Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Quantum gravity (2)
- Topology (2)
- 3-D wave propagation (1)
- Aluminum oxide (1)
- Atmospheric gravity waves (1)
-
- Auroral roar (1)
- Ceramic materials (1)
- Daytime auroral pulsations (1)
- Doping (1)
- Electric conductivity (1)
- Exotic smoothness (1)
- GPS scintillation (1)
- General relativity (1)
- Geomagnetic coordinates (1)
- High-latitude irregularities (1)
- Interhemispheric (1)
- Intermittency (1)
- Inverse modeling (1)
- Ionizing radiation (1)
- Ionosphere (1)
- Loop quantum gravity (1)
- Magnetometer (1)
- Magnetosphere (1)
- Neutron irradiation (1)
- Nonlinear wave-wave interaction (1)
- Outer magnetospheric dynamics (1)
- Polar cap (1)
- Radiation (1)
- Riometer radio-wave absorption (1)
- SIGMA (1)
Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
Application Of Ampere's Law To A Non-Infinite Wire And To A Moving Charge, Khaled Aledealat, Christopher L. Duston
Application Of Ampere's Law To A Non-Infinite Wire And To A Moving Charge, Khaled Aledealat, Christopher L. Duston
Physics Faculty Publications
In this work we demonstrate how to apply Ampere's law to a non-infinite wire that is a part of a complete circuit with a steady current. We show that this can be done by considering the magnetic field from the whole circuit, without having to directly introduce the displacement current. This example can be used to isolate and clarify students' confusion about the application of Ampere's law to a short wire. The second part of this work focuses on the application of Ampere's law to a non-relativistic moving charge. It exposes the students to the Dirac delta function in a …
Fast-Moving Diffuse Auroral Patches: A New Aspect Of Daytime Pc3 Auroral Pulsations, Tetsuo Motoba, Yusuke Ebihara, Akira Kadokura, Mark J. Engebretson, Marc R. Lessard, Allan T. Weatherwax, Andrew J. Gerrard
Fast-Moving Diffuse Auroral Patches: A New Aspect Of Daytime Pc3 Auroral Pulsations, Tetsuo Motoba, Yusuke Ebihara, Akira Kadokura, Mark J. Engebretson, Marc R. Lessard, Allan T. Weatherwax, Andrew J. Gerrard
Physics Faculty Publications
Auroral pulsations are a convenient diagnostic of wave-particle interactions in the magnetosphere. A case study of a daytime Pc3 (22–100 mHz) auroral pulsation event, measured with a ~2 Hz sampling all-sky camera at South Pole Station (74.4°S magnetic latitude) on 17 May 2012, is presented. The daytime Pc3 auroral pulsations were most active in a closed field line region where the aurora was dominated by diffuse green-line emissions and within ±2 h of magnetic local noon. Usually, but not always, the corresponding periodic variations were recorded with a colocated search coil magnetometer. Of particular interest is the two-dimensional auroral signature, …
Short-Period Mesospheric Gravity Waves And Their Sources At The South Pole, Dhvanit Mehta, Andrew J. Gerrard, Yusuke Ebihara, Allan T. Weatherwax, Louis J. Lanzerotti
Short-Period Mesospheric Gravity Waves And Their Sources At The South Pole, Dhvanit Mehta, Andrew J. Gerrard, Yusuke Ebihara, Allan T. Weatherwax, Louis J. Lanzerotti
Physics Faculty Publications
The sourcing locations and mechanisms for short-period, upward-propagating gravity waves at high polar latitudes remain largely unknown. Using all-sky imager data from the Amundsen–Scott South Pole Station, we determine the spatial and temporal characteristics of 94 observed small-scale waves in 3 austral winter months in 2003 and 2004. These data, together with background atmospheres from synoptic and/or climatological empirical models, are used to model gravity wave propagation from the polar mesosphere to each wave's source using a ray-tracing model. Our results provide a compelling case that a significant proportion of the observed waves are launched in several discrete layers in …
Satellite-Beacon Ionospheric-Scintillation Global Model Of The Upper Atmosphere (Sigma) Ii: Inverse Modeling With High Latitude Observations To Deduce Irregularity Physics, K. B. Deshpande, G. S. Bust, C. R. Clauer, W. A. Scales, N. A. Frissell, J. M. Ruohoniemi, L. Spogli, C. Mitchell, Allan T. Weatherwax
