Articoli di riviste: "Airglow Observations"

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Wüst, Sabine, Michael Bittner, Patrick J. Espy, W. John R. French e Frank J. Mulligan. "Hydroxyl airglow observations for investigating atmospheric dynamics: results and challenges". Atmospheric Chemistry and Physics 23, n. 2 (27 gennaio 2023): 1599–618. http://dx.doi.org/10.5194/acp-23-1599-2023.

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Abstract. Measurements of hydroxyl (OH*) airglow intensity are a straightforward and cost-efficient method which allows the derivation of information about the climate and dynamics of the upper mesosphere/lower thermosphere (UMLT) on different spatiotemporal scales during darkness. Today, instrument components can be bought “off-the-shelf” and developments in detector technology allows operation without cooling, or at least without liquid nitrogen cooling, which is difficult to automate. This makes instruments compact and suitable for automated operation. Here, we briefly summarize why an OH* airglow layer exists, how atmospheric dynamics influence it and how temperature can be derived from OH* airglow measurements. Then, we provide an overview of the scientific results regarding atmospheric dynamics (mainly gravity waves (GWs) but also planetary waves (PWs) and infrasound) achieved with OH* airglow measurements. We focus on long-term ground-based OH* airglow measurements or airglow measurements using a network of ground-based instruments. The paper includes further results from global or near-global satellite-based OH* airglow measurements, which are of special importance for characterizing the OH* airglow layer. Additionally, the results from the very few available airborne case studies using OH* airglow instruments are summarized. Scientific and technical challenges for the next few years are described.

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Duann, Yi, Loren C. Chang, Chi-Yen Lin, Yueh-Chun Hsieh, Yun-Cheng Wen, Charles C. H. Lin e Jann-Yenq Liu. "A Methodology of Retrieving Volume Emission Rate from Limb-Viewed Airglow Emission Intensity by Combining the Techniques of Abel Inversion and Deep Learning". Atmosphere 14, n. 1 (30 dicembre 2022): 74. http://dx.doi.org/10.3390/atmos14010074.

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The conversion of airglow intensity to volume emission rate (VER) is a common method for studying the ionosphere, but the contribution of the intensity conversion process to the uncertainty in estimated electron or ion density is significant. The Abel inversion is a commonly used method for retrieving VERs from vertical profiles of airglow intensities accumulated along the rays horizontally at the tangent point, but it requires that the intensities converge to zero at their uppermost height, which is often not the case due to observational limitations. In this study, we present a method for optimizing the retrieval of VER from satellite-measured airglow intensities using the techniques of deep learning and Abel inversion. This method can be applied to fill in unobserved or discontinuous observations in airglow intensity profiles with the Chapman function, allowing them to be used with the Abel inversion to determine VERs. We validate the method using limb 135.6 nm airglow emission intensity data from the NASA Global-scale Observations of the Limb and Disk (GOLD) mission. Our training process involves using three hidden layers with varying numbers of neurons, and we compare the performance of the best-performing deep learning models to Abel-transformed results from real-time observations. The combination of Abel inversion and deep learning has the potential to optimize the process of converting intensity to VER and improve the capacity for analyzing ionospheric observations.

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Huang, Tai-Yin. "Special Issue Editorial: Atmospheric Airglow—Recent Advances in Observations, Experimentations, and Modeling". Atmosphere 12, n. 2 (3 febbraio 2021): 202. http://dx.doi.org/10.3390/atmos12020202.

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Xu, J. Y., W. J. Liu, J. C. Bian, X. Liu, W. Yuan e C. Wang. "Method for retrieval of atmospheric water vapor using OH airglow for correction of astronomical observations". Astronomy & Astrophysics 639 (luglio 2020): A29. http://dx.doi.org/10.1051/0004-6361/201834621.

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Context. Water vapor in the atmosphere undergoes quick spatial and temporal variations. This has a serious impact on ground-based astronomical observations from the visible band to the infrared band resulting from water vapor attenuation and emission. Aims. We seek to show how the sky spectrum of an astronomical observation can be used to determine the amount of precipitable water vapor (PWV) along the line of sight toward the science target. Methods. In this work, we discuss a method to retrieve the PWV from the OH(8-3) band airglow spectrum. We analyzed the influences of the pressure and temperature of the atmosphere and the different water vapor vertical distributions on the PWV retrieval method in detail. Meanwhile, the accuracy of the method was analyzed via Monte Carlo simulations. To further verify the method of PWV retrieval, we carried out cross comparisons between the PWV retrieved from OH airglow and PWV from the standard star spectra of UVES using equivalent widths of telluric absorption lines observed from 2000 to 2016 at Cerro Paranal in Chile. Results. The Monte Carlo tests and the comparison between the two different methods prove the availability the PWV retrieval method from OH airglow. These results show that using OH airglow spectra in astronomical observations, PWVs along the same line of sight as the astronomical observations can be retrieved in real time. Conclusions. We provide a quick and economical method for retrieving the water vapor along the same line of sight of astronomical observation in the real time. This is especially helpful to correcting the effect of water vapor on astronomical observations.

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McDade, Ian C., e Edward J. Llewellyn. "Satellite airglow limb tomography: Methods for recovering structured emission rates in the mesospheric airglow layer". Canadian Journal of Physics 71, n. 11-12 (1 novembre 1993): 552–63. http://dx.doi.org/10.1139/p93-084.

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In this paper, we investigate the possibility of using satellite airglow limb tomography to study spatial structures in the airglow emissions of the upper mesosphere and lower thermosphere. We describe inversion procedures for converting satellite airglow limb observations into two-dimensional distributions of volume emission rates. The performance of the inversion procedures is assessed using simulated limb observations and we demonstrate the potential of this tomographic technique for studying the horizontal and vertical characteristics of wave-driven disturbances in the 80–100 km region.

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Sarkhel, Sumanta, Gunter Stober, Jorge L. Chau, Steven M. Smith, Christoph Jacobi, Subarna Mondal, Martin G. Mlynczak e James M. Russell III. "A case study of a ducted gravity wave event over northern Germany using simultaneous airglow imaging and wind-field observations". Annales Geophysicae 40, n. 2 (22 marzo 2022): 179–90. http://dx.doi.org/10.5194/angeo-40-179-2022.

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Abstract. An intriguing and rare gravity wave event was recorded on the night of 25 April 2017 using a multiwavelength all-sky airglow imager over northern Germany. The airglow imaging observations at multiple altitudes in the mesosphere and lower thermosphere region reveal that a prominent upward-propagating wave structure appeared in O(1S) and O2 airglow images. However, the same wave structure was observed to be very faint in OH airglow images, despite OH being usually one of the brightest airglow emissions. In order to investigate this rare phenomenon, the altitude profile of the vertical wavenumber was derived based on colocated meteor radar wind-field and SABER temperature profiles close to the event location. The results indicate the presence of a thermal duct layer in the altitude range of 85–91 km in the southwest region of Kühlungsborn, Germany. Utilizing these instrumental data sets, we present evidence to show how a leaky duct layer partially inhibited the wave progression in the OH airglow emission layer. The coincidental appearance of this duct layer is responsible for the observed faint wave front in the OH airglow images compared O(1S) and O2 airglow images during the course of the night over northern Germany.

