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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Flare model sensitivity of the Balmer spectrum

Careful studies of various chromospheric spectral signatures are very important in order to explore their possible sensitivity to the modifications of the thermodynamic quantities produced by the flare occurrence. Pioneer work of Canfield and co-workers have shown how the H alpha behavior is able to indicate different changes in the atmospheric parameters structure associated to the flare event. It was decided to study the behavior of the highest Balmer lines and of the Balmer continuum in different solar flare model atmospheres. These spectral features, originating in the deep photosphere in a quiet area, may have a sensitivity different from H alpha to the modification of a flare atmosphere. The details of the method used to compute the Stark profile of the higher Balmer line (n is greater than or equal to 6) and their merging were extensively given elsewhere (Donati-Falchi et al., 1985; Falchi et al., 1989). The models used were developed by Ricchiazzi in his thesis (1982) evaluating the chromospheric response to both the nonthermal electron flux, for energy greater than 20 kev, (F sub 20) and to the thermal conduction, (F sub c). The effect of the coronal pressure values (P sub O) at the apex of the flare loop is also included.

Falchi, A.↗
NASA NTRS2018

Biosignature Anisotropy Modeled on Temperate Tidally Locked M-Dwarf Planets

A planet’s atmospheric constituents (e.g., O2, O3, H2Ov, CO2, CH4, and N2O) can provide clues to its surface habitability, and may offer biosignature targets for remote life detection efforts. The plethora of rocky exoplanets found by recent transit surveys (e.g., the Kepler mission) indicates that potentially habitable systems orbiting K- and M-dwarf stars may have very different orbital and atmospheric characteristics than Earth. To assess the physical distribution and observational prospects of various biosignatures and habitability indicators, it is important to understand how they may change under different astrophysical and geophysical configurations, and to simulate these changes with models that include feedbacks between different subsystems of a planet’s climate. Here we use a three-dimensional (3D) Chemistry–Climate model (CCM) to study the effects of changes in stellar spectral energy distribution (SED), stellar activity, and planetary rotation on Earth analogs and tidally locked planets. Our simulations show that, apart from shifts in stellar SEDs and UV radiation, changes in illumination geometry and rotation-induced circulation can influence the global distribution of atmospheric biosignatures. We find that the stratospheric day-to-nightside mixing ratio differences on tidally locked planets remain low (<20%) across the majority of the canonical biosignatures. Interestingly, however, secondary photosynthetic biosignatures (e.g., C2H6S) show much greater (∼67%) day-to-nightside differences, and point to regimes in which tidal locking could have observationally distinguishable effects on phase curve, transit, and secondary eclipse measurements. Overall, this work highlights the potential and promise for 3D CCMs to study the atmospheric properties and habitability of terrestrial worlds.

Chen, Howard↗
NASA NTRS1972

The earth's atmosphere.

Topics discussed include the effects of solar radiation on the heat balance of the earth and its atmosphere, the physicomathematical models of the atmosphere and the computational schemes used in numerical investigations of the general circulation of the atmosphere, the effects of atmospheric turbulence on aeronautical systems, te chemistry of different regions of the atmosphere, the use of hot-filament and cold-cathode vacuum gauges to measure upper-atmosphere densities, methods of determining the air density at heights near a satellite's perigee by analyzing changes in its orbit, and an evaluation of various atmospheric models in the 100- to 1000-km altitude range.

Vaughan, W. W.↗
NASA NTRS1991

Sodium and potassium in the lunar atmosphere

The discovery that sodium and potassium vapor can be observed in the lunar atmosphere using ground-based telescopes has opened up a field of investigation that was closed after the last Apollo mission to the Moon. Sodium has been detected at altitudes up to 1500 km above the surface. This implies a high effective temperature for sodium, of the order of 1000 K. However, there is some evidence for two populations of sodium and potassium, one at temperatures corresponding to the surface, and another corresponding to high temperatures. The sources for the lunar atmosphere are not understood. Meteoric bombardment of the surface, solar wind sputtering of the surface, and photo-sputtering of the surface have all been suggested as possible sources for the lunar atmosphere. One of the objectives of the current research is to test different hypotheses by measurements of the atmosphere under different conditions of solar illumination and shielding from the solar wind by the Earth.

