, T. Kikuchi, M. A. Abdu, J. L. Chau
Equatorial Ionospheric Electric Fields During The November 2004 Magnetic Storm, Bela G. Fejer, J. W. Jensen, T. Kikuchi, M. A. Abdu, J. L. Chau
Bela G. Fejer
[1] We use radar measurements from the Jicamarca Radio Observatory, magnetometer observations from the Pacific sector and ionosonde data from Brazil to study equatorial ionospheric electric fields during the November 2004 geomagnetic storm. Our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour (indicative of undershielding and overshielding prompt penetration electric fields) in the Pacific equatorial region during the November 7 main phase of the storm, when the southward IMF, the solar wind and reconnection electric fields, and the polar cap potential drops had very large and nearly steady values. This result …
Coherent Excitation Of The Optic Phonon In Si: Transiently Stimulated Raman Scattering With Afinite-Lifetime Electronic Excitation, D. Mark Riffe, A. J. Sabbah
Coherent Excitation Of The Optic Phonon In Si: Transiently Stimulated Raman Scattering With Afinite-Lifetime Electronic Excitation, D. Mark Riffe, A. J. Sabbah
All Physics Faculty Publications
Using 28-fs, 800-nm laser pulses we have coherently excited and subsequently probed, with time-dependent reflectivity, the Si zone-center optic phonon. The phonon-induced reflectivity change ΔR∕R is well described by the response of an underdamped oscillator: ΔR∕R∝ exp(−t∕τph) cos(2πt∕Tph+ϕ). The measured phase ϕ indicates that transiently stimulated Raman scattering (TSRS) is responsible for the coherent-phonon generation: our results are in good agreement with a recent theory of TSRS for opaque materials [ T. E. Stevens et al. Phys. Rev. B 65 144304 (2002)] when we extend the theory to include the finite lifetime of the excited charge …
Characteristics Of Short-Period Wavelike Features Near 87 Km Altitude From Airglow And Lidar Observations Over Maui, J. H. Hecht, A. Z. Liu, R. L. Walterscheid, S. J. Franke, R. J. Rudy, Michael J. Taylor, Pierre-Dominique Pautet
Characteristics Of Short-Period Wavelike Features Near 87 Km Altitude From Airglow And Lidar Observations Over Maui, J. H. Hecht, A. Z. Liu, R. L. Walterscheid, S. J. Franke, R. J. Rudy, Michael J. Taylor, Pierre-Dominique Pautet
All Physics Faculty Publications
Small-scale (less than 15 km horizontal wavelength) wavelike structures known as ripples are a common occurrence in OH airglow images. Recent case studies attribute their origin to the presence of either convective or dynamical instabilities. However, little is known about their frequency of occurrence and period. The Maui-MALT Observatory, located at Mt. Haleakala, is instrumented with a Na wind/temperature lidar, which allows the determination of whether the atmosphere is dynamically or convectively unstable, and a fast OH airglow camera which takes images every 3 s with a sensitivity high enough to see the ripples. This study reports on 2 months …
Gravitational Wave Bursts From The Galactic Massive Black Hole, Clovis Hopman, Marc Freitag, Shane L. Larson
Gravitational Wave Bursts From The Galactic Massive Black Hole, Clovis Hopman, Marc Freitag, Shane L. Larson
All Physics Faculty Publications
The Galactic massive black hole (MBH), with a mass of M•= 3.6 × 106 M⊙, is the closest known MBH, at a distance of only 8 kpc. The proximity of this MBH makes it possible to observe gravitational waves (GWs) from stars with periapse in the observational frequency window of the Laser Interferometer Space Antenna (LISA). This is possible even if the orbit of the star is very eccentric, so that the orbital frequency is many orders of magnitude below the LISA frequency window, as suggested by Rubbo, Holley-Bockelmann & Finn (2006). …
The Effects Of Large Data Gaps On Estimating Linear Trend In Autocorrelated Data, Troy A. Wynn, Vincent B. Wickwar
The Effects Of Large Data Gaps On Estimating Linear Trend In Autocorrelated Data, Troy A. Wynn, Vincent B. Wickwar
Conference publications
It is well known that atmospheric data is autocorrelated. Techniques for fitting a model to autocorrelated data without data gaps are well known. However in cases where large data gaps exist the analysis ins more challenging. By large data gaps we mean 16-24% of the possible data present. This paper explores the challenges of estimating the correlation coefficient in an autocorrelated data set containing large data gaps and suggests ways to accurately estimate the autocorrelation and linear trend in a signal when such cases arise.
