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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

WHAT IS THE SOURCE OF QUIET SUN TRANSITION REGION EMISSION?

Dating back to the first observations of the on-disk corona, there has been a qualitative link between the photosphere’s magnetic network and enhanced transition-temperature plasma emission. These observations led to the development of a general model that describes emission structures through the partitioning of the atmospheric volume with different magnetic loop geometries that exhibit different energetic equilibria. Does the internetwork produce transition-temperature emission? What fraction of network flux connects to the corona? How does quiet Sun emission compare with low-activity Sun-like stars? In this work, we revisit the canonical model of the quiet Sun, with high-resolution observations from the Interface Region Imaging Spectrograph ( IRIS ) and HMI in hand, to address those questions. We use over 900 deep exposures of Si iv 1393 Å from IRIS along with nearly simultaneous HMI magnetograms to quantify the correlation between transition-temperature emission structures and magnetic field concentrations through a number of novel statistics. Our observational results are coupled with analysis of the Bifrost MHD model and a large-scale potential field model. Our results paint a complex portrait of the quiet Sun. We measure an emission signature in the distant internetwork that cannot be attributed to network contribution. We find that the dimmest regions of emission are not linked to the local vertical magnetic field. Using the MHD simulation, we categorize the emission contribution from cool mid-altitude loops and high-altitude coronal loops and discuss the potential emission contribution of spicules. Our results provide new constraints on the coupled solar atmosphere so that we can build on our understanding of how dynamic thermal and magnetic structures generate the observed phenomena in the transition region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Effect of Solar Radiation on the Optical Properties and Molecular Composition of Laboratory Proxies of Atmospheric Brown Carbon

Sources, optical properties, and chemical composition of atmospheric brown carbon (BrC) aerosol are uncertain, making it challenging to estimate its contribution to radiative forcing. Furthermore, optical properties of BrC may change significantly during its atmospheric aging. We examined the effect of solar photolysis on the molecular composition, mass absorption coefficient, and fluorescence of secondary organic aerosol prepared by high-NO x photooxidation of naphthalene (NAP SOA). The aqueous solutions of NAP SOA was observed to photobleach with an effective half-time of ~15 hours (with sun in its zenith) for the loss of the near-UV (300 -400 nm) absorbance. The molecular composition of NAP SOA was significantly modified by photolysis, with the average SOA formula changing from C 14.1 H 14.5 O 5.1 N 0.08 to C 11.8 H 14.9 O 4.5 N 0.02 after 4 hours of irradiation. The average O/C ratio did not change significantly, however, suggesting that it is not a good metric for assessing the extent of photolysis-driven aging in NAP SOA (and in BrC in general). In contrast to NAP SOA, the photolysis of BrC material produced by aqueous reaction of limonene+O 3 SOA (LIM/O 3 SOA) with ammonium sulfate was much faster, but it did not result in a significant change in the molecular level composition. The characteristic absorbance of the aged LIM/O 3 SOA in the 450-600 nm range decayed with an effective half-time of <0.5 hour. This result emphasizes the highly variable and dynamic nature of different types of atmospheric BrC.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2019

Corrosion Behavior of Q235 Steel in Atmospheres Containing SO{sub 2} and NaCl

The atmospheric corrosion of metals is a severe problem in marine environments. However, the effects of SO{sub 2} and NaCl on the atmospheric corrosion of Q235 steel have not been widely studied. In the present work, electrochemical impedance spectroscopy was conducted to exploit the initial corrosion properties of Q235 in simulated atmospheric environments containing different contents of SO{sub 2} and NaCl. The solution resistance (R{sub s}) and polarization resistance (R{sub p}) of electrodes covered with pre-deposited NaCl were continuously monitored. The results showed that both SO{sub 2} and NaCl promoted the corrosion rate of Q235 steel. The pre-deposited NaCl maintained the moisture of the metal surface to ensure continued corrosion. The thickness of the electrolyte layer on the metal surface decreased with increasing SO{sub 2} content. A thin electrolyte layer could increase the Cl{sup −} concentration and reduce the pH value of the layer. The thin electrolyte layer could also promote the mass transfer of oxygen, thereby accelerating the cathodic reduction reaction. However, the NaCl content played a more important role than that of SO{sub 2} in the simulated environments.

