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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Observing Traveling Ionospheric Disturbances Caused by Tsunamis Using GPS TEC Measurements

Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the American Samoa earthquake of September 29, 2009, and the Chile earthquake of February 27, 2010. Fluctuations in TEC correlated in time, space, and wave properties with these tsunamis were observed in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with wavelengths and periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the tsunamis in certain locations, but not in others. Where variations are observed, the typical amplitude tends to be on the order of 1% of the background TEC value. Variations with amplitudes ~ 0.1 - 0.2 TECU are observable with periods and timing affiliated with the tsunami. These observations are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement in some locations, though there are cases when the model predicts an observable tsunami-driven signature and none is observed. These TEC variations are not always seen when a tsunami is present, but in these two events the regions where a strong ocean tsunami was observed did coincide with clear TEC observations, while a lack of clear TEC observations coincided with smaller tsunami amplitudes. There exists the potential to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for early warning systems.

Galvan, David A.↗
DOE OSTI2017

Photometric Properties of Network and Faculae Derived from HMI Data Compensated for Scattered Light

We report on the photometric properties of faculae and network, as observed in full-disk, scattered-light-corrected images from the Helioseismic Magnetic Imager. We use a Lucy–Richardson deconvolution routine that corrects an image in less than one second. Faculae are distinguished from network through proximity to active regions. This is the first report that full-disk observations, including center-to-limb variations, reproduce the photometric properties of faculae and network observed previously only in sub-arcsecond-resolution; small field-of-view studies, i.e. that network, as defined by distance from active regions, exhibit higher photometric contrasts. Specifically, for magnetic flux values larger than approximately 300 G, the network is brighter than faculae and the contrast differences increase toward the limb, where the network contrast is about twice the facular one. For lower magnetic flux values, network appear darker than faculae. Contrary to reports from previous full-disk observations, we also found that network exhibits a higher center-to-limb variation. Our results are in agreement with reports from simulations that indicate magnetic flux alone is a poor proxy of the photometric properties of magnetic features. We estimate that the contribution of faculae and network to Total Solar Irradiance variability of the current Cycle 24 is overestimated by at least 11%, due to the photometric properties of network and faculae not being recognized as different. This estimate is specific to the method employed in this study to reconstruct irradiance variations, so caution should be paid when extending it to other techniques.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

KIC 10975348: A Double-mode or Triple-mode High-amplitude δ Scuti Star?

In this paper, we analyze the light variations of KIC 10975348 using photometric data delivered from the Kepler mission. This star is exceptionally faint (K {sub p} = 18.6 mag) compared to most well-studied δ Scuti stars. The Fourier analysis of the short-cadence data (i.e., Q14, Q15, and Q16, spanning 220 days) reveals that the variations are dominated by the strongest mode with a frequency of F0 = 10.231899 day{sup −1}, which is compatible with that obtained from RATS–Kepler. The other two independent modes with F1 (=13.4988 day{sup −1}) and F2 (=19.0002 day{sup −1}) are newly detected and have amplitudes two orders of magnitude smaller than F0. We note that, for the first time, this star is identified to be a high-amplitude δ Sct (HADS) star with an amplitude of about 0.7 mag, and the lower ratio of F0/F1 = 0.758 suggests that it might be a metal-rich variable star. The frequency F2 may be a third overtone mode, suggesting that this target might be a new radial triple-mode HADS star. We perform an O − C analysis using 1018 newly determined times of maximum light and derive an ephemeris formula of T {sub max} = 2456170.241912(0)+0.097734(1) × E. The O − C diagram shows that the pulsation period of KIC 10975348 seems to show no obvious change, which is in contrast to that of the majority of HADS stars. The possible cause of that may be due to the current short time span of the observations. To verify its possible period variations, regular observation from space with a longer time span in the future is needed.

47 OTHER INSTRUMENTATION↗
NASA NTRS1974

Further evidence for an interstellar source of nighttime He I 584 A radiation

The intensity of He I, 584 A radiation in the night sky was measured from a sounding rocket at altitudes between 160 and 217 km. The results obtained confirm previous measurements of this radiation. The observed intensity and spatial variations can be entirely accounted for by resonance scattering of solar 584 A radiation from interstellar helium. The best fit to the observations in this case is obtained with an interstellar helium model in which the bulk velocity of the gas is 5 km/sec, the temperature is 10,000 K, and the helium number density is 0.032 per cu cm. Even if a geocoronal scattering component is present, the data can be used to set a lower limit to the temperature of the local interstellar medium of 1,500 (plus or minus 500) K, assuming a normal interstellar helium abundance.

