OH Rotational Temperature Research Articles

OH and O2airglow emissions during the 1998 leonid outburst and the 2002 leonid storm

In order to enhance our understanding of the possible influence of meteor ablation on the enrichment in OH and O2 of the lower thermosphere we studied intense Leonid meteor activity by using the SATI (Spectral Airglow Temperature Imager) interferometer of the Instituto de Astrofísica de Andalucía. We measured the emission rate and rotational temperature of OH and O2 airglow emission layers during two observation periods of high meteoric activity: the 1998 Leonid outburst and the 2002 Leonid storm. The results show that there is not a clear relation of O2 and OH airglow emission and rotational temperature with meteoric activity.

Polar cap observations of mesospheric and lower thermospheric 4‐hour waves in temperature

Lower thermospheric and upper mesospheric rotational temperatures have been derived from ground‐based measurements of the O2(0–1) and OH(6–2) nightglow emissions over Resolute Bay, Canada (74.68°N, 94.90°W) and OH(4–2) nightglow emission over Kiruna, Sweden (67.90°N, 21.10°E). From measurements taken during two nights in November, 2001, we have observed a dominant and coherent 4‐hr oscillation in both the O2 and OH airglow emission rates and rotational temperatures. The phases for the two oscillation events remain almost constant at each location, indicating that these oscillations may not be caused by transient passage of instantaneous gravity waves. More importantly, there is little phase difference in universal time between the 4‐hr oscillations in temperature at Resolute and Kiruna. The small phase difference gives a strong indication that the oscillation maybe related to a zonally symmetric tide, since any tidal waves in temperature with a nonzero zonal wavenumber are very weak at high latitudes. Waves in both events have large vertical wavelengths (76 and 175 km). The 4‐hr wave shows almost no latitudinal variation from Resolute to Kiruna.

The lowest mesopause temperature in 1996 and 1997 at 23°S

From the long period airglow data at Cachoeira Paulista (22.7°S, 45.0°W), from 1990 to 1999, unusually low level of the OH rotational temperature was observed in 1996 and 1997. Compared to the other temperature observation results, it is concluded that it was lower than that expected from the solar cycle trends. A possible relation of the mesopause temperature and the atmospheric wave activities (gravity, tidal and Kelvin waves) is discussed.

Role of powering geometries and sheath gas composition on operation characteristics and the optical emission in the liquid sampling-atmospheric pressure glow discharge

Characterization of the liquid sampling-atmospheric pressure glow discharge optical emission spectroscopy (LS-APGD-OES) source is described with regards to applications in low-flow separations such as capillary liquid chromatography and electrophoresis. Four powering modes are investigated, including the effects of the individual modes on current–voltage characteristics, analyte emission response, and temporal broadening of flow injection profiles. A concentric sheath gas is employed to stabilize the solution delivery at low liquid flow rates. Sheath gas composition (N 2 or He) effects analyte emission responses as well as gas phase rotational and excitation temperatures. The respective powering modes both measures of temperature, with the OH rotational gas temperatures ranging from ∼2100 to 3000 K and the Fe (I) excitation temperatures ranging from ∼2400 to 3600 K. Rotational temperature values increase slightly when helium is employed as a sheath gas as opposed to nitrogen, with the corresponding excitation temperatures increasing somewhat as well. Analytical response curves for Na and Hg in the various powering modes demonstrate good linearity, with the limits of detection for the analytes found to be on the order of ∼4–10 ppm for 5 μl injections; equating to absolute detection limits of between 20 and 45 ng. It is believed that the approach demonstrated here suggests further improvements that will permit applications in a wide variety of aqueous solution analyses where low-flow rates and limited volumes are encountered.

First measurement of atmospheric density and pressure by meteor diffusion coefficient and airglow OH temperature in the mesopause region

Atmospheric density and pressure in the mesopause region, around 87 km, are inferred using meteor trail ambipolar diffusion coefficient, D, and simultaneously observed airglow OH rotational temperature, TOH. This is the first time to determine the atmospheric density, temperature and pressure by this method. From the 17 nights of data, we found that the number density at around 87 km of altitude varied from 0.9 to 1.2 × 1014 cm−3, and the pressure varied from 0.27 to 0.35 Pascal. The density variation is opposite to the temperature. The OH (6,2) band emission rates showed negative correlation with the density, contrast to positive relation with the temperature. In order to explain temporal variation of the OH emission rate, therefore, it is necessary to assume change of atomic oxygen mixing ratio in the emission heights.

