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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Observations of Carbon Chain Chemistry in the Envelopes of Low-Mass Protostars

Observational results are reported from our surveys in the Northern Hemisphere (using the Onsala 20 m telescope) and the Southern Hemisphere (using the Mopra 22 m telescope) to search for 3 mm emission lines from carbon-chain-bearing species and other complex molecules in the envelopes of low-mass protostars. Based on a sample of approximately 60 sources, we find that carbon-chain-bearing species including HC3N (and C4H) are highly abundant in the vicinity of more than half of the observed protostars. The origin and evolution of these species, including their likely incorporation into ices in protoplanetary disks will be discussed

Cordiner, M.↗
NASA NTRS2015

Variability of Phenology and Fluxes of Water and Carbon with Observed and Simulated Soil Moisture in the Ent Terrestrial Biosphere Model (Ent TBM Version 1.0.1.0.0)

The Ent Terrestrial Biosphere Model (Ent TBM) is a mixed-canopy dynamic global vegetation model developed specifically for coupling with land surface hydrology and general circulation models (GCMs). This study describes the leaf phenology submodel implemented in the Ent TBM version 1.0.1.0.0 coupled to the carbon allocation scheme of the Ecosystem Demography (ED) model. The phenology submodel adopts a combination of responses to temperature (growing degree days and frost hardening), soil moisture (linearity of stress with relative saturation) and radiation (light length). Growth of leaves, sapwood, fine roots, stem wood and coarse roots is updated on a daily basis. We evaluate the performance in reproducing observed leaf seasonal growth as well as water and carbon fluxes for four plant functional types at five Fluxnet sites, with both observed and prognostic hydrology, and observed and prognostic seasonal leaf area index. The phenology submodel is able to capture the timing and magnitude of leaf-out and senescence for temperate broadleaf deciduous forest (Harvard Forest and Morgan- Monroe State Forest, US), C3 annual grassland (Vaira Ranch, US) and California oak savanna (Tonzi Ranch, US). For evergreen needleleaf forest (Hyytiäla, Finland), the phenology submodel captures the effect of frost hardening of photosynthetic capacity on seasonal fluxes and leaf area. We address the importance of customizing parameter sets of vegetation soil moisture stress response to the particular land surface hydrology scheme. We identify model deficiencies that reveal important dynamics and parameter needs.

Soil moisture↗
NASA NTRS2001

Stratospheric Age Spectra and Mean Ages From In Situ Observations of Carbon Dioxide

Tropospheric CO2 mixing ratios exhibit latitudinally varying seasonal and interannual oscillations superimposed on the long-term positive trend due to fossil fuel combustion. In situ observations of CO2 obtained from 1992-2000 using the NASA ER-2 aircraft and high-altitude balloons show that these time-varying signals propagate into the stratosphere, providing information about the transport history of sampled air. We have used these data to derive age spectra and mean ages that can be compared with results from models of the stratospheric circulation. Age spectra have been derived for altitudes below approximately 20 km for the tropics and for northern midlatitudes, where there is sufficient data and where the amplitudes of the seasonal and interannual oscillations are large enough to be detected. The midlatitude CO2 data are consistent with bimodal age spectra, which may result from a subtropical "barrier" to horizontal exchange. Seasonally resolved mean ages are available with nearly pole-to-pole coverage below 20 km and in the tropics and at middle and high northern latitudes up to the maximum altitude reached by the balloons (approximately 30 km). The oldest air sampled was in the Arctic polar vortex with a mean age of 6.5 +/- 0.5 years.