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Maihara, Toshinori, Fumihide Iwamuro, Takuya Yamashita, Donald N. B. Hall, Lennox L. Cowie, Alan T. Tokunaga e Andrew Pickles. "Observations of the OH airglow emission". Publications of the Astronomical Society of the Pacific 105 (settembre 1993): 940. http://dx.doi.org/10.1086/133259.

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Unterguggenberger, Stefanie, Stefan Noll, Wuhu Feng, John M. C. Plane, Wolfgang Kausch, Stefan Kimeswenger, Amy Jones e Sabine Moehler. "Measuring FeO variation using astronomical spectroscopic observations". Atmospheric Chemistry and Physics 17, n. 6 (28 marzo 2017): 4177–87. http://dx.doi.org/10.5194/acp-17-4177-2017.

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Abstract. Airglow emission lines of OH, O2, O and Na are commonly used to probe the MLT (mesosphere–lower thermosphere) region of the atmosphere. Furthermore, molecules like electronically excited NO, NiO and FeO emit a (pseudo-) continuum. These continua are harder to investigate than atomic emission lines. So far, limb-sounding from space and a small number of ground-based low-to-medium resolution spectra have been used to measure FeO emission in the MLT. In this study the medium-to-high resolution echelle spectrograph X-shooter at the Very Large Telescope (VLT) in the Chilean Atacama Desert (24°37′ S, 70°24′ W; 2635 m) is used to study the FeO pseudo-continuum in the range from 0.5 to 0.72 µm based on 3662 spectra. Variations of the FeO spectrum itself, as well as the diurnal and seasonal behaviour of the FeO and Na emission intensities, are reported. These airglow emissions are linked by their common origin, meteoric ablation, and they share O3 as a common reactant. Major differences are found in the main emission peak of the FeO airglow spectrum between 0.58 and 0.61 µm, compared with a theoretical spectrum. The FeO and Na airglow intensities exhibit a similar nocturnal variation and a semi-annual seasonal variation with equinoctial maxima. This is satisfactorily reproduced by a whole atmosphere chemistry climate model, if the quantum yields for the reactions of Fe and Na with O3 are 13 ± 3 and 11 ± 2 % respectively. However, a comparison between the modelled O3 in the upper mesosphere and measurements of O3 made with the SABER satellite instrument suggests that these quantum yields may be a factor of ∼ 2 smaller.

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Lee, Dae-Hee, Kwang-Il Seon, Jang-Hyun Park, Ho Jin, In-Soo Yuk, Uk-Won Nam, Won-Yong Han et al. "FIMS WAVELENGTH CALIBRATION VIA AIRGLOW LINE OBSERVATIONS". Journal of Astronomy and Space Sciences 21, n. 4 (1 dicembre 2004): 391–98. http://dx.doi.org/10.5140/jass.2004.21.4.391.

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López-Moreno, José J., Carmen Morales, José F. Gómez, Joaquín Trapero, Stuart Bowyer, Jerry Edelstein, Michael Lampton e Eric J. Korpela. "EURD observations of EUV nightime airglow lines". Geophysical Research Letters 25, n. 15 (1 agosto 1998): 2937–40. http://dx.doi.org/10.1029/98gl52079.

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Shepherd, Gordon G., Jacek Stegman, Werner Singer e Raymond G. Roble. "Equinox transition in wind and airglow observations". Journal of Atmospheric and Solar-Terrestrial Physics 66, n. 6-9 (aprile 2004): 481–91. http://dx.doi.org/10.1016/j.jastp.2004.01.005.

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Wraight, P. C., e R. J. Forsyth. "A multi-channel spectrometer for airglow observations". Planetary and Space Science 36, n. 11 (novembre 1988): 1269–83. http://dx.doi.org/10.1016/0032-0633(88)90078-5.

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Otsuka, Y., K. Shiokawa, T. Ogawa e P. Wilkinson. "Geomagnetic conjugate observations of equatorial airglow depletions". Geophysical Research Letters 29, n. 15 (agosto 2002): 43–1. http://dx.doi.org/10.1029/2002gl015347.

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14

Martinis, Carlos, Dustin Hickey, Joei Wroten, Jeffrey Baumgardner, Rebecca Macinnis, Caity Sullivan e Santiago Padilla. "All-Sky Imager Observations of the Latitudinal Extent and Zonal Motion of Magnetically Conjugate 630.0 nm Airglow Depletions". Atmosphere 11, n. 6 (16 giugno 2020): 642. http://dx.doi.org/10.3390/atmos11060642.

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630.0 nm all-sky imaging data are used to detect airglow depletions associated with equatorial spread F. Pairs of imagers located at geomagnetically conjugate locations in the American sector at low and mid-latitudes provide information on the occurrence rate and zonal motion of airglow depletions. Airglow depletions are seen extending to magnetic latitudes as high as 25°. An asymmetric extension is observed with structures in the northern hemisphere reaching higher latitudes. By tracking the zonal motion of airglow depletions, zonal plasma drifts in the thermosphere can be inferred and their simultaneous behavior in both hemispheres investigated. Case studies using El Leoncito and Mercedes imagers in the southern hemisphere, and the respective magnetically conjugate imagers at Villa de Leyva and Arecibo, provide consistent evidence of the influence of the South Atlantic Magnetic Anomaly on the dynamics and characteristics of the thermosphere–ionosphere system at low and mid-latitudes.

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López-González, M. J., E. Rodríguez, R. H. Wiens, G. G. Shepherd, S. Sargoytchev, S. Brown, M. G. Shepherd et al. "Seasonal variations of O2 atmospheric and OH(6−2) airglowand temperature at mid-latitudes from SATI observations". Annales Geophysicae 22, n. 3 (19 marzo 2004): 819–28. http://dx.doi.org/10.5194/angeo-22-819-2004.

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Abstract. More than 3 years of airglow observations with a Spectral Airglow Temperature Imager (SATI) installed at the Sierra Nevada Observatory (37.06°N, 3.38°W) at 2900m height have been analyzed. Values of the column emission rate and vertically averaged temperature of the O2 atmospheric (0–1) band and of the OH Meinel (6–2) band from 1998 to 2002 have been presented. From these observations a clear seasonal variation of both emission rates and rotational temperatures is inferred at this latitude. It is found that the annual variation of the temperatures is larger than the semi-annual variation, while for the emission rates the amplitudes are comparable. Key words. Atmospheric composition and structure (airglow and aurora; pressure density and temperature; instruments and techniques)

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Franzen, Christoph, Robert Edward Hibbins, Patrick Joseph Espy e Anlaug Amanda Djupvik. "Optimizing hydroxyl airglow retrievals from long-slit astronomical spectroscopic observations". Atmospheric Measurement Techniques 10, n. 8 (25 agosto 2017): 3093–101. http://dx.doi.org/10.5194/amt-10-3093-2017.

