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All Physics Faculty Publications

2016

Articles 1 - 16 of 16

Full-Text Articles in Physics

Dynamical Interactions Between Two Uniformly Magnetized Spheres, Boyd F. Edwards, John M. Edwards Nov 2016

Dynamical Interactions Between Two Uniformly Magnetized Spheres, Boyd F. Edwards, John M. Edwards

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Studies of the two-dimensional motion of a magnet sphere in the presence of a second, fixed sphere provide a convenient venue for exploring magnet-magnet interactions, inertia, friction, and rich nonlinear dynamical behavior. These studies exploit the equivalence of these magnetic interactions to the interactions between two equivalent point dipoles. We show that magnet-magnet friction plays a role when magnet spheres are in contact, table friction plays a role at large sphere separations, and eddy currents are always negligible. Web-based simulation and visualization software, called MagPhyx, is provided for education, exploration, and discovery

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Evidence Of The Excitation Of A Ring-Like Gravity Wave In The Mesosphere Over The Andes Lidar Observatory, F. Vargas, G. Swenson, A. Liu, Pierre-Dominique Pautet Aug 2016

Evidence Of The Excitation Of A Ring-Like Gravity Wave In The Mesosphere Over The Andes Lidar Observatory, F. Vargas, G. Swenson, A. Liu, Pierre-Dominique Pautet

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On 23 March 2012, our all-sky imager recorded a concentric, ring-like gravity wave pattern. The wave arose within the area covered by images of both OH and O(1S) nightglow emissions taken at the Andes Lidar Observatory (ALO), Chile (30.3ÁS, 70.7ÁW). We have estimated the observed and intrinsic parameters of the event and located the wave source within the lower mesosphere altitude range using a reverse ray tracing method. By the analysis of GOES and LIS satellite images, we have not found evidence of neither convective nor lightning activity nearby ALO, indicating that the source of the ring-like wave was not …

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Scale Analysis Of Equatorial Plasma Irregularities Derived From Swarm Constellation, Chao Xiong, Claudia Stolle, Hermann Lühr, Jaeheung Park, B. G. Fejer, Guram N. Kervalishvili Jul 2016

Scale Analysis Of Equatorial Plasma Irregularities Derived From Swarm Constellation, Chao Xiong, Claudia Stolle, Hermann Lühr, Jaeheung Park, B. G. Fejer, Guram N. Kervalishvili

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In this study, we investigated the scale sizes of equatorial plasma irregularities (EPIs) using measurements from the Swarm satellites during its early mission and final constellation phases. We found that with longitudinal separation between Swarm satellites larger than 0.4°, no significant correlation was found any more. This result suggests that EPI structures include plasma density scale sizes less than 44 km in the zonal direction. During the Swarm earlier mission phase, clearly better EPI correlations are obtained in the northern hemisphere, implying more fragmented irregularities in the southern hemisphere where the ambient magnetic field is low. The previously reported inverted-C …

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Stratospheric Gravity Wave Fluxes And Scales During Deepwave, Ronald B. Smith, Allison D. Nugent, Christopher G. Kruse, David C. Fritts, James D. Doyle, Steven D. Eckermann, Michael J. Taylor, Andreas Dornbrack, M. Uddstrom, William Cooper, Jorgen Jensen, Stuart Beaton Jul 2016

Stratospheric Gravity Wave Fluxes And Scales During Deepwave, Ronald B. Smith, Allison D. Nugent, Christopher G. Kruse, David C. Fritts, James D. Doyle, Steven D. Eckermann, Michael J. Taylor, Andreas Dornbrack, M. Uddstrom, William Cooper, Jorgen Jensen, Stuart Beaton