An 18-year time series of OH rotational temperatures and middle atmosphere decadal variations

Rotational temperatures are derived from measurements of the (3-1) transitions of the OH Meinel bands. They are found to be a reasonable proxy for atmospheric kinetic temperatures at an altitude of 3×10 −3 hPa (87 km ). Measurements were taken in Wuppertal (51°N/7°E) from 1980 to 1998. A second (shorter) data set (1980–1991) is available for Northern Scandinavia (Andoya, 69°N/16°E, and Kiruna, 68°N/21°E). Data are analyzed for seasonal variations (annual, semi-annual, terannual) and for long-term changes of the temperature. Furthermore atmospheric wave activity is studied by means of measured short-term temperature fluctuations. Amplitudes and phases of the seasonal components do not change much during the measurement period. On the contrary annual mean temperatures and wave activity show strong long-term and even decadal variations. Similar decadal “episodes” are found in data from the Stratospheric Sounding Units (SSU) and from radiosondes at lower altitudes ( 1 hPa/47 km and 10 hPa/31 km , respectively). Temperature variations during these episodes are rather large ( 10 K ) and need to be taken into account when using reference or standard atmospheres. Episodic variations of temperature and wave activity are found to be correlated. They appear to be consistent with the “downward control principle” (Rev. Geophys. 33 (1995) 403).

First results from mesospheric airglow observations at 7.5º S.

The Cariri Airglow Observatory has been in operation since November, 1997. This observatory has a multi-filter photometer to measure the airglow emission intensities in the frequencies of OI557.7 nm, OI630.0 nm, NaD, OH(6,2) band, O2 Atmospheric (0-1) band , and the OH and O2 rotational temperatures. The observatory is located at Sao Joao do Cariri, State of Paraiba, one of the driest region in Northeast Brazil, situated at 7.4oS, 36.5oW. Day to day continuous observations (13 days around the new moon period) allow us to study nocturnal, day to day and seasonal variation of the airglow emission intensities. The nocturnal variations of the mesospheric emissions and OH(6,2) rotational temperature have shown strong seasonal dependence with maxima in equinox and minima in solstice. The OI557.7 nm presented the largest relative amplitude (0.42) whereas the rotational temperature presented the smallest relative amplitude (~0.03) and annual averages equal to 231 K. The annual averages of the intensities in OI557.7 nm, O2(0,1) and OH(6,2) were 124 R, 321 R and 1323 R, respectively. Variation of airglow intensities of 2 and 3 days were observed in OI5577 and O2(0,1).

Long-period wave signatures in mesospheric OH Meinel (6,2) band intensity and rotational temperature at mid-latitudes

Abstract A high performance imaging system has been used to investigate the signature of long-period, ∼8-hr, wave-like oscillations evident in the OH Meinel (6,2) band emission (peak altitude ∼87 km) during the fall and early winter months. The measurements were made from two mid-latitude sites in the western USA during 1996/7. Previous investigations of the induced temperature perturbations (amplitude and phase) suggest that many of these events exhibit characteristics akin to the mid-latitude terdiurnal tide (Pendleton, 2000). To further investigate the origin of these waves we have performed an initial investigation using the Krassovsky ratio (η) method, to determine the amplitude ratio of the induced perturbations in the zenith OH emission intensity and rotational temperature and to study their phase relationship (φ). A range of values for the magnitude and phase of η were found with a mean value of |η| = 6 ± 2 (range ∼2–10), and φ = −51° ± 21° (range −11° to −94°) with the temperature perturbation always leading the intensity wave. These results are in good agreement with existing high-latitude studies of distinct 8-hr oscillations in the literature. However, comparison with realistic gravity wave and terdiurnal tidal model computations reveal a conflicting situation where the observed negative phase results point more towards a long-period gravity wave interpretation rather than a terdiurnal tide.

