[1] The Global Ultraviolet Imager (GUVI) instrument carried aboard the NASA TIMED satellite measures spectral radiance of Earth's far ultraviolet airglow in region from 120 to 180 nm using a cross-track scanning spectrometer design. Continuous operation provides images disk and limb five selectable bands. Also, spectra at fixed mirror position can be obtained. Initial results demonstrate quantitative functionality for studies dayglow, aurora, ionosphere. Moreover, through forward modeling,...

In this analysis we show that vertically propagating internal gravity waves induce a downward transfer of sensible heat from regions wave dissipation, and may result in net cooling the upper atmosphere.

The semidiurnal harmonic exhibits great day‐to‐day variability in amplitude and phase. In addition, the appears to be substantially local random, suggesting a connection with gravity wave activity. We suggest that significant contribution observed at meteor heights might result from inertio‐gravity induced accelerations of mean flow. rate forcing wind is related Doppler‐shifted phase velocity, so during alternate phases an imposed oscillation interactions waves accelerate opposite senses may...

Recent observations have revealed large F‐region electron density perturbations (∼100%) and total content (TEC) (∼30%) that appear to be correlated with tsunamis. The characteristic speed horizontal wavelength of the disturbances are ∼200 m/s ∼400 km. We describe numerical simulations using our spectral full‐wave model (SFWM) upward propagation a spectrum gravity waves forced by tsunami, interaction these ionosphere. SFWM describes linear, steady‐state acoustic‐gravity in nonisothermal...

The Aerospace Corporation's Nightglow Imager observed a large step function change in airglow the form of traveling front OH Meinel (OHM) and O 2 atmospheric (O2A) emissions over Alice Springs, Australia, on February 2003. exhibited nearly factor stepwise increase OHM brightness decrease O2A brightness. There was significant (∼25 K) cooling behind fronts. among brightest for Springs that we have measured 7 years observations. event associated with strong phase‐locked day wave (PL/TDW). We...

Wave‐induced temporal fluctuations in the intensity of OH nightglow are related to temperature oscillations wave field by a model that incorporates five‐reaction photochemical scheme and complete dynamics linearized acoustic‐gravity waves an isothermal, motionless atmosphere. The I rotational T oscillations, δ , conveniently ratio where overbar refers time‐averaged quantities. η is complex quantity depends on properties basic state atmosphere (temperature, thermodynamic parameters, major...

A numerical simulation of the nonlinear evolution an upward propagating gravity wave shows that over-turning (the turning over isopotential temperature surfaces) is mechanism responsible for limiting growth wave. Wave saturation state in which amplitude constant with height) mesosphere results turbulence (random, subkilometer-scale motions), but not amplitude. Therefore, parameterizations drag and wave-associated eddy diffusivity derive from model have no rigorous justification could give...

The Collaborative Observations Regarding the Nightglow (CORN) campaign took place at Urbana Atmospheric Observatory during September 1992. instrumentation included, among others, Aerospace Corporation narrowband nightglow CCD camera, which observes OH Meinel (6–2) band (hereafter designated OH) and O 2 atmospheric (0–1) ) emissions; University of Illinois Na density/temperature lidar; MF radar. Here we report on observations small‐scale (below 10‐km horizontal wavelength) structures in...

The TIMED/GUVI instrument is a far ultraviolet spectrograph that obtains images in five spectrally resolved wavelength channels. These yield information on the dayside composition, temperature, solar EUV flux, large‐scale wave structures, and auroral processes. In this paper we present an overview analysis of Earth‐disk for four seasons (March, July, September 2002 January 2003). Days were selected during geomagnetically quiet periods when Sun was nearly orbital plane (noon orbits). Two...

A time‐dependent, nonlinear, fully compressible, axisymmetric, ƒ‐plane, numerical model is used to simulate the generation of small‐scale gravity waves in upper mesosphere and lower thermosphere by intense deep convection troposphere. The simulations show that major convective storms tropics excite a broad spectrum mesosphere‐lower above storm centers. wave field includes component guided thermal duct propagates horizontally outward from storm. Storms oscillations over source which are...

From analyzing nine months of airglow imaging observations atmospheric gravity waves (AGWs) over Adelaide, Australia (35°S) [ Walterscheid et al ., 1999] have proposed that many the quasi‐monochromatic seen in images were primarily thermally ducted. Here are presented 15 observations, from February 1996 to May 1997, for AGW frequency and propagation direction a northern latitude site, Urbana Illinois (40°N). As is geographically distant large orographic features. Similar what was found AGWs...