Paresce, F.↗
NASA NTRS1998

Microgravity Crystallization of Alpha-Crustacyanin Onboard the Unmanned Carrier, EURECA

alpha-Crustacyanin, the lobster carapace astaxanthin-protein, was crystallized using the European Space Agency's (ESA) automated Protein Crystallization Facility (PCF) which flew onboard the unmanned EUropean REtrievable CArrier (EURECA). A free interface linear, liquid - liquid diffusion, method was used. Crystals grew larger and thicker in the microgravity case compared to the biggest crystals grown on earth. Video observation on EURECA revealed variations in crystal sizes through-out the reactor neatly correlated with depletion of this coloured protein from the solution. The video observations most importantly revealed no visible movement of crystals over the initial 7 weeks of the experiment, although an obvious temperature induced jump occurred at that time in a mission spanning 11 months. An important observation from this mission, over the first 7 weeks, of completely stationary crystal growth contrasts with crystal motions viewed on manned microgravity missions, even using linear liquid - liquid geometries, and much shorter flights (eg. 12 to 16 days).

Boggon, T. J.↗
NASA NTRS1981

Spatial and temporal variations of EUV coronal bright points

This paper reports results of an analysis of Skylab observations of coronal bright points made in EUV spectral lines formed in the chromosphere, chromospheric-coronal transition region and corona. The most important result is that the observed bright points exhibited large variations in EUV emission over time scales as short as 5.5 min, the temporal resolution of the data. In most cases strong enhancements in the coronal line were accompanied by strong enhancements in the chromospheric and transition region lines. The intensity variations appear to take place within substructures of the bright points, which most likely consist of miniature loops evolving on time scales of a few minutes. Coronal cooling times derived from the data are consistent with an intermittent, impulsive coronal heating mechanism for bright points.

Habbal, S. R.↗
NASA NTRS1975

Ultraviolet variations of epsilon UMa

OAO-2 spectrometer observations of the Ap variable epsilon UMa indicate that the photometric variations are due to variable ultraviolet absorption from apparently overabundant metals. These data also point out the presence of a secondary maximum of the Fe-group elements, notably Cr, that has not been reported.

Molnar, M. R.↗
NASA NTRS1987

Observations of annual and El Nino thermal and flow variations at 0 deg, 110 deg W and 0 deg, 95 deg W during 1980-1985

The paper describes the low-frequency (i.e., time scales longer than a month) upper ocean (above 250 m) current and temperature moored measurements conducted from March 1980 to September 1985 at 0, 110 deg W and from July 1981 to November 1983 (i.e., including the period of the 1982-1983 El Nino) at 0, 95 deg W. Estimates of the annual cycle were removed from the observations to determine the current and temperature fluctuations due to the 1982-1983 El Nino. The circulation of the upper ocean was found to be dramatically altered during the El Nino: the normally westward flowing surface current in autumn months reversed direction, and the equatorial undercurrent, normally considered to be a permanent feature, disappeared. Associated with the El Nino was a massive redistribution of heat throughout the mixed layer and the thermocline.

Halpern, David↗
NASA NTRS2022

Uncertainty Estimation for SMAP Level-1 Brightness Temperature Assimilation at Different Timescales

Soil Moisture Active Passive (SMAP) mission brightness temperature (T(b) ) observations are assimilated into NASA’s Catchment Land Surface Model using an Ensemble Kalman filter to update simulations of surface and root-zone soil moisture. Different time series components of the T(b) observations are assimilated including anomalies, inter-annual variations, and high frequency variations. To optimize the weights that the data assimilation (DA) puts on the observations, the ratio between the uncertainties of modeled and observed T(b) is approximated using modeled and observed soil moisture uncertainties estimated using triple collocation analysis. In a benchmark experiment, T(b) observations are assimilated using a spatially constant 4 Kelvin (K) observation uncertainty, as in the operational SMAP Level-4 algorithm. All DA experiments exhibit notable skill improvements in most regions. Improvements are largest for the inter-annual variations in the simulations of both surface and root-zone soil moisture (mean improvements in terms of Pearson correlation (-) are 0.08 and 0.06, respectively). Anomaly simulations improve similarly (0.07), and improvements in the high-frequency variations are only observed for surface soil moisture simulations (0.06). No notable difference in skill - neither improvement nor deterioration - is observed between the experiments that use optimized observation uncertainty parameters and the 4 K benchmark experiment. This may be explained by the presence of large observation operator errors, which are analytically shown to have the potential to render post-update uncertainty insensitive to inaccuracies in estimates of the Kalman gain. These results have important implications for the design of soil moisture DA systems, in particular for parameterizing model and observation uncertainties.