Satellite-Beacon Ionospheric-Scintillation Global Model Of The Upper Atmosphere (Sigma) Ii: Inverse Modeling With High Latitude Observations To Deduce Irregularity Physics, K. B. Deshpande, G. S. Bust, C. R. Clauer, W. A. Scales, N. A. Frissell, J. M. Ruohoniemi, L. Spogli, C. Mitchell, Allan T. Weatherwax
Physics Faculty Publications
Ionospheric scintillation is caused by irregularities in the ionospheric electron density. The characterization of ionospheric irregularities is important to further our understanding of the underlying physics. Our goal is to characterize the intermediate (0.1–10 km) to medium (10–100 km) scale high-latitude irregularities which are likely to produce these scintillations. In this paper, we characterize irregularities observed by Global Navigation Satellite System (GNSS) during a geomagnetically active period on 9 March 2012. For this purpose, along with the measurements, we are using the recently developed model: “Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere” (SIGMA). The model is particularly applicable at …
Rethinking The Polar Cap: Eccentric Dipole Structuring Of Ulf Power At The Highest Corrected Geomagnetic Latitudes, Kevin D. Urban, Andrew J. Gerrard, Louis J. Lanzerotti, Allan T. Weatherwax
Rethinking The Polar Cap: Eccentric Dipole Structuring Of Ulf Power At The Highest Corrected Geomagnetic Latitudes, Kevin D. Urban, Andrew J. Gerrard, Louis J. Lanzerotti, Allan T. Weatherwax
Physics Faculty Publications
The day-to-day evolution and statistical features of Pc3-Pc7 band ultralow frequency (ULF) power throughout the southern polar cap suggest that the corrected geomagnetic (CGM) coordinates do not adequately organize the observed hydromagnetic spatial structure. It is shown that that the local-time distribution of ULF power at sites along CGM latitudinal parallels exhibit fundamental differences and that the CGM latitude of a site in general is not indicative of the site's projection into the magnetosphere. Thus, ULF characteristics observed at a single site in the polar cap cannot be freely generalized to other sites of similar CGM latitude but separated in …
Right-Hand Polarized 4FCe Auroral Roar Emissions: 2. Nonlinear Generation Theory, P. H. Yoon, J. Labelle, Allan T. Weatherwax
Right-Hand Polarized 4FCe Auroral Roar Emissions: 2. Nonlinear Generation Theory, P. H. Yoon, J. Labelle, Allan T. Weatherwax
Physics Faculty Publications
Auroral roar emissions are commonly interpreted as Z (or upper hybrid) mode naturally excited by precipitating auroral electrons. Subsequent conversion to escaping radiation makes it possible for these emissions to be detected on the ground. Most emissions are detected as having left-hand (L) circular (or ordinary O) polarization, but the companion paper presents a systematic experimental study on the rare occurrence of the right-hand polarized, or equivalently, extraordinary (X) mode 4fce emission. A similar observation was reported earlier by Sato et al. (2015). The suggested emission mechanism is the nonlinear coalescence of …
Intermittency On Simultaneous Observations Of Riometer At Several Antarctic Locations, E. M. Ovalle, A. J. Foppiano, M. V. Stepanova, Allan T. Weatherwax
Intermittency On Simultaneous Observations Of Riometer At Several Antarctic Locations, E. M. Ovalle, A. J. Foppiano, M. V. Stepanova, Allan T. Weatherwax
Physics Faculty Publications
It is well known that auroral radio wave absorption, as measured by riometers, consists of periods of relative quiescence which are interrupted by short bursts of activity. Such patterns in activity are observed in systems ranging from the stock market to turbulence, i.e. they exhibit intermittency. In the case of the auroral absorption it has also been found that intermittency strongly depends on the magnetic local time, being largest in the night-time sector. This can be interpreted as indicating that the precipitating particles responsible of the absorption exhibit intermittency, especially near the substorm eye, where the level of turbulence increases. …
Semiclassical Partition Functions For Gravity With Cosmic Strings, Christopher L. Duston
Semiclassical Partition Functions For Gravity With Cosmic Strings, Christopher L. Duston
Physics Faculty Publications
