Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 30 of 625

Full-Text Articles in Physics

Generalized Near Horizon Extreme Binary Black Hole Geometry, Jacob Ciafre, Shahar Hadar, Erin Rickenbach, Maria J. Rodriguez Aug 2019

Generalized Near Horizon Extreme Binary Black Hole Geometry, Jacob Ciafre, Shahar Hadar, Erin Rickenbach, Maria J. Rodriguez

All Physics Faculty Publications

We present a new vacuum solution of Einstein’s equations describing the near horizon region of two neutral, extreme (zero-temperature), corotating, nonidentical Kerr black holes. The metric is stationary, asymptotically near horizon extremal Kerr (NHEK), and contains a localized massless strut along the symmetry axis between the black holes. In the deep infrared, it flows to two separate throats which we call “pierced-NHEK” geometries: each throat is NHEK pierced by a conical singularity. We find that in spite of the presence of the strut for the pierced-NHEK geometries the isometry group SL(2,R)×U(1) is restored. We find ...


Equatorial Disturbance Dynamo Vertical Plasma Drifts Over Jicamarca: Bi‐Monthly And Solar Cycle Dependence, Luis Navarro Dominguez, Bela G. Fejer, Ludger Scherliess Jun 2019

Equatorial Disturbance Dynamo Vertical Plasma Drifts Over Jicamarca: Bi‐Monthly And Solar Cycle Dependence, Luis Navarro Dominguez, Bela G. Fejer, Ludger Scherliess

All Physics Faculty Publications

We use extensive incoherent scatter radar observations from the Jicamarca Radio Observatory to study the local time and bi‐monthly dependence of the equatorial disturbance dynamo vertical plasma drifts on solar flux and geomagnetic activity. We show that the daytime disturbance drifts have generally small magnitudes with largest values before noon and an apparent annual variation. Near dusk, they are downward throughout the year with largest values during the equinoxes and smallest during June solstice. These downward drifts increase strongly with solar flux, and shift to later local times. They also increase with increasing geomagnetically active conditions with no apparent ...


Pmc Turbo: Studying Gravity Wave And Instability Dynamics In The Summer Mesosphere Using Polar Mesospheric Cloud Imaging And Profiling From A Stratospheric Balloon, David C. Fritts, Amber D. Miller, C. Bjorn Kjellstrand, Christopher Geach, Bifford P. Williams, Bernd Kaifler, Natalie Kaifler, Glenn Jones, Markus Rapp, Michele Limon, Jason Reimuller, Ling Wang, Shaul Hanany, Sonja Gisinger, Yucheng Zhao, Gunter Stober, Cora E. Randall May 2019

Pmc Turbo: Studying Gravity Wave And Instability Dynamics In The Summer Mesosphere Using Polar Mesospheric Cloud Imaging And Profiling From A Stratospheric Balloon, David C. Fritts, Amber D. Miller, C. Bjorn Kjellstrand, Christopher Geach, Bifford P. Williams, Bernd Kaifler, Natalie Kaifler, Glenn Jones, Markus Rapp, Michele Limon, Jason Reimuller, Ling Wang, Shaul Hanany, Sonja Gisinger, Yucheng Zhao, Gunter Stober, Cora E. Randall

All Physics Faculty Publications

The Polar Mesospheric Cloud Turbulence (PMC Turbo) experiment was designed to observe and quantify the dynamics of small‐scale gravity waves (GWs) and instabilities leading to turbulence in the upper mesosphere during polar summer using instruments aboard a stratospheric balloon. The PMC Turbo scientific payload comprised seven high‐resolution cameras and a Rayleigh lidar. Overlapping wide and narrow camera field of views from the balloon altitude of ~38 km enabled resolution of features extending from ~20 m to ~100 km at the PMC layer altitude of ~82 km. The Rayleigh lidar provided profiles of temperature below the PMC altitudes and ...