Hydrology↗
DOE OSTI2022

Correspondence: Bill of Materials Variation and Module Degradation in Utility-Scale PV Systems

We report photovoltaic (PV) modules of the same make and model are often assembled with different bills of materials (BOMs). In this correspondence, we revisit two case studies of utility-scale silicon PV systems in which these differing BOMs were associated with faster-than-expected degradation. In one of the sites, we found that different metallization paste had been used for grid lines in some cells leading to loss of contact to the cell and severe series resistance degradation. We provide details on the observation of this mechanism at two additional sites not described in the original article. In a second case study, we found that two different types of cell had been used, and that they could be distinguished by their back contact. Cells with uniform back contacts suffered from light and elevated temperature induced degradation (LeTID), while those with local back contacts did not. We also briefly describe BOM variations observed at other sites to illustrate the extent of the challenge. Our results from both sites underscore that variations in BOM, even among modules of the same make and model can lead to reliability challenges.

14 SOLAR ENERGY↗
NASA NTRS1978

Effect of concentration dependence of the diffusion coefficient on homogenization kinetics in multiphase binary alloy systems

Diffusion calculations were performed to establish the conditions under which concentration dependence of the diffusion coefficient was important in single, two, and three phase binary alloy systems. Finite-difference solutions were obtained for each type of system using diffusion coefficient variations typical of those observed in real alloy systems. Solutions were also obtained using average diffusion coefficients determined by taking a logarithmic average of each diffusion coefficient variation considered. The constant diffusion coefficient solutions were used as reference in assessing diffusion coefficient variation effects. Calculations were performed for planar, cylindrical, and spherical geometries in order to compare the effect of diffusion coefficient variations with the effect of interface geometries. In most of the cases considered, the diffusion coefficient of the major-alloy phase was the key parameter that controlled the kinetics of interdiffusion.

Tenney, D. R.↗
NASA NTRS2005

Discovery of a Be/X-Ray Binary Consistent with the Location of GRO J2058+42

GRO J2058+42 is a 195 s transient X-ray pulsar discovered in 1995 with BATSE. In 1996, RXTE located GRO J2058+42 to a 90% confidence error circle with a 4 radius. On 2004 February 20, the region including the error circle was observed with Chandra ACIS-I. No X-ray sources were detected within the error circle; however, two faint sources were detected in the ACIS-I field of view. We obtained optical observations of the brightest object, CXOU J205847.5+414637, which had about 64 X-ray counts and was just 013 outside the error circle. The optical spectrum contains a strong Ha line and corresponds to an inhued object in the Two Micron All Sky Survey catalog, indicating a Be/X-ray binary system. Pulsations were not detected in the Chandra observations, but similar flux variations and distance estimates suggest that CXOU J205847.5+414637 and GRO J2058+42 are the same object. We present results from the Chandra observation, optical observations, new and previously unreported RXTE observations, and a reanalysis of a ROSAT observation.

Wilson, Colleen↗
NASA NTRS1992

Compositional variations in Apollo 17 soils and their relationship to the geology of the Taurus-Littrow site

New compositional data for major and trace elements in Apollo 17 solids are combined with data from the literature in order to constrain a mass-balance model that accounts for the compositions of most solids as mixtures of a small number of lithologic components observed at the site. Variation in the proportions of six chemical components accounts for most of the compositional variation in the solids. Each of the components is represented by lithological components observed in the regolith. Three of the chemical components are of mare origin: high-Ti mare basalt, LTV basalt, and pyroclastic orange glass. Three are of highland origin: noritic impact-melt breccia, anorthositic norite breccia, and high-Mg/Fe troctolites and norites. Results from a six-component mass-balance model indicate that VLT basalt composes only about 8 percent of the total basalt component, while orange glass composes up to 26 percent of some solids. The troctolite/norite component is only important in soils from the North Massif.