36 MATERIALS SCIENCE↗
NASA NTRS2017

A Library of ATMO Forward Model Transmission Spectra for Hot Jupiter Exoplanets

We present a grid of forward model transmission spectra, adopting an isothermal temperature-pressure profile, alongside corresponding equilibrium chemical abundances for 117 observationally significant hot exoplanets (equilibrium temperatures of 547-2710 K). This model grid has been developed using a 1D radiative-convective-chemical equilibrium model termed ATMO, with up-to-date high-temperature opacities. We present an interpretation of observations of 10 exoplanets, including best-fitting parameters and X(exp 2) maps. In agreement with previous works, we find a continuum from clear to hazy/cloudy atmospheres for this sample of hot Jupiters. The data for all the 10 planets are consistent with subsolar to solar C/O ratio, 0.005 to 10 times solar metallicity and water rather than methane-dominated infrared spectra. We then explore the range of simulated atmospheric spectra for different exoplanets, based on characteristics such as temperature, metallicity, C/O ratio, haziness and cloudiness. We find a transition value for the metallicity between 10 and 50 times solar, which leads to substantial changes in the transmission spectra. We also find a transition value of C/O ratio, from water to carbon species dominated infrared spectra, as found by previous works, revealing a temperature dependence of this transition point ranging from approximately 0.56 to approximately 1-1.3 for equilibrium temperatures from approximately 900 to approximately 2600 K. We highlight the potential of the spectral features of HCN and C2H2 to constrain the metallicities and C/O ratios of planets, using James Webb Space Telescope (JWST) observations. Finally, our entire grid (approximately 460 000 simulations) is publicly available and can be used directly with the JWST simulator PandExo for planning observations.

techniques: spectroscopic – planets and satellit↗
DOE OSTI2016

DAMPING OF ALFVÉN WAVES BY TURBULENCE AND ITS CONSEQUENCES: FROM COSMIC-RAY STREAMING TO LAUNCHING WINDS

This paper considers turbulent damping of Alfvén waves in magnetized plasmas. We identify two cases of damping, one related to damping of cosmic-ray streaming instability, the other related to damping of Alfvén waves emitted by a macroscopic wave source, e.g., a stellar atmosphere. The physical difference between the two cases is that in the former case the generated waves are emitted with respect to the local direction of the magnetic field, and in the latter, waves are emitted with respect to the mean field. The scaling of damping is different in the two cases. We explore effects of turbulence in the regimes from sub-Alfvénic to super-Alfvénic to obtain analytical expressions for the damping rates and define the ranges of applicability of these expressions. In describing the damping of the streaming instability, we find that for sub-Alfvénic turbulence, the range of cosmic-ray energies influenced by weak turbulence is unproportionally large compared to the range of scales where weak turbulence is present. On the contrary, the range of cosmic-ray energies affected by strong Alfvénic turbulence is rather limited. A number of astrophysical applications of the process ranging from launching of stellar and galactic winds to propagation of cosmic rays in galaxies and clusters of galaxies is considered. In particular, we discuss how to reconcile the process of turbulent damping with the observed isotropy of the Milky Way cosmic rays.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Vegetation controls on surface heat flux partitioning, and land-atmosphere coupling

Here, we provide observational evidence that land-atmosphere coupling is underestimated by a conventional metric defined by the correlation between soil moisture and surface evaporative fraction (latent heat flux normalized by the sum of sensible and latent heat flux). Land-atmosphere coupling is 3 times stronger when using leaf area index as a correlate of evaporative fraction instead of soil moisture, in the Southern Great Plains. The role of vegetation was confirmed using adjacent flux measurement sites having identical atmospheric forcing but different vegetation phenology. Transpiration makes the relationship between evaporative fraction and soil moisture nonlinear and gives the appearance of weak coupling when using linear soil moisture metrics. Regions of substantial coupling extend to semiarid and humid continental climates across the United States, in terms of correlations between vegetation metrics and evaporative fraction. The hydrological cycle is more tightly constrained by the land surface than previously inferred from soil moisture.

