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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 235 records · Page 13
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NASA NTRS2007

A Spitzer Infrared Radius for the Transiting Extrasolar Planet HD 209458 b

We have measured the infrared transit of the extrasolar planet HD 209458 b using the Spitzer Space Telescope. We observed two primary eclipse events (one partial and one complete transit) using the 24 micrometer array of the Multiband Imaging Photometer for Spitzer (MIPS). We analyzed a total of 2392 individual images (10-second integrations) of the planetary system, recorded before, during, and after transit. We perform optimal photometry on the images and use the local zodiacal light as a short-term flux reference. At this long wavelength, the transit curve has a simple box-like shape, allowing robust solutions for the stellar and planetary radii independent of stellar limb darkening, which is negligible at 24 micrometers. We derive a stellar radius of R(sub *) = 1.06 plus or minus 0.07 solar radius, a planetary radius of R(sub p) = 1.26 plus or minus 0.08 R(sub J), and a stellar mass of 1.17 solar mass. Within the errors, our results agree with the measurements at visible wavelengths. The 24 micrometer radius of the planet therefore does not differ significantly compared to the visible result. We point out the potential for deriving extrasolar transiting planet radii to high accuracy using transit photometry at slightly shorter IR wavelengths where greater photometric precision is possible.

Richardson, L. Jeremy↗
NASA NTRS2008

On the Relationship between Solar Wind Speed, Earthward-Directed Coronal Mass Ejections, Geomagnetic Activity, and the Sunspot Cycle Using 12-Month Moving Averages

For 1996 .2006 (cycle 23), 12-month moving averages of the aa geomagnetic index strongly correlate (r = 0.92) with 12-month moving averages of solar wind speed, and 12-month moving averages of the number of coronal mass ejections (CMEs) (halo and partial halo events) strongly correlate (r = 0.87) with 12-month moving averages of sunspot number. In particular, the minimum (15.8, September/October 1997) and maximum (38.0, August 2003) values of the aa geomagnetic index occur simultaneously with the minimum (376 km/s) and maximum (547 km/s) solar wind speeds, both being strongly correlated with the following recurrent component (due to high-speed streams). The large peak of aa geomagnetic activity in cycle 23, the largest on record, spans the interval late 2002 to mid 2004 and is associated with a decreased number of halo and partial halo CMEs, whereas the smaller secondary peak of early 2005 seems to be associated with a slight rebound in the number of halo and partial halo CMEs. Based on the observed aaM during the declining portion of cycle 23, RM for cycle 24 is predicted to be larger than average, being about 168+/-60 (the 90% prediction interval), whereas based on the expected aam for cycle 24 (greater than or equal to 14.6), RM for cycle 24 should measure greater than or equal to 118+/-30, yielding an overlap of about 128+/-20.

Wilson, Robert M.↗
NASA NTRS2008

Suzaku Observations of Thermal and Non-Thermal X-Ray Emission from the Middle-Aged Supernova Remnant G156.2+5.7

We present results from X-ray analysis of a Galactic middle-aged supernova remnant (SNR) G156.2+5.7 which is bright and largely extended in X-ray wavelengths, showing a clear circular shape (radius approx.50'). Using the Suzaku satellite, we observed this SNR in three pointings; partially covering the northwestern (NW) rim, the eastern (E) rim, and the central portion of this SNR. In the NW rim and the central portion, we confirm that the X-ray spectra consist of soft and hard-tail emission, while in the E rim we find no significant hard-tail emission. The soft emission is well fitted by either a one-component or two-component non-equilibrium ionization (NEI) model. In the NW and E rims, a one-component (the swept-up interstellar medium) NEI model well represents the soft emission. On the other hand, in the central portion, a two-component (the interstellar medium and the metal-rich ejecta) NEI model fits the soft emission better than the one-component NEI model from a statistical point of view. The relative abundances in the ejecta component suggest that G156.2+5.7 is a remnant from a core-collapse SN explosion whose progenitor mass is less than 15 Solar Mass. The origin of the hard-tail emission detected in the NW rim and the central portion of the SNR is highly likely non-thermal synchrotron emission from relativistic electrons. In the NW rim, the relativistic electrons seems to be accelerated by a forward shock with a slow velocity of APPROX.500 km/sec.