Potter, A. E.↗
DOE OSTI2020

Advancing Measurements and Understanding of the Rate and Structure of Atmospheric Warming

The rate and geographic pattern of atmospheric warming are key indicators of historical climate change and play a role in modulating future changes in Earth’s climate. The past and future evolution of atmospheric temperature is simulated using global climate models while observational estimates of past warming are derived from satellite microwave measurements. Individual climate models simulate widely varying rates of past and future atmospheric warming and most model simulations exhibit greater tropospheric (lowest ~10 km of atmosphere) temperature change than satellite observations between 1979 and 2020. This project examined intermodel differences in the pattern of atmospheric warming and how these differences influence climate feedbacks that can amplify or damp the rate of global surface warming. A key result is that climate model representation of the current climate can influence climate feedbacks and the simulation of future changes in climate. Another focus of this project was to analyze how models respond to different input datasets, such as volcanic aerosols or sea surface temperature (in atmosphere-only simulations). We find that different prescribed inputs can affect simulated changes in atmospheric temperature, even though “input uncertainty” is often unconsidered in model-observational comparisons. A final focus of this research project was to consider the influence of natural internal climate variability on satellite era changes in climate. Although the Earth is warming substantially due to anthropogenic emissions of greenhouse gases, the observed warming rate can be modulated by natural variations in the Earth’s climate. We find that natural climate variability has slowed the rate of tropical tropospheric warming, which explains model-satellite differences in the rate of tropospheric warming.

58 GEOSCIENCES↗
NASA NTRS2010

High C/O Chemistry and Weak Thermal Inversion in the Extremely Irradiated Atmosphere of Exoplanet WASP-12b

The carbon-to-oxygen ratio (C/O) in a planet provides critical information about its primordial origins and subsequent evolution. A primordial C/O greater than 0.8 causes a carbide-dominated interior as opposed to the silicate-dominated composition as found on Earth; the solar C/O is 0.54. Theory, shows that high C/O leads to a diversity of carbon-rich planets that can have very different interiors and atmospheres from those in the solar system. Here we report the detection of C/O greater than or equal to 1 in a planetary atmosphere. The transiting hot Jupiter WASP-12b has a dayside atmosphere depleted in water vapour and enhanced in methane by over two orders of magnitude compared to a solar-abundance chemical equilibrium model at the expected temperatures. The observed concentrations of the prominent molecules CO, CH4, and H2O are consistent with theoretical expectations for an atmosphere with the observed C/O = 1. The C/O ratios are not known for giant planets in the solar system, although they are expected to equal the solar value. If high C/O ratios are common, then extrasolar planets are likely very different in interior composition, and formed very differently, from expectations based on solar composition, potentially explaining the large diversity in observed radii. We also find that the extremely irradiated atmosphere (greater than 2500 K) of WASP-12b lacks a prominent thermal inversion, or a stratosphere, and has very efficient day-night energy circulation. The absence of a strong thermal inversion is in stark contrast to theoretical predictions for the most highly irradiated hot-Jupiter atmospheres.

Madhusudhan, Nikku↗
NASA NTRS1992

Water inventories on Earth and Mars: Clues to atmosphere formation

Water is distributed differently on Earth and on Mars and the differences may have implications for the accretion of the two planets and the formation of their atmospheres. The Earth's mantle appears to contain at least several times the water content of the Martian mantle even accounting for differences in plate tectonics. One explanation is that the Earth's surface melted during accretion, as a result of development of a steam atmosphere, thereby allowing impact-devolitalized water at the surface to dissolve into the Earth's interior. In contrast, because of Mars' smaller size and greater distance from the Sun, the Martian surface may not have melted, so that the devolatilized water could not dissolve into the surface. A second possibility is suggested by the siderophile elements in the Earth's mantle, which indicates the Earth acquired a volatile-rich veneer after the core formed. Mars may have acquired a late volatile-rich veneer, but it did not get folded into the interior as with the Earth, but instead remained as a water rich veneer. This perception of Mars with a wet surface but dry interior is consistent with our knowledge of Mars' geologic history.

Carr, M. H.↗
NASA NTRS2006

Theory of Radiation Transfer in Neutron Star Atmospheres

The possibility for direct investigation of thermal emission from isolated neutron stars opened about a quarter of century ago with the launch of the first X-ray observatories Einstein and EXOSAT stimulated developing models of the neutron star surface radiation which began at the end of 80's. Confronting observational data with theoretical models of thermal emission allows one to infer the surface temperatures, magnetic fields, chemical composition, and neutron star masses and radii. This information, supplemented with the model equations of state and neutron star cooling models, provides an opportunity to understand the fundamental properties of the superdense matter in the stars' interiors. Almost all available models are based on the assumption that thermal radiation emitted by a neutron star is formed in the superficial star's layers--atmosphere. The neutron star atmospheres are very different from those of usual stars due to the immense gravity and huge magnetic fields. In this presentation we review the current status of the neutron star atmosphere modeling, present most important results, discuss problems and possible future developments.