General Relativity As A Biconformal Gauge Theory, James T. Wheeler Apr 2019

General Relativity As A Biconformal Gauge Theory, James T. Wheeler

All Physics Faculty Publications

We consider the conformal group of a space of dim n=p+q, with SO(p,q) metric. The quotient of this group by its homogeneous Weyl subgroup gives a principal fiber bundle with 2n-dim base manifold and Weyl fibers. The Cartan generalization to a curved 2n-dim geometry admits an action functional linear in the curvatures. Because symmetry is maintained between the translations and the special conformal transformations in the construction, these spaces are called biconformal; this same symmetry gives biconformal spaces overlapping structures with double field theories, including manifest T-duality. We establish that biconformal geometry ...


On The Long Lasting “C‐Type” Structures In The Sodium Lidargram: The Lifetime Of Kelvin‐Helmholtz Billows In The Mesosphere And Lower Thermosphere Region, S. Mondal, S. Sarkhel, Jay Agarwal, D. Chakrabarty, R. Sekar, Tao Yuan, Xuguang Cai, Alan Z. Liu, Satonori Nozawa, Norihito Saito, Takuya D. Kawahara, Martin G. Mlynczak, James M. Russell Iii Apr 2019

On The Long Lasting “C‐Type” Structures In The Sodium Lidargram: The Lifetime Of Kelvin‐Helmholtz Billows In The Mesosphere And Lower Thermosphere Region, S. Mondal, S. Sarkhel, Jay Agarwal, D. Chakrabarty, R. Sekar, Tao Yuan, Xuguang Cai, Alan Z. Liu, Satonori Nozawa, Norihito Saito, Takuya D. Kawahara, Martin G. Mlynczak, James M. Russell Iii

All Physics Faculty Publications

In order to understand the characteristics of long‐lasting “C‐type” structure in the Sodium (Na) lidargram, six cases from different observational locations have been analyzed. The Na lidargram, collected from low‐, middle‐, and high‐latitude sites, show long lifetime of the C‐type structures which is believed to be the manifestation of Kelvin‐Helmholtz (KH) billows in the Mesosphere and Lower Thermosphere (MLT) region. In order to explore the characteristics of the long‐lasting C‐type structures, the altitude profile of square of Brunt‐Väisälä frequency in the MLT region has been derived using the temperature profile collected from ...


On The Long Lasting “C‐Type” Structures In The Sodium Lidargram: The Lifetime Of Kelvin‐Helmholtz Billows In The Mesosphere And Lower Thermosphere Region, S. Mondal, S. Sarkhel, Jay Agarwal, D. Chakrabarty, R. Sekar, Tao (Titus) Yuan, Xuguang Cai, Alan Z. Liu, Satonori Nozawa, Norihito Saito, Takuya D. Kawahara, Martin G. Mlynczak, James M. Russell Iii Apr 2019

On The Long Lasting “C‐Type” Structures In The Sodium Lidargram: The Lifetime Of Kelvin‐Helmholtz Billows In The Mesosphere And Lower Thermosphere Region, S. Mondal, S. Sarkhel, Jay Agarwal, D. Chakrabarty, R. Sekar, Tao (Titus) Yuan, Xuguang Cai, Alan Z. Liu, Satonori Nozawa, Norihito Saito, Takuya D. Kawahara, Martin G. Mlynczak, James M. Russell Iii

All Physics Faculty Publications

In order to understand the characteristics of long‐lasting “C‐type” structure in the Sodium (Na) lidargram, six cases from different observational locations have been analyzed. The Na lidargram, collected from low‐, middle‐, and high‐latitude sites, show long lifetime of the C‐type structures which is believed to be the manifestation of Kelvin‐Helmholtz (KH) billows in the Mesosphere and Lower Thermosphere (MLT) region. In order to explore the characteristics of the long‐lasting C‐type structures, the altitude profile of square of Brunt‐Väisälä frequency in the MLT region has been derived using the temperature profile collected from ...