Katsuda, Satoru↗
NASA NTRS2013

Energy Release from Impacting Prominence Material Following the 2011 June 7 Eruption

Solar filaments exhibit a range of eruptive-like dynamic activity, ranging from the full or partial eruption of the filament mass and surrounding magnetic structure as a coronal mass ejection to a fully confined or failed eruption. On 2011 June 7, a dramatic partial eruption of a filament was observed by multiple instruments on board the Solar Dynamics Observatory (SDO) and Solar-Terrestrial Relations Observatory. One of the interesting aspects of this event is the response of the solar atmosphere as non-escaping material falls inward under the influence of gravity. The impact sites show clear evidence of brightening in the observed extreme ultraviolet wavelengths due to energy release. Two plausible physical mechanisms for explaining the brightening are considered: heating of the plasma due to the kinetic energy of impacting material compressing the plasma, or reconnection between the magnetic field of low-lying loops and the field carried by the impacting material. By analyzing the emission of the brightenings in several SDO/Atmospheric Imaging Assembly wavelengths, and comparing the kinetic energy of the impacting material (7.6 × 10(exp 26) - 5.8 × 10(exp 27) erg) to the radiative energy (approx. 1.9 × 10(exp 25) - 2.5 × 10(exp 26) erg), we find the dominant mechanism of energy release involved in the observed brightening is plasma compression.

Sun: corona↗
NASA NTRS2001

Microwave Polarized Signatures Generated within Cloud Systems: SSM/I Observations Interpreted with Radiative Transfer Simulations

Special Sensor Microwave /Imager (SSM/I) observations in cloud systems are studied over the tropics. Over optically thick cloud systems, presence of polarized signatures at 37 and 85 GHz is evidenced and analyzed with the help of cloud top temperature and optical thickness extracted from visible and IR satellite observations. Scattering signatures at 85 GHz (TbV(85) less than or = 250 K) are associated with polarization differences greater than or = 6 K, approx. 50%, of the time over ocean and approx. 40% over land. In addition. over thick clouds the polarization difference at 37 GHz is rarely negligible. The polarization differences at 37 and 85 GHz do not stem from the surface but are generated in regions of relatively homogeneous clouds having high liquid water content. To interpret the observations, a radiative transfer model that includes the scattering by non-spherical particles is developed. based on the T-matrix approach and using the doubling and adding method. In addition to handling randomly and perfectly oriented particles, this model can also simulate the effect of partial orientation of the hydrometeors. Microwave brightness temperatures are simulated at SSM/I frequencies and are compared with the observations. Polarization differences of approx. 2 K can be simulated at 37 GHz over a rain layer, even using spherical drops. The polarization difference is larger for oriented non-spherical particles. The 85 GHz simulations are very sensitive to the ice phase of the cloud. Simulations with spherical particles or with randomly oriented non-spherical ice particles cannot replicate the observed polarization differences. However, with partially oriented non-spherical particles, the observed polarized signatures at 85 GHz are explained, and the sensitivity of the scattering characteristics to the particle size, asphericity, and orientation is analyzed. Implications on rain and ice retrievals are discussed.

Prigent, Catherine↗
NASA NTRS1994

Changes of snow cover, temperature, and radiative heat balance over the Northern Hemisphere

Contemporary large-scale changes in satellite-derived snow cover were examined over the Northern Hemisphere extratropical land (NEL) areas. These areas encompass 55% of the land in the Northern Hemisphere. Snow cover (S) transient regions, the 'centers of action' relative to interannual variations of snow cover, were identified for the years 1972-1992. During these years a global retreat in snow cover extent (SE) occurred in the second half of the hydrologic year (April-September). Mean annual SE has decreased by 10% (2.3 x 10(exp 6) sq km). Negative trends account for one-third to one-half of the interannual continental variance of SE. The historical influence of S on the planetary albedo and outgoing longwave radiation (OLR) is investigated. The mean annual response of the S feedback on the radiative balance (RB) is negative and suggests a largescale heat redistribution. During autumn and early winter (up to January), however, the feedback of S on the planetary RB may be positive. Only by February does the cooling effect of S (due to albedo increase) dominate the planetary warming due to reduced OLR over the S. Despite a wintertime maximum in SE, the feedback in spring has the greatest magnitude. The global retreat of spring SE should lead to a positive feedback on temperature. Based on observed records of S, changes in RB are calculated that parallel an observed increase of spring temperature during the past 20 years. The results provide a partial explanation of the significant increase in spring surface air temperature observed over the land areas of the Northern Hemisphere during the past century. The mean SE in years with an El Nino and La Nina were also evaluated. El Nino events are generally accompanied by increased SE over the NEL during the first half of the hydrological year. In the second half of the hydrologic year (spring and summer), the El Nino events are accompanied by a global retreat of SE.

Groisman, Pavel YA.↗
NASA NTRS2014

Ocean Surface Carbon Dioxide Fugacity Observed from Space

We have developed and validated a statistical model to estimate the fugacity (or partial pressure) of carbon dioxide (CO2) at sea surface (pCO2sea) from space-based observations of sea surface temperature (SST), chlorophyll, and salinity. More than a quarter million in situ measurements coincident with satellite data were compiled to train and validate the model. We have produced and made accessible 9 years (2002-2010) of the pCO2sea at 0.5 degree resolutions daily over the global ocean. The results help to identify uncertainties in current JPL Carbon Monitoring System (CMS) model-based and bottom-up estimates over the ocean. The utility of the data to reveal multi-year and regional variability of the fugacity in relation to prevalent oceanic parameters is demonstrated.

