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The near-UV spectrum of plumes produced by the second and third stages of a Strypii XI launch vehicle, as well as the reentry bow shock, were obtained by a sounding-rocket experiment in conjunction with complementary Langmuir-probe... more
The near-UV spectrum of plumes produced by the second and third stages of a Strypii XI launch vehicle, as well as the reentry bow shock, were obtained by a sounding-rocket experiment in conjunction with complementary Langmuir-probe measurements of total plasma density and electron temperature in the reentry boundary layer. Attention is given to the solid-rocket propellant plumes' spectroscopic data; their
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Comparison is made between the results obtained from a state-of-the-art flow and radiative model and bow shock vacuum ultraviolet (VUV) data obtained the recent Bow Shock 2 Flight Experiment. An extensive data set was obtained from... more
Comparison is made between the results obtained from a state-of-the-art flow and radiative model and bow shock vacuum ultraviolet (VUV) data obtained the recent Bow Shock 2 Flight Experiment. An extensive data set was obtained from onboard rocket measurements at a reentry speed of 5 km/sec between the altitudes of approximately 65-85 km. A description of the NO photoionization cell
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<p>Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models with interactive chemistry in the upper atmosphere, such as... more
<p>Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models with interactive chemistry in the upper atmosphere, such as WACCM-X or EDITh, usually parametrize this ionization and calculate the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra. These satellites provide in-situ measurements of the particle populations at the satellite altitude, but require interpolation and modelling to infer the actual input into the upper atmosphere.</p><p>Here we use the electron energy and flux data products from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of currently three operating satellites observes both auroral zones in the far UV from (115--180 nm) with a 3000 km wide swath and 10 x 10 km (nadir) pixel resolution during each orbit. From the N<sub>2</sub> LBH emissions, the precipitating electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate auroral ionization rates in the lower thermosphere (≈ 90–150 km), which have been validated previously against ground-based electron density measurements from EISCAT. We present an empirical model of these ionization rates derived for the entire satellite operating time and sorted according to magnetic local time and geomagnetic latitude and longitude. The model is based on geomagnetic and solar flux indices, and a sophisticated noise model is used to account for residual noise correlations. The model will be particularly targeted for use in climate models that include the upper atmosphere, such as the aforementioned WACCM-X or EDITh models. Further applications include the derived conductances in the auroral region, as well as modelling and forecasting E-region disturbances related to Space Weather.</p>
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<p>The middle atmospheric circulation is driven by atmospheric waves, which carry energy and momentum from their source to the area of their dissipation and thus providing an energetic coupling between different atmospheric layers.... more
<p>The middle atmospheric circulation is driven by atmospheric waves, which carry energy and momentum from their source to the area of their dissipation and thus providing an energetic coupling between different atmospheric layers. A comprehensive understanding of the wave-wave or wave-mean flow interactions often requires a spatial characterization of these waves. Multistatic meteor radar observations provide an opportunity to investigate the spatial and temporal variability of mesospheric/lower thermospheric winds on regional scales. We apply the 3DVAR+div retrievals to observations from the Nordic Meteor Radar Cluster and the Chilean Observation Network De Meteor Radars (CONDOR). Here we present preliminary results of a new 3DVAR+div retrieval to infer the vertical wind variability using spatially resolved observations. The new retrieval includes the continuity equation in the forward model to ensure physical consistency in the vertical winds. Our preliminary results indicate that the vertical wind variability is about +/-2m/s. The 3DVAR+div algorithm provides spatially resolved winds resolves body forces of breaking gravity waves, which are typically indicated by two counterrotating vortices. Furthermore, we infer horizontal wavelength spectra for all 3 wind components to obtain spectral slopes indicating a transition of the vertical to the divergent mode at scales of about 80-120 km at the mesosphere.</p>
Research Interests: Remote Sensing and Radar
Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the rela...