Photochemistry On The Bottom Side Of The Mesospheric Na Layer, Tao Yuan, Wuhu Feng, John M. C. Plane, Daniel R. Marsh Mar 2019

Photochemistry On The Bottom Side Of The Mesospheric Na Layer, Tao Yuan, Wuhu Feng, John M. C. Plane, Daniel R. Marsh

All Physics Faculty Publications

Lidar observations of the mesospheric Na layer have revealed considerable diurnal variations, particularly on the bottom side of the layer, where more than an order-of-magnitude increase in Na density has been observed below 80 km after sunrise. In this paper, multi-year Na lidar observations are utilized over a full diurnal cycle at Utah State University (USU) (41.8o N, 111.8o W) and a global atmospheric model of Na with 0.5 km vertical resolution in the mesosphere and lower thermosphere (WACCM-Na) to explore the dramatic changes of Na density on the bottom side of the layer. Photolysis of the ...


Photochemistry On The Bottom Side Of The Mesospheric Na Layer, Tao Yuan, Wuhu Feng, John M. C. Plane, Daniel R. Marsh Mar 2019

Photochemistry On The Bottom Side Of The Mesospheric Na Layer, Tao Yuan, Wuhu Feng, John M. C. Plane, Daniel R. Marsh

All Physics Faculty Publications

Lidar observations of the mesospheric Na layer have revealed considerable diurnal variations, particularly on the bottom side of the layer, where more than an order-of-magnitude increase in Na density has been observed below 80 km after sunrise. In this paper, multi-year Na lidar observations are utilized over a full diurnal cycle at Utah State University (USU) (41.8∘ N, 111.8∘ W) and a global atmospheric model of Na with 0.5 km vertical resolution in the mesosphere and lower thermosphere (WACCM-Na) to explore the dramatic changes of Na density on the bottom side of the layer. Photolysis of the ...


Radar Studies Of Height-Dependent Equatorial F Region Vertical And Zonal Plasma Drifts, S. A. Shidler, F. S. Rodrigues, Bela G. Fejer, M. A. Milla Feb 2019

Radar Studies Of Height-Dependent Equatorial F Region Vertical And Zonal Plasma Drifts, S. A. Shidler, F. S. Rodrigues, Bela G. Fejer, M. A. Milla

All Physics Faculty Publications

We present the results of an analysis of long-term measurements of ionospheric F region E × B plasma drifts in the American/Peruvian sector. The analysis used observations made between 1986 and 2017 by the incoherent scatter radar of the Jicamarca Radio Observatory. Unlike previous studies, we analyzed both vertical and zonal components of the plasma drifts to derive the geomagnetically quiet time climatological variation of the drifts as a function of height and local time. We determine the average behavior of the height profiles of the drifts for different seasons and distinct solar flux conditions. Our results show good agreement ...


Validation Of Ionospheric Specifications During Geomagnetic Storms: Tec And Fof2 During The 2013 March Storm Event, Jasoon S. Shim, Ioanna Tsagouri, Larisa Goncharenko, Lutz Rastaetter, Maria Kuznetsova, Dieter Bilitza, M. Codrescu, A. J. Coster, Stanley C. Solomon, M. Fedrizzi, Matthias Förster, Timothy J. Fuller-Rowell, Larry Gardner, Joseph Huba, A. A. Namgaladze, Boris E. Prokhorov, Aaron J. Ridley, Ludger Scherliess, Robert W. Schunk, Jan J. Sojka, Lie Zhu Oct 2018

Validation Of Ionospheric Specifications During Geomagnetic Storms: Tec And Fof2 During The 2013 March Storm Event, Jasoon S. Shim, Ioanna Tsagouri, Larisa Goncharenko, Lutz Rastaetter, Maria Kuznetsova, Dieter Bilitza, M. Codrescu, A. J. Coster, Stanley C. Solomon, M. Fedrizzi, Matthias Förster, Timothy J. Fuller-Rowell, Larry Gardner, Joseph Huba, A. A. Namgaladze, Boris E. Prokhorov, Aaron J. Ridley, Ludger Scherliess, Robert W. Schunk, Jan J. Sojka, Lie Zhu

All Physics Faculty Publications

To address challenges of assessing space weather modeling capabilities, the CommunityCoordinated Modeling Center is leading a newly establishedInternational Forum for Space WeatherModeling Capabilities Assessment. This paper presents preliminary results of validation of modeled foF2 (F2 layer critical frequency) and TEC (total electron content) during the first selected 2013 March storm event (17 March 2013). In this study, we used eight ionospheric models ranging from empirical to physics-based, coupled ionosphere-thermosphere and data assimilation models. The quantities we considered are TEC and foF2 changes and percentage changes compared to quiet time background, and the maximum and minimum percentage changes. In addition ...


