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Full-Text Articles in Physics

Climatology Of F Region Zonalplasma Drifts Over Jicamarca, Bela G. Fejer, J. R. Souza, A. S. Santos, A. E. Costa Pereira Dec 2005

Climatology Of F Region Zonalplasma Drifts Over Jicamarca, Bela G. Fejer, J. R. Souza, A. S. Santos, A. E. Costa Pereira

Bela G. Fejer

[1] We use extensive incoherent scatter radar observations made at the Jicamarca Radio Observatory between 1970 and 2003 to study and model empirically the equatorial zonal plasma drifts near the F region peak using Bernstein polynomials as base functions. Our quiet-time model results confirm that the daytime drifts are westward and are nearly season and solar cycle independent. The nighttime drifts are eastward, have larger magnitudes, and increase strongly with solar flux, particularly near equinox and December solstice. Enhanced geomagnetic activity drives small eastward perturbation drifts during the day and much larger westward disturbance drifts at night. The nighttime drift ...


Assimilative Modeling Of The Equatorial Ionosphere For Scintillation Forecasting: Modeling With Vertical Drifts, J. M. Retterer, D. T. Decker, W. S. Borer, R. E. Daniell, Bela G. Fejer Nov 2005

Assimilative Modeling Of The Equatorial Ionosphere For Scintillation Forecasting: Modeling With Vertical Drifts, J. M. Retterer, D. T. Decker, W. S. Borer, R. E. Daniell, Bela G. Fejer

Bela G. Fejer

[1] Knowledge of the vertical plasma drift velocity observed by the Jicamarca incoherent radar in seven events is assimilated into a theoretical model for the ambient F region plasma density. Comparisons of the calculated plasma density model and the observed plasma density show that, apart from the signature effects of equatorial plasma bubbles, the ambient model captures much of the detail of the plasma density profiles. Rayleigh-Taylor growth rates calculated with the ambient model show a good correlation with the occurrence of spread F.


Concurrent Ohimager And Sodium Temperature/Wind Lidar Observation Of Localized Ripples Over Northern Colorado, L. Tao, C. Y. She, B. P. Williams, Titus Yuan, R. L. Collins, L. Kieffabar, A. Peterson Jul 2005

Concurrent Ohimager And Sodium Temperature/Wind Lidar Observation Of Localized Ripples Over Northern Colorado, L. Tao, C. Y. She, B. P. Williams, Titus Yuan, R. L. Collins, L. Kieffabar, A. Peterson

All Physics Faculty Publications

On 3 and 5 September 2002 the OH all-sky imager at Platteville, Colorado (40.2°N, 104.7°W), observed small-scale, wavelike patterns (known as ripples), with horizontal wavelengths of ∼9 km and ∼7 km and lifetimes of ∼9 min and ∼15 min, respectively. The Colorado State University sodium lidar at nearby Fort Collins, Colorado (40.6°N, 105°W), also made concurrent observations of temperature and zonal and meridional winds, which allowed us to determine the nature of the ripples observed. Our observations suggest that the 3 September ripple was induced by a convective instability located at 87.5 ...


Pulsed System For Optical Discharge Of Thin-Film Insulators, Jared Otterstrom, Ryan C. Hoffman, Jr Dennison May 2005

Pulsed System For Optical Discharge Of Thin-Film Insulators, Jared Otterstrom, Ryan C. Hoffman, Jr Dennison

Senior Theses and Projects

Much research is being performed in order to characterize the charging of spacecraft materials. The importance and applications of this research is numerous and especially useful to the development of satellites1. The USU Materials Physics group is currently performing research in this field related to electron emission for spacecraft materials1. This includes testing sample material in an ultra high vacuum chamber. A problem encountered in this testing is that negative charge can build up on the sample material and modify the electron emission measurements2. To remedy this problem, my senior project was to develop, install and test ...


An Operational Data Assimilation Model Of The Global Ionosphere, R. W. Schunk, L. Scherliess, Jan Josef Sojka, D. C. Thompson, L. Zhu May 2005

An Operational Data Assimilation Model Of The Global Ionosphere, R. W. Schunk, L. Scherliess, Jan Josef Sojka, D. C. Thompson, L. Zhu

All Physics Faculty Publications

Physics-based data assimilation models of the ionosphere were developed at Utah State University as part of a DoD Multidisciplinary University Research Initiative (MURI) program. The USU effort was called Global Assimilation of Ionospheric Measurements (GAIM). One of the USU Data assimilation models has been selected for operational use at the Air Force Weather Agency (AFWA in Omaha, Nebraska. This model is a Gauss-Markov Kalman Filter model, and it uses a physic-based model of the global ionosphere and a Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) measurements. The model has been designed to ...


