Martian visible and ultraviolet dayglow: altitude, latitudinal and seasonal variations observed with NOMAD/TGO

2020 ◽  
Author(s):  
Jean-Claude Gérard ◽  
Shohei Aoki ◽  
Leonardos Gkouvelis ◽  
Yannick Willame ◽  
Cédric Depiesse ◽  
...  
Keyword(s):  
Green Emission ◽  
Trace Gas ◽  
Main Peak ◽  
Green Line ◽  
Model Calculations ◽  
Special Mode ◽  
Bright Green ◽  
Far Ultraviolet ◽  
First Time ◽  
Applied Optics

<p>The OI 557.7 nm green line has been measured in the Martian dayglow for the first time with the UVIS visible-ultraviolet spectrograph on board ESA’s Trace Gas Orbiter (Gérard et al., 2020). The first observations started in April 2019 in a special mode where the spacecraft is tilted to observe the limb with the UVIS nadir channel (Vandaele et al., 2015, Patel et al., 2017). The instrument detected the presence of bright green dayglow emission on every of those observations. The main peak altitude is located near 80 km, and its intensity varies as a result of the changing distance from sun, the local time and latitude of the observations. A second, less pronounced, emission peak is observed near 110 km. Photochemical model simulations (Gkouvelis et al., 2018) used the MCD density distribution (Forget et al., 1999) have been made to understand the sources of this airglow emission. It is able to reproduce the altitude and the brightness of the airglow layer. It indicates that the green line dayglow on Mars is essentially produced by photodissociation of CO<sub>2</sub> molecules by solar far ultraviolet radiation (Fox & Dalgarno, 1979). A fraction of the oxygen atoms is formed in the <sup>1</sup>S metastable state that produces the green emission.</p> <p>In this presentation, we describe additional dayside observations obtained since December 2019. For this purpose, the spacecraft has been used in a special mode where it is re-oriented so that the UVIS channel observed the sunlit limb (Lopez-Valverde et al., 2018). We analyse the observed limb profile variations and the changing altitude of the peak emission resulting from the variations of the pressure levels in the mesosphere (Gkouvelis et al., 2020). The measured intensities are compared with model calculations of the O(<sup>1</sup>S) density in the conditions of the observations. The ratio of ultraviolet spectral features relative to the oxygen emission also observed with UVIS will also be analysed. </p> <p>REFERENCES</p> <p>Forget, F. et al., J. Geophys. Res. <strong>104</strong>(E10), 24155-24175 (1999).</p> <p>Fox, J.L. & Dalgarno, J. Geophys. Res. <strong>84</strong>(A12), 7315-7333 (1979).</p> <p>Gérard, J.C. et al., Nature Astronomy, 1-4 (2020), https://doi.org/10.1038/s41550-020-1123-2</p> <p>Gkouvelis, L. et al., J. Geophys.Res., <strong>123</strong>(12), 3119-3132. (2018).</p> <p>Gkouvelis, L. et al.,  Icarus, 341, 113666 (2020).</p> <p>López-Valverde M. et al.,  Space Science Reviews, <strong>214</strong>(1), 29 (2018).</p> <p>Patel, M. R. et al.,  Applied optics, <strong>56</strong>(10), 2771-2782 (2017).</p> <p>Vandaele, A. C. et al.,  Optics Express, <strong>23</strong>(23), 30028-30042 (2015).</p>

Isopotential points in square-wave voltammetry of reversible electrode reactions

2009 ◽  
Vol 74 (10) ◽  
pp. 1489-1501 ◽  
Author(s):  
Marina Zelić ◽  
Milivoj Lovrić
Keyword(s):  
Square Wave Voltammetry ◽  
Electrode Reaction ◽  
Time Model ◽  
Model Calculations ◽  
Square Wave ◽  
Electrode Reactions ◽  
Wave Voltammetry ◽  
Electron Transfer Processes ◽  
Diagnostic Criterion ◽  
First Time

