scholarly journals Upper limit of hydrogen and helium concentrations on Titan

1971 ◽  
Vol 40 ◽  
pp. 394-400
Author(s):  
Wayne E. McGovern
Keyword(s):  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Mixing Ratios ◽  
Upper Limit ◽  
Upper Limits

The satellite Titan is commonly quoted as possessing an atmosphere consisting of at least 2 × 104 cm atm of methane. Plausible additional atmospheric constituents like hydrogen and helium are assumed to have completely escaped from the satellite. However, the employment of recent techniques to the upper atmosphere of Titan permits an improved estimate of the upper limits of the hydrogen to methane and helium to methane mixing ratios existing in the lower atmosphere of Titan, namely 10−6±1 and 10−3.5±0.5.

scholarly journals Atmospheric implications of the lack of H 3 + detection at Neptune

2020 ◽  
Vol 378 (2187) ◽  
pp. 20200100 ◽  
Author(s):  
L. Moore ◽  
J. I. Moses ◽  
H. Melin ◽  
T. S. Stallard ◽  
J. O’Donoghue
Keyword(s):  
Giant Planet ◽  
Atmospheric Temperature ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Observational Constraints ◽  
Atmospheric Conditions ◽  
Atmospheric Escape ◽  
Upper Limits ◽  
Voyager 2 ◽  
The Impact

H 3 + has been detected at all of the solar system giant planets aside from Neptune. Current observational upper limits imply that there is far less H 3 + emission at Neptune than rudimentary modelling would suggest. Here, we explore via modelling a range of atmospheric conditions in order to find some that could be consistent with observational constraints. In particular, we consider that the upper atmosphere might be much cooler than it was during the 1989 Voyager 2 encounter, and we examine the impact of an enhanced influx of external material that could act to reduce H 3 + density. Resulting ionosphere models that are consistent with existing H 3 + observational constraints have an exospheric temperature of 450 K or less, 300 K lower than the Voyager 2 value. Alternatively, if a topside CO influx of 2 × 10 8  cm −2  s −1 is imposed, the upper atmospheric temperature can be higher, up to 550 K. The potential cooling of Neptune’s atmosphere is relevant for poorly understood giant planet thermospheric energetics, and would also impact aerobreaking manoeuvers for any future spacecraft. Such a large CO influx, if present, could imply Triton is a very active moon with prominent atmospheric escape, and/or that Neptune’s rings significantly modify its upper atmosphere, and the introduction of so much exogenic material would complicate interpretation of the origin of species observed in Neptune’s lower atmosphere. This article is part a discussion meeting issue ‘Future exploration of ice giant systems’.

scholarly journals What do <sup>14</sup>CO measurements tell us about OH?

2007 ◽  
Vol 7 (4) ◽  
pp. 10405-10438 ◽  
Author(s):  
M. C. Krol ◽  
J. Fokke Meirink ◽  
P. Bergamaschi ◽  
J. E. Mak ◽  
D. Lowe ◽  
...  
Keyword(s):  
Source Region ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Atmospheric Measurements ◽  
Model Calculations ◽  
Mixing Ratios ◽  
Short Time Span ◽  
The Tropics ◽  
Short Time ◽  
Model Measurement

Abstract. The possible use of 14CO measurements to constrain hydroxyl radical (OH) concentrations in the atmosphere is investigated.14CO is mainly produced in the upper atmosphere from cosmic radiation. During transport to measurement locations at the Earth's surface 14CO is oxidized by OH. In this paper, the sensitivity of 14CO mixing ratio measurements to the 3-D OH distribution is assessed with the TM5 model. Simulated 14CO mixing ratios compare reasonably well with atmospheric measurements taken at five locations worldwide. As a next step, the sensitivity of 14CO measurements to OH is calculated with the adjoint TM5 model. For our sensitivity calculations the adjoint methodology outlined in the paper offers computational advantages compared to forward model calculations. The results indicate that 14CO measurements, especially those taken in the tropics, are sensitive to OH in a spatially confined region. Moreover, the OH sensitivity at a certain location varies strongly over time due to meteorological variability. On average, 14CO measurements are about 5 times more sensitive to OH at high latitudes than to OH in the tropics. Moreover, the measurements are sensitive to OH in the main 14CO source region in the upper atmosphere. It will therefore be difficult to assign model-measurement discrepancies to either the 14CO source uncertainty or to the OH sink. Nevertheless, the large distance between the 14CO source region and the measurement locations should allow the retrieval of information on OH. Specifically, the sensitivity to OH in the lower atmosphere during a relatively short time span may offer the possibility to constrain local OH. These efforts will strongly depend on the number of measurements available and on our ability to accurately model the 14CO transport.