Measurements Of The Secondary Electron Emission Properties Of Insulators, Clint D. Thomson May 2005

Measurements Of The Secondary Electron Emission Properties Of Insulators, Clint D. Thomson

All Graduate Theses and Dissertations

Measurements of the electron-induced electron emission properties of insulators are important to many applications including spacecraft charging, scanning electron microscopy, electron sources, and particle detection technology. However, these measurements are difficult to make since insulators can charge either negatively or positively under charge particle bombardment that in turn alters insulator emissions. In addition, incident electron bombardment can modify the conductivity, internal charge distribution, surface potential, and material structure in ways that are not well understood. A primary goal of this dissertation work has been to make consistent and accurate measurements of the uncharged electron yields for insulator materials using innovative ...


Wavelength Control For A Potassium Resonance Lidar, Everett E. A., Vincent B. Wickwar Apr 2005

Wavelength Control For A Potassium Resonance Lidar, Everett E. A., Vincent B. Wickwar

Posters

An important ground-based way to measure temperatures and winds in the transition region between the upper mesosphere and lower thermosphere (80 to 105 km) is with a resonance-scatter lidar. An alexandrite laser, with a wavelength in the near infrared at 770 nm, is being added to the Atmospheric Lidar Observatory to make this type of observation of potassium. These observations will complement those that have been made for many years with the green Rayleigh-scatter lidar. For these resonance-scatter observations it is necessary to accurately and precisely control the laser wavelength. The intent is to carefully step across the 4 pm ...


Charge Storage Measuremens Of Resistivity For Dielectric Samples From The Crres Internal Discharge Monitor, Nelson W. Green, A. R. Frederickson, Jr Dennison Apr 2005

Charge Storage Measuremens Of Resistivity For Dielectric Samples From The Crres Internal Discharge Monitor, Nelson W. Green, A. R. Frederickson, Jr Dennison

Presentations

No abstract provided.


The Importance Of Accurate Computation Of Secondary Electron Emission For Modeling Spacecraft Charging, Sebastien Clerc, Jr Dennison, Clint Thomson Apr 2005

The Importance Of Accurate Computation Of Secondary Electron Emission For Modeling Spacecraft Charging, Sebastien Clerc, Jr Dennison, Clint Thomson

Presentations

No abstract provided.


State Of Utah Space Environment & Contamination Study (Suspecs) Misse-6 Payload To Investigate Their Effects On Electron Emission And Resistivity Of Spacecraft Materials, Jr Dennison, L. Pearson, L. Davis, J. W. Burns, R. S. Hyde, James S. Dyer, Tina Andrus, Andrew Jay Auman, Jeff Duce, Tim Neilsen, Rob Leishman Apr 2005

State Of Utah Space Environment & Contamination Study (Suspecs) Misse-6 Payload To Investigate Their Effects On Electron Emission And Resistivity Of Spacecraft Materials, Jr Dennison, L. Pearson, L. Davis, J. W. Burns, R. S. Hyde, James S. Dyer, Tina Andrus, Andrew Jay Auman, Jeff Duce, Tim Neilsen, Rob Leishman

All Physics Faculty Publications

A study of the effects of prolonged exposure to the space environment and of charge-enhanced contamination on the electron emission and resistivity of spacecraft materials, the State of Utah Space Environment & Contamination Study (SUSpECS), is planned for flight aboard the MISSE-6 payload. The Materials International Space Station Experiment (MISSE-6) program is designed to characterize the performance of candidate new space materials over the course of approximately four to eight month exposure periods on-orbit on the International Space Station, with a target flight date of mid-2006. The study is conducted by the Utah State University Materials Physics Group, in cooperation with ...


Classical Resistivity Method In Atmosphere And Vacuum, Shigeyuki Takahashi Feb 2005

Classical Resistivity Method In Atmosphere And Vacuum, Shigeyuki Takahashi

Senior Theses and Projects

In the space industry one of the most serious problems is charge storage on spacecrafts caused by plasma, solar-photoemission that causes damage to the spacecrafts. Therefore, the research by government and industry about spacecraft charging is thriving because there are still plenty of unknown faces in the space. A key first step for research of the phenomenon in ground-based laboratory test is to know well the most suitable experimental methods for measuring resistivity of spacecraft materials.

This talk describes my investigations of the Classical Resistivity (constant voltage capacitor) Method to measure resistivity. I concentrate on understanding the differences between tests ...