Liu, W. Timothy↗
NASA NTRS2014

Ocean surface carbon dioxide fugacity observed from space

We have developed and validated a statistical model to estimate the fugacity (or partial pressure) of carbon dioxide (CO2) at sea surface (pCO2sea) from space-based observations of sea surface temperature (SST), chlorophyll, and salinity. More than a quarter million in situ measurements coincident with satellite data were compiled to train and validate the model. We have produced and made accessible 9 years (2002–2010) of the pCO2sea at 0.5 degree resolutions daily over the global ocean. The results help to identify uncertainties in current JPL Carbon Monitoring System (CMS) model-based and bottom-up estimates over the ocean. The utility of the data to reveal multi-year and regional variability of the fugacity in relation to prevalent oceanic parameters is demonstrated.

Xie, Xiaosu↗
NASA NTRS1982

A chemical study of individual green glasses and brown glasses from 15426 - Implications for their petrogenesis

Systematic chemical analyses of individual Apollo 15 green glasses were performed in order to: (1) study chemical variations among them; (2) understand their petrogenesis and source region; and (3) study their possible relationships with mare basalts in general. Brown glasses were also analyzed in order to study their chemical variations and their petrogenetic relationships to green glasses and mare basalts. The chemical composition of green and brown glasses is shown and variation diagrams of Sc, Cr2O3, FeO, and Co abundances in green glasses are presented. Igneous fractionation, two component magma mixing, and partial melting of heterogeneous source materials are alternate scenarios to explain strong observed correlations. The composition of green glasses indicates that they were derived by partial melting of the fractionated cumulate source materials formed from a magma ocean which had experienced certain degrees of olivine and plagioclase fractional crystallization.

Ma, M.-S.↗
NASA NTRS1991

Percepts of rigid motion within and across apertures

Humans consistently err in their percepts of rotational motion viewed through an aperture. Such errors provide insight into the constraints observers use to interpret retinal images. In the first of two experiments, Ss consistently perceived the fixed center of rotation for an unmarked line viewed through an aperture as located on the line, regardless of its actual location. Accuracy greatly improved with visible line endings. This finding was extended to explain why a square appears nonrigid when it rotates behind a partial occluder. This illusion may result from observers misperceiving the center of rotation of the unmarked square sides. In this situation, Ss seemed unable to apply an object rigidity constraint across apertures. These findings support a conceptualization of the visual system in which consistent local information must be clearly present before prior knowledge can be used to interpret retinal stimulation.

Shiffrar, Maggie↗
NASA NTRS1976

An alternative interpretation of Jupiter's 'plasmapause'

It has recently been suggested that Io is an important source of ions for the plasma detected by Pioneer 10 in the inner magnetosphere of Jupiter. Assuming this to be true, we show that near the orbit of Io the central collector of the Pioneer-10 plasma instrument could detect only inwardly diffusing ions created at a radial distance greater than that of the spacecraft. The rapid decrease in ion density observed beyond Io's orbit is attributed, at least partially, to this effect and thus may not represent a real plasma boundary such as a 'plasmapause'. Instead, the drop in observed ion density could correspond to a decrease in the density of Io-associated neutral particles orbiting Jupiter.

Neugebauer, M.↗
NASA NTRS1983

Cardiovascular examinations and observations of deconditioning during the Space Shuttle orbital flight test program

During the first four flights of the Space Shuttle, cardiovascular data were obtained on each crewmember as part of the operational medicine requirements for crew health and safety. From monitoring blood pressure and electrocardiographic data, it was possible to estimate the degree of deconditioning imposed by exposure to the microgravity environment. For this purpose, a quantitative cardiovascular index of deconditioning (CID) was derived to aid the clinician in his assessment. Isotonic saline was then investigated as a countermeasure against orthostatic intolerance and found to be effective in partially reversing the hemodynamic consequences. It was observed that the space flight environment of reentry might potentially be arrhythmogenic in at least one individual.

Bungo, M. W.↗
NASA NTRS2011

Ion-Neutral Coupling in Solar Prominences

Interactions between ions and neutrals in a partially ionized plasma are important throughout heliophysics, including near the solar surface in prominences. Understanding how ion-neutral coupling affects formation, support, structure, and dynamics of prominences will advance our physical understanding of magnetized systems involving a transition from a weakly ionized dense gas to a fully ionized tenuous plasma. We address the fundamental physics of prominence support, which is normally described in terms of a magnetic force on the prominence plasma that balances the solar gravitational force, and the implications for observations. Because the prominence plasma is only partially ionized, it is necessary to consider the support of the both the ionized and neutral components. Support of the neutrals is accomplished through a frictional interaction between the neutral and ionized components of the plasma, and its efficacy depends strongly on the degree of ionization of the plasma. More specifically, the frictional force is proportional to the relative flow of neutral and ion species, and for a sufficiently weakly ionized plasma, this flow must be relatively large to produce a frictional force that balances gravity. A large relative flow, of course, implies significant draining of neutral particles from the prominence. We evaluate the importance of this draining effect for a hydrogen-helium plasma, and consider the observational evidence for cross-field diffusion of neutral prominence material.