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The atmospheric winds, density and temperature of the region between 80 and 100 km, known as the mesosphere and lower thermosphere (MLT), are subject to the effects of solar and particle precipitation from above as well as to tidal and... more
The atmospheric winds, density and temperature of the region between 80 and 100 km, known as the mesosphere and lower thermosphere (MLT), are subject to the effects of solar and particle precipitation from above as well as to tidal and gravity-wave forcing from below (Fritts and Alexander 2003). Additionally, the solar heating of ozone and chemical heating due to oxygen recombination chemistry in this region compete with long-term cooling of the upper atmosphere caused by increases in greenhouse gases (Robel and Dickenson 1989; Akmaev et al. 2006; Hervig et al. 2016). However, naturally occurring fluctuations associated with variations in ozone, solar or wave forcing can mask, or even mimic, the evidence of secular change in measurements of the temperature, density and winds of the MLT. Thus, these naturally occurring variations, their mechanisms and their seasonal and solar cycle behaviour must be quantified along with the driving forces associated with small-scale wave activity th...
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&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to... more
&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;We present electron energy and flux measurements from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) satellite instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of now four satellites observes the auroral zone in the UV from which electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate ionization rates and electron densities in the upper mesosphere and lower thermosphere (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8776; 70&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;200 km). We present an initial comparison of these rates to other models and compare the electron densities to those measured by the EISCAT radar. This comparison shows that with the current standard parametrizations, the SSUSI inferred auroral (90&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;120 km) electron densities are larger than the ground-based measured ones by a factor of 2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;5. It is still under investigation if this difference is due to collocation (in space and time) and EISCAT mode characteristics or caused by incompletely modelling the ionization and recombination in that energy range.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;
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Spectroscopic measurements of the hydroxyl (OH) airglow emissions are often used to infer neutral temperatures near the mesopause. Correct Einstein coefficients for the various transitions in the OH airglow are needed to calculate... more
Spectroscopic measurements of the hydroxyl (OH) airglow emissions are often used to infer neutral temperatures near the mesopause. Correct Einstein coefficients for the various transitions in the OH airglow are needed to calculate accurate temperatures. However, studies from some studys showed experimentally and theoretically that the most commonly used Einstein spontaneous emission transition probabilities for the Q-branch of the OH Meinel (6,2) transition are overestimated. Extending their work to several Δv = 2 and 3 transitions from v′ = 3 to 9, we have determined Einstein coefficients for the first four Q-branch rotational lines. These have been derived from high resolution, high signal to noise spectroscopic observations of the OH airglow in the night sky from the Nordic Optical Telescope. The Q-branch Einstein coefficients calculated from these spectra show that values currently tabulated in the HITRAN database overestimate many of the Q-branch transition probabilities. The i...
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ABSTRACT Using ground-based measurements of the hydroxyl (OH) Meinel (3,1) band nightglow near 1500 nm, nightly means of mesospheric temperature and OH radiance from 1991 to 1998 have been derived over Stockholm (59.5°N, 18.2°E).... more
ABSTRACT Using ground-based measurements of the hydroxyl (OH) Meinel (3,1) band nightglow near 1500 nm, nightly means of mesospheric temperature and OH radiance from 1991 to 1998 have been derived over Stockholm (59.5°N, 18.2°E). Time-series analysis techniques applied both to the eight-year data set as well as to an annual superposed epoch revealed several statistically significant periodic components. A trend analysis that included these periodic components revealed a small positive trend over the eight-year temperature time series. However, examining the trends on a month-to-month basis revealed positive trends during winter, small negative trends during equinox, and no significant trend during summer. This seasonal variability indicates that dynamic feedbacks, rather than radiative forcing of the mesosphere by infrared active gases, may dominate the response of the mesosphere to greenhouse gas emissions. In support of this an examination of the variability in the superposed epoch of OH temperature and radiance showed strong impulses near equinox. A simple gravity-wave transmission and dissipation model indicates that these are due in part to seasonal increases in the gravity-wave transmission of the lower atmosphere, and enhanced wave heating and mixing in the mesosphere.