58 GEOSCIENCES↗
DOE OSTI2017

Experimental Study of Gas-Hydrate Dissociation Kinetics at Constant Temperatures Above 0°C

Recently, gas-hydrate storage technology has been drawing increasing attention as a new means of gas storage and transportation and may in the future become the optimal means of gas storage as compared with LNG technology because of its economic and safety advantages. The main purpose of the present work was to investigate experimentally the hydrate dissociation mechanism using a kinetic model at different temperatures and atmospheric pressure in the range 5-15°C. The obtained results have great significance for gas-hydrate storage technology and its application in industry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Analysis of measurements from an array of radioxenon samplers near to Hartlepool Nuclear Power Station

As part of a scientific research and development project, the radionuclide fingerprint of an operating advanced gas-cooled reactor 25 (AGR) has been studied across several facets (Goodwin et al., 2024). One part of this project was to deploy an array of 26 radioxenon samplers to the region for a period of around 1 year, to measure any radioxenon emissions from the reactors of the 27 Hartlepool nuclear power station at a range of tens of kilometres away. The array of 3 sensors was operational for around 12 28 months from March 2022 and detected many occurrences of isotopes of radioxenon. Here we provide a detailed analysis and 29 interpretation of the data and where possible, attribution of detections to a source or region. Whilst a key part of this work is to 30 measure any emissions of radioxenon from Hartlepool, this work presents one of the most comprehensive efforts to determine the 31 source of a great number of (mostly) 133Xe detections. A combination of different types of atmospheric dispersion modelling 32 techniques, including the use of stack monitoring data from nearby civil radioxenon-emitting nuclear facilities has enabled the 33 majority of detections to be attributed to one or more possible sources. Whilst emissions from Hartlepool have been detected on 34 the systems, the majority of detections are associated with a medical isotope production facility in Fleurus, Belgium (IRE).

Advanced gas-cooled reactor↗
DOE OSTI2014

Spectral selective radio frequency emissions from laser induced breakdown of target materials

The radio frequency emissions scanned over broad spectral range (30 MHz–1 GHz) from single shot nanosecond (7 ns) and picosecond (30 ps) laser induced breakdown (LIB) of different target materials (atmospheric air, aluminum, and copper) are presented. The dominant emissions from ns-LIB, compared to those from the ps-LIB, indicate the presence and importance of atomic and molecular clusters in the plasma. The dynamics of laser pulse-matter interaction and the properties of the target materials were found to play an important role in determining the plasma parameters which subsequently determine the emissions. Thus, with a particular laser and target material, the emissions were observed to be spectral selective. The radiation detection capability was observed to be relatively higher, when the polarization of the input laser and the antenna is same.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Interaction between indium tin oxide nanoparticles and cytochrome c: A surface-enhanced Raman scattering and absorption spectroscopic study

Indium-tin-oxide (ITO) nanoparticles were annealed in vacuum or reducing atmosphere to obtain different surface structures and investigate their influence on the adsorptive character and conformation of cytochrome c (Cyt c) molecule. Annealing-induced morphometric or structural changes of ITO nanoparticles were characterized by instruments of transmission electron microscopy, x-ray diffraction, and Raman scattering. Semiconductor ITO nanoparticle-enhanced Raman scattering of Cyt c was observed and the enhanced efficiency was found to closely depend on the surface structures which control the adsorbance of buffer anions needed for Cyt c loading. Direct electron transfer between Cyt c and ITO surface at the moment of molecular elastic collision was found and a reverse electron transfer process for O-terminated surface and metal-terminated surface was observed, according to absorption spectroscopic measurement on the residual solution.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Exploring stellar evolution models of sdB stars using MESA

Stellar evolution calculations have had great success reproducing the observed atmospheric properties of different classes of stars. Recent detections of g-mode pulsations in evolved He burning stars allow a rare comparison of their internal structure with stellar models. Asteroseismology of subdwarf B (sdB) stars suggests convective cores of 0.22–0.28 M{sub ⊙}, ≳45% of the total stellar mass. Previous studies found significantly smaller convective core masses (≲0.19 M{sub ⊙}) at a comparable evolutionary stage. We evolved stellar models with Modules for Experiments in Stellar Astrophysics (MESA) to explore how well the interior structures inferred from asteroseismology can be reproduced by standard algorithms. Our qualitative evolutionary paths, position in the logg−T{sub eff} diagram, and model timescales are consistent with previous results. The sdB masses from our full evolutionary sequences fall within the range of the empirical sdB mass distribution, but are nearly always lower than the median. Using standard MLT with atomic diffusion we find convective core masses of ∼0.17–0.18 M{sub ⊙}, averaged over the entire sdB lifetime. We can increase the convective core sizes to be as large as those inferred from asteroseismology, but only for extreme values of the overshoot parameter (overshoot gives numerically unstable and physically unrealistic behavior at the boundary). High resolution three-dimensional simulations of turbulent convection in stars suggest that the Schwarzschild criterion for convective mixing systematically underestimates the actual extent of mixing because a boundary layer forms. Accounting for this would decrease the errors in both sdB total and convective core masses.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Insight of BaCe 0.5 Fe 0.5 O 3– δ twin perovskite oxide composite for solid oxide electrochemical cells