Gilbert, Holly↗
NASA NTRS1980

Impulsive phase of solar flares

The present understanding of the impulsive phase of a solar flare, characterized by short-duration bursts of impulsive hard X-ray, EUV, optical and radio emission indicating the release of energetic electrons is reviewed. Observations of the spectral distribution of impulsive hard X-ray bursts and of Type III and radio continuum bursts are presented and interpreted in terms of energetic electron distributions, and impulsive EUV, XUV, soft X-ray and optical observations, which provide a lower limit to total energy release during the impulsive phase, are discussed. The role of energetic electrons in exciting the hard X-ray, EUV and microwave emissions is considered, and thin-target, thick-target, partial-precipitation and thermal models of impulsive phase electron acceleration are evaluated in light of the observations. It is noted that available data do not allow discrimination between a thermal or a nonthermal electron distribution, on which depends the proportion of flare energy supplied by the energetic electrons, and that data favors models which permit at least partial electron precipitation. Future observational and theoretical work is indicated.

Kane, S. R.↗
NASA NTRS1991

The SiH vibrational stretch as an indicator of the chemical state of interstellar grains

The infrared spectra of amorphous silicate grains and films formed in a variety of laboratory experiments have been measured. It is found that the frequency of the SiH fundamental stretch is extremely sensitive to the chemical environment of the grain in which the silicon is bound and varies from 2270/cm in oxidized grains to 2110/cm in a reducing environment. It is proposed that features previously observed in W33A could be due to -SiH groups in amorphous silica, partially reduced silica, silicon nitride or slightly oxidized silicon carbide. It is predicted that observations at 2270/cm will reveal a feature due to -SiH groups in highly oxidized interstelar and circumstellar grains. Such a feature might also appear in the spectra of comets.

Moore, Marla H.↗
NASA NTRS1999

High-Altitude Aircraft and Balloon-Borne Observations of OH, HO2, ClO, BrO, NO2, ClONO2, ClOOCl, H2O, and O3 in Earth's Stratosphere

Using observations from balloon-borne instruments and aircraft-borne instruments the investigation arrived at the following developments.: (1) Determination of the dominant catalytic cycles that destroy ozone in the lower stratosphere; (2) The partial derivatives of the rate limiting steps are observables in the lower stratosphere; (3) Recognition that the "Low NOx" condition is the regime that holds the greatest potential for misjudgement of Ozone loss rates; (4) Mapping of the Bromine radical contribution to the ozone destruction rate in the lower stratosphere; (5) Observation of OH, HO2 and ClO in the plume of the Concorde SST in the stratosphere; (6) Determination of the diurnal behavior of OH in the lower stratosphere; (7) Observed OH and H02 in the Troposphere and the interrelationship between Ozone and OH, HO2, CO and NO; (8) Analysis of the Catalytic Production of Ozone and Reactions that Couple OH and H02 in the Troposphere; (9) The continuing development of the understanding of the Tropopause temperatures, water vapor mixing ratios, and vertical advection and the mixing in of mid-latitude air; (10) Performed Multiple Tracer Analyses as a diagnostic of water vapor intrusion into the "Middle World" (i.e., the lowermost stratsophere); (11) Flight testing of a new instrument for the In Situ detection of ClON02 from the ER-2; (12) Laser induced fluorescence detection of NO2. There is included an in depth discussion of each of these developments and observations.

Anderson, James G.↗
NASA NTRS1974

The effects of shock wave compaction on the transition temperatures of A15 structure superconductors

Several superconductors with the A15 structure exhibit a positive pressure coefficient, indicating that their transition temperatures increase with applied pressure. Powders of the composition Nb3Al, Nb3Ge, Nb3(Al0.75Ge0.25), and V3Si were compacted by explosive shock waves. The superconducting properties of these materials were measured before and after compaction and it was found that regardless of the sign of the pressure coefficient, the transition temperature is always lowered. The decrease in transition temperature is associated with a decrease in the particle diameter. The shock wave passage through a 3Nb:1Ge powder mixture leads to the formation of at least one compound (probably Nb5Ge3). However, the formation of the A15 compound Nb3Ge is not observed. Elemental niobium powder can be compacted by converging shock waves close to the expected value of the bulk density. Under special circumstances a partial remelting in the center of the sample is observed.

Otto, G. H.↗