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Abstract. Astronomical spectroscopic observations from ground-based telescopes contain background emission lines from the terrestrial atmosphere's airglow. In the near infrared, this background is composed mainly of emission from Meinel bands of hydroxyl (OH), which is produced in highly excited vibrational states by reduction of ozone near 90 km. This emission contains a wealth of information on the chemical and dynamical state of the Earth's atmosphere. However, observation strategies and data reduction processes are usually optimized to minimize the influence of these features on the astronomical spectrum. Here we discuss a measurement technique to optimize the extraction of the OH airglow signal itself from routine J-, H-, and K-band long-slit astronomical spectroscopic observations. As an example, we use data recorded from a point-source observation by the Nordic Optical Telescope's intermediate-resolution spectrograph, which has a spatial resolution of approximately 100 m at the airglow layer. Emission spectra from the OH vibrational manifold from v′ = 9 down to v′ = 3, with signal-to-noise ratios up to 280, have been extracted from 10.8 s integrations. Rotational temperatures representative of the background atmospheric temperature near 90 km, the mesosphere and lower thermosphere region, can be fitted to the OH rotational lines with an accuracy of around 0.7 K. Using this measurement and analysis technique, we derive a rotational temperature distribution with v′ that agrees with atmospheric model conditions and the preponderance of previous work. We discuss the derived rotational temperatures from the different vibrational bands and highlight the potential for both the archived and future observations, which are at unprecedented spatial and temporal resolutions, to contribute toward the resolution of long-standing problems in atmospheric physics.

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Mishin, E. V., W. J. Burke e T. Pedersen. "HF-induced airglow at magnetic zenith: theoretical considerations". Annales Geophysicae 23, n. 1 (31 gennaio 2005): 47–53. http://dx.doi.org/10.5194/angeo-23-47-2005.

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Abstract. Observations of airglow at 630nm (red line) and 557.7nm (green line) during HF modification experiments at the High Frequency Active Auroral Research Program (HAARP) heating facility are analyzed. We propose a theoretical framework for understanding the generation of Langmuir and ion acoustic waves during magnetic zenith injections. We show that observations of HF-induced airglow in an underdense ionosphere as well as a decrease in the height of the emitting volume are consistent with this scenario.

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Sun, Kang, Mahdi Yousefi, Christopher Chan Miller, Kelly Chance, Gonzalo González Abad, Iouli E. Gordon, Xiong Liu, Ewan O'Sullivan, Christopher E. Sioris e Steven C. Wofsy. "An optimal estimation-based retrieval of upper atmospheric oxygen airglow and temperature from SCIAMACHY limb observations". Atmospheric Measurement Techniques 15, n. 12 (23 giugno 2022): 3721–45. http://dx.doi.org/10.5194/amt-15-3721-2022.

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Abstract. An optimal estimation-based algorithm is developed to retrieve the number density of excited oxygen (O2) molecules that generate airglow emissions near 0.76 µm (b1Σg+ or A band) and 1.27 µm (a1Δg or 1Δ band) in the upper atmosphere. Both oxygen bands are important for the remote sensing of greenhouse gases. The algorithm is applied to the limb spectra observed by the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument in both the nominal (tangent heights below ∼ 90 km) and mesosphere–lower thermosphere (MLT) modes (tangent heights spanning 50–150 km). The number densities of emitting O2 in the a1Δg band are retrieved in an altitude range of 25–100 km near-daily in 2010, providing a climatology of O2 a1Δg-band airglow emission. This climatology will help disentangle the airglow from backscattered light in nadir remote sensing of the a1Δg band. The global monthly distributions of the vertical column density of emitting O2 in a1Δg state show mainly latitudinal dependence without other discernible geographical patterns. Temperature profiles are retrieved simultaneously from the spectral shapes of the a1Δg-band airglow emission in the nominal limb mode (valid altitude range of 40–100 km) and from both a1Δg- and b1Σg+-band airglow emissions in the MLT mode (valid range of 60–105 km). The temperature retrievals from both airglow bands are consistent internally and in agreement with independent observations from the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), with the absolute mean bias near or below 5 K and root mean squared error (RMSE) near or below 10 K. The retrieved emitting O2 number density and temperature provide a unique dataset for the remote sensing of greenhouse gases and constraining the chemical and physical processes in the upper atmosphere.

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Suzuki, S., K. Shiokawa, A. Z. Liu, Y. Otsuka, T. Ogawa e T. Nakamura. "Characteristics of equatorial gravity waves derived from mesospheric airglow imaging observations". Annales Geophysicae 27, n. 4 (6 aprile 2009): 1625–29. http://dx.doi.org/10.5194/angeo-27-1625-2009.

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Abstract. We present the characteristics of small-scale (<100 km) gravity waves in the equatorial mesopause region derived from OH airglow imaging observations at Kototabang (100.3° E, 0.2° S), Indonesia, from 2002 to 2005. We adopted a method that could automatically detect gravity waves in the airglow images using two-dimensional cross power spectra of gravity waves. The propagation directions of the waves were likely controlled by zonal filtering due to stratospheric mean winds that show a quasi-biennial oscillation (QBO) and the presence of many wave sources in the troposphere.

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Song, Rui, Martin Kaufmann, Jörn Ungermann, Manfred Ern, Guang Liu e Martin Riese. "Tomographic reconstruction of atmospheric gravity wave parameters from airglow observations". Atmospheric Measurement Techniques 10, n. 12 (30 novembre 2017): 4601–12. http://dx.doi.org/10.5194/amt-10-4601-2017.

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Abstract. Gravity waves (GWs) play an important role in the dynamics of the mesosphere and lower thermosphere (MLT). Therefore, global observations of GWs in the MLT region are of particular interest. The small scales of GWs, however, pose a major problem for the observation of GWs from space. We propose a new observation strategy for GWs in the mesopause region by combining limb and sub-limb satellite-borne remote sensing measurements for improving the spatial resolution of temperatures that are retrieved from atmospheric soundings. In our study, we simulate satellite observations of the rotational structure of the O2 A-band nightglow. A key element of the new method is the ability of the instrument or the satellite to operate in so-called target mode, i.e. to point at a particular point in the atmosphere and collect radiances at different viewing angles. These multi-angle measurements of a selected region allow for tomographic 2-D reconstruction of the atmospheric state, in particular of GW structures. The feasibility of this tomographic retrieval approach is assessed using simulated measurements. It shows that one major advantage of this observation strategy is that GWs can be observed on a much smaller scale than conventional observations. We derive a GW sensitivity function, and it is shown that target mode observations are able to capture GWs with horizontal wavelengths as short as ∼ 50 km for a large range of vertical wavelengths. This is far better than the horizontal wavelength limit of 100–200 km obtained from conventional limb sounding.

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Ogawa, T., Y. Otsuka, F. Onoma, K. Shiokawa e M. Yamamoto. "The first coordinated observations of mid-latitude E-region quasi-periodic radar echoes and lower thermospheric 557.7-nm airglow". Annales Geophysicae 23, n. 7 (14 ottobre 2005): 2391–99. http://dx.doi.org/10.5194/angeo-23-2391-2005.