In this paper we describe an approach to construct semiclassical partition functions in gravity which are complete in the sense that they contain a complete description of the differentiable structures of the underlying 4-manifold. In addition, we find our construction naturally includes cosmic strings. We prove that the mass density of these strings uniquely specifies the topology of the leaves of a dimension 2 foliation, and conjecture that spacetime topology emerges as a result of the symmetry breaking of the fundamental fields. We discuss some possible applications of the partition functions in the fields of both quantum gravity and topological …
Topspin Networks In Loop Quantum Gravity, Christopher L. Duston
Topspin Networks In Loop Quantum Gravity, Christopher L. Duston
Physics Faculty Publications
We discuss the extension of loop quantum gravity to topspin networks, a proposal which allows topological information to be encoded in spin networks. We will show that this requires minimal changes to the phase space, C*-algebra and Hilbert space of cylindrical functions. We will also discuss the area and Hamiltonian operators, and show how they depend on the topology. This extends the idea of 'background independence' in loop quantum gravity to include topology as well as geometry. It is hoped this work will confirm the usefulness of the topspin network formalism and open up several new avenues for research into …
Exotic Smoothness In Four Dimensions And Euclidean Quantum Gravity, Christopher L. Duston
Exotic Smoothness In Four Dimensions And Euclidean Quantum Gravity, Christopher L. Duston
Physics Faculty Publications
In this paper we calculate the effect of the inclusion of exotic smooth structures on typical observables in Euclidean quantum gravity. We do this in the semiclassical regime for several gravitational free-field actions and find that the results are similar, independent of the particular action that is chosen. These are the first results of their kind in dimension four, which we extend to include one-loop contributions as well. We find these topological features can have physically significant results without the need for additional exotic physics.
In Situ Measurement Of Radiation Induced Conductivity In Oxide Insulators During Neutron Irradiation, D. P. White, L. L. Snead, S. J. Zinkle, W. S. Earthley
In Situ Measurement Of Radiation Induced Conductivity In Oxide Insulators During Neutron Irradiation, D. P. White, L. L. Snead, S. J. Zinkle, W. S. Earthley
Physics Faculty Publications
No abstract provided.
The Effect Of Ionizing And Displacive Radiation On The Thermal Conductivity Of Alumina, D. P. White
The Effect Of Ionizing And Displacive Radiation On The Thermal Conductivity Of Alumina, D. P. White
Physics Faculty Publications
The effects of ionizing and displacive radiation on the thermal conductivity of alumina at high temperatures have been studied. The phonon scattering relaxation times for several scattering mechanisms have been used to determine the effect on the thermal conductivity. The scattering mechanisms considered are scattering by electrons excited into the conduction band, vacancies, aluminum precipitates, and voids. It is found that under irradiation conditions where the electrical conductivity and dielectric loss tangent are greatly increased there is not a significant decrease in the thermal conductivity due to phonon-electron scattering. The conditions under which the scattering due to vacancies, aluminum precipitates, …
Thermal Conductivity Of Thermoelectric Si0.8‐Ge0.2 Alloys, D. P. White, P. G. Clemens
Thermal Conductivity Of Thermoelectric Si0.8‐Ge0.2 Alloys, D. P. White, P. G. Clemens
Physics Faculty Publications
The thermal conductivity of heavily doped, n-type Si-Ge alloys has been studied from 300 to 1200 K. The scattering rate of several phonon scattering mechanisms has been calculated, including intrinsic scattering, mass defect and distortion scattering, phonon-electron scattering, and scattering by inclusions. These rates were then used to calculate the lattice thermal conductivity. The electronic component of the thermal conductivity was calculated from the calculated Lorenz ratio and measured values of the electrical conductivity. The total thermal conductivity was then compared to measured values for a specimen studied by Vining et al.