One-pot synthesized twin perovskite oxide composite of BaCe 0.5 Fe 0.5 O 3–δ (BCF), comprising cubic and orthorhombic perovskite phases, shows triple-conducting properties for promising solid oxide electrochemical cells. Phase composition evolution of BCF under various conditions was systematically investigated, revealing that the cubic perovskite phase could be fully/partially reduced into the orthorhombic phase under certain conditions. The reduction happened between the two phases at the interface, leading to the microstructure change. As a result, the corresponding apparent conducting properties also changed due to the difference between predominant conduction properties for each phase. Based on the revealed phase composition, microstructure, and electrochemical properties changes, a deep understanding of BCF's application in different conditions (oxidizing atmospheres, reducing/oxidizing gradients, cathodic conditions, and anodic conditions) was achieved. Triple-conducting property (H + /O 2– /e – ), fast open-circuit voltage response (~16–~470 mV) for gradients change, and improved single-cell performance (~31% lower polarization resistance at 600°C) were comprehensively demonstrated. Besides, the performance was analyzed under anodic conditions, which showed that the microstructure and phase change significantly affected the anodic behavior.

08 HYDROGEN↗
DOE OSTI2015

A Hybrid Global Ocean Data Assimilation System at NCEP

Seasonal forecasting with a coupled model requires accurate initial conditions for the ocean. A hybrid data assimilation has been implemented within the National Centers for Environmental Prediction (NCEP) Global Ocean Data Assimilation System (GODAS) as a future replacement of the operational three-dimensional variational data assimilation (3DVar) method. This Hybrid-GODAS provides improved representation of model uncertainties by using a combination of dynamic and static background error covariances, and by using an ensemble forced by different realizations of atmospheric surface conditions. An observing system simulation experiment (OSSE) is presented spanning January 1991 to January 1999, with a bias imposed on the surface forcing conditions to emulate an imperfect model. The OSSE compares the 3DVar used by the NCEP Climate Forecast System (CFSv2) with the new hybrid, using simulated in situ ocean observations corresponding to those used for the NCEP Climate Forecast System Reanalysis (CFSR). The Hybrid-GODAS reduces errors for all prognostic model variables over the majority of the experiment duration, both globally and regionally. Compared to an ensemble Kalman filter (EnKF) used alone, the hybrid further reduces errors in the tropical Pacific. The hybrid eliminates growth in biases of temperature and salinity present in the EnKF and 3DVar, respectively. A preliminary reanalysis using real data shows that reductions in errors and biases are qualitatively similar to the results from the OSSE. Finally, the Hybrid-GODAS is currently being implemented as the ocean component in a prototype next-generation CFSv3, and will be used in studies by the Climate Prediction Center to evaluate impacts on ENSO prediction.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Subseasonal Earth System Prediction with CESM2