A function that approximates atmospheric tidal behavior in the polar regions is described. This fitted to multistation radar measurements of wind mesosphere and lower thermosphere with aim obtaining a latitude‐longitude‐height description variation tides over whole Antarctic continent. Archival data sets are combined present‐day ones fill spatial distribution observations reduce potential effects aliasing. Multiple years through compilation monthly station composite days, yielding results...

Small‐scale (less than 15 km horizontal wavelength) wavelike structures known as ripples are a common occurrence in OH airglow images. Recent case studies attribute their origin to the presence of either convective or dynamical instabilities. However, little is about frequency and period. The Maui‐MALT Observatory, located at Mt. Haleakala, instrumented with Na wind/temperature lidar, which allows determination whether atmosphere dynamically convectively unstable, fast camera takes images...

Previous incoherent radar studies at Arecibo Observatory, Puerto Rico have demonstrated that ∼1–3% electron density “imprints” of internal gravity waves are routinely present in the thermosphere (∼118–500 km). A special technique involving photoelectron‐enhanced plasma (PEPWs) was used for these observations. Recently, it discovered trails can be detected standard scatter power profiles when properly filtered. This result validated using simultaneous PEPW new development opens up possibility...

Calculations of the semidiurnal atmospheric tide at solstice using improved heating rates are presented. The for solar absorption by water vapor based on a global distribution (Jenne, 1969, 1975; Jenne et al., 1974), data McClatchey al. (1972), and an absorptivity parameterization Lacis Hansen (1974); ozone midlatitude U.S. Standard Atmosphere (COESA, 1976) detailed radiative calculations fluxes cross sections Ackerman (1971) with Schumann-Runge band Kockarts (1971). quite similar to those...

[1] Total wave heating is the sum of convergence sensible heat flux and divergence viscous kinetic energy. Numerical simulations, using a full-wave model damping atmospheric gravity waves propagating in nonisothermal atmosphere, are carried out to explore relative contributions these sources as function properties altitude. It shown that always dominates lower thermosphere, giving region an upper stronger cooling. The due energy significant only for fast (horizontal phase speed greater than...

Abstract The Aerospace Corporation's Nightglow Imager (ANI) observes nighttime OH emission (near 1.6 μm) every 2 s over an approximate 73° field of view. ANI had previously been used to study instability features seen Maui. Here we describe observations instabilities from 5 8 UT on 24 March 2012 Cerro Pachon, Chile, and compare them with previous results Maui, theory, Direct Numerical Simulations (DNS). atmosphere reduced stability because the large negative temperature gradients measured by...

The neutral wind pattern over the summer polar cap can be driven by plasma convection to resemble pattern. For a north‐south component of interplanetary magnetic field B z directed southward, speeds in conducting E‐region become ∼ 25% electric drift speeds. If ceases, this distribution drive significant current system for 6 hours. currents are reversed from those fields southward , and Hall field‐aligned components observed during periods northward . magnitudes similar small, ; however...

Temporal variations in the absolute intensity ( I ) and rotational temperature T of polar winter airglow OH(8, 3) bands were observed over Longyearbyen, Spitsbergen (78.2°N), December 1984. The high latitude observatory places it a continuous night around solstice period, thereby permitting 24‐hour optical measurements. Spectral analyses time series reveal dominant semidiurnal component wave with period 3.7 hours. Other waves shorter periods may be present for part total observing but...

The neutral response to changes in the energy source associated with appearance of a symmetric stable auroral arc is simulated using sophisticated two‐dimensional numerical model. model time‐dependent one which describes nonlinear, nonhydrostatic viscous flow rotating atmosphere. sources are ion drag momentum and Joule particle precipitation heating sources. an idealization rocket observations fairly wide intense arc. distribution production electric potential were assumed be about center...

A spectral full‐wave model is used to study the upward propagation of a gravity wave disturbance and its effect on atmospheric nightglow emissions. Gravity waves are generated by surface displacement that mimics tsunami having maximum amplitude 0.5 m, characteristic horizontal wavelength 400 km, phase speed 200 m/s. The can reach F region altitudes before significant viscous dissipation occurs. response OH Meinel in mesopause (∼87 km altitude) produces relative brightness fluctuations, which...

Abstract A very high spatial resolution ( ∼ 25 m pixel at 90 km altitude) OH airglow imager was installed the Andes Lidar Observatory on Cerro Pachón, Chile, in February 2016. This instrument collocated with a Na wind‐temperature lidar. On 1 March 2016, lidar data showed that atmosphere dynamically unstable before 0100 UT and thus conducive to formation of Kelvin‐Helmholtz instabilities (KHIs). The revealed presence KHI an apparent atmospheric gravity wave (AGW) propagating approximately...