Research Interests: Environmental Science, Geology, Geochemistry, Geophysics, Physics, and 15 moreTime Series, Time series analysis, Seasonality, Atmospheric sciences, Mesosphere, Statistical Significance, Greenhouse Gas Emissions, Trend Analysis, RADIANCE, Infrared, Meteorology and Climatology, Radiative Forcing, Airglow, Latitude, and equinox
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Gravity waves (GWs) play an important role in the dynamics of global middle and upper atmosphere. Quantitatively characterizing GW in the upper stratosphere and mesosphere are still rare in Antarctica. In this paper we present a study of... more
Gravity waves (GWs) play an important role in the dynamics of global middle and upper atmosphere. Quantitatively characterizing GW in the upper stratosphere and mesosphere are still rare in Antarctica. In this paper we present a study of GWs using the lidar data obtained at South Pole (90°S) from December 1999 to January 2001 and at Rothera (67.5°S, 68.0°W) from
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Based on two and half years of lidar observations made by the British Antarctic Survey and the University of Illinois at Rothera (67.5S, 68.0W), Antarctica with an Fe Boltzmann temperature lidar, a systematic analysis was made to... more
Based on two and half years of lidar observations made by the British Antarctic Survey and the University of Illinois at Rothera (67.5S, 68.0W), Antarctica with an Fe Boltzmann temperature lidar, a systematic analysis was made to characterize the mesospheric Fe layers at this high southern latitude. Rothera Fe layer characteristics are then compared to the South Pole results reported
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As part of a joint programme between the University of Illinois and the British Antarctic Survey, Rayleigh and Fe resonance lidar observations have been made from Rothera Station (68S, 68W) on the Antarctic peninsula. Gravity wave... more
As part of a joint programme between the University of Illinois and the British Antarctic Survey, Rayleigh and Fe resonance lidar observations have been made from Rothera Station (68S, 68W) on the Antarctic peninsula. Gravity wave perturbations in both the vertical density and temperature structure have been measured, and the seasonal variation of the gravity-wave potential energy has been compiled.
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The data collected by Fe Boltzmann lidar from 2003 to 2005 at Rothera, Antarctica (67.5 S, 68.0 W) are used to generate temperature morphology in stratosphere and mesosphere covering an entire year. Satellite temperatures by the Sounding... more
The data collected by Fe Boltzmann lidar from 2003 to 2005 at Rothera, Antarctica (67.5 S, 68.0 W) are used to generate temperature morphology in stratosphere and mesosphere covering an entire year. Satellite temperatures by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) are compared to the lidar data and show good agreements in general. SABER provides near
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OH-imagers and resonant lidars have been shown to measure atmospheric gravity wave structure in different wavelength regions. This is due to the fact that imagers are most sensitive to waves with long vertical wavelengths whereas lidars... more
OH-imagers and resonant lidars have been shown to measure atmospheric gravity wave structure in different wavelength regions. This is due to the fact that imagers are most sensitive to waves with long vertical wavelengths whereas lidars observe the short vertical wavelength waves, hence both instruments are needed to cover the spectral region of atmospheric gravity waves. Here it will be
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The international Network for the Detection of Mesopause Change (NDMC, http://wdc.dlr.de/ndmc) is a global program with the mission to promote international cooperation among research groups investigating the mesopause region (80-100 km)... more
The international Network for the Detection of Mesopause Change (NDMC, http://wdc.dlr.de/ndmc) is a global program with the mission to promote international cooperation among research groups investigating the mesopause region (80-100 km) with the goal of early identification of changing climate signals. NDMC is contributing to the European Project "Atmospheric dynamics Research Infrastructure in Europe, ARISE". Measurements of the airglow at the mesopause altitude region (80-100km) from most of the European NDMC stations including spectro-photometers and imagers allow monitoring atmospheric variability at time scales comprising long-term trends, annual and seasonal variability, planetary and gravity waves and infrasonic signals. The measurements also allow validating satellite-based measurements such as from the TIMED-SABER instrument. Examples will be presented for airglow measurements and for related atmospheric dynamics analysis on the abovementioned spatio-temporal sca...