Korotev, Randy L.↗
DOE OSTI2020

Imaging the Phase Transformation in Single Particles of Lithium Titanate Anode for Lithium-ion Batteries

Lithium uptake and release in lithium titanate (LTO) anode materials during a discharge and charge cycle is one of the fundamental processes of a Lithium-ion battery (LIB), still not fully understood at the microscopic level.During discharge cycle, LTO undergoes a phase transformation between Li 4 Ti 5 O 12 and Li 7 Ti 5 O 12 states within a cubic crystal lattice. To reveal the details of the microscopic mechanism,it is necessary to track the sequence of phase transformation sat different discharge/charge states under operating conditions.Here we use in-situ Bragg Coherent Diffraction Imaging (BCDI) and in-situ X-ray diffraction (XRD) experiments to examine the lithium insertion-induced materials phase transformation within a single LTO particle anda bulk battery analogue,respectively. BCDI analysis from (111) Bragg peak, shows the two-phase transformation manifesting as a distinct image phase modulation within a single LTO nanoparticle occurring in the middle of the discharge region then subsiding towards the end of the discharge cycle. We observe the biggest phase variation at the two-phase stage,indicating the formation of phase domains of 200 nm in size during the discharge process. Additionally, we also observe a lattice contraction of >0.2% in a single LTO nanoparticle at the (400) Bragg peak measurement, larger than that in the corresponding bulk material. Our observation of this phase transformation at a single particle level has implications for the understanding of the microscopic/mesoscale picture of the phase transformation in anode and cathode LIBs materials.

25 ENERGY STORAGE↗
NASA NTRS1994

Vital phase of space science

Space science began with the indirect phase where the activity in space was inferred from such terrestrial phenomena as geomagnetic storms, ionospheric variations, and fluctuations in the cosmic ray intensity. The direct phase was initiated with spaceflight placing instruments directly in space and permitting the direct observation of UV and X rays, as well as precision observations of solar luminosity variations. The evidence from these many direct studies, together with the historical record of terrestrial conditions, shows that the variations of the luminosity of the Sun affect the terrestrial atmosphere at all levels, with devastating changes in climate tracking the major changes in the activity level and luminosity of the Sun. The quantification and understanding of this vital connection should be the first priority of space science and geophysics, from oceans and atmosphere through the ionosphere, magnetosphere, and all the way to the convective zone of the Sun. It becomes the vital phase of space science, focused on the basic science of the changing habitability of Earth.

Parker, E. N.↗
NASA NTRS1982

UV emission from he M1 supergiant TV Gem

Low and high dispersion ultraviolet spectra were obtained of the M1 supergiant TV Gem with IUE. Previous IUE observations of this late type supergiant revealed unexpected UV continuum emission, perhaps arising from an early B companion. Low resolution spectra obtained approximately one year apart suggest that the strong Si III in combination perhaps with O I at wavelengths approximately 1300 A varies considerably with time. Large variation in the column density is required to explain these changes. Sporadic mass expulsion with mass loss rates dM/dt approximately 0.00001 solar mass yr minus 1st power from the M supergiant could lead to a dense circumstellar wind near the hot early companion, and thus could account for these observed variations in equivalent width. The high resolution spectrum in the 2000 to 3200 A wavelength range is characterized by narrow absorption lines primarily due to Fe II, Mn II and Mg II (h and k), which are skewed in profile with an extended red wing. This profile structure is tentatively attributed to interstellar absorption and an intervening differentially moving cloud in the direction of Gem OB1, of which TV Gem is a known association member.

Michalitsianos, A. G.↗
NASA NTRS1985

Dynamics of two-year cosmic ray variations inferred from the data of spacecraft and stratospheric measurements and from the neutron monitor data in 1959-1981

The two year cosmic ray variations are studied using the spacecraft measurements of 1967 to 1976, the sonde measurements at high latitudes in the stratosphere (Murmansk, Mirny), and the neutron monitor data of 1959 to 1981. The two year variations are most pronounced from 1967 to 1975. An anticorrelation is observed between the two year variations in cosmic rays and in geomagnetic activity.

Charakhchyan, T. N.↗
NASA NTRS1979

Interplanetary discontinuities - Temporal variations and the radial gradient from 1 to 8.5 AU

A dependence of the rate of occurrence and properties of interplanetary discontinuities on radial distance were investigated using Pioneer 10 and 11 vector helium magnetometer observations. Spatial and temporal variations were separated and discontinuities identified, noting that their rate of occurrence undergoes large variations well outside the deviations expected from statistical fluctuations. Temporal changes in the occurrence rate averaged over Bartels solar rotations were well correlated at Pioneer 10 and 11, separated by a distance of 2 AU, and time variations consisted of slow modulation of the occurrence rate due to changing solar conditions. The correlation over widely separated distances is interpreted by a model in which the discontinuities originate inside 1 AU and are convected outward by the solar wind. Evidence of spatial dependence was provided by a decrease in the rates of occurrence at both spacecraft with increasing radial distance, and it was shown that the Pioneer 11 rate, nearer the sun, exceeded the Pioneer 10 rate at greater distances.

Tsurutani, B. T.↗