Vitamin-A-Exzess durch Pferdefleischprodukte mit hohen Leberanteilen

2013 ◽  
Vol 41 (01) ◽  
pp. 31-36
Author(s):  
E. Kienzle ◽  
N. Becker
Keyword(s):  
Vitamin A ◽  
Eine Analyse ◽  
Upper Limit ◽  
Upper Limits

ZusammenfassungIm Rahmen einer Eliminationsdiät wird regelmäßig Pferdefleisch eingesetzt. Aus Gründen der Praktikabilität verwenden Tierbesitzer häufig kommerziell erhältliches Pferdefleisch aus der Dose. Aufgrund eines Berichts von Zervikalspondylosen bei einer auf Futtermittel allergischen Katze erfolgte eine Analyse verschiedener auf Pferdefleisch basierender Produkte hinsichtlich des Vitamin-AGehalts.In 14 Pferdefleischerzeugnissen wurde der Vitamin-A-Gehalt (Retinol) analysiert. Der Gehalt an umsetzbarer Energie wurde mithilfe von Schätzformeln auf Basis der Deklaration berechnet.In Produkten mit deklarierten Anteilen von Leber, Innereien oder tierischen Nebenprodukten konnten zum Teil erhebliche Vitamin-A-Gehalte festgestellt werden. Bei alleiniger Verfütterung eines dieser Produkte (Deckung des durchschnittlichen Energiebedarfs) würde die Vitamin-A-Versorgung nur knapp unter dem Safe Upper Limit der Katze sowie oberhalb des Safe Upper Limits beim Hund liegen.Bei All-Meat-Produkten sollte nicht nur die Deklaration, sondern auch der Inhalt näher betrachtet werden, um einen Hinweis auf eventuell hohe Leberanteile zu erhalten.Aufgrund der Ergebnisse ist eine exzessive Vitamin-A-Aufnahme bei langfristiger Verfütterung von Pferdefleischprodukten mit hohen Leberanteilen nicht auszuschließen.

scholarly journals Search for π0 decays to invisible particles

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Scalar Mixing ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Model Independent

Abstract The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

scholarly journals Upper limits on the extent of seafloor anoxia during the PETM from uranium isotopes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Matthew O. Clarkson ◽  
Timothy M. Lenton ◽  
Morten B. Andersen ◽  
Marie-Laure Bagard ◽  
Alexander J. Dickson ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Global Scale ◽  
Uranium Isotopes ◽  
Biogeochemical Model ◽  
Emission Scenarios ◽  
Isotope Data ◽  
Upper Limit ◽  
Thermal Maximum ◽  
Upper Limits ◽  
Anoxic Events

AbstractThe Paleocene Eocene Thermal Maximum (PETM) represents a major carbon cycle and climate perturbation that was associated with ocean de-oxygenation, in a qualitatively similar manner to the more extensive Mesozoic Oceanic Anoxic Events. Although indicators of ocean de-oxygenation are common for the PETM, and linked to biotic turnover, the global extent and temporal progression of de-oxygenation is poorly constrained. Here we present carbonate associated uranium isotope data for the PETM. A lack of resolvable perturbation to the U-cycle during the event suggests a limited expansion of seafloor anoxia on a global scale. We use this result, in conjunction with a biogeochemical model, to set an upper limit on the extent of global seafloor de-oxygenation. The model suggests that the new U isotope data, whilst also being consistent with plausible carbon emission scenarios and observations of carbon cycle recovery, permit a maximum ~10-fold expansion of anoxia, covering <2% of seafloor area.

Global upper-atmospheric heating at Jupiter by the recirculation of auroral energy

2021 ◽  
Author(s):  
James O'Donoghue ◽  
Luke Moore ◽  
Tanapat Bhakyapaibul ◽  
Henrik Melin ◽  
Tom Stallard ◽  
...  
Keyword(s):  
Heat Source ◽  
Acoustic Waves ◽  
Temperature Gradients ◽  
Upper Atmosphere ◽  
Global Temperature ◽  
Lower Atmosphere ◽  
Polar Regions ◽  
High Resolution Data ◽  
Coriolis Forces ◽  
Global Circulation Models