Modeling The Midlatitude Ionosphere Storm-Enhanced Density Distribution With A Data Assimilation Model, Larry C. Gardner, Robert W. Schunk, Ludger Scherliess, Vincent Eccles, Susanto Basu, Cesar Valladeres Oct 2018

Modeling The Midlatitude Ionosphere Storm-Enhanced Density Distribution With A Data Assimilation Model, Larry C. Gardner, Robert W. Schunk, Ludger Scherliess, Vincent Eccles, Susanto Basu, Cesar Valladeres

All Physics Faculty Publications

The Utah State University Global Assimilation of Ionospheric Measurements‐Gauss Markov model has been used to investigate the distribution of ionospheric plasma during storm times over the continental United States. Storm periods dramatically increase the effects of space weather on the ionosphere and upper atmosphere, leading to impacts on over‐the‐horizon radars, Global Positioning System location determination, spacecraft charging, power grid overloads, and disruption of the Federal Aviation Administration Wide Area Augmentation System to name a few. Four storm periods were investigated where strong storm‐enhanced densities (SEDs) were present: two strong, October 2003 and November 2003, and two ...


Analytical Representations For Characterizing The Global Aviation Radiation Environment Based On Model And Measurement Databases, W. Kent Tobiska, Leonid Didkovsky, Kevin Judge, Seth Weiman, Dave Bouwer, Justin Bailey, Bill Atwell, Molly Maskrey, Chris Mertens, Yihua Zheng, Margaret Shea, Don Smart, Brad Gersey, Richard Wilkins, Duane Bell, Larry Gardner, Robert Fuschino Sep 2018

Analytical Representations For Characterizing The Global Aviation Radiation Environment Based On Model And Measurement Databases, W. Kent Tobiska, Leonid Didkovsky, Kevin Judge, Seth Weiman, Dave Bouwer, Justin Bailey, Bill Atwell, Molly Maskrey, Chris Mertens, Yihua Zheng, Margaret Shea, Don Smart, Brad Gersey, Richard Wilkins, Duane Bell, Larry Gardner, Robert Fuschino

All Physics Faculty Publications

The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety climatological model and the Automated Radiation Measurements for Aerospace Safety (ARMAS) statistical database are presented as polynomial fit equations. Using equations based on altitude, L shell, and geomagnetic conditions an effective dose rate for any location from a galactic cosmic ray (GCR) environment can be calculated. A subset of the ARMAS database is represented by a second polynomial fit equation for the GCR plus probable relativistic energetic particle (REP; Van Allen belt REP) effective dose rates within a narrow band of L shells with altitudinal and geomagnetic dependency. Solar energetic particle ...


Simultaneous Rayleigh-Scatter And Sodium Resonance Lidar Temperature Comparisons In The Mesosphere-Lower Thermosphere, Leda Sox, Vincent B. Wickwar, Tao Yuan, Neal R. Criddle Aug 2018

Simultaneous Rayleigh-Scatter And Sodium Resonance Lidar Temperature Comparisons In The Mesosphere-Lower Thermosphere, Leda Sox, Vincent B. Wickwar, Tao Yuan, Neal R. Criddle

All Physics Faculty Publications

The Utah State University (USU) campus (41.7°N, 111.8°W) hosts a unique upper atmospheric observatory that houses both a high-power, large-aperture Rayleigh lidar and a Na lidar. For the first time, we will present 19 nights of coordinated temperature measurements from the two lidars, overlapping in the 80–110 km observational range, over one annual cycle (summer 2014 to summer 2015). This overlap has been achieved through upgrades to the existing USU Rayleigh lidar that increased its observational altitude from 45–95 to 70–115 km and by relocating the Colorado State Na lidar to the USU ...


