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Physics

All Physics Faculty Publications

2017

Articles 1 - 17 of 17

Full-Text Articles in Physical Sciences and Mathematics

Ion Parallel Closures, Jeong-Young Ji, Hankyu Q. Lee, Eric D. Held Dec 2017

Ion Parallel Closures, Jeong-Young Ji, Hankyu Q. Lee, Eric D. Held

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Ion parallel closures are obtained for arbitrary atomic weights and charge numbers. For arbitrary collisionality, the heat flow and viscosity are expressed as kernel-weighted integrals of the temperature and flow-velocity gradients. Simple, fitted kernel functions are obtained from the 1600 parallel moment solution and the asymptotic behavior in the collisionless limit. The fitted kernel parameters are tabulated for various temperature ratios of ions to electrons. The closures can be used conveniently without solving the kinetic equation or higher order moment equations in closing ion fluid equations.

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Electron Parallel Transport For Arbitrary Collisionality, Jeong-Young Ji, Gunsu S. Yun, Yong-Su Na, Eric D. Held Nov 2017

Electron Parallel Transport For Arbitrary Collisionality, Jeong-Young Ji, Gunsu S. Yun, Yong-Su Na, Eric D. Held

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Integral (nonlocal) closures [J.-Y. Ji and E. D. Held, Phys. Plasmas 21, 122116 (2014)] are combined with the momentum balance equation to derive electron parallel transport relations. For a single harmonic fluctuation, the relations take the same form as the classical Spitzer theory (with possible additional terms): the electric current and heat flux densities are connected to the modified electric field and temperature gradient by transport coefficients. In contrast to the classical theory, the dimensionless coefficients depend on the collisionality quantified by a Knudsen number, the ratio of the collision length to the angular wavelength. The key difference comes from …

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A Numerical Investigation On Tidal And Gravity Wave Contributions To The Summer Time Na Variations In The Midlatitude E Region, Xuguang Cai, Tao Yuan, J. Vincent Eccles Oct 2017

A Numerical Investigation On Tidal And Gravity Wave Contributions To The Summer Time Na Variations In The Midlatitude E Region, Xuguang Cai, Tao Yuan, J. Vincent Eccles

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The Na density variations in the E region have been studied over the past few decades. Although considerable progress in understanding and in modeling the metal layer observations has been made, Na density features above 100 km have yet to be explained. Various studies have linked them to the Na+variations, a major reservoir for Na in E region. But the lack of comprehensive modeling investigations and of wind and temperature observations prevents further understanding on this important ion‐neutral coupling topic. In this study, we conduct a numerical simulation on the summer time Na density behavior in the midlatitude …

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Secondary Gravity Wave Generation Over New Zealand During The Deepwave Campaign, K. Bossert, C. G. Kruse, C. J. Heale, D. C. Fritts, B. P. Williams, J. B. Snively, Pierre-Dominique Pautet, Michael J. Taylor Aug 2017

Secondary Gravity Wave Generation Over New Zealand During The Deepwave Campaign, K. Bossert, C. G. Kruse, C. J. Heale, D. C. Fritts, B. P. Williams, J. B. Snively, Pierre-Dominique Pautet, Michael J. Taylor

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Multiple events during the Deep Propagating Gravity Wave Experiment measurement program revealed mountain wave (MW) breaking at multiple altitudes over the Southern Island of New Zealand. These events were measured during several research flights from the National Science Foundation/National Center for Atmospheric Research Gulfstream V aircraft, utilizing a Rayleigh lidar, an Na lidar, and an Advanced Mesospheric Temperature Mapper simultaneously. A flight on 29 June 2014 observed MWs with horizontal wavelengths of ~80_120ækm breaking in the stratosphere from ~10 to 50ækm altitude. A flight on 13 July 2014 observed a horizontal wavelength of ~200_240ækm MW extending from 20 to 90ækm …

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Characteristics Of Mesospheric Gravity Waves Over Antarctica Observed By Antarctic Gravity Wave Instrument Network Imagers Using 3-D Spectral Analyses, Takashi S. Matsuda, Takuji Nakamura, Mitsumu K. Ejiri, Masaki Tsutsumi, Joshihiro Tomikama, Michael J. Taylor, Yucheng Zhao, P.-Dominique Pautet, Damian J. Murphy, Tracy Moffat-Griffin Jul 2017