Isopotential points in square-wave voltammetry are described for the first time. Model calculations and real measurements (performed with UO22+ and Eu3+ in perchlorate and bromide solutions, respectively) indicate that such an intersection could be observed when backward components of the net response, resulting from an increase in frequency or reactant concentration, are presented together. The electrode reaction should be fully reversible because quasireversible or slower electron transfer processes give the isopoints only at increasing reactant concentrations but not at increasing square-wave frequencies. The effect could be used as an additional diagnostic criterion for recognition of reversible electrode reactions where products remain dissolved in the electrolyte solution.

scholarly journals Solar Extreme and Far Ultraviolet Radiation Modeling for Aeronomic Calculations

2021 ◽  
Vol 13 (8) ◽  
pp. 1454
Author(s):  
Anatoliy A. Nusinov ◽  
Tamara V. Kazachevskaya ◽  
Valeriya V. Katyushina
Keyword(s):  
Ultraviolet Radiation ◽  
Input Parameter ◽  
Solar Spectrum ◽  
Upper Atmosphere ◽  
Model Calculations ◽  
Radiation Fluxes ◽  
Main Components ◽  
Comparison Of The Results ◽  
Far Ultraviolet ◽  
Radiation Modeling

Modeling the upper atmosphere and ionospheres on the basis of a mathematical description of physical processes requires knowledge of ultraviolet radiation fluxes from the Sun as an integral part of the model. Aeronomic models of variations in the radiation flux in the region of extreme (EUV) and far (FUV) radiation, based mainly on the data of the last TIMED mission measurements of the solar spectrum, are proposed. The EUVT model describes variations in the 5–105 nm spectral region, which are responsible for the ionization of the main components of the earth’s atmosphere. The FUVT model describes the flux changes in the 115–242 nm region, which determines heating of the upper atmosphere and the dissociation of molecular oxygen. Both models use the intensity of the hydrogen Lyman-alpha line as an input parameter, which can currently be considered as one of the main indices of solar activity and can be measured with relatively simpler photometers. A comparison of the results of model calculations with observations shows that the model error does not exceed 1–2% for the FUVT model, and 5.5% for EUVT, which is sufficient for calculating the parameters of the ionosphere and thermosphere.

scholarly journals Model calculations of the age of firn air across the Antarctic continent

2004 ◽  
Vol 4 (5) ◽  
pp. 1365-1380 ◽  
Author(s):  
K. A. Kaspers ◽  
R. S. W. van de Wal ◽  
M. R. van den Broeke ◽  
J. Schwander ◽  
N. P. M. van Lipzig ◽  
...  
Keyword(s):  
Climate Model ◽  
Accumulation Rate ◽  
Methyl Chloride ◽  
Trace Gas ◽  
Model Calculations ◽  
Antarctic Plateau ◽  
Input Surface ◽  
Antarctic Continent ◽  
High Level ◽  
Air Diffusion

Abstract. The age of firn air in Antarctica at pore close-off depth is only known for a few specific sites where firn air has been sampled for analyses. We present a model that calculates the age of firn air at pore close-off depth for the entire Antarctic continent. The model basically uses four meteorological parameters as input (surface temperature, pressure, accumulation rate and wind speed). Using parameterisations for surface snow density, pore close-off density and tortuosity, in combination with a density-depth model and data of a regional atmospheric climate model, distribution of pore close-off depth for the entire Antarctic continent is determined. The deepest pore close-off depth was found for the East Antarctic Plateau near 72° E, 82° S, at 150±15 m (2σ). A firn air diffusion model was applied to calculate the age of CO2 at pore close-off depth. The results predict that the oldest firn gas (CO2 age) is located between Dome Fuji, Dome Argos and Vostok at 43° E, 78° S being 148±23 (1σ or 38 for 2σ) years old. At this location an atmospheric trace gas record should be obtained. In this study we show that methyl chloride could be recorded with a predicted length of 125 years as an example for trace gas records at this location. The longest record currently available from firn air is derived at South Pole, being 80 years. Sensitivity tests reveal that the locations with old firn air (East Antarctic Plateau) have an estimated uncertainty (2σ) for the modelled CO2 age at pore close-off depth of 30% and of about 40% for locations with younger firn air (CO2 age typically 40 years). Comparing the modelled age of CO2 at pore close-off depth with directly determined ages at seven sites yielded a correlation coefficient of 0.90 and a slope close to 1, suggesting a high level of confidence for the modelled results in spite of considerable remaining uncertainties.