First Observed Temporal Development Of A Noctilucent Cloud Ice Void, Linda Megner, Jacek Stegman, Pierre-Dominique Pautet, Michael J. Taylor Aug 2018

First Observed Temporal Development Of A Noctilucent Cloud Ice Void, Linda Megner, Jacek Stegman, Pierre-Dominique Pautet, Michael J. Taylor

All Physics Faculty Publications

Noctilucent clouds are ice clouds that appear high in the atmosphere, about 80 km above the summer pole. By observing them we have learned a lot about the remote and inaccessible region where they form. Recently, a satellite borne instrument discovered nearly circular ice-free regions within the clouds, denoted as “ice voids.” The origin of these voids is a mystery—we do not know what causes the clouds to disappear in large circular areas. So far these voids have only been observed from satellites, which only can take pictures of the clouds when they pass above once every 1.5 ...


The Geometry Of N = 3 Ads4 In Massive Iia, G. Bruno De Luca, Gabriele Lo Monaco, Niall T. Macpherson, Alessandro Tomasiello, Oscar Varela Aug 2018

The Geometry Of N = 3 Ads4 In Massive Iia, G. Bruno De Luca, Gabriele Lo Monaco, Niall T. Macpherson, Alessandro Tomasiello, Oscar Varela

All Physics Faculty Publications

The geometry of the N=3" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">=3N=3, SO(4)-invariant, AdS4 solution of massive type IIA supergravity that uplifts from the N=3" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">=3N=3 ...


The Geometry Of N=3 Ads4 In Massive Iia, G. Bruno De Luca, Gabriele Lo Monaco, Niall T, Macpherson, Alessandro Tomasiello, Oscar Varela Aug 2018

The Geometry Of N=3 Ads4 In Massive Iia, G. Bruno De Luca, Gabriele Lo Monaco, Niall T, Macpherson, Alessandro Tomasiello, Oscar Varela

All Physics Faculty Publications

The geometry of the N=3" role="presentation">N=3, SO(4)-invariant, AdS4 solution of massive type IIA supergravity that uplifts from the N=3" role="presentation">N=3 vacuum of D = 4 N=8" role="presentation">N=8 dyonic ISO(7) supergravity is investigated. Firstly, a D = 4, SO(4)-invariant restricted duality hierarchy is constructed and used to uplift the entire, dynamical SO(4)-invariant sector to massive type IIA. The resulting consistent uplift formulae are used to obtain a new local expression for the N=3" role="presentation">N=3 AdS4 solution in massive ...


On The Responses Of Mesosphere And Lower Thermosphere Temperatures To Geomagnetic Storms At Low And Middle Latitudes, Jingyuan Li, Wenbin Wang, Jianyong Lu, Tao Yuan, Jia Yue, Xiao Liu, Kedeng Zhang, Alan G. Burns, Yongliang Zhang, Zheng Li Aug 2018

On The Responses Of Mesosphere And Lower Thermosphere Temperatures To Geomagnetic Storms At Low And Middle Latitudes, Jingyuan Li, Wenbin Wang, Jianyong Lu, Tao Yuan, Jia Yue, Xiao Liu, Kedeng Zhang, Alan G. Burns, Yongliang Zhang, Zheng Li

All Physics Faculty Publications

Observations from lidars and satellites have shown that large neutral temperature increases and decreases occur in the middle and low latitudes of the mesosphere and lower thermosphere region during geomagnetic storms. Here we undertake first-principles simulations of mesosphere and lower thermosphere temperature responses to storms using the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model to elucidate the nature and causes of these changes. Temperature variations were not uniform; instead, nighttime temperatures changed earlier than daytime temperatures, and temperatures changed earlier at high latitudes than at low ones. Furthermore, temperatures increased in some places/times and decreased in others. As the ...