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During the Deep Propagating Gravity Wave Experiment (DEEPWAVE) project in June and July 2014, the Gulfstream V research aircraft flew 97 legs over the Southern Alps of New Zealand and 150 legs over the Tasman Sea and Southern Ocean, mostly in the low stratosphere at 12.1-km altitude. Improved instrument calibration, redundant sensors, longer flight legs, energy flux estimation, and scale analysis revealed several new gravity wave properties. Over the sea, flight-level wave fluxes mostly fell below the detection threshold. Over terrain, disturbances had characteristic mountain wave attributes of positive vertical energy flux (EFz), negative zonal momentum flux, and …

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The Response Of Equatorial Electrojet, Vertical Plasma Drift, And Thermospheric Zonal Wind To Enhanced Solar Wind Input, Chao Xiong, Hermann LüHr, B. G. Fejer Jun 2016

The Response Of Equatorial Electrojet, Vertical Plasma Drift, And Thermospheric Zonal Wind To Enhanced Solar Wind Input, Chao Xiong, Hermann LüHr, B. G. Fejer

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In this study we used observations from the CHAMP and ROCSAT-1 satellites to investigate the solar wind effects on the equatorial electrojet (EEJ), vertical plasma drift, and thermospheric zonal wind. We show that an abrupt increase in solar wind input has a significant effect on the low-latitude ionosphere-thermosphere system, which can last for more than 24 h. The disturbance EEJ and zonal wind are mainly westward for all local times and show most prominent responses during 07–12 and 00–06 magnetic local time (MLT), respectively. The equatorial disturbance electric field is mainly eastward at night (most prominent for 00–05 MLT) and …

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Positive And Negative Gps-Tec Ionospheric Storm Effects During The Extreme Space Weather Event Of March 2015 Over The Brazilian Sector, P. R. Fagundes, F. A. Cardoso, B. G. Fejer, K. Venkatsch, B.A. G. Ribeiro, V. G. Pillat Jun 2016

Positive And Negative Gps-Tec Ionospheric Storm Effects During The Extreme Space Weather Event Of March 2015 Over The Brazilian Sector, P. R. Fagundes, F. A. Cardoso, B. G. Fejer, K. Venkatsch, B.A. G. Ribeiro, V. G. Pillat

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We studied the response of the ionosphere (F region) in the Brazilian sector during extreme space weather event of 17 March 2015 using a large network of 102 GPS- total electron content (TEC) stations. It is observed that the vertical total electron content (VTEC) was severely disturbed during the storm main and recovery phases. A wavelike oscillation with three peaks was observed in the TEC diurnal variation from equator to low latitudes during the storm main phase on 17_18 March 2015. The latitudinal extent of the wavelike oscillation peaks decreased from the beginning of the main phase toward the recovery …

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Solar Cycle Variability In Mean Thermospheric Composition And Temperature Induced By Atmospheric Tides, M. Jones Jr., J. M. Forbes, M. E. Hagan Jun 2016

Solar Cycle Variability In Mean Thermospheric Composition And Temperature Induced By Atmospheric Tides, M. Jones Jr., J. M. Forbes, M. E. Hagan

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In this paper we demonstrate that dissipation of upward propagating tides produces significant changes in the mean temperature of the thermosphere, ranging from +19æK at solar minimum to _15æK at solar maximum in the equatorial region. Our methodology consists of measuring the differential response of the thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM) under solar minimum and solar maximum conditions to constant tidal forcing at its 97ækm lower boundary, as specified by the observationally based Climatological Tidal Model of the Thermosphere. Diagnosis of the model reveals that these changes are mainly driven by 5.3æ_m nitric oxide (NO) cooling, which more efficiently cools …

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Polar Cap Patches And The Tongue Of Ionization: A Survey Of Gps Tec Maps From 2009 To 2015, Michael David, Jan Josef Sojka, A. J. Coster Mar 2016

Polar Cap Patches And The Tongue Of Ionization: A Survey Of Gps Tec Maps From 2009 To 2015, Michael David, Jan Josef Sojka, A. J. Coster