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A new 30 kW Skiymet meteor radar has been operational at Trondheim, Norway (63°N, 10°E) during the winter of 2012-13. The transmitter array is designed to direct the majority of the radar power into eight beams at 45° azimuth increments... more
A new 30 kW Skiymet meteor radar has been operational at Trondheim, Norway (63°N, 10°E) during the winter of 2012-13. The transmitter array is designed to direct the majority of the radar power into eight beams at 45° azimuth increments with peak power around 35° off zenith. Meteor count rates up to 15000 per day are observed with this system. Co-located with the radar is an all sky camera filtered to observe perturbations in the hydroxyl airglow layer due to gravity waves. High temporal resolution observations reveal the horizontal wavelength, amplitude and propagation speed and direction of gravity waves as they pass through the airglow layer. During clear-sky conditions clearly-defined gravity wave structure is frequently observed in the hydroxyl airglow. We compare the strength and direction of gravity wave activity imaged in the airglow with estimates of the vertical flux of horizontal momentum derived from the line of sight meteor drift perturbation velocities observed in the ...
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ABSTRACT A sensitive, all-sky camera has been used to image mesospheric airglow emissions at Trondheim, Norway (63.4N, 10.3W) during the winter of 2012-2013. Images of the hydroxyl and sodium airglows have been used to infer the presence... more
ABSTRACT A sensitive, all-sky camera has been used to image mesospheric airglow emissions at Trondheim, Norway (63.4N, 10.3W) during the winter of 2012-2013. Images of the hydroxyl and sodium airglows have been used to infer the presence of gravity waves passing through these layers located between 87 and 93km. Simultaneously, a new, 30kW, momentum-flux meteor-radar system observed the horizontal wind field. These data, along with meteorological balloon soundings, have been combined with a code to trace gravity-waves from their source regions in order to differentiate primary from secondary wave generation mechanisms. We will present the image analysis and the effects of the background wind field on the gravity-wave transmission in order to ascertain the source region of the waves observed near the mesopause.
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Rich lidar datasets have been collected by the University of Illinois Fe Boltzmann temperature lidar at the British Rothera Station in Antarctica (67.5°S, 68.0&amp;amp;degW) for 2.5 years from December 2002 to March 2005. A systematic... more
Rich lidar datasets have been collected by the University of Illinois Fe Boltzmann temperature lidar at the British Rothera Station in Antarctica (67.5°S, 68.0&amp;amp;degW) for 2.5 years from December 2002 to March 2005. A systematic data analysis on the polar mesospheric clouds (PMC) will be presented in this paper to characterize the PMC morphology, seasonal, and inter-annual variations at this
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Recently, the University of Illinois Fe Boltzmann temperature lidar was moved from the South Pole to Rothera (67.5° N, 68° W), Antarctica. The normal and sporadic Fe layers were observed at both locations. A few meteor trails were also... more
Recently, the University of Illinois Fe Boltzmann temperature lidar was moved from the South Pole to Rothera (67.5° N, 68° W), Antarctica. The normal and sporadic Fe layers were observed at both locations. A few meteor trails were also recorded at Rothera in January 2003. We characterize the Fe layers at both locations and make a detail comparison. The summertime
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Gravity waves (GWs) play an important role in the dynamics of global middle and upper atmosphere. However, quantitative characterization of GWs in the upper stratosphere is still rare in Antarctica. Here we present a study of... more
Gravity waves (GWs) play an important role in the dynamics of global middle and upper atmosphere. However, quantitative characterization of GWs in the upper stratosphere is still rare in Antarctica. Here we present a study of stratospheric GW parameters and seasonal variations using the data obtained with the University of Illinois Fe Boltzmann/Rayleigh lidar at the South Pole (90°S) from
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ABSTRACT The University of Illinois Fe (iron) Boltzmann temperature lidar was operated at the South Pole (90°S) from November 1999 to October 2001, and then at the Rothera Station (67.5°S, 68.0°W) from December 2002 to March 2005. This... more
ABSTRACT The University of Illinois Fe (iron) Boltzmann temperature lidar was operated at the South Pole (90°S) from November 1999 to October 2001, and then at the Rothera Station (67.5°S, 68.0°W) from December 2002 to March 2005. This lidar transmits two UV wavelengths at 372 and 374 nm, and is able to measure the middle and upper atmosphere temperature, Fe density, polar mesospheric clouds (PMC), and polar stratospheric clouds (PSCs). In this paper, we analyze the PSC data collected in the winters and springs of 2003 and 2004 at Rothera, and compare them with the PSC data collected at the South Pole in the 2000 and 2001. PSCs were observed in the range of 15-28 km during the seasons from May/June to October at both locations. The PSC backscatter ratio, width, and altitude at Rothera are comparable to those at the South Pole. However, Rothera PSCs occur less frequently (~17.7%) and in shorter periods, compared to PSCs at the South Pole (~64.9%). At Rothera, PSC occurrence frequency in 2004 is only half of that in 2003, which is likely due to warmer stratospheric temperatures in 2004 associated with changes of the polar vortex. These are the first ground-based lidar observations of PSC at Rothera, and also the first in West Antarctica.