Oscillation Of The Ionosphere At Planetary-Wave Periods, Jeffrey M. Forbes, Astrid Maute, Xiaoli Zhang, Maura E. Hagan Aug 2018

Oscillation Of The Ionosphere At Planetary-Wave Periods, Jeffrey M. Forbes, Astrid Maute, Xiaoli Zhang, Maura E. Hagan

All Physics Faculty Publications

F‐region ionospheric oscillations at planetary‐wave (PW) periods (2–20 days) are investigated, with primary focus on those oscillations transmitted to the ionosphere by PW modulation of the vertically propagating tidal spectrum. Tidal effects are isolated by specifically designed numerical experiments performed with the National Center for Atmospheric Research thermosphere‐ionosphere‐electrodynamics general circulation model for October 2009, when familiar PW and tides are present in the model. Longitude versus day‐of‐month perturbations in topside F‐region electron density (Ne) of order ±30–50% at PW periods occur as a result of PW‐modulated tides. At a given ...


Affine Symmetry, Geodesics, And Homogeneous Spacetimes, David Maughan, Charles G. Torre Jul 2018

Affine Symmetry, Geodesics, And Homogeneous Spacetimes, David Maughan, Charles G. Torre

All Physics Faculty Publications

We show that the conservation laws for the geodesic equation which are associated to affine symmetries can be obtained from symmetries of the Lagrangian for affinely parametrized geodesics according to Noether's theorem, in contrast to claims found in the literature. In particular, using Aminova's classification of affine motions of Lorentzian manifolds, we show in detail how affine motions define generalized symmetries of the geodesic Lagrangian. We compute all infinitesimal proper affine symmetries and the corresponding geodesic conservation laws for all homogeneous solutions to the Einstein field equations in four spacetime dimensions with each of the following energy-momentum contents ...


Massive Spin 2 Excitations In Ads6 × S2 Warped Spacetimes, Michael Gutperle, Christoph F. Uhlemann, Oscar J. Varela Jul 2018

Massive Spin 2 Excitations In Ads6 × S2 Warped Spacetimes, Michael Gutperle, Christoph F. Uhlemann, Oscar J. Varela

All Physics Faculty Publications

We study (massive) spin-2 fluctuations around warped AdS6 solutions with 16 supersymmetries in type IIB supergravity. We identify two classes of fluctuations which are universally present for all solutions of this form. The holographically dual operators have scaling dimensions Δ = 5 + 3 and Δ = 6 + 3, where the integer ℓ encodes the R-symmetry charge. They are identified as descendant states in respective BPS multiplets (the current multiplet for Δ = 5). We also compute the normalization of the energy-momentum tensor two-point function and show that it is related to the S5 partition function of the dual ...


Seminal Evidence Of A 2.5-Sol Ultra-Fast Kelvin Wave In Mars’ Middle And Upper Atmosphere, Federico Gasperini, Maura E. Hagan, Jeffrey M. Forbes Jul 2018

Seminal Evidence Of A 2.5-Sol Ultra-Fast Kelvin Wave In Mars’ Middle And Upper Atmosphere, Federico Gasperini, Maura E. Hagan, Jeffrey M. Forbes

All Physics Faculty Publications

The structure and dynamics of Mars' middle and upper atmosphere is significantly impacted by waves propagating from the lower atmosphere. Using concurrent temperature and neutral density measurements taken by the Mars Reconnaissance Orbiter and Mars Atmosphere and Volatile EvolutioN satellites, we demonstrate for the first time that a 2.5‐sol ultra‐fast Kelvin wave is a prominent global‐scale feature of the low‐latitude middle (i.e., 30–80 km) and upper (approximately 150 km) atmosphere of Mars. Further, we present evidence of secondary waves arising from nonlinear interactions between this ultra‐fast Kelvin wave and solar tides, and ...