Characteristics Of Mesospheric Gravity Waves Over Antarctica Observed By Antarctic Gravity Wave Instrument Network Imagers Using 3-D Spectral Analyses, Takashi S. Matsuda, Takuji Nakamura, Mitsumu K. Ejiri, Masaki Tsutsumi, Joshihiro Tomikama, Michael J. Taylor, Yucheng Zhao, P.-Dominique Pautet, Damian J. Murphy, Tracy Moffat-Griffin

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We have obtained horizontal phase velocity distributions of the gravity waves around 90 km from four Antarctic airglow imagers, which belong to an international airglow imager/instrument network known as ANGWIN (Antarctic Gravity Wave Instrument Network). Results from the airglow imagers at Syowa (69°S, 40°E), Halley (76°S, 27°W), Davis (69°S, 78°E), and McMurdo (78°S, 167°E) were compared, using a new statistical analysis method based on 3-D Fourier transform (Matsuda et al., 2014) for the observation period between 7 April and 21 May 2013. Significant day-to-day and site-to-site differences were found. The averaged phase velocity spectrum during the observation period showed preferential …

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Wave Coupling From The Lower To The Middle Thermosphere: Effects Of Mean Winds And Dissipation, F. Gasperini, J. M. Forbes, M. E. Hagan Jul 2017

Wave Coupling From The Lower To The Middle Thermosphere: Effects Of Mean Winds And Dissipation, F. Gasperini, J. M. Forbes, M. E. Hagan

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Recent observational and modeling evidence has demonstrated that planetary waves can modulate atmospheric tides, and secondary waves arising from their nonlinear interactions are an important source of both temporal and longitude variability in the thermosphere. While significant progress has been made on understanding how this form of vertical coupling occurs, uncertainty still exists on how the horizontal structures of primary and secondary waves evolve with height and the processes responsible for this evolution, in part due to lack of global observations between 120ækm and 260ækm. In this work we employ a Thermosphere Ionosphere Mesosphere Electrodynamics general circulation model simulation covering …

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Periodic Nonlinear Sliding Modes For Two Uniformly Magnetized Spheres, Boyd F. Edwards, John M. Edwards May 2017

Periodic Nonlinear Sliding Modes For Two Uniformly Magnetized Spheres, Boyd F. Edwards, John M. Edwards

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A uniformly magnetized sphere slides without friction along the surface of a second, identical sphere that is held fixed in space, subject to the magnetic force and torque of the fixed sphere and the normal force. The free sphere has two stable equilibrium positions and two unstable equilibrium positions. Two small-amplitude oscillatory modes describe the sliding motion of the free sphere near each stable equilibrium, and an unstable oscillatory mode describes the motion near each unstable equilibrium. The three oscillatory modes remain periodic at finite amplitudes, one bifurcating into mixed modes and circumnavigating the free sphere at large energies. For …

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Logarithmic Corrections To Black Hole Entropy From Kerr/Cft, Abhishek Pathak, Achilleas P. Porfyriadis, Andrew Strominger, Oscar J. Varela Apr 2017

Logarithmic Corrections To Black Hole Entropy From Kerr/Cft, Abhishek Pathak, Achilleas P. Porfyriadis, Andrew Strominger, Oscar J. Varela

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It has been shown by A. Sen that logarithmic corrections to the black hole area-entropy law are entirely determined macroscopically from the massless particle spectrum. They therefore serve as powerful consistency checks on any proposed enumeration of quantum black hole microstates. Sen’s results include a macroscopic computation of the logarithmic corrections for a five-dimensional near extremal Kerr-Newman black hole. Here we compute these corrections microscopically using a stringy embedding of the Kerr/CFT correspondence and find perfect agreement.