Hydroxyl (6−2) airglow emission intensity ratios for rotational temperature determination

Abstract. OH(6–2) Q1/P1 and R1/P1 airglow emission intensity ratios, for rotational states up to j' = 4.5, are measured to be lower than implied by transition probabilities published by various authors including Mies, Langhoff et al. and Turnbull and Lowe. Experimentally determined relative values of j' transitions yield OH(6–2) rotational temperatures 2 K lower than Langhoff et al., 7 K lower than Mies and 13 K lower than Turnbull and Lowe.Key words: Atmospheric composition and structure (airglow and aurora; pressure, density and temperature)

Rotational temperature measurements in atmosphericpulsed dielectric barrier discharge - gas temperature andmolecular fraction effects

This study was dedicated to the correlation betweenthe rotational temperature and the plasma gas temperature in anon-thermal atmospheric plasma obtained by a dielectric barrierdischarge. Different parameters were modified (e.g. gastemperature, molecular fraction) in argon water gas mixtures.The rotational temperature of OH(A) was spectroscopicallymeasured. It is shown that in mixtures mainly composed ofatomic species, namely rare gases, the OH(A) rotationaltemperature is strongly correlated with a gas temperaturestreamer. In mixed (atomic and molecular) plasmas it seems thatthe rotational temperature can constitute an approach to thetranslational energy of heavy particles in the streamer areas.

Infrared Digital Spectrograph for Hydroxyl Rotational Temperature Measurements

A digital spectrograph designed for registration of nightglow intensity variations and estimation of the atmospheric temperature by the rotational structure of the hydroxyl emission luminosity is described. The spectrograph is based on an MДP-2 monochromator and an ST-6 CCD detector. The instrument records the nightglow spectrum in a wavelength range of 800–1000 nm, in which strong molecular hydroxyl (OH) bands emitted at the mesopause height (∼87 km) are present. The rotational temperature of OH is estimated by the least square fitting of the synthetic spectrum constructed for various temperatures to an experimental one. The temperature measurement errors are 2–10 K.

First results on daytime mesopause OH rotational temperatures using ground-based photometry from equatorial latitudes

Daytime mesospheric OH (8,3) rotational temperatures were estimated from the measurements of the relative intensities of the rotational lines in the same vibrational band, using the unique multiwavelength daytime photometer, from Tirunelveli (8.7°N; 77.8°E; 0.5°N dip latitude), an equatorial station in the Indian zone. On a couple of days when simultaneous measurements were available in the vicinity of the experimental site, the estimated temperatures compared well with those measured by the Wind Imaging Interferometer (WINDII) onboard the Upper Atmosphere Research Satellite (UARS). These results, the first of their kind, revealed: (1) large day-to-day variabilities; (2) oscillatory features with periodicities ranging from 0.5 to 6 h; and (3) large deviations of ±30–50 K, on occasions, from the MSIS-90 model temperatures. Comparisons have also been made with simultaneous measurements of neutral winds around mesopause altitudes using the Partial Reflection radar from the same site to look for any possible association of neutral dynamical parameters with the mesopause temperature variabilities. These results are presented and discussed.

Response of the airglow OH emission, temperature and mesopause wind to the atmospheric wave propagation over Shigaraki, Japan

Simultaneous observations of the night airglow OH (6, 2) band emission intensity and rotational temperature, by a sky scanning airglow spectrophotometer, and meteor winds, by a middle and upper atmosphere radar (MU radar), were carried out at Shigaraki (34.9°N, 136.1°E), Japan, from October 29 to November 11, 1994, as the first phase of a campaign, and from July 25 to July 31, 1995 as the second phase. Horizontal structures in the OH emission intensity and rotational temperature were monitored optically, together with the background wind and its wave induced fluctuations, measured by MU radar. Since the MU radar makes a direct measurement of the vertical wavelength, and the OH spectrophotometer makes a direct measurement of the horizontal wavelength, the two techniques are mutually complementary to determine intrinsic wave parameters. Gravity waves with intrinsic periods of 2 to 9 hours, horizontal wavelengths of 500 to 3000 km and vertical wavelengths of 12 to 75 km were identified. Between the two different observation techniques, there is a reasonable agreement in the inferred wave characteristics.