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Abstract. We present the first coordinated observations of quasi-periodic (QP) radar echoes from sporadic-E (Es) field-aligned irregularities (FAIs), OI 557.7-nm airglow, and neutral winds in a common volume over Shigaraki, Japan (34.9° N, 136.1° E) on the night of 5 August 2002 during the SEEK-2 campaign. QP echo altitudes of 90-110 km were lower than usual by 10 km, enabling us to make a detailed comparison among QP echoes, airglow intensity, and neutral wind at around 96 km altitude. Eastward movement of the QP echo regions is consistent with the motions of neutral winds, airglow structures, and FAIs, suggesting that the electrodynamics of Es-layers is fundamentally controlled by the neutral atmospheric dynamics. During the QP echo event, the echo altitudes clearly went up (down) in harmony with an airglow enhancement (subsidence) that also moved to the east. This fact suggests that the eastward-moving enhanced airglow region included an upward (downward) component of neutral winds to raise (lower) the altitude of the wind-shear node responsible for the Es formation. The airglow intensity, echo intensity, and Doppler velocity of FAIs at around 96 km altitude fluctuated with periods from 10 min to 1h, indicating that these parameters were modulated with short-period atmospheric disturbances. Some QP echo regions below 100km altitude contained small-scale QP structures in which very strong neutral winds exceeding 100 m/s existed. The results are compared with recent observations, theories, and simulations of QP echoes. Keywords. Ionosphere (Ionosphere-atmosphere interactions; Ionospheric irregularities; Mid-latitude ionosphere)

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Evans, W. F. J., R. L. Gattinger, A. L. Broadfoot e E. J. Llewellyn. "The observation of chemiluminescent NiO* emissions in the laboratory and in the night airglow". Atmospheric Chemistry and Physics Discussions 11, n. 4 (15 aprile 2011): 11839–59. http://dx.doi.org/10.5194/acpd-11-11839-2011.

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Abstract. The recent finding of an orange spectral feature in OSIRIS/Odin spectra of the night airglow near 85 km has raised interest in the origin of the emission. The feature was positively identified as the chemiluminescent FeO* emission where the iron is of meteoric origin. Since the meteorite source of atomic metals in the mesosphere contains both iron and nickel, with Ni being typically 6% of Fe, it is expected that faint emissions involving Ni should also be present in the night airglow. The present study summarizes the laboratory observations of chemiluminescent NiO* emissions and includes a search for the NiO* signature in the night airglow. A faint previously unidentified "continuum" extending longwave of 440 nm has been identified in night airglow spectra obtained with two space-borne limb viewing instruments and through a comparison with laboratory spectra this continuum is identified as arising from the NiO* emission. The FeO* and NiO* emissions both originate from a reaction of the metal atoms with mesospheric ozone and so support the presence of NiO* in the night airglow.

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Михалев, Александр, Aleksandr Mikhalev, Степан Подлесный, Stepan Podlesny, Пенка Стоева e Penka Stoeva. "Night airglow in RGB mode". Solar-Terrestrial Physics 2, n. 3 (27 ottobre 2016): 106–14. http://dx.doi.org/10.12737/22289.

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To study dynamics of the upper atmosphere, we consider results of the night sky photometry, using a color CCD camera and taking into account the night airglow and features of its spectral composition. We use night airglow observations for 2010–2015, which have been obtained at the ISTP SB RAS Geophysical Observatory (52° N, 103° E) by the camera with KODAK KAI-11002 CCD sensor. We estimate average brightness of the night sky in R, G, B channels of the color camera for eastern Siberia with typical values ranging from ~0.008 to 0.01 erg·cm–2·s–1. Besides, we determine seasonal variations in the night sky luminosities in R, G, B channels of the color camera. In these channels, luminosities decrease in spring, increase in autumn, and have a pronounced summer maximum, which can be explained by scattered light and is associated with the location of the Geophysical Observatory. We consider geophysical phenomena with their optical effects in R, G, B channels of the color camera. For some geophysical phenomena (geomagnetic storms, sudden stratospheric warmings), we demonstrate the possibility of quantitative relationship between enhanced signals in R and G channels and increases in intensities of discrete 557.7 and 630 nm emissions, which are predominant in the airglow spectrum.

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Kristoffersen, S. K., W. E. Ward, S. Brown e J. R. Drummond. "Calibration and validation of the advanced E-Region Wind Interferometer". Atmospheric Measurement Techniques Discussions 5, n. 6 (14 novembre 2012): 8271–311. http://dx.doi.org/10.5194/amtd-5-8271-2012.

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Abstract. The advanced E-Region Wind Interferometer (ERWIN II) combines the imaging capabilities of a CCD detector with the wide field associated with field widened Michelson interferometry. This instrument is capable of simultaneous multi-directional wind observations for three different airglow emissions (oxygen green line (O(1S)), the PQ(7) and PP(7) emission lines in the O2(0–1) atmospheric band and P1(3) emission line in the (6,2) hydroxyl Meinel band) on a three minute cadence. In each direction, for 45 s measurements for typical airglow brightness the instrument is capable of line-of-sight wind precisions of ~ 1 m s−1 for hydroxyl and O(1S) and ~ 4 m s−1 for O2. This precision is achieved using a new data analysis algorithm which takes advantage of the imaging capabilities of the CCD detector along with knowledge of the instrument phase variation as a function of pixel location across the detector. This instrument is currently located in Eureka, Nunavut as part of the Polar Environment Atmospheric Research Laboratory (PEARL). The details of the physical configuration, the data analysis algorithm, the measurement calibration and validation of the observations are described. Field measurements which demonstrate the capabilities of this instrument are presented. To our knowledge, the wind determinations with this instrument are the most accurate and have the highest observational cadence for airglow wind observations of this region of the atmosphere and match the capabilities of other wind measuring techniques.

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Evans, W. F. J., R. L. Gattinger, A. L. Broadfoot e E. J. Llewellyn. "The observation of chemiluminescent NiO* emissions in the laboratory and in the night airglow". Atmospheric Chemistry and Physics 11, n. 18 (16 settembre 2011): 9595–603. http://dx.doi.org/10.5194/acp-11-9595-2011.

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Abstract. The recent finding of an orange spectral feature in OSIRIS/Odin spectra of the night airglow near 87 km has raised interest in the origin of the emission. The feature was positively identified as the chemiluminescent FeO* emission where the iron is of meteoric origin. Since the meteorite source of atomic metals in the mesosphere contains both iron and nickel, with Ni being typically 6 % of Fe, it is expected that faint emissions involving Ni should also be present in the night airglow. The present study summarizes the laboratory observations of chemiluminescent NiO* emissions and includes a search for the NiO* signature in the night airglow. A very faint previously unidentified "continuum" extending longwave of 440 nm has been detected in the night airglow spectra obtained with two space-borne limb viewing instruments. Through a comparison with laboratory spectra this continuum is identified as arising from the NiO* emission. The altitude profile of the new airglow emission has also been measured. The similarity of the altitude profiles of the FeO* and NiO* emissions also suggests the emission is NiO as both can originate from reaction of the metal atoms with mesospheric ozone. The observed NiO* to FeO* ratio exhibits considerable variability; possible causes of this observed variation are briefly discussed.

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26

Hecht, J. H., R. L. Walterscheid, J. Woithe, L. Campbell, R. A. Vincent e I. M. Reid. "Trends of airglow imager observations near Adelaide, Australia". Geophysical Research Letters 24, n. 5 (1 marzo 1997): 587–90. http://dx.doi.org/10.1029/97gl00128.

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27

Lowe, R. P., K. L. Gilbert e D. N. Turnbull. "High latitude summer observations of the hydroxyl airglow". Planetary and Space Science 39, n. 9 (settembre 1991): 1263–70. http://dx.doi.org/10.1016/0032-0633(91)90040-h.

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28

Gattinger, R. L., W. F. J. Evans, D. A. Degenstein e E. J. Llewellyn. "A spectral model of the FeO orange bands with a comparison between a laboratory spectrum and a night airglow spectrum observed by OSIRIS on Odin". Canadian Journal of Physics 89, n. 2 (febbraio 2011): 239–48. http://dx.doi.org/10.1139/p11-003.