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The Magnetic Storms Of 3_4 August 2010 And 5_6 August 2011: 1. Ground- And Space-Based Observations, Cesar E. Valladares, J. V. Eccles, S. Basu, Robert W. Schunk, R. Sheehan, R. Pradipta, J. M. Ruohoniemi Mar 2017

The Magnetic Storms Of 3_4 August 2010 And 5_6 August 2011: 1. Ground- And Space-Based Observations, Cesar E. Valladares, J. V. Eccles, S. Basu, Robert W. Schunk, R. Sheehan, R. Pradipta, J. M. Ruohoniemi

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We have used total electron content (TEC) values from low, middle, and high latitudes recorded over the American continent and density and ion temperature measured in situ by the DMSP-F15 and F17 satellites during the geomagnetic storms of 3_4 August 2010 and 5_6 August 2011 to study the formation and dynamics of plasma density enhancements that developed during these two storms. Common to both storms are the timing of the main phase that extends between 20 and 24 UT and their seasonality with both storms occurring near the end of the Northern Hemisphere summer solstice. During both storms, TEC data …

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How Hospitable Are Space Weather Affected Habitable Zones? The Role Of Ion Escape, Vladimir S. Airapetian, Alex Glocer, George V. Khazanov, Robert O Parke Loyd, Kevin France, Jan Josef Sojka, William C. Danchi, Michael W. Liemohn Feb 2017

How Hospitable Are Space Weather Affected Habitable Zones? The Role Of Ion Escape, Vladimir S. Airapetian, Alex Glocer, George V. Khazanov, Robert O Parke Loyd, Kevin France, Jan Josef Sojka, William C. Danchi, Michael W. Liemohn

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Atmospheres of exoplanets in the habitable zones around active young G-K-M stars are subject to extreme X-ray and EUV (XUV) fluxes from their host stars that can initiate atmospheric erosion. Atmospheric loss affects exoplanetary habitability in terms of surface water inventory, atmospheric pressure, the efficiency of greenhouse warming, and the dosage of the UV surface irradiation. Thermal escape models suggest that exoplanetary atmospheres around active K-M stars should undergo massive hydrogen escape, while heavier species including oxygen will accumulate forming an oxidizing atmosphere. Here, we show that non-thermal oxygen ion escape could be as important as thermal, hydrodynamic H escape …

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Climatology Of Plasmaspheric Total Electron Content Obtained From Jason 1 Satellite, Ja Soon Shim, Geonhwa Jee, Ludger Scherliess Feb 2017

Climatology Of Plasmaspheric Total Electron Content Obtained From Jason 1 Satellite, Ja Soon Shim, Geonhwa Jee, Ludger Scherliess

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We used more than 40 million total electron content (TEC) measurements obtained from the GPS TurboRogue Space Receiver receiver on board the Jason 1 satellite in order to investigate the global morphology of the plasmaspheric TEC (pTEC) including the variations with local time, latitude, longitude, season, solar cycle, and geomagnetic activity. The pTEC corresponds to the total electron content between Jason 1 (1336 km) and GPS (20,200 km) satellite altitudes. The pTEC data were collected during the 7 year period from January 2002 to December 2008. It was found that pTEC increases by about 10–30% from low to high solar …

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Large-Scale Gravity Wave Perturbations In The Mesopause Region Above Northern Hemisphere Midlatitudes During Autumnal Equinox: A Joint Study By The Usu Na Lidar And Whole Atmosphere Community Climate Model, Xuguang Cai, Tao Yuan, Han-Li Liu Feb 2017

Large-Scale Gravity Wave Perturbations In The Mesopause Region Above Northern Hemisphere Midlatitudes During Autumnal Equinox: A Joint Study By The Usu Na Lidar And Whole Atmosphere Community Climate Model, Xuguang Cai, Tao Yuan, Han-Li Liu

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To investigate gravity wave (GW) perturbations in the midlatitude mesopause region during boreal equinox, 433h of continuous Na lidar full diurnal cycle temperature measurements in September between 2011 and 2015 are utilized to derive the monthly profiles of GW-induced temperature variance, T′2, and the potential energy density (PED). Operating at Utah State University (42°N, 112°W), these lidar measurements reveal severe GW dissipation near 90km, where both parameters drop to their minima (∼ 20K2 and ∼50m2s−2, respectively). The study also shows that GWs with periods of 3–5h dominate the midlatitude mesopause region during …

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Interactions Between Uniformly Magnetized Spheres, Boyd F. Edwards, D. Mark Riffe, Jeong-Young Ji, William A. Booth Feb 2017

Interactions Between Uniformly Magnetized Spheres, Boyd F. Edwards, D. Mark Riffe, Jeong-Young Ji, William A. Booth