Zavlin, Vyacheslav↗
NASA NTRSDate not supplied

The Representation of Aerosols in GMAO’s Newest Reanalyses

Over the past few years, NASA’s Global Modelling and Assimilation Office has been working on the configuration and production of three new reanalysis products, GEOS-IT, GiOcean, and MERRA-21C. GEOS-IT, or the Goddard Earth Observing System for Instrument Teams, is a 3D variational data assimilation system that runs in a near real time framework however retrospectively provides data back through 1998 to deliver a consistent view of the Earth-atmosphere system for the production of observational NASA products. Retrospective production for GEOS-IT is complete and the meteorology has since been used to produce the one way weakly coupled GiOcean reanalysis. Due to differences in the atmospheric model, particularly related to scavenging, aerosols are not identical in GEOS-IT and GiOcean. MERRA-21C, or the Modern Era Restrospective analysis for Research and Applications in the 21st century, is a hybrid 4D ensemble variational system at a finer horizontal resolution of 0.25 degrees. Although different in their intended use, and therefore configuration, these systems prominently feature coupling between meteorology and aerosols. The differences and similarities in the aerosol configuration between the three systems will be discussed, covering biomass burning and anthropogenic emissions as well as observations used for the assimilation of aerosol optical depth. A large emphasis will be placed on the version of the underlying aerosol module, GOCART, which underwent a complete refactoring and the addition of radiatively active brown carbon between GEOS-IT and MERRA-21C. Independent observations will be used to evaluate the performance of aerosols in both reanalyses, focusing on aerosol optical depth, surface particulate matter, and vertical profiles of aerosol backscatter.

Allison Collow↗
DOE OSTI2017

Formation Mechanisms of Naphthalene and Indene: From the Interstellar Medium to Combustion Flames

The article addresses the formation mechanisms of naphthalene and indene, which represent prototype polycyclic aromatic hydrocarbons (PAH) carrying two six-membered and one five- plus a six-membered ring. Theoretical studies of the relevant chemical reactions are overviewed in terms of their potential energy surfaces, rate constants, and product branching ratios; these data are compared with experimental measurements in crossed molecular beams and the pyrolytic chemical reactor emulating the extreme conditions in the interstellar medium (ISM) and the combustion-like environment, respectively. The outcome of the reactions potentially producing naphthalene and indene is shown to critically depend on temperature and pressure or collision energy and hence the reaction mechanisms and their contributions to the PAH growth can be rather different in the ISM, planetary atmospheres, and in combustion flames at different temperatures and pressures. Specifically, this paradigm is illustrated with new theoretical results for rate constants and product branching ratios for the reaction of phenyl radical with vinylacetylene. The analysis of the formation mechanisms of naphthalene and its derivatives shows that in combustion they can be produced via hydrogen-abstraction-acetylene-addition (HACA) routes, recombination of cyclopentadienyl radical with itself and with cyclopentadiene, the reaction of benzyl radical with propargyl, methylation of indenyl radical, and the reactions of phenyl radical with vinylacetylene and 1,3-butadiene. In extreme astrochemical conditions, naphthalene and dihydronaphthalene can be formed in the C 6 H 5 + vinylacetylene and C 6 H 5 + 1,3-butadiene reactions, respectively. Ethynyl-substituted naphthalenes can be produced via the ethynyl addition mechanism beginning with benzene (in dehydrogenated forms) or with styrene. The formation mechanisms of indene in combustion include the reactions of the phenyl radical with C 3 H 4 isomers allene and propyne, reaction of the benzyl radical with acetylene, and unimolecular decomposition of the 1-phenylallyl radical originating from 3-phenylpropene, a product of the C 6 H 5 + propene reaction, or from C 6 H 5 + C 3 H 5 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