&lt;p&gt;Jupiter's upper atmosphere is significantly hotter than expected based on the amount of solar heating it receives. This temperature discrepency is known as the 'energy crisis' due to it's nearly 50-year duration and the fact it also occurs at Saturn, Uranus and Neptune. At Jupiter, magnetosphere-ionosphere coupling gives rise to intense auroral emissions and enormous energy deposition in the magnetic polar regions, so it was presumed long ago that redistribution of this energy could heat the rest of the planet. However, most global circulation models have difficulty redistributing auroral energy globally due to the strong Coriolis forces and ion drag on this rapidly rotating planet. Consequently, other possible heat sources have continued to be studied, such as heating by gravity and acoustic waves emanating from the lower atmosphere. Each global heating mechanism would imprint a unique signature on global temperature gradients, thus revealing the dominant heat source, but these gradients have not been determined due a lack of planet-wide, high-resolution data. The last global map of Jovian upper-atmospheric temperatures was produced using ground-based data taken in 1993, in which the region between 45&lt;sup&gt;o&lt;/sup&gt; latitude (north &amp; south) and the poles was represented by just 2 pixels. As a result, those maps did not (or could not) show a clear temperature gradient, and furthermore, they even showed regions of hot atmosphere near the equator, supporting the idea of an equatorial heat source, e.g. gravity and/or acoustic wave heating. Therefore observationally and from a modeling perspective, a concensus has not been reached to date. Here we report new infrared spectroscopy of Jupiter's major upper-atmospheric ion H&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;, with a spatial resolution of 2&lt;sup&gt;o&lt;/sup&gt; longitude and latitude extending from pole to equator, capable of tracing the global temperature gradients. We find that temperatures decrease steadily from the auroral polar regions to the equator. Further, during a period of enhanced activity possibly driven by a solar wind compression, a high-temperature planetary-scale structure was observed which may be propagating from the aurora. These observations indicate that Jupiter's upper atmosphere is predominantly heated via the redistribution of auroral energy, and therefore that Coriolis forces and ion drag are observably overcome.&lt;/p&gt;

scholarly journals Reactive quenching of electronically excited NO<sub>2</sub><sup>∗</sup> and NO<sub>3</sub><sup>∗</sup> by H<sub>2</sub>O as potential sources of atmospheric HO<sub><i>x</i></sub> radicals

2018 ◽  
Vol 18 (19) ◽  
pp. 14005-14015 ◽  
Author(s):  
Terry J. Dillon ◽  
John N. Crowley
Keyword(s):  
Gas Phase ◽  
Laser Excitation ◽  
Pulsed Laser ◽  
Work Rate ◽  
Rate Coefficients ◽  
Phase Reaction ◽  
Gas Phase Reaction ◽  
Upper Limit ◽  
Upper Limits ◽  
Electronically Excited

Abstract. Pulsed laser excitation of NO2 (532–647 nm) or NO3 (623–662 nm) in the presence of H2O was used to initiate the gas-phase reaction NO2∗+H2O → products (Reaction R5) and NO3∗+H2O → products (Reaction R12). No evidence for OH production in Reactions (R5) or (R12) was observed and upper limits for OH production of k5b/k5<1×10-5 and k12b/k12<0.03 were assigned. The upper limit for k5b∕k5 renders this reaction insignificant as a source of OH in the atmosphere and extends the studies (Crowley and Carl, 1997; Carr et al., 2009; Amedro et al., 2011) which demonstrate that the previously reported large OH yield by Li et al. (2008) was erroneous. The upper limit obtained for k12b∕k12 indicates that non-reactive energy transfer is the dominant mechanism for Reaction (R12), though generation of small but significant amounts of atmospheric HOx and HONO cannot be ruled out. In the course of this work, rate coefficients for overall removal of NO3∗ by N2 (Reaction R10) and by H2O (Reaction R12) were determined: k10=(2.1±0.1)×10-11 cm3 molecule−1 s−1 and k12=(1.6±0.3)×10-10 cm3 molecule−1 s−1. Our value of k12 is more than a factor of 4 smaller than the single previously reported value.

scholarly journals Eta-CMAQ air quality forecasts for O<sub>3</sub> and related species using three different photochemical mechanisms (CB4, CB05, SAPRC-99): comparisons with measurements during the 2004 ICARTT study

2010 ◽  
Vol 10 (6) ◽  
pp. 3001-3025 ◽  
Author(s):  
S. Yu ◽  
R. Mathur ◽  
G. Sarwar ◽  
D. Kang ◽  
D. Tong ◽  
...  
Keyword(s):  
Air Quality ◽  
Production Efficiency ◽  
Gulf Of Maine ◽  
Ozone Production ◽  
Eastern United States ◽  
Forecast Performance ◽  
Transport And Transformation ◽  
Mixing Ratios ◽  
Upper Limits ◽  
The Impact