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The source and structuring mechanisms for F region density patches have been subjects of speculation and debate for many years. We have made a survey of mappings of total electron content (TEC) between the years 2009 and 2015 from the web‐based Madrigal data server in order to determine when patches and/or a tongue of ionization (TOI) have been present in the Northern Hemisphere polar cap; we find that there is a UT and seasonal dependence that follows a specific pattern. This finding sheds considerable light upon the old question of the source of polar cap patches, since it virtually eliminates …

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Electron Parallel Closures For Various Ion Charge Numbers, Jeong-Young Ji, Sang-Kyeum Kim, Eric D. Held, Yong-Su Na Mar 2016

Electron Parallel Closures For Various Ion Charge Numbers, Jeong-Young Ji, Sang-Kyeum Kim, Eric D. Held, Yong-Su Na

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Electron parallel closures for the ion charge number Z = 1 [J.-Y. Ji and E. D. Held, Phys. Plasmas 21, 122116 (2014)] are extended for 1 ≤ Z ≤ 10. Parameters are computed for various Z with the same form of the Z = 1 kernels adopted. The parameters are smoothly varying in Z and hence can be used to interpolate parameters and closures for noninteger, effective ion charge numbers.

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Large-Amplitude Mesospheric Response To An Orographic Wave Generated Over The Southern Ocean Auckland Islands (50.7°S) During The Deepwave Project, Pierre-Dominique Pautet, Michael J. Taylor, D. C. Fritts, K. Bossert, B. P. Williams, D. Broutman, J. Ma, S. D. Eckermann, J. D. Doyle Feb 2016

Large-Amplitude Mesospheric Response To An Orographic Wave Generated Over The Southern Ocean Auckland Islands (50.7°S) During The Deepwave Project, Pierre-Dominique Pautet, Michael J. Taylor, D. C. Fritts, K. Bossert, B. P. Williams, D. Broutman, J. Ma, S. D. Eckermann, J. D. Doyle

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The Deep Propagating Gravity Wave Experiment (DEEPWAVE) project was conducted over New Zealand and the surrounding regions during June and July 2014, to more fully understand the generation, propagation, and effects of atmospheric gravity waves. A large suite of instruments collected data from the ground to the upper atmosphere (~100 km), with several new remote-sensing instruments operating on board the NSF Gulfstream V (GV) research aircraft, which was the central measurement platform of the project. On 14 July, during one of the research flights (research flight 23), a spectacular event was observed as the GV flew in the lee of …

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Equatorial Vertical Drift Modulation By The Lunar And Solar Semidiurnal Tides During The 2013 Sudden Stratospheric Warming, A. Maute, B. G. Fejer, J. M. Forbes, X. Zhang, V. Yudin Feb 2016

Equatorial Vertical Drift Modulation By The Lunar And Solar Semidiurnal Tides During The 2013 Sudden Stratospheric Warming, A. Maute, B. G. Fejer, J. M. Forbes, X. Zhang, V. Yudin

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During the 2013 stratospheric sudden warming (SSW) period the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere (JULIA) radar at Jicarmarca, Peru, observed low-latitude vertical drift modulation with lows of 0-12 m/s daytime maximum drifts between 6-13 and 22-25 January and enhanced drifts up to 43 m/s between 15 snd 19 January. The NCAR thermosphere-ionosphere-mesosphere-electrodynamics general circulation model reproduces the prevailing vertical drift feature and is used to examine possible causes. The simulations indicate that the modulation of the vertical drift is generated by the beating of the semidiurnal solar SW2 and lunar M2 tides. During the SSW period …

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Coherent And Incoherent Scatter Radar Study Of The Climatology And Day-To-Day Variability Of Mean F Region Vertical Drifts And Equatorial Spread F, J. M. Smith, F. S. Rodriques, B. G. Fejer, M. A. Milla Feb 2016

Coherent And Incoherent Scatter Radar Study Of The Climatology And Day-To-Day Variability Of Mean F Region Vertical Drifts And Equatorial Spread F, J. M. Smith, F. S. Rodriques, B. G. Fejer, M. A. Milla

