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Full-Text Articles in Physics

Investigating The Photoyield Of Spacecraft Materials, Jennifer Albretsen, Ryan Hoffmann, Jr Dennison Oct 2007

Investigating The Photoyield Of Spacecraft Materials, Jennifer Albretsen, Ryan Hoffmann, Jr Dennison

Presentations

No abstract provided.


Resistivity Of Kapton E At Intermediate Time Scales Following High-Energy Electron Irradiation, S Hart, Jr Dennison, J Brunson, Jodie C. Gillespie Oct 2007

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.


Equatorial Ionospheric Electric Fields During The November 2004 Magnetic Storm, Bela G. Fejer, J. W. Jensen, T. Kikuchi, M. A. Abdu, J. L. Chau Oct 2007

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 Aug 2007

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 ...


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 Aug 2007

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 ...


Gravitational Wave Bursts From The Galactic Massive Black Hole, Clovis Hopman, Marc Freitag, Shane L. Larson Jun 2007

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). Here we give an analytical estimate of the ...


The Effects Of Large Data Gaps On Estimating Linear Trend In Autocorrelated Data, Troy A. Wynn, Vincent B. Wickwar May 2007

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.


Climatology Of Middle And Low-Latitude F-Region Plasma Drifts From Satellite Measurements, John W. Jensen May 2007

Climatology Of Middle And Low-Latitude F-Region Plasma Drifts From Satellite Measurements, John W. Jensen

All Graduate Theses and Dissertations

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 ...


Rayleigh-Scatter Lidar Observations At Usu's Atmospheric Lidar Observatory (Logan,Ut) - Temperature Climatology, Temperature Comparisons With Msis, And Noctilucent Clouds, Joshua P. Herron May 2007

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

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 ...


The Effect Of Voltage Ramp Rate On Dielectric Breakdown Of Thin Film Polymers, Anthony Thomas May 2007

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 ...


Electric Field Induced Hopping Conductivity And Polarization In Hytrel, Steve Hart Apr 2007

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 in ...


Gauging Newton’S Law, James Thomas Wheeler Apr 2007

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 Mar 2007

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 Mar 2007

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 ...


A Very Active Sprite-Producing Storm Observed Over Argentina, J. N. Thomas, Michael J. Taylor, Pierre-Dominique Pautet, M. Bailey, 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 Mar 2007

A Very Active Sprite-Producing Storm Observed Over Argentina, J. N. Thomas, Michael J. Taylor, Pierre-Dominique Pautet, M. Bailey, 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 ...


On The Use Of Simultaneous Measurements Of Oh And O2 Emissions To Investigate Wave Growth And Dissipation, A. Taori, A. Guharay, Michael J. Taylor Mar 2007

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 ...


Investigation Of A "Wall" Wave Event, F. Li, G. R. Swenson, A. Z. Liu, Michael J. Taylor, Y. Zhao Feb 2007

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 ...


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 Jan 2007

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.


Phys 6210 - Quantum Mechanics, Spring 2007, Charles G. Torre Jan 2007

Phys 6210 - Quantum Mechanics, Spring 2007, Charles G. Torre

Physics - OCW

After completing this course you should (1) have a working knowledge of the foundations, techniques and key results of quantum mechanics; (2) be able to comprehend basic quantum mechanical applications at the research level, e.g., in research articles; (3) be able to competently explain/teach these topics to others; (4) be able to teach yourself any other related quantum mechanics material as you need it.


Longitudinal Dependence Of Middle And Low Latitude Zonal Plasmadrifts Measured By De-2, J. Jensen, Bela Fejer Jan 2007

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 ...


Dependence Of Resistivity In Low-Density Polyethylene On Space Environment Parameters, Jr Dennison, J. Brunson Jan 2007

Dependence Of Resistivity In Low-Density Polyethylene On Space Environment Parameters, Jr Dennison, J. 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 ...


Triggering Threshold Spacecraft Charging With Changes In Electron Emission From Materials, Jr Dennison, R. C. Hoffmann, J. Abbott Jan 2007

Triggering Threshold Spacecraft Charging With Changes In Electron Emission From Materials, Jr 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 ...


Hopping Conductivity In Low-Density Polyethylene, Jerilyn Brunson, Jr Dennison Jan 2007

Hopping Conductivity In Low-Density Polyethylene, Jerilyn Brunson, Jr 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.


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 Jan 2007

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.


Hands-On Gravitational Wave Astronomy: Extracting Astrophysical Information From Simulated Signals, Louis J. Rubbo, Shane L. Larson, Michelle B. Larson, Dale R. Ingram Jan 2007

Hands-On Gravitational Wave Astronomy: Extracting Astrophysical Information From Simulated Signals, Louis J. Rubbo, Shane L. Larson, Michelle B. Larson, Dale R. Ingram

All Physics Faculty Publications

In this article we introduce an activity in which introductory astronomy students act as gravitational wave astronomers by extracting information from simulated gravitational wave signals. The process mimics the way real gravitational wave analysis is handled by using plots of a pure gravitational wave signal. The students measure the properties of the simulated signal and use these measurements to evaluate standard relations for astrophysical source parameters. Although the activity described focuses on circular binaries, the techniques described can be applied to other gravitational wave sources as well. A problem based on the discussion in this paper is available for use ...


Recent Progress In Mesospheric Gravity Wave Studies Usingnightglow Imaging Systems, Michael J. Taylor, W. R. Pendleton, Pierre-Dominique Pautet, Y. Zhao, C. Olsen, H. K. Surendra-Babu, A. F. Medeiros, H. Takahashi Jan 2007

Recent Progress In Mesospheric Gravity Wave Studies Usingnightglow Imaging Systems, Michael J. Taylor, W. R. Pendleton, Pierre-Dominique Pautet, Y. Zhao, C. Olsen, H. K. Surendra-Babu, A. F. Medeiros, H. Takahashi

All Physics Faculty Publications

No abstract provided.


Deep Dielectric Charging Of Spacecraft Polymers By Energetic Protons, Nelson W. Green, Jr Dennison Jan 2007

Deep Dielectric Charging Of Spacecraft Polymers By Energetic Protons, Nelson W. Green, Jr Dennison

All Physics Faculty Publications

The majority of research in the field of spacecraft charging concentrates on electron charging effects with little discussion of charging by protons. For spacecraft orbiting in the traditional LEO and GEO environments, this emphasis on electrons is appropriate since energetic electrons are the dominant species. But for spacecraft in orbits within the inner radiation belts or for interplanetary and lunar space probes, proton charging effects may also be of concern. To examine bulk spacecraft charging effects in these environments several typical highly insulating spacecraft polymers were exposed to energetic protons with energies from 1 MeV to 10 MeV to simulate ...


Low Temperature Measurements Of Resistivity In Low-Density Polyethylene, Jr Dennison, J. Brunson Jan 2007

Low Temperature Measurements Of Resistivity In Low-Density Polyethylene, Jr 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.


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, R. W. Schunk, T. J. Harris Jan 2007

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, R. 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, J P. Herron, Vincent B. Wickwar, P J. Espy, J W. Merriwether Jan 2007

Observations Of A Noctilucent Cloud Above Logan, Utah (41.7°N, 111.8°W) In 1995, J 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 ...