Polar Topside Ionosphere During Geomagnetic Storms: Comparison Of Isis-Ii With Tdim, Jan J. Sojka, Donald Rice, Vince Eccles, Michael David, Robert W. Schunk, Robert Frederick Benson, H. G. James Jun 2018

Polar Topside Ionosphere During Geomagnetic Storms: Comparison Of Isis-Ii With Tdim, Jan J. Sojka, Donald Rice, Vince Eccles, Michael David, Robert W. Schunk, Robert Frederick Benson, H. G. James

All Physics Faculty Publications

Space weather deposits energy into the high polar latitudes, primarily via Joule heating that is associated with the Poynting flux electromagnetic energy flow between the magnetosphere and ionosphere. One way to observe this energy flow is to look at the ionospheric electron density profile (EDP), especially that of the topside. The altitude location of the ionospheric peak provides additional information on the net field‐aligned vertical transport at high latitudes. To date, there have been few studies in which physics‐based ionospheric model storm simulations have been compared with topside EDPs. A rich database of high‐latitude topside ionograms obtained ...


What Is A Photon? Foundations Of Quantum Field Theory, Charles G. Torre Jun 2018

What Is A Photon? Foundations Of Quantum Field Theory, Charles G. Torre

All Physics Faculty Publications

This is a brief, informal, and relatively low-level course on the foundations of quantum field theory. The prerequisites are undergraduate courses in quantum mechanics and electromagnetism.


Weyl Geometry, James Thomas Wheeler Jun 2018

Weyl Geometry, James Thomas Wheeler

All Physics Faculty Publications

We develop the properties of Weyl geometry, beginning with a review of the conformal properties of Riemannian spacetimes. Decomposition of the Riemann curvature into trace and traceless parts allows an easy proof that the Weyl curvature tensor is the conformally invariant part of the Riemann curvature, and shows the explicit change in the Ricci and Schouten tensors required to insure conformal invariance. We include a proof of the well-known condition for the existence of a conformal transformation to a Ricci-flat spacetime. We generalize this to a derivation of the condition for the existence of a conformal transformation to a spacetime ...


The Ionospheric Impact Of An Icme-Driven Sheath Region Over Indian And American Sectors In The Absence Of A Typical Geomagnetic Storm, Diptiranjan Rout, D. Chakrabarty, S. Sarkhel, R. Sekar, Bela G. Fejer, G. D. Reeves, Atul S. Kulkarni, Nestor Aponte, Mike Sulzer, John D. Mathews, Robert B. Kerr, John Noto May 2018

The Ionospheric Impact Of An Icme-Driven Sheath Region Over Indian And American Sectors In The Absence Of A Typical Geomagnetic Storm, Diptiranjan Rout, D. Chakrabarty, S. Sarkhel, R. Sekar, Bela G. Fejer, G. D. Reeves, Atul S. Kulkarni, Nestor Aponte, Mike Sulzer, John D. Mathews, Robert B. Kerr, John Noto

All Physics Faculty Publications

On 13 April 2013, the ACE spacecraft detected arrival of an interplanetary shock at 2250 UT, which is followed by the passage of the sheath region of an interplanetary coronal mass ejection (ICME) for a prolonged (18‐hr) period. The polarity of interplanetary magnetic field Bz was northward inside the magnetic cloud region of the ICME. The ring current (SYM‐H) index did not go below −7 nT during this event suggesting the absence of a typical geomagnetic storm. The responses of the global ionospheric electric field associated with the passage of the ICME sheath region have been investigated using ...


Does The Black Hole Shadow Probe The Event Horizon Geometry?, Pedro V. P. Cunha, Carlos A. R. Herdeiro, Maria J. Rodriguez Apr 2018

Does The Black Hole Shadow Probe The Event Horizon Geometry?, Pedro V. P. Cunha, Carlos A. R. Herdeiro, Maria J. Rodriguez

All Physics Faculty Publications

There is an exciting prospect of obtaining the shadow of astrophysical black holes (BHs) in the near future with the Event Horizon Telescope. As a matter of principle, this justifies asking how much one can learn about the BH horizon itself from such a measurement. Since the shadow is determined by a set of special photon orbits, rather than horizon properties, it is possible that different horizon geometries yield similar shadows. One may then ask how sensitive is the shadow to details of the horizon geometry? As a case study, we consider the double Schwarzschild BH and analyze the impact ...