The Effect Of Voltage Ramp Rate On Dielectric Breakdown Of Thin Film Polymers, Anthony Thomas
The Effect Of Voltage Ramp Rate On Dielectric Breakdown Of Thin Film Polymers, Anthony Thomas
Senior Theses and Projects
Electrical insulators are used in many applications in industry, education and the home environment. They work by keeping electricity contained. They are not however perfect and under stress can become ineffective. Every insulator has a dielectric strength, a measurement of how much electrical stress it can withstand. If the material is stressed beyond that strength the material will breakdown. Electrostatic breakdown is defined as “the abrupt irreversible drop in resistivity at high fields, often accompanied by destruction of the material” (See Fig. 1) [McGraw-Hill]. The point at which the material breaks down is called the electrostatic discharge breakdown voltage, or …
Rayleigh-Scatter Lidar Observations At Usu's Atmospheric Lidar Observatory (Logan,Ut) - Temperature Climatology, Temperature Comparisons With Msis, And Noctilucent Clouds, Joshua P. Herron
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The Earth's atmosphere is typically characterized by its temperature structure, which naturally divides the atmosphere into several discrete regions. They are in order of increasing altitude the troposphere, stratosphere, mesosphere, and thermosphere. The first layer and a large portion of the second layer of the Earth's atmosphere are routinely measured via weather balloons that are launched twice daily around the globe. Satellites and their development have motivated the study of the thermosphere. It is the middle region of the Earth atmosphere, which is mainly composed of the mesosphere that lacks routine in situ measurements. Routine observations are therefore carried out …
Climatology Of Middle And Low-Latitude F-Region Plasma Drifts From Satellite Measurements, John W. Jensen
Climatology Of Middle And Low-Latitude F-Region Plasma Drifts From Satellite Measurements, John W. Jensen
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
We used ion drift observations from the DE-2 satellite to study for the first time the longitudinal variations of middle and low latitude F-region zonal plasma drifts during quiet and disturbed conditions. The daytime quiet-time drifts do not change much with longitude. In the dusk-premidnight period, the equinoctial middle latitude westward drifts are smallest in the European sector, and the low latitude eastward drifts are largest in the American-Pacific sector. The longitudinal variations of the late night-early morning drifts during June and December solstice are anti-correlated. During geomagnetically active time s, there are large westward perturbation drifts in the late …
Electric Field Induced Hopping Conductivity And Polarization In Hytrel, Steve Hart
Electric Field Induced Hopping Conductivity And Polarization In Hytrel, Steve Hart
Senior Theses and Projects
The focus of my 4900 research project is centered on the conductivity of Hytrel, a complex, newly developed block co-polymer. I first began to study Hytrel during the summer of 2006, as part of the USU College of Science Mini-Grant program1. My general objective was to study the relationship between the resistivity of Hytrel and hopping conductivity. Hopping conductivity is a theory of electron transport for nonconducting solids, originally developed for amorphous semiconductors2,3. The theory will be examined in greater detail later in this document. While studying this relationship last summer, I noticed an unusual phenomenon …
Gauging Newton’S Law, James Thomas Wheeler
Gauging Newton’S Law, James Thomas Wheeler
All Physics Faculty Publications
We derive both Lagrangian and Hamiltonian mechanics as gauge theories of Newtonian mechanics. Systematic development of the distinct symmetries of dynamics and measurement suggest that gauge theory may be motivated as a reconciliation of dynamics with measurement. Applying this principle to Newton's law with the simplest measurement theory leads to Lagrangian mechanics, while use of conformal measurement theory leads to Hamiltonian mechanics.PACS Nos.: 45.20.Jj, 11.25.Hf, 45.10.–b [ABSTRACT FROM AUTHOR]
The Green Beam—Lidar Investigations Of The Mesosphere, Vincent B. Wickwar
The Green Beam—Lidar Investigations Of The Mesosphere, Vincent B. Wickwar
Presentations
No abstract provided.