L4 Milestone Report for MixEOS 2016 experiments and simulations

Accurate simulations of fluid and plasma flows require accurate thermodynamic properties of the fluids or plasmas. This thermodynamic information is represented by the equations of state of the materials. For pure materials, the equations of state may be represented by analytical models for idealized circumstances, or by tabular means, such as the Sesame tables. However, when a computational cell has a mixture of two or more fluids, the equations of state are not well understood, particularly under the circumstances of high energy densities. This is a particularly difficult issue for Eulerian codes, wherein mixed cells arise simply due to the advection process. LANL Eulerian codes typically assume an “Amagat’s Law” (or Law of Partial Volumes) for the mixture in which the pressures and temperatures of fluids are at an equilibrium that is consistent with the fluids being segregated within the cell. However, for purposes of computing other EOS properties, e.g., bulk modulus, or sound speed, the fluids are considered to be fully “mixed”. LANL has also been investigating implementing instead “Dalton’s Law” in which the total pressure is considered to be the sum of the partial pressures within the cell. For ideal gases, these two laws give the same result. Other possibilities are nonpressure- temperature-equilibrated approaches in which the two fluids are not assumed to “mix” at all, and the EOS properties of the cell are computed from, say, volume-weighted averages of the individual fluid properties. The assumption of the EOS properties within a mixed cell can have a pronounced effect on the behavior of the cell, resulting in, for example, different shock speeds, pressures, temperatures and densities within the cell. There is no apparent consensus as to which approach is best under HED conditions, though we note that under typical atmospheric and near atmospheric conditions the differences may be slight.

36 MATERIALS SCIENCE↗
DOE OSTI2023

GeoCarb Calibration Campaign Field Campaign Report

The GeoCarb Calibration Campaign, referred to as the Total Carbon Column Observing Network (TCCON) calibration campaign within this report for clarity, involved a series of single- and multiple-day Bruker EM27/SUN Fourier transform infrared (FTIR) spectrometer deployments at the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) user facility’s Southern Great Plains (SGP) observatory in Oklahoma. The EM27/SUN instruments directly measure infrared solar radiation in a wavelength range from 4000 to 11000 cm -1 at a spectral resolution of 0.5 cm -1 and varied temporal resolution of approximately 15 seconds. The solar radiation observed by these spectrometers contains information about the concentrations of atmospheric constituents present between the instruments and the top of the atmosphere, as every gas and particle in the atmosphere absorbs solar radiation at different wavelengths depending on their physical and chemical makeup. Through retrieval algorithm processing, the solar radiation data collected by EM27/SUN instruments can be used to infer total column dry-air mole fractions, or total column concentrations, of different trace gases present in the atmosphere. These total column concentrations, denoted as Xgas , represent the concentration, in ppb or ppm, of a trace gas in the column of atmosphere between an instrument and the top of the atmosphere. EM27/SUN instruments are primarily used to infer total column concentrations of carbon dioxide (CO 2 ), carbon monoxide (CO), methane (CH 4 ), and water vapor.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2021

Deep Domain Adaptation based Cloud Type Detection using Active and Passive Satellite Data

Domain adaptation techniques have been developed to handle data from multiple sources or domains. Most existing domain adaptation models assume that source and target domains are homogeneous, i.e., they have the same feature space. Nevertheless, many real world applications often deal with data from heterogeneous domains that come from completely different feature spaces. In our remote sensing application, data in source domain (from an active spaceborne Lidar sensor CALIOP onboard CALIPSO satellite) contain 25 attributes, while data in target domain (from a passive spectroradiometer sensor VIIRS onboard Suomi-NPP satellite) contain 20 different attributes. CALIOP has better representation capability and sensitivity to aerosol types and cloud phase, while VIIRS has wide swaths and better spatial coverage but has inherent weakness in differentiating atmospheric objects on different vertical levels. To address this mismatch of features across the domains/sensors, we propose a novel end-to-end deep domain adaptation with domain mapping and correlation alignment (DAMA) to align the heterogeneous source and target domains in active and passive satellite remote sensing data. It can learn domain invariant representation from source and target domains by transferring knowledge across these domains, and achieve additional performance improvement by incorporating weak label information into the model (DAMA-WL). Our experiments on a collocated CALIOP and VIIRS dataset show that DAMA and DAMA-WL can achieve higher classification accuracy in predicting cloud types.

domain adaptation↗
NASA NTRS1993

The Feasibility of Tropospheric and Total Ozone Determination Using a Fabry-perot Interferometer as a Satellite-based Nadir-viewing Atmospheric Sensor