Zonally Symmetric Oscillations Of The Thermosphere At Planetary Wave Periods, Jeffrey M. Forbes, Xiaoli Zhang, Astrid Maute, Maura E. Hagan Apr 2018

Zonally Symmetric Oscillations Of The Thermosphere At Planetary Wave Periods, Jeffrey M. Forbes, Xiaoli Zhang, Astrid Maute, Maura E. Hagan

All Physics Faculty Publications

New mechanisms for imposing planetary wave (PW) variability on the ionosphere‐thermosphere system are discovered in numerical experiments conducted with the National Center for Atmospheric Research thermosphere‐ionosphere‐electrodynamics general circulation model. First, it is demonstrated that a tidal spectrum modulated at PW periods (3–20 days) entering the ionosphere‐thermosphere system near 100 km is responsible for producing ±40 m/s and ±10–15 K PW period oscillations between 110 and 150 km at low to middle latitudes. The dominant response is broadband and zonally symmetric (i.e., “S0”) over a range of periods and is attributable to tidal ...


Multi-Instrumented Observations Of The Equatorial F-Region During June Solstice: Large-Scale Wave Structures And Spread-F, Fabiano S. Rodrigues, Dustin A. Hickey, Weijia Zhan, Carlos R. Martinis, Bela G. Fejer, Marco A. Milla, Juan F. Arratia Mar 2018

Multi-Instrumented Observations Of The Equatorial F-Region During June Solstice: Large-Scale Wave Structures And Spread-F, Fabiano S. Rodrigues, Dustin A. Hickey, Weijia Zhan, Carlos R. Martinis, Bela G. Fejer, Marco A. Milla, Juan F. Arratia

All Physics Faculty Publications

Typical equatorial spread-F events are often said to occur during post-sunset, equinox conditions in most longitude sectors. Recent studies, however, have found an unexpected high occurrence of ionospheric F-region irregularities during June solstice, when conditions are believed to be unfavorable for the development of plasma instabilities responsible for equatorial spread-F (ESF). This study reports new results of a multi-instrumented investigation with the objective to better specify the occurrence of these atypical June solstice ESF in the American sector and better understand the conditions prior to their development. We present the first observations of June solstice ESF events ...


Electron Parallel Closures For The 3 + 1 Fluid Model, Jeong-Young Ji, Ilon Joseph Mar 2018

Electron Parallel Closures For The 3 + 1 Fluid Model, Jeong-Young Ji, Ilon Joseph

All Physics Faculty Publications

Linear closures are obtained for arbitrary collisionality for the 3 þ 1 fluid model which includes the evolution of density, flow velocity, and pressure both parallel and perpendicular to a preferred direction, usually a magnetic field. A large set of 6400 moment equations is solved to provide closures that are accurate in the collisional regime and well into the collisionless regime. The closures in the collisionless limit are determined by solving the kinetic equation with a model collision operator. Simple fits for the kernel functions that define the closures are obtained for arbitrary collisionality in wave number space. The results ...


Observations Of The Breakdown Of Mountain Waves Over The Andes Lidar Observatory At Cerro Pachon On 8/9 July 2012, James Hecht, Dave Fritts, L. Wang, L. J. Gelinas, R. J. Rudy, Richard L. Walterscheid, Michael J. Taylor, Pierre-Dominique Pautet, Steven Smith, S. J. Franke Jan 2018

Observations Of The Breakdown Of Mountain Waves Over The Andes Lidar Observatory At Cerro Pachon On 8/9 July 2012, James Hecht, Dave Fritts, L. Wang, L. J. Gelinas, R. J. Rudy, Richard L. Walterscheid, Michael J. Taylor, Pierre-Dominique Pautet, Steven Smith, S. J. Franke

All Physics Faculty Publications

Although mountain waves (MWs) are thought to be a ubiquitous feature of the wintertime southern Andes stratosphere, it was not known whether these waves propagated up to the mesopause region until Smith et al. (2009) confirmed their presence via airglow observations. The new Andes Lidar Observatory at Cerro Pachon in Chile provided the opportunity for a further study of these waves. Since MWs have near-zero phase speed, and zero wind lines often occur in the winter upper mesosphere (80 to 100 km altitude) region due to the reversal of the zonal mean and tidal wind, MW breakdown may routinely occur ...