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We conducted a comprehensive analysis of the vertical drifts and equatorial spread F (ESF) measurements made by the Jicamarca incoherent scatter radar (ISR) between 1994 and 2013. The ISR measurements allowed us to construct not only updated climatological curves of quiet-time vertical plasma drifts but also time-versus-height maps of ESF occurrence over the past two solar cycles. These curves and maps allowed us to better relate the observed ESF occurrence patterns to features in the vertical drift curves than previously possible. We identified an excessively high occurrence of post-midnight F region irregularities during December solstice and low solar flux conditions. …

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Linearized Conformal Gravity, James Thomas Wheeler Jan 2016

Linearized Conformal Gravity, James Thomas Wheeler

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We examine the linearization of Weyl conformal gravity, showing that the only solutions are also solutions to linearized general relativity

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Canonical Models Of Dielectric Response, D. Mark Riffe Jan 2016

Canonical Models Of Dielectric Response, D. Mark Riffe

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The interaction of electromagnetic fields with a solid is characterized by several interconnected response functions: the dielectric function ε(ω), index of refraction N(ω), conductivity σ(ω), and optical impedance Z(ω). Here we utilize three canonical models of dielectric response -- the damped harmonic oscillator, Debye polarization response, and the Drude model -- to discuss these four optical response functions. Special emphasis is devoted to the response of a Drude metal. Our main focus is on electromagnetic wave propagation through a material. We also discuss the relaxation of charge fluctuations within the context of the three canonical models of response.

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Electron Heat Flow Due To Magnetic Field Fluctuations, Jeong-Young Ji, Gunyoung Park, Sung Sik Kim, Eric D. Held Jan 2016

Electron Heat Flow Due To Magnetic Field Fluctuations, Jeong-Young Ji, Gunyoung Park, Sung Sik Kim, Eric D. Held

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Radial heat transport induced by magnetic field line fluctuations is obtained from the integral parallel heat flow closure for arbitrary collisionality. The parallel heat flow and its radial component are computed for a single harmonic sinusoidal field line perturbation. In the collisional and collisionless limits, averaging the heat flow over an unperturbed surface yields Rechester-Rosenbluth like formulae with quantitative factors. The single harmonic result is generalized to multiple harmonics given a spectrum of small magnetic perturbations. In the collisionless limit, the heat and particle transport relations are also derived. © 2016 IOP Publishing Ltd.

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Evidence Of Dispersion And Refraction Of A Spectrally Broad Gravity Wave Packet In The Mesopause Region Observed By The Na Lidar And Mesospheric Temperature Mapper Above Logan, Utah, T. Yuan, C. J. Heale, J. B. Snively, Xuguang Cai, P.-D. Pautet, C. Fish, Y. Zhao, Michael J. Taylor, W. R. Pendleton Jr., V. Wickmar, N. J. Michell Jan 2016

Evidence Of Dispersion And Refraction Of A Spectrally Broad Gravity Wave Packet In The Mesopause Region Observed By The Na Lidar And Mesospheric Temperature Mapper Above Logan, Utah, T. Yuan, C. J. Heale, J. B. Snively, Xuguang Cai, P.-D. Pautet, C. Fish, Y. Zhao, Michael J. Taylor, W. R. Pendleton Jr., V. Wickmar, N. J. Michell

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Gravity wave packets excited by a source of finite duration and size possess a broad frequency and wave number spectrum and thus span a range of temporal and spatial scales. Observing at a single location relatively close to the source, the wave components with higher frequency and larger vertical wavelength dominate at earlier times and at higher altitudes, while the lower frequency components, with shorter vertical wavelength, dominate during the latter part of the propagation. Utilizing observations from the Na lidar at Utah State University and the nearby Mesospheric Temperature Mapper at Bear Lake Observatory (41.9ÁN, 111.4ÁW), we investigate a …

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