Strong Electric Fields From Positive Lightning Strokes In The Stratosphere, R. H. Holzworth, M. C. Mccarthy, J. N. Thomas, J. Chin, T. M. Chinowsky, Michael J. Taylor, O. Pinto Jr. Feb 2005

Strong Electric Fields From Positive Lightning Strokes In The Stratosphere, R. H. Holzworth, M. C. Mccarthy, J. N. Thomas, J. Chin, T. M. Chinowsky, Michael J. Taylor, O. Pinto Jr.

All Physics Faculty Publications

A balloon payload launched in Brazil has measured vector electric fields from lightning at least an order of magnitude larger than previously reported above 30 km in the stratosphere. During the flight hundreds of lightning events were recorded, including several positive cloud to ground lightning strokes. A two stroke flash, with small (15 kA peak current) and moderate (53 kA) positive strokes at a horizontal range of 34 km, produced field changes over 140 V/m at 34 km altitude. On-board optical lightning detection, recorded with GPS timing, coupled with ground based lightning location gives high time resolution for study ...


Gobal Change In The Mesosphere And Usu’S Green Beam, Vincent B. Wickwar, Joshua P. Herron, Troy A. Wynn Jan 2005

Gobal Change In The Mesosphere And Usu’S Green Beam, Vincent B. Wickwar, Joshua P. Herron, Troy A. Wynn

Presentations

No abstract provided.


Coherent State Path Integral For Linear Systems, Charles G. Torre Jan 2005

Coherent State Path Integral For Linear Systems, Charles G. Torre

All Physics Faculty Publications

We present a computation of the coherent state path integral for a generic linear system using "functional methods'' (as opposed to discrete time approaches). The Gaussian phase space path integral is formally given by a determinant built from a first-order differential operator with coherent state boundary conditions. We show how this determinant can be expressed in terms of the symplectic transformation generated by the (in general, time-dependent) quadratic Hamiltonian for the system. We briefly discuss the conditions under which the coherent state path integral for a linear system actually exists. A necessary -- but not sufficient -- condition for existence of the ...


Universe Interactive: Static Displays With Active Components, Michelle B. Larson Jan 2005

Universe Interactive: Static Displays With Active Components, Michelle B. Larson

All Physics Faculty Publications

As the World Year of Physics (WYP) approaches, the AAPT WYP Committee would like to encourage everyone to consider ways to engage those around us in celebrating the science that makes us the proud geeks we are. The geek sentiment is my own, and does not necessarily reflect the views and opinions of the committee. This paper offers simple and inexpensive astronomy-related ideas for a bulletin-board-type display. The particular ideas presented below are hands-on classroom activities that I've adapted for display purposes. The display is static in that once constructed it does not require a personal facilitator, but each ...


Semi-Relativistic Approximation To Gravitational Radiation From Encounters With Non-Spinning Black Holes, Jonathan R. Gair, Daniel J. Kennefick, Shane L. Larson Jan 2005

Semi-Relativistic Approximation To Gravitational Radiation From Encounters With Non-Spinning Black Holes, Jonathan R. Gair, Daniel J. Kennefick, Shane L. Larson

All Physics Faculty Publications

The capture of compact bodies by black holes in galactic nuclei is an important prospective source for low frequency gravitational wave detectors, such as the planned Laser Interferometer Space Antenna. This paper calculates, using a semirelativistic approximation, the total energy and angular momentum lost to gravitational radiation by compact bodies on very high eccentricity orbits passing close to a supermassive, nonspinning black hole; these quantities determine the characteristics of the orbital evolution necessary to estimate the capture rate. The semirelativistic approximation improves upon treatments which use orbits at Newtonian order and quadrupolar radiation emission, and matches well onto accurate Teukolsky ...


Polar F-Layer Model-Observation Comparisons: A Neutral Wind Surprise, Jan Josef Sojka, M. David, R. W. Schunk, A. P. Van Eyken Jan 2005

Polar F-Layer Model-Observation Comparisons: A Neutral Wind Surprise, Jan Josef Sojka, M. David, R. W. Schunk, A. P. Van Eyken

All Physics Faculty Publications

The existence of a month-long continuous database of incoherent scatter radar observations of the ionosphere from the EISCAT Savlbard Radar (ESR) at Longyearbyen, Norway, provides an unprecedented opportunity for model/data comparisons. Physics-based ionospheric models, such as the Utah State University Time Dependent Ionospheric Model (TDIM), are usually only compared with observations over restricted one or two day events or against climatological averages. In this study, using the ESR observations, the daily weather, day-to-day variability, and month-long climatology can be simultaneously addressed to identify modeling shortcomings and successes. Since for this study the TDIM is driven by climatological representations of ...