Andrews, Arlyn E.↗
NASA NTRS2012

Observations of Carbon Isotopic Fractionation in Interstellar Formaldehyde

Primitive Solar System materials (e.g. chondrites. IDPs, the Stardust sample) show large variations in isotopic composition of the major volatiles (H, C, N, and O ) even within samples, witnessing to various degrees of processing in the protosolar nebula. For ex~ ample. the very pronounced D enhancements observed in IDPs [I] . are only generated in the cold. dense component of the interstellar medium (ISM), or protoplanetary disks, through ion-molecule reactions in the presence of interstellar dust. If this isotopic anomaly has an interstellar origin, this leaves open the possibility for preservation of other isotopic signatures throughout the form ation of the Solar System. The most common form of carbon in the ISM is CO molecules, and there are two potential sources of C-13 fractionation in this reservoir: low temperature chemistry and selective photodissociation. While gas-phase chemistry in cold interstellar clouds preferentially incorporates C-13 into CO [2], the effect of self-shielding in the presence of UV radiation instead leads to a relative enhancement of the more abundant isotopologue, 12CO. Solar System organic material exhibit rather small fluctuations in delta C-13 as compared to delta N-15 and delta D [3][1], the reason for which is still unclear. However, the fact that both C-13 depleted and enhanced material exists could indicate an interstellar origin where the two fractionation processes have both played a part. Formaldehyde (H2CO) is observed in the gas-phase in a wide range of interstellar environments, as well as in cometary comae. It is proposed as an important reactant in the formation of more complex organic molecules in the heated environments around young stars, and formaldehyde polymers have been suggested as the common origin of chondritic insoluable organic matter (IOM) and cometary refractory organic solids [4]. The relatively high gas-phase abundance of H2CO observed in molecular clouds (10(exp- 9) - 10(exp- 8) relative to H2) makes it feasible to observe its less common isotopologues. As a step in our investigation of C-13 fractionation patterns in the ISM, we here present comparisons between observations of the C-13 fraction in formaldehyde, and chemical fractionation models.

Wirstrom, E. S.↗
NASA NTRS1987

Radio observations of carbon monoxide toward Zeta Ophiuchi - Velocity structure, isotopic abundances, and physical properties

This paper presents a small-scale map of the molecular gas around the line of sight toward Zeta Oph made with measurements of the (C-12)O (1-0) emission obtained at high signal-to-noise ratio and high velocity resolution. In addition, a measurement of the (C-12)O (2-1) line emission and a detection of (C-13)O along the line of sight to the star are reported. The results show that the CO emission toward the star is composed from at least four components with peak velocities at -2.0, -0.7, 0.0, and +0.6 km/s. The radio observations yield a total CO column density of 1.4 x 10 to the 15th/sq cm, with about one-half of the total CO column density being in the main component at -0.7 km/s. The main cmponent is uniform over the map, but the other components are variable, suggesting that the cloud is clumpy. The data on the two CO transitions imply that the excitation temperature and the density of the main component are about 7 K and 800/cu cm, respectively.

Langer, William D.↗
NASA NTRSDate not supplied

Observation of Carbon Monoxide and Ozone from 2019-2020 Australia Fires Using Thermal Infrared and Near-Infrared Satellite Sensors

The Single Field-of-view Sounder Atmospheric Products (SiFSAP), including ozone (O3) and carbon monoxide (CO), from CrIS on SNPP have a spatial resolution of about 14 km. Such high-resolution sounder products enable us to make process-oriented analysis of CO emission and transport from biomass burning as well as the O3 production along the transport of fire plumes from large wildfires. An analysis of SiFSAP CO from Australia’s unprecedented wildfires in the end of 2019 to early 2020 and comparison with other satellite products, such as TROPOMI and MOPPIT, demonstrate a good agreement of CO observations among these space-borne sensors. This study also demonstrates the advantage of the SiFSAP CO in capturing the feature of CO transport and O3 production from wildfires, which will benefit air quality study.

Xiaozhen Xiong↗
NASA NTRS1977

Carbon monoxide observations of a rotating dust globule

Results are presented for observations of the J = 1-0 rotational lines of (C-12)(O-16), (C-13)(O-16), and (C-12)(O-18) at rest frequencies of 115.2712, 110.2014, and 109.7822 GHz, respectively, in the direction of the small dust cloud B361. For a distance of 350 pc, the cloud is found to have an overall radius of about 1.2 pc and a core radius of about 0.4 pc. The core density is estimated to be about 10,000 per cu cm, and it is shown that the density at the center is high enough for the CO to be collisionally thermalized. A cloud temperature of 8.5 K is determined, a lower limit of 125 solar masses is placed on the core mass, and it is suggested that most of the mass is contained within the inner 6% of the cloud volume. The dense inner core is found to be rotating with a velocity gradient of 2.9 km/s per pc. A n(CO)/n(H) ratio that is no more than 0.07 of the solar n(C)/n(H) ratio is derived, indicating that most of the carbon present in the cloud is not in the form of CO.