Ho-doped SrBi2 Nb2 O9 multifunctional ceramics with bright green emission and good electrical properties

2017 ◽  
Vol 214 (10) ◽  
pp. 1700276 ◽  
Author(s):  
Lei Yu ◽  
Jigong Hao ◽  
Zhijun Xu ◽  
Wei Li ◽  
Ruiqing Chu
Keyword(s):  
Electrical Properties ◽  
Green Emission ◽  
Bright Green

scholarly journals Oxygen isotopic ratios in Martian water vapour observed by ACS MIR on board the ExoMars Trace Gas Orbiter

2019 ◽  
Vol 630 ◽  
pp. A91 ◽  
Author(s):  
J. Alday ◽  
C. F. Wilson ◽  
P. G. J. Irwin ◽  
K. S. Olsen ◽  
L. Baggio ◽  
...  
Keyword(s):  
Water Vapour ◽  
Atmospheric Chemistry ◽  
Trace Gas ◽  
Oxygen Isotope Ratios ◽  
Infrared Measurements ◽  
History Of ◽  
Oxygen Isotopic ◽  
Atmospheric Loss ◽  
The Impact ◽  
First Time

Oxygen isotope ratios provide important constraints on the history of the Martian volatile system, revealing the impact of several processes that might fractionate them, such as atmospheric loss into space or interaction with the surface. We report infrared measurements of the Martian atmosphere obtained with the mid-infrared channel (MIR) of the Atmospheric Chemistry Suite (ACS), onboard the ExoMars Trace Gas Orbiter. Absorption lines of the three main oxygen isotopologues of water vapour (H216O, H218O, and H217O) observed in the transmission spectra allow, for the first time, the measurement of vertical profiles of the 18O/16O and 17O/16O ratios in atmospheric water vapour. The observed ratios are enriched with respect to Earth-like values (δ18O = 200 ± 80‰ and δ17O = 230 ± 110‰ corresponding to the Vienna Standard Mean Ocean Water). The vertical structure of these ratios does not appear to show significant evidence of altitudinal variations.

Temperature and composition measurements from the l.r.i.r. and l.i.m.s. experiments on Nimbus 6 and 7

1980 ◽  
Vol 296 (1418) ◽  
pp. 205-218 ◽  
Keyword(s):  
High Precision ◽  
Trace Gas ◽  
Transport Problems ◽  
Rocket Measurements ◽  
Inversion Techniques ◽  
And Inversion ◽  
First Time ◽  
Good Agreement ◽  
Composition Measurements

The limb radiance inversion radiometer (l.r.i.r.) on Nimbus 6 was the first orbiting infrared limb scanner. It had four channels with which to determine temperature, Oz and H aO in the stratosphere and low mesosphere. The limb infrared monitor of the stratosphere (l.i.m.s.) is a similar six-channel instrument launched on Nimbus 7 in October 1978 to measure temperature, O 3 , H 2 O , NO 2 and HNO 3 . The instrumentation and inversion techniques are briefly described. In this method, the outwelling radiance in the 15 pm bands of CO 2 is inverted to yield temperatures as a function of pressure; the temperature is then used w ith the radiance emitted by a trace gas to determine its concentration. L.r.i.r. temperature and ozone results show high precision and good agreement with rocket measurements from the tropopause into the mesosphere. Preliminary l.i.m.s. results show that temperatures may be retrieved into the troposphere, and the capability to determine constituent concentrations in the part / 10 9 range from a satellite for the first time. The application of such data for photochemical dynamical and transport problems is discussed.