Doppler Ducting Of Short-Period Waves By Mid-Latitude Tidal Wind Structure, J. B. Snively, V. P. Pasko, Michael J. Taylor, W. K. Hocking
Doppler Ducting Of Short-Period Waves By Mid-Latitude Tidal Wind Structure, J. B. Snively, V. P. Pasko, Michael J. Taylor, W. K. Hocking
All Physics Faculty Publications
Multiwavelength airglow image data depicting a short-period (4.9 min) atmospheric gravity wave characterized by a sharp leading front have been analyzed together with synoptic meteor radar wind data recorded simultaneously from Bear Lake Observatory, Utah (41.6N, 111.6W). The wind data suggest the presence of a semidiurnal tide with horizontal winds peaking at around 60 m/s along the SSE direction of motion (170 from north) of this short-period wave. It was found that the gravity wave was most probably ducted because of the Doppler shift imposed by this wind structure. A marked 180 phase shift was observed between the near-infrared OH …
On The Use Of Simultaneous Measurements Of Oh And O2 Emissions To Investigate Wave Growth And Dissipation, A. Taori, A. Guharay, Michael J. Taylor
On The Use Of Simultaneous Measurements Of Oh And O2 Emissions To Investigate Wave Growth And Dissipation, A. Taori, A. Guharay, Michael J. Taylor
All Physics Faculty Publications
Simultaneous measurements of mesospheric OH (6–2) Meinel and O2 (0–1) Atmospheric band emissions from a low-latitude station, Maui, Hawaii (20.8 N, 156.2 W) are utilized to study the wave characteristics and associated processes. Deduced temperatures show large variability in both OH and O2 data. The seasonal variability in the temperature shows a well-defined, semiannual type of oscillation, which are comparable to the ground-based rocket sounding data. The “Wave Growth Factor”, a ratio of normalized perturbation amplitude in O2 to the OH temperature variability, is estimated for principal as well as residual smaller period components of the nocturnal variability. It is …
A Very Active Sprite-Producing Storm Observed Over Argentina, J. N. Thomas, Michael J. Taylor, Pierre-Dominique Pautet, T. Berkey, N. N. Solorzano, R. H. Holzworth, M. P. Mccarthy, M. Kokorowski, F. Sao Sabbas, O. Pinto Jr., S. A. Cummer, N. Jaugey, J. Li, N. J. Schuch
A Very Active Sprite-Producing Storm Observed Over Argentina, J. N. Thomas, Michael J. Taylor, Pierre-Dominique Pautet, T. Berkey, N. N. Solorzano, R. H. Holzworth, M. P. Mccarthy, M. Kokorowski, F. Sao Sabbas, O. Pinto Jr., S. A. Cummer, N. Jaugey, J. Li, N. J. Schuch
All Physics Faculty Publications
During the night of 22–23 February 2006, more than 400 middle- atmospheric optical discharges were observed above one large thunderstorm system over northeastern Argentina. These transient luminous events (TLEs) were imaged during the Southern Brazil Sprite Campaign, the first campaign to focus on TLEs over southern Brazil, northeastern Argentina, and Uruguay. All of the TLEs were imaged from the Brazilian Southern Space Observatory (SSO) near Santa Maria, which is nearly in the center of the southernmost Brazilian state of Rio Grande do Sul. Although the fields of view of the imaging cameras were too narrow to view the entire storm, …