Milman, A. S.↗
NASA NTRS1974

Scanner observations of carbon stars from 5000 to 7000 A

New photoelectric spectral scans of 26 N-type and 11 R-type carbon stars are presented. The spectral energy distributions were also measured to gain new insight into the composition, chemistry, and structure of carbon star atmospheres. Using the best continuum points in the wavelength region from 5000 to 7000 A a color index is defined, taking into account fluxes at 0.57 and 0.68 microns. The new color index correlates well with the widely used (V-R) broad-band color index.-

Fay, T. D., Jr.↗
NASA NTRS2015

Airborne Observations of Carbon Dioxide and Methane Emission Ratios from the Yosemite Rim Wildfire, California

This paper presents airborne in situ measurements of carbon dioxide (CO2) and methane (CH4) downwind of an exceptionally large wildfire, the Rim Fire, near Yosemite, California, during two flights. Data analyses are discussed in terms of emission ratios (ER) and emission factors (EF) and are compared to previous studies. CH4 ER’s were 7.5-7.9 parts per billion (ppb) CH4 for every 1 part per million (ppm) of CO2 (ppb CH4 (ppm CO2)(exp.-1)) on 29 August 2013 and 14.2-16.7 ppb CH4 (ppm CO2)(exp. -1) on 10 September 2013. This study measured only CO2 and CH4; however, estimated emission factors (EEF’s) are used as rough estimates of EF’s of CO2 and CH4 and are in close agreement with EF’s reported in previous studies. In the western US, wildfires dominate over prescribed fires, contributing to atmospheric trace gas budgets and regional and local air pollution. Limited sampling of emissions from wildfires means western US emission estimates rely largely on data from prescribed fires, which may not be a suitable proxy for wildfire emissions. Given the magnitude of the Yosemite Rim wildfire, the impacts it had on regional air quality and the limited sampling of wildfire emissions in the western US to date, this study provides a valuable measurement dataset and may have important implications for forestry and regional air quality management.

Yates, Emma L.↗
NASA NTRS2020

Direct Measurement of the Cosmic-Ray Carbon and Oxygen Spectra from 10 GeV/n to 2.2 TeV/n with the Calorimetric Electron Telescope on the International Space Station

In this paper, we present the measurement of the energy spectra of carbon and oxygen in cosmic rays based on observations with the Calorimetric Electron Telescope on the International Space Station from October 2015 to October 2019. Analysis, including the detailed assessment of systematic uncertainties, and results are reported. The energy spectra are measured in kinetic energy per nucleon from 10 GeV/n to 2.2 TeV/n with an all-calorimetric instrument with a total thickness corresponding to 1.3 nuclear interaction length. The observed carbon and oxygen fluxes show a spectral index change of ∼0.15 around 200 GeV/n established with a significance > 3σ. They have the same energy dependence with a constant C/O flux ratio 0.911 ± 0.006 above 25 GeV/n. The spectral hardening is consistent with that measured by AMS-02, but the absolute normalization of the flux is about 27% lower, though in agreement with observations from previous experiments including the PAMELA spectrometer and the calorimetric balloon-borne experiment CREAM.

O. Adriani↗
NASA NTRS1977

Carbon monoxide on Jupiter and implications for atmospheric convection

A study of the equilibrium and disequilibrium thermochemistry of the recently discovered carbon monoxide on Jupiter suggests that the presence of this gas in the visible atmosphere is a direct result of very rapid upward mixing from levels in the deep atmosphere where the temperature is about 1100 K and where carbon monoxide is thermodynamically much more stable. As a consequence the observed carbon monoxide mixing ratio is a sensitive function of the vertical eddy mixing coefficient. We infer a value for this latter coefficient which is about three to four orders of magnitude greater than that in the earth's troposphere. This result directly supports existing structural and dynamical theories implying very rapid convection in the deep Jovian atmosphere, driven by an internal heat source.

Prinn, R. G.↗
NASA NTRS1976

Carbon recombination line observations of the sharpless 140 region

Carbon recombination-line emission has been detected at two frequencies from a dark cloud contiguous with the small H II region Sharpless 140. The observations show the dark cloud to be of unusually low temperature and to have a markedly inhomogeneous density distribution, with localized region of high density surrounding one or more embedded stars. The carbon is probably ionized by photons from both the exciting star of S140 and the embedded stars. The dark cloud and S140 apparently represent two stages of star formation which have occurred over a period of at least 500,000 years in adjacent regions of the same dark cloud.

Knapp, G. R.↗