Highly Efficient Multifunctional Phosphorescent Dendrimers Consisting of an Iridium-Complex Core and Charge-Transporting Dendrons for Organic Light-Emitting Devices

2005 ◽  
Vol 871 ◽  
Author(s):  
Toshimitsu Tsuzuki ◽  
Nobuhiko Shirasawa ◽  
Toshiyasu Suzuki ◽  
Shizuo Tokito
Keyword(s):  
First Generation ◽  
Green Emission ◽  
Iridium Complex ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Organic Light ◽  
Hole Transporting ◽  
Complex Core ◽  
Bright Green ◽  
Organic Light Emitting Devices

AbstractWe report a novel class of emitting materials for use in the organic light-emitting devices (OLEDs): multifunctional phosphorescent dendrimers that have a phosphorescent core and have charge transporting dendrons. We have synthesized first-generation and second-generation dendrimers consisting of a fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] core and hole transporting phenylcarbazole-based dendrons. Smooth amorphous films of these dendrimers were formed by spin-coating them from solutions. The OLEDs using the dendrimer exhibited bright green or yellowish-green emission from the Ir(ppy)3 core. The external quantum efficiency of the OLED using the mixture film of the first-generation dendrimer and an electron-transporting material was as high as 7.6%.

FIRST γ-RAY SPECTROSCOPY AND ISOSPIN SYMMETRY STUDY OF THE N = Z - 2 NUCLEUS 44V

2010 ◽  
Vol 25 (21n23) ◽  
pp. 2028-2029 ◽  
Author(s):  
M. J. TAYLOR ◽  
M. A. BENTLEY ◽  
J. BROWN ◽  
R. WADSWORTH ◽  
P.E. KENT ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Shell Model ◽  
Excited States ◽  
State Of The Art ◽  
Isospin Symmetry ◽  
Charge Symmetry Breaking ◽  
Charge Symmetry ◽  
Model Calculations ◽  
Γ Ray ◽  
First Time

Excited states in the Tz = -1 nucleus 44 V have been observed for the first time. The states have been identified through recoil-γ-γ coincidences and comparison with analogue states in the mirror nucleus 44 Sc . Mirror energy differences have been extracted and compared to state-of-the-art fp shell-model calculations which include charge symmetry breaking forces.

scholarly journals Trace gas emissions from combustion of peat, crop residue, domestic biofuels, grasses, and other fuels: configuration and Fourier transform infrared (FTIR) component of the fourth Fire Lab at Missoula Experiment (FLAME-4)

2014 ◽  
Vol 14 (18) ◽  
pp. 9727-9754 ◽  
Author(s):  
C. E. Stockwell ◽  
R. J. Yokelson ◽  
S. M. Kreidenweis ◽  
A. L. Robinson ◽  
P. J. DeMott ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Crop Residue ◽  
Crop Residues ◽  
Trace Gas ◽  
Fire Emissions ◽  
The Us ◽  
Peat Fire ◽  
Peat Fires ◽  
First Time ◽  
Emission Ratios

