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- AdS-CFT correspondence (2)
- Nonlinear interactions (2)
- AMISR (1)
- ARMAS (1)
- Acoustic-gravity waves (1)
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- AdS-CFT Correspondence (1)
- Affine collineations (1)
- Affine symmetry (1)
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- Aviation radiation database (1)
- Black hole shadow (1)
- Black holes (1)
- Cartan geometry (1)
- Chern-Simons Theories (1)
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- Collisionless regime (1)
- Conformal gravity (1)
- Density distribution (1)
- Diurnal tides (1)
- Equatorial F-region (1)
- Equatorial ionosphere (1)
- Equatorial spread-F (1)
- Extended Supersymmetry (1)
- Fluid model (1)
- Flux compactifications (1)
- FoF2 (1)
- Gauge-gravity correspondence (1)
Articles 1 - 22 of 22
Full-Text Articles in Physics
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 Josef Sojka, Lie Zhu
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 Josef 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 Gardner, Robert W. Schunk, Ludger Scherliess, Vincent Eccles, Susanto Basu, Cesar E. Valladares
Modeling The Midlatitude Ionosphere Storm-Enhanced Density Distribution With A Data Assimilation Model, Larry Gardner, Robert W. Schunk, Ludger Scherliess, Vincent Eccles, Susanto Basu, Cesar E. Valladares
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 moderate, August 2010 and …
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
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
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 campus. Previous climatological comparisons between Rayleigh and …
First Observed Temporal Development Of A Noctilucent Cloud Ice Void, Linda Megner, Jacek Stegman, Pierre-Dominique Pautet, Michael J. Taylor
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 hr—longer than …
The Geometry Of N=3 Ads4 In Massive Iia, G. Bruno De Luca, Gabriele Lo Monaco, Niall T, Macpherson, Alessandro Tomasiello, Oscar J. Varela
The Geometry Of N=3 Ads4 In Massive Iia, G. Bruno De Luca, Gabriele Lo Monaco, Niall T, Macpherson, Alessandro Tomasiello, Oscar J. 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 IIA and analyse its geometry. Locally, the internal S6 geometry corresponds to a warped fibration of …
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
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 simulation …
Oscillation Of The Ionosphere At Planetary-Wave Periods, Jeffrey M. Forbes, Astrid Maute, Xiaoli Zhang, Maura E. Hagan
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 height, these oscillations are mainly due to vertical oscillations in …
Affine Symmetry, Geodesics, And Homogeneous Spacetimes, David Maughan, Charles G. Torre
Affine Symmetry, Geodesics, And Homogeneous Spacetimes, David Maughan, Charles G. Torre
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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: vacuum, cosmological …
Massive Spin 2 Excitations In Ads6 × S2 Warped Spacetimes, Michael Gutperle, Christoph F. Uhlemann, Oscar J. Varela
Massive Spin 2 Excitations In Ads6 × S2 Warped Spacetimes, Michael Gutperle, Christoph F. Uhlemann, Oscar J. Varela
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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 + 3ℓ and Δ = 6 + 3ℓ, 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 S …
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
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 based on their amplitudes we surmise that they …
Polar Topside Ionosphere During Geomagnetic Storms: Comparison Of Isis-Ii With Tdim, Jan Josef Sojka, Donald Rice, Vince Eccles, Michael David, Robert W. Schunk, Robert Frederick Benson, H. G. James
Polar Topside Ionosphere During Geomagnetic Storms: Comparison Of Isis-Ii With Tdim, Jan Josef 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 from polar orbiting …
Weyl Geometry, James Thomas Wheeler
Weyl Geometry, James Thomas Wheeler
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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, B. G. Fejer, G. D. Reeves, Atul S. Kulkarni, Nestor Aponte, Mike Sulzer, John D. Mathews, Robert B. Kerr, John Noto
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, B. G. Fejer, G. D. Reeves, Atul S. Kulkarni, Nestor Aponte, Mike Sulzer, John D. Mathews, Robert B. Kerr, John Noto
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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 incoherent scatter …
Does The Black Hole Shadow Probe The Event Horizon Geometry?, Pedro V. P. Cunha, Carlos A. R. Herdeiro, Maria J. Rodriguez
Does The Black Hole Shadow Probe The Event Horizon Geometry?, Pedro V. P. Cunha, Carlos A. R. Herdeiro, Maria J. Rodriguez
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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
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 dissipation; essentially, the ionosphere‐thermosphere system “vacillates” in response …
Electron Parallel Closures For The 3 + 1 Fluid Model, Jeong-Young Ji, Ilon Joseph
Electron Parallel Closures For The 3 + 1 Fluid Model, Jeong-Young Ji, Ilon Joseph
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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 …
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, B. G. Fejer, Marco A. Milla, Juan F. Arratia
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, B. 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 …
Spectrum Universality Properties Of Holographic Chern-Simons Theories, Yi Pang, Junchen Rong, Oscar J. Varela
Spectrum Universality Properties Of Holographic Chern-Simons Theories, Yi Pang, Junchen Rong, Oscar J. Varela
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We give a master formula for the sin-2 spectrum of a class of three-dimensional Chern-Simons theories at large N, with flavour group containing SU(3), that arise as infrared fixed points of the D2-brane worldvolume field theory and have AdS4 duals in massive type IIA supergravtiy. We use this formula to compute the spin-2 spectrum of the individual theories discuss its supermultiplet structure and, for an N = 2 theory in this class, the spectrum of protected operators with spin 2. We also show that the trace of the Kaluza-Klein graviton mass matrix on the dual AdS4 solutions …
Exploring Wave-Wave Interactions In A General Circulation Model, Virginia Nystrom, Federico Gasperini, Jeffrey M. Forbes, Maura E. Hagan
Exploring Wave-Wave Interactions In A General Circulation Model, Virginia Nystrom, Federico Gasperini, Jeffrey M. Forbes, Maura E. Hagan
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Nonlinear interactions involving Kelvin waves with (periods, zonal wave numbers) = (3.7d, s =− 1) (UFKW1) and = (2.4d, s =− 1) (UFKW2) and s = 0 and s = 1 quasi 9 day waves (Q9DW) with diurnal tides DW1, DW2, DW3, DE2, and DE3 are explored within a National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM) simulation driven at its ∼30 km lower boundary by interpolated 3-hourly output from Modern-Era Retrospective Analysis for Research and Applications (MERRA). The existence of nonlinear wave-wave interactions between the above primary waves is determined by the presence of secondary …
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
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
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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 …
Mid-Latitude Climatologies Of Mesospheric Temperature And Geophysical Temperature Variability Determined With The Rayleigh-Scatter Lidar At Alo-Usu, Joshua P. Herron, Vincent B. Wickwar
Mid-Latitude Climatologies Of Mesospheric Temperature And Geophysical Temperature Variability Determined With The Rayleigh-Scatter Lidar At Alo-Usu, Joshua P. Herron, Vincent B. Wickwar
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From 1993-2004, 839 nights were observed with the Rayleigh-scatter lidar at Utah State University’s Atmospheric Lidar Observatory. They were reduced to obtain nighttime mesospheric temperatures between 45 and ~90 km, which were then combined to derive composite annual climatologies of mid-latitude temperatures and geophysical temperature variability. At 45 km, near the stratopause, there is a ~250 K temperature minimum in mid-winter and a 273 K maximum in mid-May. The variability behaves oppositely, being 7-10 K in winter and 2.5 K in summer. At 85 km, there is a 215 K temperature maximum at the end of December and a 170 …