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Abstract (sommario):

Emissions from the FeO orange bands have been observed in the laboratory for many decades. The transition has been identified as D(5Δi)–X(5Δi) where the subscript identifies the five Ω spin components. While the ground-state molecular constants are well-known, information on the upper state is less precise, and this is primarily due to significant energy level perturbations. Using the available constants, a preliminary spectral simulation model of the orange bands has been developed with a wavelength accuracy of approximately 1/3 nm. Using data from the OSIRIS spectrograph on board the Odin spacecraft, these FeO orange bands have been identified as a component of the night airglow spectrum emanating from the upper mesosphere. The spectral simulation model is combined with the OSIRIS observations to determine the vibrational development of the FeO emissions in the airglow. The model is also applied to published laboratory observations of the orange bands, conducted at much higher pressure than for the airglow, to test for different vibrational development.

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29

Sekar, R., D. Chakrabarty, R. Narayanan, S. Sripathi, A. K. Patra e K. S. V. Subbarao. "Characterization of VHF radar observations associated with equatorial Spread F by narrow-band optical measurements". Annales Geophysicae 22, n. 9 (23 settembre 2004): 3129–36. http://dx.doi.org/10.5194/angeo-22-3129-2004.

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Abstract. The VHF radars have been extensively used to investigate the structures and dynamics of equatorial Spread F (ESF) irregularities. However, unambiguous identification of the nature of the structures in terms of plasma depletion or enhancement requires another technique, as the return echo measured by VHF radar is proportional to the square of the electron density fluctuations. In order to address this issue, co-ordinated radar backscatter and thermospheric airglow intensity measurements were carried out during March 2003 from the MST radar site at Gadanki. Temporal variations of 630.0-nm and 777.4-nm emission intensities reveal small-scale ("micro") and large-scale ("macro") variations during the period of observation. The micro variations are absent on non-ESF nights while the macro variations are present on both ESF and non-ESF nights. In addition to the well-known anti-correlation between the base height of the F-region and the nocturnal variation of thermospheric airglow intensities, the variation of the base height of the F-layer, on occasion, is found to manifest as a bottomside wave-like structure, as seen by VHF radar on an ESF night. The micro variations in the airglow intensities are associated with large-scale irregular plasma structures and found to be in correspondence with the "plume" structures obtained by VHF radar. In addition to the commonly observed depletions with upward movement, the observation unequivocally reveals the presence of plasma enhancements which move downwards. The observation of enhancement in 777.4-nm airglow intensity, which is characterized as plasma enhancement, provides an experimental verification of the earlier prediction based on numerical modeling studies.

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30

Gattinger, R. L., I. C. McDade, A. L. Broadfoot, W. F. J. Evans, J. Stegman e E. J. Llewellyn. "Vibrational populations of near-ultraviolet O2 band systems in the night airglow 1This article is part of a Special issue that honours the work of Dr. Donald M. Hunten FRSC who passed away in December 2010 after a very illustrious career." Canadian Journal of Physics 90, n. 8 (agosto 2012): 741–51. http://dx.doi.org/10.1139/p2012-010.

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Abstract (sommario):

Observations of the limb night airglow spectrum from 250 to 475 nm, emitted from the upper mesosphere and lower thermosphere, are compared with model spectra. Data from the Arizona GLO-1 imaging spectrograph and the OSIRIS spectrograph are combined to form the observed mean airglow spectrum; a tabulated version of this spectrum is included. Model spectra of the individual O2 Herzberg I, II, and III, Chamberlain, and Slanger band systems are combined to simulate the observed mean spectrum. Franck–Condon relative band intensities are used to form a series of basis functions for the upper vibrational levels in each band system. These functions are fitted to the observed airglow spectrum with a least-squares method, the relative vibrational populations are derived and discussed.

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31

Kristoffersen, S. K., W. E. Ward, S. Brown e J. R. Drummond. "Calibration and validation of the advanced E-Region Wind Interferometer". Atmospheric Measurement Techniques 6, n. 7 (23 luglio 2013): 1761–76. http://dx.doi.org/10.5194/amt-6-1761-2013.

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Abstract (sommario):

Abstract. The advanced E-Region Wind Interferometer (ERWIN II) combines the imaging capabilities of a CCD detector with the wide field associated with field-widened Michelson interferometry. This instrument is capable of simultaneous multi-directional wind observations for three different airglow emissions (oxygen green line (O(1S)) at a height of ~97 km, the PQ(7) and P(7) emission lines in the O2(0–1) atmospheric band at ~93 km and P1(3) emission line in the (6, 2) hydroxyl Meinel band at ~87 km) on a three minute cadence. In each direction, for 45 s measurements for typical airglow volume emission rates, the instrument is capable of line-of-sight wind precisions of ~1 m s−1 for hydroxyl and O(1S) and ~4 m s−1 for O2. This precision is achieved using a new data analysis algorithm which takes advantage of the imaging capabilities of the CCD detector along with knowledge of the instrument phase variation as a function of pixel location across the detector. This instrument is currently located in Eureka, Nunavut as part of the Polar Environment Atmospheric Research Laboratory (PEARL) (80°N, 86° W). The details of the physical configuration, the data analysis algorithm, the measurement calibration and validation of the observations from December 2008 and January 2009 are described. Field measurements which demonstrate the capabilities of this instrument are presented. To our knowledge, the wind determinations with this instrument are the most accurate and have the highest observational cadence for airglow wind observations of this region of the atmosphere and match the capabilities of other wind-measuring techniques.

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32

Wüst, Sabine, Carsten Schmidt, Patrick Hannawald, Michael Bittner, Martin G. Mlynczak e James M. Russell III. "Observations of OH airglow from ground, aircraft, and satellite: investigation of wave-like structures before a minor stratospheric warming". Atmospheric Chemistry and Physics 19, n. 9 (16 maggio 2019): 6401–18. http://dx.doi.org/10.5194/acp-19-6401-2019.

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Abstract (sommario):

Abstract. In January and February 2016, the OH airglow camera system FAIM (Fast Airglow Imager) measured during six flights on board the research aircraft FALCON in northern Scandinavia. Flight 1 (14 January 2016) covering the same ground track in several flight legs and flight 5 (28 January 2016) along the shoreline of Norway are discussed in detail in this study. The images of the OH airglow intensity are analysed with a two-dimensional FFT regarding horizontal periodic structures between 3 and 26 km horizontal wavelength and their direction of propagation. Two ground-based spectrometers (GRIPS, Ground-based Infrared P-branch Spectrometer) provided OH airglow temperatures. One was placed at ALOMAR, Northern Norway (Arctic Lidar Observatory for Middle Atmosphere Research; 69.28∘ N, 16.01∘ E) and the other one at Kiruna, northern Sweden (67.86∘ N, 20.24∘ E). Especially during the last third of January 2016, the weather conditions at Kiruna were good enough for the computation of nightly means of gravity wave potential energy density. Coincident TIMED-SABER (Thermosphere Ionosphere Mesosphere Energetics Dynamics–Sounding of the Atmosphere using Broadband Emission Radiometry) measurements complete the data set. They allow for the derivation of information about the Brunt–Väisälä frequency and about the height of the OH airglow layer as well as its thickness. The data are analysed with respect to the temporal and spatial evolution of mesopause gravity wave activity just before a minor stratospheric warming at the end of January 2016. Wave events with periods longer (shorter) than 60 min might mainly be generated in the troposphere (at or above the height of the stratospheric jet). Special emphasis is placed on small-scale signatures, i.e. on ripples, which may be signatures of local instability and which may be related to a step in a wave-breaking process. The most mountainous regions are characterized by the highest occurrence rate of wave-like structures in both flights.