Comparison of terdiurnal tidal oscillations in mesospheric OH rotational temperature and Na lidar temperature measurements at mid-latitudes for fall/spring conditions

Results from two different instrumental techniques, an Na Wind/Temperature Lidar and an OH Mesospheric Temperature Mapper, have been combined to investigate the occurrence and properties of the mid-latitude terdiurnal (8-hr) tide at near mesopause altitudes (80–105 km). High-resolution Na lidar measurements were taken throughout the diurnal and annual cycle (1996–98) at Urbana, Illinois (40°N, 88°W) to characterize the seasonal behavior of the 24, 12, 8 and 6-hr tides. Complementary measurements using a recently developed CCD imager capable of mapping OH temperature (at ∼87 km altitude) were made from Bear Lake Observatory, Utah (41.9°N, 111.6°W) and Ft. Collins, Colorado (40.6°N, 105°W) within the same time period. The “mean day” lidar data for the spring and fall periods investigated here each indicate an average amplitude variation of ∼2–5 K over the depth of the OH layer but distinct phases of <1-hr LST and ∼7-hr LST, respectively, for the 8-hr component. The Temperature Mapper data are in excellent agreement with these findings but in addition have shown that the amplitude of this tidal component can vary by as much as an order of magnitude (1.5–15 K) on a night-by-night basis resulting in an apparent 8-hr dominance of the nocturnal variation during investigated portions of the spring and fall seasons with little or no diurnal and semi-diurnal variability evident. Reports of terdiurnal tidal measurements in the mid-latitude nightglow emissions are exceptionally rare and have yet to be modeled. These innovative joint measurements pave the way for new research in this important area.

Simultaneous measurements of airglow oh emissionand meteor wind by a scanning photometer and the muradar

Simultaneous observations of the night airglow OH (6,2) band emission intensity androtational temperature, by a sky scanning airglow spectrophotometer, and meteor winds, by amiddle and upper atmosphere radar (MU radar), were carried out at Shigaraki (34.9°N, 136.1°E), Japan, from 29 October to 11 November 1994, during the CRISTA/MAHRSIcampaign. Horizontal structures in the OH emission intensity and rotational temperature weremonitored optically, together with the background wind and its wave induced fluctuations,measured by MU radar. A total of 5 nights among the 7 nights of useful data showed wavelikeoscillations in both the emission intensity and temperature. Good agreement was found betweenindividual wave parameters—intrinsic period, phase velocity, horizontal and verticalwavelength—obtained from the radar and optical techniques. On some occasions a short period(∼3 h) gravity wave was observed to propagate, superposed on a long period (∼9 h) wave.

OH(6-2) spectra and rotational temperature measurements at Davis, Antarctica

Abstract. The OH(6-2) band was monitored during 1990 at Davis, Antarctica (68.6°S, 78.0°E) using a Czerny-Turner scanning spectrometer. Spectra obtained with a 0.15-nm bandwidth and wavelength steps of 0.005 nm have been recorded in an attempt to isolate auroral features. This has enabled detailed study of weak features in the region λ837.5–855.5 nm. These weak features can contribute to the apparent intensity of P-branch lines and to the background. Their presence is allowed for in our calculation of rotational temperature, but the P1(3) line is excluded because of significant contamination. An average temperature of 221±2 K is obtained from a selected data set of 104 spectra. The mid-winter average temperature, for the months of May, June and July, is 224±2 K, which is consistent with the 1986 CIRA model values for mid-winter at this height and latitude, but this result is dependent on the choice of transition probabilities. Preliminary assessments of seasonal and diurnal variations in rotational temperature and intensity are presented. Key words. Atmospheric composition and structure · Airglow and aurora; Middle-atmosphere composition and chemistry · Pressure · density and temperature

RDX ignition flame structure

Quantitative CN, OH, and OH rotational temperature, and velocity two-dimensional profiles have been imaged using planar laser-induced fluorescence (PLIF) imaging or particle-imaging velocimetry (PIV) during ignition and deradiative extinguishment of cyclotrimethylene-trimitramine, (RDX) at three different heat flux levels. Relative NO2 and NO profiles were also imaged with PLIF. Decomposition products, such as NO and NO2 were formed early in the laser heating process and the gas plume moved, away from the surface. At a later time, ignition occurred in the gas phase, as evidenced by radical buildup such as CN and OH. This often showed as a spherical ignition kernel away from the surface. The flame then transitioned rapidly to a thin flame sheet that moved toward the surface. With longer heating times, laser-supported quasi-steady-state-deflagration develops as the flame sheet again moves somewhat further from the surface. This data can be used as an aide in the development of fully time-dependent RDX combustion models. The ignition and deradiative extinguishment data will help validate these time-accurate models, which can then be used to study combustion instability.