Investigation Of A "Wall" Wave Event, F. Li, G. R. Swenson, A. Z. Liu, Michael J. Taylor, Y. Zhao
Investigation Of A "Wall" Wave Event, F. Li, G. R. Swenson, A. Z. Liu, Michael J. Taylor, Y. Zhao
All Physics Faculty Publications
A bright airglow event was observed at Maui, Hawaii, on the night of 11–12 August 2004 with multiple instruments including a Na wind/temperature lidar, an airglow imager, and a mesospheric temperature mapper. The characteristics of this event were investigated with measurements from these instruments. Analysis showed that this event was caused by a large-amplitude, upward-propagating gravity wave with a period of about 4–5 hours and a vertical wavelength of about 20 km, i.e., a ‘‘wall’’ wave. This wall wave induced dramatic changes in temperature (60 K), airglow intensity (doubled in the OH and tripled in the O2 emissions), and Na …
Longitudinal Dependence Of Middle And Low Latitude Zonal Plasmadrifts Measured By De-2, J. Jensen, Bela Fejer
Longitudinal Dependence Of Middle And Low Latitude Zonal Plasmadrifts Measured By De-2, J. Jensen, Bela Fejer
Bela G. Fejer
We used ion drift observations from the DE-2 satellite to study for the first time the longitudinal variations of middle and low latitude F region zonal plasma drifts during quiet and disturbed conditions. The quiet-time middle latitude drifts are predominantly westward; the low latitude drifts are westward during the day and eastward at night. The daytime quiet-time drifts do not change much with longitude; the nighttime drifts have strong season dependent longitudinal variations. In the dusk-premidnight period, the equinoctial middle latitude westward drifts are smallest in the European sector and the low latitude eastward drifts are largest in the American-Pacific …
Low-Temperature Charge Transport In Ga-Acceptor Nanowires Implanted By Focused-Ion Beams, S. J. Robinson, C. L. Perkins, T. -C. Shen, J. R. Tucker, T. Schenkel, X. W. Wang, T. P. Ma
Low-Temperature Charge Transport In Ga-Acceptor Nanowires Implanted By Focused-Ion Beams, S. J. Robinson, C. L. Perkins, T. -C. Shen, J. R. Tucker, T. Schenkel, X. W. Wang, T. P. Ma
T. -C. Shen
Ga-acceptor nanowires were embedded in crystalline Si using focused-ion beams. The dc current-voltage characteristics of these wires after annealing are highly nonlinear at low temperatures. A conductance threshold of less than 50mV is observed independent of Ga+ dosage and implant beam overlap. These features suggest a Coulomb blockade transport mechanism presumably caused by a network of Ga precipitates in the substrate. This granular scenario is further supported by measurements of gated nanowires. Nanowires with metallic conductance at low temperatures could be achieved by reducing the current density of the focused-ion beams.