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33

Pilger, Christoph, Carsten Schmidt, Florian Streicher, Sabine Wüst e Michael Bittner. "Airglow observations of orographic, volcanic and meteorological infrasound signatures". Journal of Atmospheric and Solar-Terrestrial Physics 104 (novembre 2013): 55–66. http://dx.doi.org/10.1016/j.jastp.2013.08.008.

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34

Hecht, James H., Suzanne K. Ramsay Howat, Richard L. Walterscheid e Joseph R. Isler. "Observations of variations in airglow emissions during ALOHA-93". Geophysical Research Letters 22, n. 20 (15 ottobre 1995): 2817–20. http://dx.doi.org/10.1029/95gl03019.

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35

Mikhalev, A. V., M. A. Tashchilin e S. M. Sakerin. "Effect of Atmospheric Aerosol on Ground-Based Airglow Observations". Atmospheric and Oceanic Optics 32, n. 4 (luglio 2019): 410–15. http://dx.doi.org/10.1134/s1024856019040109.

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36

Yang, Yu-Ming, Olga Verkhoglyadova, Martin G. Mlynczak, Anthony J. Mannucci, Xing Meng, Richard B. Langley e Linda A. Hunt. "Satellite-based observations of tsunami-induced mesosphere airglow perturbations". Geophysical Research Letters 44, n. 1 (10 gennaio 2017): 522–32. http://dx.doi.org/10.1002/2016gl070764.

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37

Colerico, M. J., M. Mendillo, C. G. Fesen e J. Meriwether. "Comparative investigations of equatorial electrodynamics and low-to-mid latitude coupling of the thermosphere-ionosphere system". Annales Geophysicae 24, n. 2 (23 marzo 2006): 503–13. http://dx.doi.org/10.5194/angeo-24-503-2006.

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Abstract (sommario):

Abstract. The thermospheric midnight temperature maximum (MTM) is a highly variable, but persistent, large scale neutral temperature enhancement which occurs at low latitudes. Its occurrence can impact many fundamental upper atmospheric parameters such as pressure, density, neutral winds, neutral density, and F-region plasma. Although the MTM has been the focus of several investigations employing various instrumentation including photometers, satellites, and Fabry-Perot interferometers, limited knowledge exists regarding the latitude extent of its influence on the upper atmosphere. This is largely due to observational limitations which confined the collective geographic range to latitudes within ±23°. This paper investigates the MTM's latitudinal extent through all-sky imaging observations of its 6300Å airglow signature referred to by Colerico et al. (1996) as the midnight brightness wave (MBW). The combined field of view of three Southern Hemisphere imaging systems located at Arequipa, Peru, and Tucuman and El Leoncito, Argentina, for the first time extends the contiguous latitudinal range of imager observations to 8° S-39° S in the American sector. Our results highlight the propagation of MBW events through the combined fields of view past 39° S latitude, providing the first evidence that the MTM's effect on the upper atmosphere extends into mid-latitudes. The observations presented here are compared with modeled 6300Å emissions calculated using the NCAR thermosphere-ionosphere-electrodynamic general circulation model (TIEGCM) in conjunction with an airglow code. We report that at this time TIEGCM is unable to simulate an MBW event due to the model's inability to reproduce an MTM of the same magnitude and occurrence time as those observed via FPI measurements made from Arequipa. This work also investigates the origins of an additional low latitude airglow feature referred to by Colerico et al. (1996) as the pre-midnight brightness wave (PMBW) and described as an enhancement in 6300Å emission which occurs typically between 20:00-22:00 LT and exhibits equatorward propagation. We present the first successful simulation of a PMBW event using the TIEGCM and the airglow code. We find that the PMBW's origin is electro-dynamical in nature, resulting from the expected evening decay of the inter-tropical arcs.

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38

Egito, Fabio, Ricardo Arlen Buriti, Amauri Fragoso Medeiros e Hisao Takahashi. "Ultrafast Kelvin waves in the MLT airglow and wind, and their interaction with the atmospheric tides". Annales Geophysicae 36, n. 1 (21 febbraio 2018): 231–41. http://dx.doi.org/10.5194/angeo-36-231-2018.

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Abstract (sommario):

Abstract. Airglow and wind measurements from the Brazilian equatorial region were used to investigate the presence and the effects of the 3–4-day ultrafast Kelvin waves in the MLT. The airglow integrated intensities of the OI557.7 nm, O2b(0-1) and OH(6-2) emissions, as well as the OH rotational temperature, were measured by a multichannel photometer, and the zonal and meridional wind components between 80 and 100 km were obtained from a meteor radar. Both instruments are installed in the Brazilian equatorial region at São João do Cariri (7.4∘ S, 36.5∘ W). Data from 2005 were used in this study. The 3–4-day oscillations appear intermittently throughout the year in the airglow. They were identified in January, March, July, August and October–November observations. The amplitudes induced by the waves in the airglow range from 26 to 40 % in the OI557.7 nm, 17 to 43 % in the O2b(0-1) and 15 to 20 % in the OH(6-2) emissions. In the OH rotational temperature, the amplitudes were from 4 to 6 K. Common 3–4-day oscillations between airglow and neutral wind compatible with ultrafast Kelvin waves were observed in March, August and October–November. In these cases, the amplitudes in the zonal wind were found to be between 22 and 28 m s−1 and the vertical wavelength ranges from 44 to 62 km. Evidence of the nonlinear interaction between the ultrafast Kelvin wave and diurnal tide was observed. Keywords. Atmospheric composition and structure (airglow and aurora) – meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

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39

López-González, M. J., E. Rodríguez, M. García-Comas, V. Costa, M. G. Shepherd, G. G. Shepherd, V. M. Aushev e S. Sargoytchev. "Climatology of planetary wave type oscillations with periods of 2–20 days derived from O2 atmospheric and OH(6-2) airglow observations at mid-latitude with SATI". Annales Geophysicae 27, n. 9 (30 settembre 2009): 3645–62. http://dx.doi.org/10.5194/angeo-27-3645-2009.

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Abstract (sommario):

Abstract. The presence of planetary wave type oscillations at mid-latitudes in the mesosphere/lower thermosphere region has been investigated using airglow observations. The observations were taken with a Spectral Airglow Temperature Imager (SATI) installed at Sierra Nevada Observatory (37.06° N, 3.38° W) at 2900 m height. Airglow data of the column emission rate of the O2 Atmospheric (0-1) band and of the OH Meinel (6-2) band and deduced rotational temperatures from 1998 to 2007 have been used in this study. From these observations a climatology of planetary wave type oscillations at this location is inferred. It has been found that the planetary wave type oscillations of 5-day period is predominant in our data throughout the year, with activity greater than 50% during March/April and October/November months. The planetary wave type oscillations of 2-day period is predominant during both solstices, being predominant during winter solstice in O2 while a 10-day oscillation appears throughout the year with activity around 20% and with maximum activity during spring and autumn equinoxes. The 16-day oscillation has maximum occurrence during autumn-winter while its activity is almost disappeared during spring-summer. No clear seasonal dependence of the amplitude of the planetary wave type oscillations was observed in the cases considered in this study. The waves simultaneously detected in the rotational temperatures deduced from both OH and O2 emissions usually show an upward energy propagation and are affected by dissipation processes.