Monitoring of the global distribution of tropospheric ozone (O3) is desirable for enhanced scientific understanding as well as to potentially lessen the ill-health impacts associated with exposure to elevated concentrations in the lower atmosphere. Such a capability can be achieved using a satellite-based device making high spectral resolution measurements with high signal-to-noise ratios; this would enable observation in the pressure-broadened wings of strong O3 lines while minimizing the impact of undesirable signal contributions associated with, for example, the terrestrial surface, interfering species, and clouds. The Fabry-Perot Interferometer (FPI) provides high spectral resolution and high throughput capabilities that are essential for this measurement task. Through proper selection of channel spectral regions, the FPI optimized for tropospheric O3 measurements can simultaneously observe a stratospheric component and thus the total O3 column abundance. Decreasing stratospheric O3 concentrations may lead to an increase in biologically harmful solar ultraviolet radiation reaching the earth's surface, which is detrimental to health. In this research, a conceptual instrument design to achieve the desired measurement has been formulated. This involves a double-etalon fixed-gap series configuration FPI along with an ultra-narrow bandpass filter to achieve single-order operation with an overall spectral resolution of approximately .068 cm(exp -1). A spectral region of about 1 cm(exp -1) wide centered at 1054.73 cm(exp -1) within the strong 9.6 micron ozone infrared band is sampled with 24 spectral channels. Other design characteristics include operation from a nadir-viewing satellite configuration utilizing a 9 inch (diameter) telescope and achieving horizontal spatial resolution with a 50 km nadir footprint. A retrieval technique has been implemented and is demonstrated for a tropical atmosphere possessing enhanced tropospheric ozone amounts. An error analysis assessing the impact on retrieved O3 amounts of the most significant uncertainties associated with this particular measurement has been performed for several different types of atmospheres. Results show the proposed instrumentation to enable a good measurement of absolute ozone amounts and an even better determination of relative changes, with a range of accuracy to within 7.55 to 20.6 percent for integrated tropospheric amounts (and 1.99 to 4.02 percent for total O3 column abundance) and a corresponding range in precision to within 7.73 to 10.4 percent (and 3.30 to 3.95 percent for total O3 column abundance), for the atmospheric conditions considered.

Larar, Allen Maurice↗
NASA NTRS1981

Precision orbit computations for an operational environment

Taking advantage of the improvements to the Earth's gravitation field and tracking station coordinates, an orbital computational consistency of the order of 5 meters was achieved for total position differences between orbital solutions for the Seasat and GEOS-3. The main source of error in these solutions was in the mathematical models that are required to generate these results, i.e., gravitation, atmospheric drag, etc. Different Earth gravitation fields and tracking coordinates were analyzed and evaluated in obtaining these computational results. Comparisons and evaluations of the Seasat results were obtained in terms of different solution types such as the Doppler only, Laser only, Doppler and Laser, etc. Other investigation using the Seasat data were made in order to determine their effect on the computational results at this particular level of consistency.

Doll, C. E.↗
NASA NTRS2014

The Ancient Martian Climate System

Today Mars is a cold, dry, desert planet. The atmosphere is thin and liquid water is not stable at the surface. But there is evidence that very early in its history, some 3.7-4.1 billion years ago, the climate system supported much warmer conditions including an active hydrological cycle with rainfall and runoff. Given the importance of liquid water to astrobiology and NASA’s Mars Exploration Program, researchers have been trying to understand the ancient martian climate system since the early 1970s when the Mariner 9 spacecraft first detected fluvial features on its oldest terrains. Though the evidence for warm wet conditions is compelling, the problem is not yet solved. The main issue is coping with the faint young sun. During the period when warmer conditions prevailed the sun’s luminosity was ~25% less than it is today. How can we explain the presence of liquid water on the surface of ancient Mars under such conditions? A similar problem exists for Earth, which would have frozen over under a faint sun even though the evidence suggests otherwise. Attempts to solve the “Faint Young Sun Paradox”, as it is commonly known, rely on greenhouse warming from an atmosphere with a different mass and composition than we see today. This is true for both Mars and Earth. However, for Mars there is no solution in sight. Long-lived continuously warm and wet atmospheres are difficult to produce and sustain. And a new and emerging idea - that ancient Mars was fundamentally a cold planet with transient episodes of warm wet conditions brought about by external forcings such as impacts, volcanism, and/or orbital changes – also has issues. In this seminar I will review this fascinating topic and discuss some of the recent ideas on how to solve it, the issues they raise, and what I believe are some promising avenues for future research.

Haberle, Robert M.↗