Electron-Induced Electron Yields Of Uncharged Insulating Materials, Ryan Carl Hoffmann, John R. Dennison, Jennifer Albretsen
Electron-Induced Electron Yields Of Uncharged Insulating Materials, Ryan Carl Hoffmann, John R. Dennison, Jennifer Albretsen
All Physics Faculty Publications
This study presents electron-induced electron yield measurements from high-resistivity, high-yield materials to validate a model for the yield of uncharged insulators. These measurements are accomplished by using a low-fluence, pulsed incident electron beam and charge neutralization to minimize charge accumulation. Our measurements show large changes in total yield curves and yield decay curves, even for incident electron fluences of/mm2. We model the evolution of the yield as charge accumulates in the material in terms of electron re-capture based on the extended Chung-Everhart model of the electron emission spectrum. This model is used to explain anomalies measured in high yield ceramics, …
Dependence Of Resistivity In Low-Density Polyethylene On Space Environment Parameters, John R. Dennison, Jerilyn Brunson
Dependence Of Resistivity In Low-Density Polyethylene On Space Environment Parameters, John R. Dennison, Jerilyn Brunson
All Physics Faculty Publications
The conductivity of high-resistivity polymer films is dependent on the magnitude of applied electric field, repeated electric field exposure, and sample temperature. A traditional constant voltage method was used, maintained under vacuum to more closely resemble the space environment. Both the strength of the applied voltage and the thickness of low-density polyethylene (LDPE) samples were varied to determine the electric field dependence of internal polarization and the leakage current most appropriate in calculating the resistivity. Repetition of same field strength measurements determined the influence of sample history and charging memory. Measuring the resistivity from cryogenic temperatures to well above the …
Low Temperature Measurements Of Resistivity In Low-Density Polyethylene, John R. Dennison, J. Brunson
Low Temperature Measurements Of Resistivity In Low-Density Polyethylene, John R. Dennison, J. Brunson
All Physics Faculty Publications
Measurements of resistivity of low density polyethylene (LDPE) have been made using the standard constant voltage method to determine the temperature dependence of resistivity. Where electrons are assumed to serve as the primary charge carriers, their mobility is believed to be dependent on their probability of hopping between trapping sites treated as potential wells. We consider our measurements of this relatively simple polymeric material using temperature-dependant models of conduction mechanisms developed for amorphous solids and semi-conductors.
The Effects Of Charging By Ultraviolet Light On Granular Lunar Simulant In A Microgravity Environment, Sydney J. Chamberlin, Troy Munro, Sarah Isert, Tracy Garin Savage
The Effects Of Charging By Ultraviolet Light On Granular Lunar Simulant In A Microgravity Environment, Sydney J. Chamberlin, Troy Munro, Sarah Isert, Tracy Garin Savage
Reports and Proposals
No abstract provided.
Triggering Threshold Spacecraft Charging With Changes In Electron Emission From Materials, John R. Dennison, R. C. Hoffmann, J. Abbott
Triggering Threshold Spacecraft Charging With Changes In Electron Emission From Materials, John R. Dennison, R. C. Hoffmann, J. Abbott
All Physics Faculty Publications
Modest changes in spacecraft charging conditions can lead to abrupt changes in the spacecraft equilibrium, from small positive potentials to large negative potentials relative to the space plasma; this phenomenon is referred to as threshold charging. It is well known that temporal changes of the space plasma environment (electron plasma temperature or density) can cause threshold charging. Threshold charging can also result from by temporal changes in the juxtaposition of the spacecraft to the environment, including spacecraft orbit, orientation, and geometry. This study focuses on the effects of possible changes in electron emission properties of representative spacecraft materials. It is …
Ionospheric Challenges Of The International Polar Year, Jan Josef Sojka, Robert W. Schunk, Tony Van Eyken, John Kelly, Craig Heinselman, Mary Mccready
Ionospheric Challenges Of The International Polar Year, Jan Josef Sojka, Robert W. Schunk, Tony Van Eyken, John Kelly, Craig Heinselman, Mary Mccready
All Physics Faculty Publications
Fifty years ago, the first International Geophysical Year (lGY) generated a huge step function increase in observations of ionospheric variability associated with the almost continuous geomagnetic activity experienced during the largest solar maximum of the past 100 years. In turn, these observations fueled more than a decade of theoretical advancement of magnetospheric-ionospheric electrodynamics and geomagnetic storm physics.