Computational and experimental study of ammonium perchlorate combustion in a counterflow geometry

We investigate the structure of ammonium perchlorate (AP) counterflow diffusion flames in which the products of AP combustion are counterflowed against a methane fuel stream. Computationally, the two dimensional set of governing equations is reduced to a one-dimensional bouandary value problem along the stagnation point streamline through the introduction of a similarity transformation. Utilizing recent developments in hydrocarbon, chlorine, NO x , N x , H y , and AP kinetics, we formulate a detailed transport, finite-rate chemistry system for the temperature, velocity, and species mass fractions of the combined flame system. We compare the results of this model with a series of experimental measurements in which the temperature is measured with radiation-corrected thermocouples and the OH rotational population distribution, and several important chemical species, including OH, CN, NH, NO, CH 4 , and O 2 are measured with planar laser-induced fluorescence (PLIF), emission spectroscopy, and Raman spectroscopy. Both the model and the measurements reveal a multistage structure within the counterflow system comprised of an AP decomposition flame (above the AP surface) folowed by a methane AP-products diffusion flame. The calculated temperature profile is predicted to be in excellent agreement with the OH rotational temperature measurements. Measured peak CN concentrations match the spatial location predicted by the model exactly. The kinetic mechanism is able to resolve the two experimentally oberved NH peaks, one very close to the AP surface, near their proper relative intensities, Quatitative OH concentration measurements are in very good agreement with the corresponding calculated profile, matching in spatial location, and differeing by 17% in peak value. Quatitative NO measurements match the corresponding calculation, with both revealing a two-tiered structure. Low number densities and spectral broad ening at high temperatures result in poorer agreement between the Raman measurements and the corresponding major species calculations, although fuel methane and AP-generated oxygen consumption are measured with reasonable agreement.

Isotope effects in rovibrational distributions of OH(A) and OD(A) produced by electron impact on H 2O and D 2O

The OH(A-X) and OD(A-X) emission spectra have been measured by 17 eV electron impact on H 2O and D 2O in a supersonic free jet. Rotational temperature and relative vibrational population have been estimated from a computer simulation of the spectra by using two kinds of rotational temperatures. As a result, it is found that in the ν′ = 0 level the rotational temperatures of OH(A) are identical with those of OD(A) within error, on the other hand, they are significantly different from each other in the ν′ = 1 level.

Tidal oscillations of the Arctic upper mesosphere and lower thermosphere in winter

The upper mesosphere and lower thermosphere of the northern polar cap was investigated using Fabry‐Perot interferometer measurements of the horizontal wind velocity in the lower thermosphere, meridian scanning photometer observations of atomic oxygen green line brightness in the lower thermosphere, and Michelson interferometer records of the infrared Meinel OH bands brightness and rotational temperature in the upper mesosphere. Tidal airglow oscillations in the absence of local solar heating were studied using a superposed epoch analysis of observations obtained around three new‐Moon intervals (November 9–22, 1993, December 7–20, 1993, and January 4–17, 1994) in Eureka (80°N). Tidal harmonics were uncovered with an iterated least chi‐squared fit, and their existence in the data tested using a goodness‐of‐fit probability against a null hypothesis of no oscillations. No single dominant tide was found at all times and altitudes of the winter Arctic upper mesosphere and lower thermosphere. The horizontal wind velocity of the lower thermosphere exhibited all the first three harmonics of the tide, with the largest‐amplitude oscillations shown by the diurnal component of the meridional wave speed. The atmospheric layer near the mesopause that contributes to the OH airglow emission experienced terdiurnal oscillations throughout the winter season. Theoretical polarization relations for evanescent tides, considerations of energy density propagation with altitude, and a day‐by‐day analysis of the zonal and meridional wind speed and temperature all indicate that the terdiurnal tide observed on November was an evanescent zonally symmetric tide. Other data indicate propagating tides, migrating tides, or a mixture of both.