A New Global Average Model Of The Coupled Thermosphere And Ionosphere, C. G. Smithtro, Jan Josef Sojka Jan 2005

A New Global Average Model Of The Coupled Thermosphere And Ionosphere, C. G. Smithtro, Jan Josef Sojka

All Physics Faculty Publications

A model representing the global average ionosphere and thermosphere (GAIT) is developed as a tool to explore the response of the coupled system to changes in the input solar irradiance between 3 and 360 nm. The GAIT model self-consistently solves the coupled continuity, momentum, and energy equations for the three major neutral species, N2, O2, and O, as well as minor neutral constituents important to the global energy budget. In the ionosphere the model includes five different ion species and two excited states of O+. The GAIT model also includes an approximate treatment of photoelectrons, in order to ...


Comparison Of Simultaneous Na Lidar And Mesospherictemperature Mapper Measurements And The Effects Of Tides On The Emission Layer Heights, Y. Zhao, Michael J. Taylor, X. Chu Jan 2005

Comparison Of Simultaneous Na Lidar And Mesospherictemperature Mapper Measurements And The Effects Of Tides On The Emission Layer Heights, Y. Zhao, Michael J. Taylor, X. Chu

All Physics Faculty Publications

No abstract provided.


Experimentally Derived Resistivity For Dielectric Samples From The Crres Internal Discharge Monitor, Nelson W. Green, A. Robb Frederickson, Jr Dennison Jan 2005

Experimentally Derived Resistivity For Dielectric Samples From The Crres Internal Discharge Monitor, Nelson W. Green, A. Robb Frederickson, Jr Dennison

All Physics Faculty Publications

Resistivity values were experimentally determined using charge storage methods for six samples remaining from the construction of the Internal Discharge Monitor (IDM) flown on the Combined Release and Radiation Effects Satellite (CRRES). Three tests were performed over a period of four to five weeks each in a vacuum of ~5×10-6 torr with an average temperature of ~25 ºC to simulate a space environment. Samples tested included FR4, PTFE, and alumina with copper electrodes attached to one or more of the sample surfaces. FR4 circuit board material was found to have a dark current resistivity of ~1×1018 Ω-cm and ...


Importance Of Accurate Computation Of Secondary Electron Emission For Modelingspacecraft Charging, Sebastien Clerc, Jr Dennison Jan 2005

Importance Of Accurate Computation Of Secondary Electron Emission For Modelingspacecraft Charging, Sebastien Clerc, Jr Dennison

All Physics Faculty Publications

The secondary electron yield is a critical process in establishing the charge balance in spacecraft charging and the subsequent determination of the equilibrium potential. Spacecraft charging codes use a parameterized expression for the secondary electron yield δ(Eo) as a function of incident electron energy, Eo. A critical step in accurately characterizing a particular spacecraft material is establishing the most efficient and accurate way to determine the fitting parameters in terms of the measured electron yield data and physics-based theoretical models. Simple two- or three- step physics models of the electron penetration, transport and emission from a solid are typically ...


Proposed Modifications To Engineering Design Guidelines Related To Resistivity Measurements And Spacecraft Charging, Jr Dennison, Prasanna Swaminathan, Randy Jost, Jerilyn Brunson, Nelson W. Green, A. Robb Frederickson Jan 2005

Proposed Modifications To Engineering Design Guidelines Related To Resistivity Measurements And Spacecraft Charging, Jr Dennison, Prasanna Swaminathan, Randy Jost, Jerilyn Brunson, Nelson W. Green, A. Robb Frederickson

All Physics Faculty Publications

A key parameter in modeling differential spacecraft charging is the resistivity of insulating materials. This parameter determines how charge will accumulate and redistribute across the spacecraft, as well as the time scale for charge transport and dissipation. Existing spacecraft charging guidelines recommend use of tests and imported resistivity data from handbooks that are based principally upon ASTM methods that are more applicable to classical ground conditions and designed for problems associated with power loss through the dielectric, than for how long charge can be stored on an insulator. These data have been found to underestimate charging effects by one to ...