Abstract. During the fourth Fire Lab at Missoula Experiment (FLAME-4, October–November 2012) a large variety of regionally and globally significant biomass fuels was burned at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. The particle emissions were characterized by an extensive suite of instrumentation that measured aerosol chemistry, size distribution, optical properties, and cloud-nucleating properties. The trace gas measurements included high-resolution mass spectrometry, one- and two-dimensional gas chromatography, and open-path Fourier transform infrared (OP-FTIR) spectroscopy. This paper summarizes the overall experimental design for FLAME-4 – including the fuel properties, the nature of the burn simulations, and the instrumentation employed – and then focuses on the OP-FTIR results. The OP-FTIR was used to measure the initial emissions of 20 trace gases: CO2, CO, CH4, C2H2, C2H4, C3H6, HCHO, HCOOH, CH3OH, CH3COOH, glycolaldehyde, furan, H2O, NO, NO2, HONO, NH3, HCN, HCl, and SO2. These species include most of the major trace gases emitted by biomass burning, and for several of these compounds, this is the first time their emissions are reported for important fuel types. The main fire types included African grasses, Asian rice straw, cooking fires (open (three-stone), rocket, and gasifier stoves), Indonesian and extratropical peat, temperate and boreal coniferous canopy fuels, US crop residue, shredded tires, and trash. Comparisons of the OP-FTIR emission factors (EFs) and emission ratios (ERs) to field measurements of biomass burning verify that the large body of FLAME-4 results can be used to enhance the understanding of global biomass burning and its representation in atmospheric chemistry models. Crop residue fires are widespread globally and account for the most burned area in the US, but their emissions were previously poorly characterized. Extensive results are presented for burning rice and wheat straw: two major global crop residues. Burning alfalfa produced the highest average NH3 EF observed in the study (6.63 ± 2.47 g kg−1), while sugar cane fires produced the highest EF for glycolaldehyde (6.92 g kg−1) and other reactive oxygenated organic gases such as HCHO, HCOOH, and CH3COOH. Due to the high sulfur and nitrogen content of tires, they produced the highest average SO2 emissions (26.2 ± 2.2 g kg−1) and high NOx and HONO emissions. High variability was observed for peat fire emissions, but they were consistently characterized by large EFs for NH3 (1.82 ± 0.60 g kg−1) and CH4 (10.8 ± 5.6 g kg−1). The variability observed in peat fire emissions, the fact that only one peat fire had previously been subject to detailed emissions characterization, and the abundant emissions from tropical peatlands all impart high value to our detailed measurements of the emissions from burning three Indonesian peat samples. This study also provides the first EFs for HONO and NO2 for Indonesian peat fires. Open cooking fire emissions of HONO and HCN are reported for the first time, and the first emissions data for HCN, NO, NO2, HONO, glycolaldehyde, furan, and SO2 are reported for "rocket" stoves: a common type of improved cookstove. The HCN / CO emission ratios for cooking fires (1.72 × 10−3 ± 4.08 × 10−4) and peat fires (1.45 × 10−2 ± 5.47 × 10−3) are well below and above the typical values for other types of biomass burning, respectively. This would affect the use of HCN / CO observations for source apportionment in some regions. Biomass burning EFs for HCl are rare and are reported for the first time for burning African savanna grasses. High emissions of HCl were also produced by burning many crop residues and two grasses from coastal ecosystems. HCl could be the main chlorine-containing gas in very fresh smoke, but rapid partitioning to aerosol followed by slower outgassing probably occurs.

scholarly journals Parameterizing radiative transfer to convert MAX-DOAS dSCDs into near-surface box averaged mixing ratios and vertical profiles

2012 ◽  
Vol 5 (5) ◽  
pp. 7641-7673 ◽  
Author(s):  
R. Sinreich ◽  
A. Merten ◽  
L. Molina ◽  
R. Volkamer
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Mexico City ◽  
Vertical Gradient ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Model Calculations ◽  
Near Surface ◽  
Mixing Ratios

Abstract. We present a novel parameterization method to convert Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) differential Slant Column Densities (dSCDs) into near-surface box averaged volume mixing ratios. The approach is applicable inside the planetary boundary layer under conditions with significant aerosol load, does not require a-priori assumptions about the trace gas vertical distribution and builds on the increased sensitivity of MAX-DOAS near the instrument altitude. It parameterizes radiative transfer model calculations and significantly reduces the computational effort. The biggest benefit of this method is that the retrieval of an aerosol profile, which usually is necessary for deriving a trace gas concentration from MAX-DOAS dSCDs, is not needed. The method is applied to NO2 MAX-DOAS dSCDs recorded during the Mexico City Metropolitan Area 2006 (MCMA-2006) measurement campaign. The retrieved volume mixing ratios of two elevation angles (1° and 3°) are compared to volume mixing ratios measured by two long-path (LP)-DOAS instruments located at the same site. Measurements are found to agree well during times when vertical mixing is expected to be strong. However, inhomogeneities in the air mass above Mexico City can be detected by exploiting the different horizontal and vertical dimensions probed by MAX-DOAS measurements at different elevation angles, and by LP-DOAS. In particular, a vertical gradient in NO2 close to the ground can be observed in the afternoon, and is attributed to reduced mixing coupled with near surface emission. The existence of a vertical gradient in the lower 250 m during parts of the day shows the general challenge of sampling the boundary layer in a representative way and emphasizes the need of vertically resolved measurements.

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