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40

Innis, J. L., F. A. Phillips, G. B. Burns, P. A. Greet, W. J. R. French e P. L. Dyson. "Mesospheric temperatures from observations of the hydroxyl (6–2) emission above Davis, Antarctica: A comparison of rotational and Doppler measurements". Annales Geophysicae 19, n. 3 (31 marzo 2001): 359–65. http://dx.doi.org/10.5194/angeo-19-359-2001.

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Abstract (sommario):

Abstract. We present observations of the hydroxyl (6–2) airglow lines from ~ 87 km altitude obtained at Davis station, Antarctica, in the austral winter of 1999. Nine nights of observations were made of the P-branch near λ840 nm with a Czerny-Turner scanning spectrometer (CTS); at the same time, high-resolution Fabry-Perot Spectrometer (FPS) spectra were collected of the Q1(1) doublet at λ834 nm. Rotational temperatures were determined from the CTS observations, while Doppler temperatures were derived from the line-widths of the FPS Q1(1) spectra. Absolute temperatures determined by these methods are uncertain by ~ 2 and ~ 20 K, respectively. For the comparison we set the value of the reflective finesse of the FPS at λ834 nm so the mean FPS temperature from one night of simultaneous data was equal to that from the CTS, and then looked at the measured variations in each data set for the other eight nights. Both instruments show the upper mesosphere temperature to vary in a similar manner to within the observational errors of the measurements, implying an equivalence of the rotational and Doppler temperatures. We believe that this is the first published simultaneous, same-site, comparison of rotational and Doppler temperatures from the OH emission. Key words. Atmospheric composition and structure (airglow and aurora; pressure density and temperature; instruments and techniques)

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41

Onoma, F., Y. Otsuka, K. Shiokawa, T. Ogawa, M. Yamamoto, S. Fukao e S. Saito. "Relationship between propagation direction of gravity waves in OH and OI airglow images and VHF radar echo occurrence during the SEEK-2 campaign". Annales Geophysicae 23, n. 7 (13 ottobre 2005): 2385–90. http://dx.doi.org/10.5194/angeo-23-2385-2005.

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Abstract (sommario):

Abstract. We report simultaneous observations of atmospheric gravity waves (AGW) in OI (557.7nm) and OH airglow images and VHF radar backscatter from field-aligned irregularities (FAI) in the E-region during the SEEK-2 (Sporadic-E Experiment over Kyushu 2) campaign period from 29 July to 9 August 2002. An all-sky imager was operated at Nishino-Omote (30.5 N, 130.1 E), Japan. On 14 nights, 17 AGW events were detected in OI and OH airglow images. AGW propagated mostly toward the northeast or southeast. From comparison with the E-region FAI occurrence, which is detected by a nearby VHF radar (31.57MHz), we found that AGW tended to propagate southeastward during FAI events. This result suggests that the interaction between AGW and E-region plasma plays an important role in generating FAI. Furthermore, polarization electric fields generated directly by AGW may contribute to the FAI generation. Keywords. Atmospheric composition and structure (Airglow and aurora), Ionosphere (Ionospheric irregularities, Mid-latitude ionosphere)

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42

Medeiros, A. F., I. Paulino, M. J. Taylor, J. Fechine, H. Takahashi, R. A. Buriti, L. M. Lima e C. M. Wrasse. "Twin mesospheric bores observed over Brazilian equatorial region". Annales Geophysicae 34, n. 1 (22 gennaio 2016): 91–96. http://dx.doi.org/10.5194/angeo-34-91-2016.

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Abstract (sommario):

Abstract. Two consecutive mesospheric bores were observed simultaneously by two all-sky cameras on 19 December 2006. The observations were carried out in the northeast of Brazil at two different stations: São João do Cariri (36.5° W, 7.4° S) and Monteiro (37.1° W, 7.9° S), which are by about 85 km apart. The mesospheric bores were observed within an interval of ∼ 3 h in the NIR OH and OI557.7 nm airglow emissions. Both bores propagated to the east and showed similar characteristics. However, the first one exhibited a dark leading front with several trailing waves behind and progressed into a brighter airglow region, while the second bore, observed in the OH layer, was comprised of several bright waves propagating into a darker airglow region. This is the first paper to report events like these, called twin mesospheric bores. The background of the atmosphere during the occurrence of these events was studied by considering the temperature profiles from the TIMED/SABER satellite and wind from a meteor radar.

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43

Franzen, Christoph, Patrick Joseph Espy, Niklas Hofmann, Robert Edward Hibbins e Anlaug Amanda Djupvik. "Airglow Derived Measurements of Q-Branch Transition Probabilities for Several Hydroxyl Meinel Bands". Atmosphere 10, n. 10 (22 ottobre 2019): 637. http://dx.doi.org/10.3390/atmos10100637.

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Abstract (sommario):

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 implications for atmospheric temperatures derived from OH Q-branch measurements are discussed.

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44

Sims, Geoff, Michael C. B. Ashley, Xiangqun Cui, Jon R. Everett, LongLong Feng, Xuefei Gong, Shane Hengst et al. "Airglow and Aurorae from Dome A, Antarctica". Proceedings of the International Astronomical Union 8, S288 (agosto 2012): 302–3. http://dx.doi.org/10.1017/s1743921312017048.

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Abstract (sommario):

AbstractDespite the absence of artificial light pollution at Antarctic plateau sites such as Dome A, other factors such as airglow, aurorae and extended periods of twilight have the potential to adversely affect optical observations. We present a statistical analysis of the airglow and aurorae at Dome A using spectroscopic data from Nigel, an optical/near-IR spectrometer operating in the 300–850 nm range. The median auroral contribution to the B, V and R photometric bands is found to be 22.9, 23.4 and 23.0 mag arcsec−2 respectively. We are also able to quantify the amount of annual dark time available as a function of wavelength; on average twilight ends when the Sun reaches a zenith distance of 102.6°.

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45

Liu, J. Y., P. K. Rajesh, I. T. Lee e T. C. Chow. "Airglow observations over the equatorial ionization anomaly zone in Taiwan". Annales Geophysicae 29, n. 5 (5 maggio 2011): 749–57. http://dx.doi.org/10.5194/angeo-29-749-2011.

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Abstract (sommario):

Abstract. Airglow imaging at mid-latitude stations often show intensity modulations associated with medium scale travelling ionospheric disturbances (MSTID), while those carried out near the equatorial regions reveal depletions caused by equatorial plasma bubbles (EPB). Two all sky cameras are used to observe plasma depletions in the 630.0 nm emission over the equatorial ionization anomaly (EIA) region, Taiwan (23° N, 121° E; 13.5° N Magnetic) during 1998–2002 and 2006–2007. The results show EPB and MSTID depletions in different solar activity conditions. Several new features of the EPB depletions such as bifurcation, secondary structure on the walls, westward tilt, etc., are discussed in this paper. Evidence of tilted depletions with secondary structures developing on the eastern wall that later evolve to appear as bifurcations, are presented for the first time. Moreover, detail investigations are carried out using International Reference Ionosphere (IRI) model as well as the electron density from Ionosonde and Global Positioning System (GPS) Occultation Experiment (GOX) onboard FORMOSAT-3/COSMIC satellite, to understand the conditions that favor the propagation of MSTID to the latitude of Taiwan.