The Importance Of Accurate Computation Of Secondary Electron Emission For Modeling Spacecraft Charging, S. Clerc, Jr Dennison, C. D. Thomson Jan 2005

The Importance Of Accurate Computation Of Secondary Electron Emission For Modeling Spacecraft Charging, S. Clerc, Jr Dennison, C. D. Thomson

All Physics Faculty Publications

Secondary electron emission is a critical contributor to the current balance in spacecraft charging. Spacecraft charging codes use a parameterized expression for the secondary electron yield δ(Eo) as a function of incident electron energy Eo. Simple three-step physics models of the electron penetration, transport and emission from a solid are typically expressed in terms of the incident electron penetration depth at normal incidence or range R(Eo ), and the mean free path of the secondary electron, λ(E). We recall classical models for the range R(Eo): a power law expression of the form b1E ...


Measuring Charge Storage Decay Time And Resistivity Of Spacecraft Insulators, J. Brunson, Jr Dennison Jan 2005

Measuring Charge Storage Decay Time And Resistivity Of Spacecraft Insulators, J. Brunson, Jr Dennison

All Physics Faculty Publications

An informal discussion of how accurate measurements of resistivity and increasing understanding of the behavior of insulating materials used on spacecraft is fundamental to advancing the design and utility of the spacecraft. Build up of charge can vary between different areas of the spacecraft, with excess charge accumulating and leading to functional anomalies or component failure. The most important parameter in determining how charge will decay through an insulator is the resistivity of the material. Current industry standards for measuring resistivity have been shown to be inconsistent with actual phenomena, and new methods of measuring resistivity must be developed and ...


Climatology Of Short-Period Gravity Wavesobserved Over Northern Australia During The Dawex Campaign And Their Dominant Sourceregions, Pierre-Dominique Pautet, Michael J. Taylor, A. Z. Liu, G. R. Swenson Jan 2005

Climatology Of Short-Period Gravity Wavesobserved Over Northern Australia During The Dawex Campaign And Their Dominant Sourceregions, Pierre-Dominique Pautet, Michael J. Taylor, A. Z. Liu, G. R. Swenson

All Physics Faculty Publications

No abstract provided.


Terdiurnal Wave Signatures In The Upper Mesospherictemperature And Their Association With The Wind Fields At Low-Latitudes (20°N), A. Taori, Michael J. Taylor, S. Franke Jan 2005

Terdiurnal Wave Signatures In The Upper Mesospherictemperature And Their Association With The Wind Fields At Low-Latitudes (20°N), A. Taori, Michael J. Taylor, S. Franke

All Physics Faculty Publications

No abstract provided.


Evolution Of The Electron Yield Curves Of Insulators As A Function Ofimpinging Electron Fluence And Energy, Alec Sim, Jr Dennison, Clint Thomson Jan 2005

Evolution Of The Electron Yield Curves Of Insulators As A Function Ofimpinging Electron Fluence And Energy, Alec Sim, Jr Dennison, Clint Thomson

All Physics Faculty Publications

Electron emission and concomitant charge accumulation near the surface of insulators is central to understanding spacecraft charging. We present a study of changes in electron emission yields as a result of internal charge build up due to electron dose. Evolution of total, backscattered and secondary yield results over a broad range of incident energies are presented for two representative insulators, KaptonTM and Al2O3. Reliable yield curves for un-charged insulators are measured and quantifiable changes in yields are observed due to fluences. We find excellent agreement with a phenomenological argument based on insulator charging predicted by the ...


Ionospheric Weather Forecasting On The Horizon, R. W. Schunk, L. Scherliess, Jan Josef Sojka, D. C. Thompson, L. Zhu Jan 2005

Ionospheric Weather Forecasting On The Horizon, R. W. Schunk, L. Scherliess, Jan Josef Sojka, D. C. Thompson, L. Zhu

All Physics Faculty Publications

Models of the ionosphere using state-of-the-art data assimilation techniques are nearing operational use.


Behavior Of The Ionosphere And Thermosphere Subject To Extreme Solar Cycle Conditions, C. G. Smithtro, Jan Josef Sojka Jan 2005

Behavior Of The Ionosphere And Thermosphere Subject To Extreme Solar Cycle Conditions, C. G. Smithtro, Jan Josef Sojka

All Physics Faculty Publications

A 1-D global average ionosphere and thermosphere (GAIT) model is used to examine the climatological behavior of the upper atmosphere, subject to both extremely low and high solar flux. These extremes are justified, in part, by the Maunder Minimum and Grand Maximum epochs described by J. A. Eddy, as well as other studies involving cosmogenic isotopes and Sun-like stars. As the irradiance falls below normal solar minimum levels, the concentration of O+ decreases rapidly relative to the molecular ions, such that the ratio ƒoF2oF1 approaches unity. When subject to exceptionally high solar fluxes ...