Abstract. A critical module of air quality models is the photochemical mechanism. In this study, the impact of the three photochemical mechanisms (CB4, CB05, SAPRC-99) on the Eta-Community Multiscale Air Quality (CMAQ) model's forecast performance for O3, and its related precursors has been assessed over the eastern United States with observations obtained by aircraft (NOAA P-3 and NASA DC-8) flights, ship and two surface networks (AIRNow and AIRMAP) during the 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) study. The results show that overall none of the mechanisms performs systematically better than the others. On the other hand, at the AIRNow surface sites, CB05 has the best performance with the normalized mean bias (NMB) of 3.9%, followed by CB4 (NMB=−5.7%) and SAPRC-99 (NMB=10.6%) for observed O3≥75 ppb, whereas CB4 has the best performance with the least overestimation for observed O3<75 ppb. On the basis of comparisons with aircraft P-3 measurements, there were consistent overestimations of O3, NOz, PAN and NOy and consistent underestimations of CO, HNO3, NO2, NO, SO2 and terpenes for all three mechanisms although the NMB values for each species and mechanisms were different. The results of aircraft DC-8 show that CB05 predicts the H2O2 mixing ratios most closely to the observations (NMB=10.8%), whereas CB4 and SAPRC-99 overestimated (NMB=74.7%) and underestimated (NMB=−25.5%) H2O2 mixing ratios significantly, respectively. For different air mass flows over the Gulf of Maine on the basis of the ship data, the three mechanisms have relatively better performance for O3, isoprene and SO2 for the clean marine or continental flows but relatively better performance for CO, NO2 and NO for southwesterly/westerly offshore flows. The results of the O3-NOz slopes over the ocean indicate that SAPRC-99 has the highest upper limits of the ozone production efficiency (εN) (5.8), followed by CB05 (4.5) and CB4 (4.0) although they are much lower than that inferred from the observation (11.8), being consistent with the fact that on average, SAPRC-99 produces the highest O3, followed by CB05 and CB4, across all O3 mixing ratio ranges

scholarly journals Ionosphere Influenced From Lower-Lying Atmospheric Regions

2021 ◽  
Vol 8 ◽  
Author(s):  
Petra Koucká Knížová ◽  
Jan Laštovička ◽  
Daniel Kouba ◽  
Zbyšek Mošna ◽  
Katerina Podolská ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Source Region ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Small Scale ◽  
Atmospheric Waves ◽  
Ionospheric Variability ◽  
Secular Variations ◽  
Wide Scale ◽  
Academy Of Sciences

The ionosphere represents part of the upper atmosphere. Its variability is observed on a wide-scale temporal range from minutes, or even shorter, up to scales of the solar cycle and secular variations of solar energy input. Ionosphere behavior is predominantly determined by solar and geomagnetic forcing. However, the lower-lying atmospheric regions can contribute significantly to the resulting energy budget. The energy transfer between distant atmospheric parts happens due to atmospheric waves that propagate from their source region up to ionospheric heights. Experimental observations show the importance of the involvement of the lower atmosphere in ionospheric variability studies in order to accurately capture small-scale features of the upper atmosphere. In the Part I Coupling, we provide a brief overview of the influence of the lower atmosphere on the ionosphere and summarize the current knowledge. In the Part II Coupling Evidences Within Ionospheric Plasma—Experiments in Midlatitudes, we demonstrate experimental evidence from mid-latitudes, particularly those based on observations by instruments operated by the Institute of Atmospheric Physics, Czech Academy of Sciences. The focus will mainly be on coupling by atmospheric waves.

Theory of the rocket-grenade method of measuring temperature, pressure, density and wind velocity in the upper atmosphere

1966 ◽  
Vol 290 (1420) ◽  
pp. 44-73 ◽  
Keyword(s):  
Experimental Data ◽  
Least Squares ◽  
Wind Velocity ◽  
Speed Of Sound ◽  
Vertical Component ◽  
Second Order ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Travel Times ◽  
Sound Waves

A theory is presented for deriving the speed of sound and wind velocity as a function of height in the upper atmosphere from observations on the travel times of sound waves from accurately located grenades, released during rocket flight, to microphones at surveyed positions on the ground. The theory is taken to a second order of approximation, which can be utilized in practice if lower atmosphere (balloon) measurements are available. By means of the gas law and the vertical equation of motion of the atmosphere, formulae are obtained for deriving temperature, pressure and density from the speed-of-sound profile, and these also may be evaluated to a higher accuracy if lower atmosphere measurements are available. An outline is given of the computational procedure followed in the processing of data on the basis of this theory by means of the Pegasus computer. Methods of calculating the correction to travel times due to the finite wave amplitude are discussed and compared, and the effect of neglecting this correction in a particular set of experimental data is examined. Other errors which may affect the determination of pressure are also discussed. Consistency between the theory and experimental data obtained in 13 Skylark rocket flights at Woomera is checked in two ways: by examining least squares residuals associated with the sound arrivals at various microphones; and by treating the vertical component of air motion as unknown and examining its distribution about zero. The reduction in the least squares residuals which occurs when account is taken of second order terms is evaluated on the basis of these sets of experimental data.

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