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We use simple symmetry arguments suitable for undergraduate students to demonstrate that the magnetic energy, forces, and torques between two uniformly magnetized spheres are identical to those between two point magnetic dipoles. These arguments exploit the equivalence of the field outside of a uniformly magnetized sphere with that of a point magnetic dipole, and pertain to spheres of arbitrary sizes, positions, and magnetizations. The point dipole/sphere equivalence for magnetic interactions may be useful in teaching and research, where dipolar approximations for uniformly magnetized spheres can now be considered to be exact. The work was originally motivated by interest in the …

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Numerical Modeling Of A Multiscale Gravity Wave Event And Its Airglow Signatures Over Mount Cook, New Zealand, During The Deepwave Campaign, C. J. Heale, K. Bossert, J. B. Snively, D. C. Fritts, Pierre-Dominique Pautet, Michael J. Taylor Jan 2017

Numerical Modeling Of A Multiscale Gravity Wave Event And Its Airglow Signatures Over Mount Cook, New Zealand, During The Deepwave Campaign, C. J. Heale, K. Bossert, J. B. Snively, D. C. Fritts, Pierre-Dominique Pautet, Michael J. Taylor

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A 2-D nonlinear compressible model is used to simulate a large-amplitude, multiscale mountain wave event over Mount Cook, NZ, observed as part of the Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign and to investigate its observable signatures in the hydroxyl (OH) layer. The campaign observed the presence of a _x=200ækm mountain wave as part of the 22nd research flight with amplitudes of >20æK in the upper stratosphere that decayed rapidly at airglow heights. Advanced Mesospheric Temperature Mapper (AMTM) showed the presence of small-scale (25_28ækm) waves within the warm phase of the large mountain wave. The simulation results show rapid breaking …

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Rainich Conditions In (2 + 1)- Dimensional Gravity, D. S. Krongos, Charles G. Torre Jan 2017

Rainich Conditions In (2 + 1)- Dimensional Gravity, D. S. Krongos, Charles G. Torre

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In (3 + 1) spacetime dimensions, the Rainich conditions are a set of equations expressed solely in terms of the metric tensor which are equivalent to the Einstein- Maxwell equations for non-null electromagnetic fields. Here we provide the analogous conditions for (2 + 1)-dimensional gravity coupled to electromagnetism. Both the non-null and null cases are treated. The construction of these conditions is based upon reducing the problem to that of gravity coupled to a scalar field, which we have treated elsewhere. These conditions can be easily extended to other theories of (2 + 1)-dimensional gravity. For example, we apply the …

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Creating Space Plasma From The Ground, Herbert C. Carlson, Frank T. Djuth, L. D. Zhang Jan 2017

Creating Space Plasma From The Ground, Herbert C. Carlson, Frank T. Djuth, L. D. Zhang

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We have performed an experiment to compare as directly as realizable the ionization production rate by HF radio wave energy versus by solar EUV. We take advantage of the commonality that ionization production by both ground-based high-power HF radio waves and by solar EUV is driven by primary and secondary suprathermal electrons near and above ~20 eV. Incoherent scatter radar (ISR)plasma-line amplitudes are used as a measure of suprathermal electron fluxes for ISR wavelengths near those for 430 MHz and are indeed a clean measure of such for those fluxes sufficiently weak to have negligible self-damping. We present data from …

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Effect Of Scrape-Off-Layer Current On Reconstructed Tokamak Equilibrium, J. R. King, Scott E. Kruger, Richard J. Groebner, James D. Hanson, J. D. Hebert, Eric D. Held, J. R. Jepson Jan 2017

Effect Of Scrape-Off-Layer Current On Reconstructed Tokamak Equilibrium, J. R. King, Scott E. Kruger, Richard J. Groebner, James D. Hanson, J. D. Hebert, Eric D. Held, J. R. Jepson

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Methods are described that extend fields from reconstructed equilibria to include scrape-off-layer current through extrapolated parametrized and experimental fits. The extrapolation includes both the effects of the toroidal-field and pressure gradients which produce scrape-off-layer current after recomputation of the Grad-Shafranov solution. To quantify the degree that inclusion of scrape-off-layer current modifies the equilibrium, the χ-squared goodness-of-fit parameter is calculated for cases with and without scrape-off-layer current. The change in χ-squared is found to be minor when scrape-off-layer current is included; however, flux surfaces are shifted by up to cm3 cm. The impact on edge modes of these scrape-off-layer modifications is …

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