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46

Yue, Jia, Septi Perwitasari, Shuang Xu, Yuta Hozumi, Takuji Nakamura, Takeshi Sakanoi, Akinori Saito, Steven D. Miller, William Straka e Pingping Rong. "Preliminary Dual-Satellite Observations of Atmospheric Gravity Waves in Airglow". Atmosphere 10, n. 11 (28 ottobre 2019): 650. http://dx.doi.org/10.3390/atmos10110650.

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Abstract (sommario):

Atmospheric gravity waves (AGWs) are among the important energy and momentum transfer mechanisms from the troposphere to the middle and upper atmosphere. Despite their understood importance in governing the structure and dynamics of these regions, mesospheric AGWs remain poorly measured globally, and largely unconstrained in numerical models. Since late 2011, the Suomi National Polar-orbiting Partnership (NPP) Visible/Infrared Imaging Radiometer Suite (VIIRS) day–night band (DNB) has observed global AGWs near the mesopause by virtue of its sensitivity to weak emissions of the OH* Meinel bands. The wave features, detectable at 0.75 km spatial resolution across its 3000 km imagery swath, are often confused by the upwelling emission of city lights and clouds reflecting downwelling nightglow. The Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere (IMAP)/ Visible and near-Infrared Spectral Imager (VISI) O2 band, an independent measure of the AGW structures in nightglow based on the International Space Station (ISS) during 2012–2015, contains much less noise from the lower atmosphere. However, VISI offers much coarser resolution of 14–16 km and a narrower swath width of 600 km. Here, we present preliminary results of comparisons between VIIRS/DNB and VISI observations of AGWs, focusing on several concentric AGW events excited by the thunderstorms over Eastern Asia in August 2013. The comparisons point toward suggested improvements for future spaceborne airglow sensor designs targeting AGWs.

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47

Ogawa, Y., A. Kadokura e M. K. Ejiri. "Optical calibration system of NIPR for aurora and airglow observations". Polar Science 26 (dicembre 2020): 100570. http://dx.doi.org/10.1016/j.polar.2020.100570.

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48

Sekar, R., D. Chakrabarty, R. Narayanan e A. K. Patra. "Equatorial Spread F structures and associated airglow intensity variations observed over Gadanki". Annales Geophysicae 26, n. 12 (2 dicembre 2008): 3863–73. http://dx.doi.org/10.5194/angeo-26-3863-2008.

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Abstract (sommario):

Abstract. Co-ordinated campaigns have been conducted from Gadanki (13.5° N, 79.2° E, dip lat 6.4° N) by operating simultaneously the Indian MST radar in ionospheric coherent backscatter mode and by monitoring thermosphere airglow line emissions (630.0 nm and 777.4 nm) using a narrow band multi-wavelength scanning photometer during January-March for the past five years (2003–2007) and also during April 2006, as a special campaign. Simultaneous radar and optical observations reveal optical signatures corresponding to a variety of equatorial spread F (ESF) structures. The optical signatures corresponding to ESF structures with wave-like bottomside modulations with plasma plumes, confined bottomside flat and wavelike structures, vertically extended plume structure in the absence of bottomside structure apart from the classical plasma depletions and enhancements are obtained during these campaigns. The plasma depletions and enhancements were identified using optical measurements. In addition, estimations of zonal wavelength of the bottomside structures and the inference of shears in the zonal plasma drift in the presence of confined structures, were carried out using bi-directional airglow measurements. Furthermore, it is found that the vertical columnar intensity of OI 630.0 nm airglow exceeded the slanted columnar intensity in the presence of large bottomside structure. The need for the appropriate physical mechanisms for some of the ESF structures and their characterizations with optical observations are discussed.

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49

Михалев, Александр, Aleksandr Mikhalev, Степан Подлесный, Stepan Podlesny, Пенка Стоева e Penka Stoeva. "Night airglow in RGB mode". Solnechno-Zemnaya Fizika 2, n. 3 (17 settembre 2016): 74–80. http://dx.doi.org/10.12737/19040.

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TTo study dynamics of the upper atmosphere, we consider results of the night sky photometry, using a color CCD camera and taking into account the night airglow and features of its spectral composition. We use night airglow observations for 2010–2015, which have been obtained at the ISTP SB RAS Geophysical Observatory (52° N, 103° E) by the camera with KODAK KAI-11002 CCD sensor. We estimate average brightness of the night sky in R, G, B channels of the color camera for eastern Siberia with typical values ranging from ~0.008 to 0.01 erg·cm–2·s–1. Besides, we determine seasonal variations in the night sky luminosities in R, G, B channels of the color camera. In these channels, luminosities decrease in spring, increase in autumn, and have a pronounced summer maximum, which can be explained by scattered light and is associated with the location of the Geophysical Observatory. We consider geophysical phenomena with their optical effects in R, G, B channels of the color camera. For some geophysical phenomena (geomagnetic storms, sudden stratospheric warmings), we demonstrate the possibility of quantitative relationship between enhanced signals in R and G channels and increases in intensities of discrete 557.7 and 630 nm emissions, which are predominant in the airglow spectrum.

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Martinis, C., J. Baumgardner, S. M. Smith, M. Colerico e M. Mendillo. "Imaging science at El Leoncito, Argentina". Annales Geophysicae 24, n. 5 (3 luglio 2006): 1375–85. http://dx.doi.org/10.5194/angeo-24-1375-2006.

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Abstract. Thermospheric and mesospheric structures are studied using an all-sky imager located at El Leoncito, Argentina (31.8° S, 69.3° W, –18° mag lat). This site has relatively high geographic latitude for a location under the crest of the equatorial ionization anomaly (EIA), and thus observations can be used to study the intrusion of several equatorial processes into the midlatitude domain. In addition, it has a conjugate point close to the field of view of our companion imager at Arecibo, PR, allowing for the study of inter-hemispheric effects. Four types of phenomena were studied using 630.0 nm and 777.4 nm observations: (1) highly-structured airglow depletions associated with the Rayleigh-Taylor instability/equatorial spread-F (RTI/ESF) process, (2) brightness waves (BW) associated with the midnight temperature maximum (MTM), (3) strong airglow enhancements associated with the positive phase of ionospheric storms, and (4) simple (non-structured) bands of airglow depletions with characteristics matching a Perkins-like instability. Using 557.7 nm mesospheric observations, a fifth category of study deals with gravity waves probably generated by lower atmospheric disturbances, and mesospheric bores related to strong vertical temperature gradients. While ESF depletions and BW events are detected fairly frequently, the mid-latitude bands are not, and thus their successful imaging at El Leoncito offers the first example of the coupling from mid-latitudes to low-latitudes in the South American longitude sector. Preliminary results on these features are presented in this paper. Taken together, these five types of optical structures offer the opportunity to investigate coupling, both in altitude and latitude, of aeronomic processes at low latitudes in an under-sampled longitude sector in the Southern Hemisphere.

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