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Mesospheric Na and Fe layer densities and temperatures were measured by lidar systems at the South Pole, Syowa (69S, 39E), and Rothera (67.5S, 68.0W) during the past several years. Comparison of the wintertime temperatures measured above... more
Mesospheric Na and Fe layer densities and temperatures were measured by lidar systems at the South Pole, Syowa (69S, 39E), and Rothera (67.5S, 68.0W) during the past several years. Comparison of the wintertime temperatures measured above these sites with TIME-GCM predictions, suggests that the model over-estimates the compressional heating associated with downwelling. When simulating the winter Na and Fe densities
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A low light TV camera coaligned with a narrow field Michelson interferometer have been used to investigate how variations in the intensity and temperature of the near-infrared hydroxyl nightglow emission are related to the passage of... more
A low light TV camera coaligned with a narrow field Michelson interferometer have been used to investigate how variations in the intensity and temperature of the near-infrared hydroxyl nightglow emission are related to the passage of short-period mesospheric gravity waves. The observations were made from Sacramento Peak, NM (32.8 deg N, 105.8 deg W) on the night of June 14/15,
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We will investigate the solar influence on the destruction of middle atmospheric ozone by looking at ozone variations with respect to the Kp and Dst indices. A microwave radiometer developed at the British Antarctic Survey has provided... more
We will investigate the solar influence on the destruction of middle atmospheric ozone by looking at ozone variations with respect to the Kp and Dst indices. A microwave radiometer developed at the British Antarctic Survey has provided 30-min temporal and 8-km vertical resolution ozone profiles between 30 and 80 km deep within the Antarctic vortex at Troll Station (72S, 2.5E, L=4.76). The Kp-index provides a measure of the geomagnetic depression at mid-latitudes occurring during enhanced geomagnetic activity, and the Dst-index indicates the geomagnetic depression at equator due to pronounced and prolonged geomagnetic activity. The number of precipitating electrons increases with increasing geomagnetic activity and thus these indices provide an indicator of the number of NO+ and HOx produced by these electrons in the upper atmosphere. The lifetime of HOx and its associated ozone destruction is short, whilst NO+ can form long-lived NOx, which will affect ozone over a wider temporal an...
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Comparison is made between the results obtained from a state-of-the-art thermochemical nonequilibrium flowfield and radiation code and data obtained from a recent experiment. The experiment obtained the first measurements of ultraviolet... more
Comparison is made between the results obtained from a state-of-the-art thermochemical nonequilibrium flowfield and radiation code and data obtained from a recent experiment. The experiment obtained the first measurements of ultraviolet radiation from the shock-heated gas in the nose region of a 0.1016-m nose radius vehicle traveling at about 3.5 km/s at altitudes between 37-75 km. The preflight computations agree at low altitudes but underpredict the data at high altitudes. Postflight flowfield and radiation sensitivity studies suggest improvements for the models at high altitudes. Specifically, excitation mechanisms that contribute to production of NO gamma-band emission need to be revised. Altitude dependence of the radiation observed from the OH radical can be understood in terms of nonequilibrium chemistry in the flow.