Abstract Prediction systems to enable Earth system predictability research on the subseasonal time scale have been developed with the Community Earth System Model, version 2 (CESM2) using two configurations that differ in their atmospheric components. One system uses the Community Atmosphere Model, version 6 (CAM6) with its top near 40 km, referred to as CESM2(CAM6). The other employs the Whole Atmosphere Community Climate Model, version 6 (WACCM6) whose top extends to ∼140 km, and it includes fully interactive tropospheric and stratospheric chemistry [CESM2(WACCM6)]. Both systems are utilized to carry out subseasonal reforecasts for the 1999–2020 period following the Subseasonal Experiment’s (SubX) protocol. Subseasonal prediction skill from both systems is compared to those of the National Oceanic and Atmospheric Administration CFSv2 and European Centre for Medium-Range Weather Forecasts (ECMWF) operational models. CESM2(CAM6) and CESM2(WACCM6) show very similar subseasonal prediction skill of 2-m temperature, precipitation, the Madden–Julian oscillation, and North Atlantic Oscillation to its previous version and to the NOAA CFSv2 model. Overall, skill of CESM2(CAM6) and CESM2(WACCM6) is a little lower than that of the ECMWF system. In addition to typical output provided by subseasonal prediction systems, CESM2 reforecasts provide comprehensive datasets for predictability research of multiple Earth system components, including three-dimensional output for many variables, and output specific to the mesosphere and lower-thermosphere (MLT) region from CESM2(WACCM6). It is shown that sudden stratosphere warming events, and the associated variability in the MLT, can be predicted ∼10 days in advance. Weekly real-time forecasts and reforecasts with CESM2(CAM6) and CESM2(WACCM6) are freely available. Significance Statement We describe here the design and prediction skill of two subseasonal prediction systems based on two configurations of the Community Earth System Model, version 2 (CESM2): CESM2 with the Community Atmosphere Model, version 6 [CESM2(CAM6)] and CESM 2 with Whole Atmosphere Community Climate Model, version 6 [CESM2(WACCM6)] as its atmospheric component. These two systems provide a foundation for community-model based subseasonal prediction research. The CESM2(WACCM6) system provides a novel capability to explore the predictability of the stratosphere, mesosphere, and lower thermosphere. Both CESM2(CAM6) and CESM2(WACCM6) demonstrate subseasonal surface prediction skill comparable to that of the NOAA CFSv2 model, and a little lower than that of the ECMWF forecasting system. CESM2 reforecasts provide a comprehensive dataset for predictability research of multiple aspects of the Earth system, including the whole atmosphere up to 140 km, land, and sea ice. Weekly real-time forecasts, reforecasts, and models are publicly available.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Cloud Condensation Nuclei Hygroscopicity Value-Added Product Report

The purpose of the Atmospheric Radiation Measurement (ARM) user facility’s cloud condensation nuclei hygroscopicity parameter (AOSCCNSMPSKAPPA) value-added product (VAP) is to calculate the hygroscopicity parameter, kappa, to quantify the ability of aerosols to activate into cloud water droplets. The hygroscopicity parameter is often used to model the cloud condensation nuclei (CCN) activity of atmospheric aerosols of different sizes and compositions, providing additional insight on the influence of aerosols on climate. Laboratory experiments show that the kappa values for highly hygroscopic aerosols, such as salts and sulfates, vary from 0.5 to 1.4 (Petters and Kreidenweis 2007). For organic compounds they are observed to vary between 0.01 and 0.5. For non-hygroscopic aerosols, such as soot, kappa values are very close to zero. Ambient aerosols are complex mixtures of organic and inorganic compounds and previous observations indicate that kappa values typically vary from 0.05 to 0.9 (Petters and Kreidenweis 2007).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Cloud Condensation Nuclei Hygroscopicity Value-Added Product Report

The purpose of the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) user facility’s Cloud Condensation Nuclei Hygroscopicity Parameter (AOSCCNSMPSKAPPA and AOSCCNUHSASKAPPA) Value-Added Product (VAP) is to calculate the hygroscopicity parameter, kappa, to quantify the ability of aerosols to activate into cloud water droplets. The hygroscopicity parameter is often used to model the cloud condensation nuclei (CCN) activity of atmospheric aerosols of different sizes and compositions, providing additional insight on the influence of aerosols on climate. The AOSCCNUHSASKAPPA VAP was recently developed to provides kappa data for ARM sites where AOSCCNSMPSKAPPA was missing.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Cloud Condensation Nuclei Hygroscopicity Value-Added Product Report

The purpose of the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) user facility’s Cloud Condensation Nuclei Hygroscopicity Parameter (AOSCCNSMPSKAPPA and AOSCCNUHSASKAPPA) Value-Added Product (VAP) is to calculate the hygroscopicity parameter, kappa, to quantify the ability of aerosols to activate into cloud water droplets. The hygroscopicity parameter is often used to model the cloud condensation nuclei (CCN) activity of atmospheric aerosols of different sizes and compositions, providing additional insight on the influence of aerosols on climate. The AOSCCNUHSASKAPPA VAP was recently developed to provides kappa data for ARM sites where AOSCCNSMPSKAPPA was missing. Laboratory experiments show that the kappa values for highly hygroscopic aerosols vary from 0.5 to 1.4 (Petters and Kreidenweis 2007). For organic compounds they are observed to vary between 0.01 and 0.5. For non-hygroscopic aerosols, such as soot, kappa values are very close to zero. Ambient aerosols are complex mixtures of organic and inorganic compounds and previous observations indicate that kappa values for these aerosols typically vary from 0.05 to 0.9 (Petters and Kreidenweis 2007).

54 ENVIRONMENTAL SCIENCES↗