Assessing Models For Ionospheric Weather Specifications Over Australia During The 2004 Climate And Weather Of The Sun-Earth-System (Cawses) Campaign, Jan Josef Sojka, D. C. Thompson, L. Scherliess, Robert W. Schunk, T. J. Harris
Assessing Models For Ionospheric Weather Specifications Over Australia During The 2004 Climate And Weather Of The Sun-Earth-System (Cawses) Campaign, Jan Josef Sojka, D. C. Thompson, L. Scherliess, Robert W. Schunk, T. J. Harris
All Physics Faculty Publications
The Utah State University (USU) Global Assimilation of Ionospheric Measurements (GAIM) program is developing assimilation models to specify ionospheric weather. In this study the Gauss Markov Kalman Filter (GMKF) GAIM model was used. The period 20 March through 19 April 2004, which spanned the Climate and Weather of the Sun-Earth-System (CAWSES) first study period, has been extensively studied to validate the performance of the GAIM model. Although the USU-GAIM model has both regional and global capabilities and can assimilate data from a wide variety of ionospheric observations, for this study the GMKF model was run in a global mode using …
Observations Of A Noctilucent Cloud Above Logan, Utah (41.7°N, 111.8°W) In 1995, Joshua P. Herron, Vincent B. Wickwar, P J. Espy, J W. Merriwether
Observations Of A Noctilucent Cloud Above Logan, Utah (41.7°N, 111.8°W) In 1995, Joshua P. Herron, Vincent B. Wickwar, P J. Espy, J W. Merriwether
All Physics Faculty Publications
A Rayleigh-scatter lidar has been operated at the Atmospheric Lidar Observatory (ALO) on the Utah State University (USU) campus (41.7°N, 111.8°W) since August 1993. During the morning of 22 June 1995, lidar returns from a noctilucent cloud (NLC) were observed for approximately 1 hr, well away from the twilight periods when NLCs are visible. This detection of an NLC at this latitude shows that the first reported sighting, in 1999 (Wickwar et al., 2002), was not a unique occurrence. This 1995 observation differs from the 1999 one in that temperatures could be deduced. Near the 83-km NLC altitude the temperatures …
Yang-Mills Gravity In Biconformal Space, L. B. Anderson, James Thomas Wheeler
Yang-Mills Gravity In Biconformal Space, L. B. Anderson, James Thomas Wheeler
All Physics Faculty Publications
We write a gravity theory with Yang–Mills-type action using the biconformal gauging of the conformal group. We show that the resulting biconformal Yang–Mills gravity theories describe 4-dim, scale-invariant general relativity in the case of slowly changing fields. In addition, we systematically extend arbitrary 4-dim Yang–Mills theories to biconformal space, providing a new arena for studying flat-space Yang–Mills theories. By applying the biconformal extension to a 4-dim pure Yang–Mills theory with conformal symmetry, we establish a 1-1, onto mapping between a set of gravitational gauge theories and 4-dim, flat-space gauge theories.
Hopping Conductivity In Low-Density Polyethylene, Jerilyn Brunson, John R. Dennison
Hopping Conductivity In Low-Density Polyethylene, Jerilyn Brunson, John R. Dennison
All Physics Faculty Publications
Measurements of resistivity of low density polyethylene (LDPE) have been made using the standard constant voltage method to determine the temperature dependence of resistivity. Where electrons are assumed to serve as the primary charge carriers, their mobility is believed to be dependent on their probability of hopping between trapping sites treated as potential wells. We consider our measurements of this relatively simple polymeric material using temperature-dependant models of conduction mechanisms developed for amorphous solids and semi-conductors.
Functional Time Evolution, Anomaly Potentials, And The Geometric Phase, Charles G. Torre
Functional Time Evolution, Anomaly Potentials, And The Geometric Phase, Charles G. Torre
All Physics Faculty Publications
A free quantum field in 1+1 dimensions admits unitary Schrödinger picture dynamics along any foliation of spacetime by Cauchy curves. Kuchař showed that the Schrödinger picture state vectors, viewed as functionals of spacelike embeddings, satisfy a functional Schrödinger equation in which the generators of time evolution are the field energy-momentum densities with a particular normal-ordering and with a (nonunique) c-number contribution. The c-number contribution to the Schrödinger equation, called the “anomaly potential,” is needed to make the equation integrable in light of the Schwinger terms present in the commutators of the normal-ordered energy-momentum densities. Here we give a quantum geometric …