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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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NASA NTRS1984

The path-length distribution for galactic cosmic-ray propagation - An energy-dependent depletion of short path lengths

It is shown that at low energies, the depletion of short path lengths in the interstellar cosmic-ray path-length distribution is a function of energy, decreasing in magnitude with increasing energy. The analysis leading to this conclusion is based on the comparison of compiled data for the B/C and sub-Fe/Fe ratios at 0.08-50 GeV per nucleon, with the results of detailed galactic propagation and solar modulation calculations, which include experimental values for the important nuclear cross sections. This energy dependence of the depletion resolves some of the conflicts between previous reports on the question of short path lengths and may be explained by models including a matter distribution around discrete sources or, possibly, by models invoking waves generated by particle-magnetic field interactions in the Galaxy.

Garcia-Munoz, M.↗
NASA NTRS1992

Energetic magnetospheric protons in the plasma depletion layer

The characteristics of energetic protons (between a few keV/e and about 100 keV/e) leaked from the magnetosphere were determined using observations for 13 plasma depletion layer events recorded by AMPTE/CCE. Results indicate that, when the IMF has orientation such that the angle between the IMF and the X(GSE) direction is 60 deg (the condition under which the energetic ion regions upstream and downstream from the quasi-parallel bow shock are located on the flanks of the dawnside bow shock), the magnetospheric leakage provides only about 10 percent of the energetic proton distribution in the energy range from a few keV/e to 100 keV/e in the region upstream from the earth's bow shock. The other 90 percent come from the bow shock accelerated source.

Fuselier, Stephen A.↗
NASA NTRS1994

Possible identification of a cluster of galaxies at redshift z = 3.4

We report the possible detection of a cluster of 16 radio-quiet galaxies at z = 3.4, identified in the field around the optically thick absorption system toward Q0000-263 at z(sub abs) = 3.390. Two of them, a Lyman alpha emitter at z = 3.428 and the galaxy responsible for the absorption system, have redshifts spectroscopically confirmed. The other 14 galaxies identified using a multicolor imaging technique designed to detect sources in the redshift interval 3 approximately less than z approximately less than 3.5 which are characterized by a Lyman discontinuity in an otherwise flat spectrum, have broad-band spectral energy distributions identical to the two galaxies with known redshift. They are spatially distributed in two apparent clumps, around the damped absorber and the Lyman alpha galaxy, respectively. A clustering analysis excludes with 98.8% confidence that this association is a realization of a Poissonian distribution and confirms that the observed clumps are real. The implications are that the 16 galaxies are members of a cluster at z approximately equals 3.4, by far the most distant ever detected. An estimate of the mass bounded in stars of this cluster is 3 x 10(exp 12) solar mass (q(sub 0) = 0 and H(sub 0) = 50 km/s/Mpc throughout this Letter), while the total mass (baryonic + dark) is 6 x 10(exp 14) solar mass. We also estimate that at z = 3.4 the correlation length is 2.2 Mpc, which, compared to the present value of 11 Mpc, suggests that the clustering evolution is still close to the linear regime.

Giavalisco, Mauro↗
NASA NTRS2001

Gamma-Ray Bursts: An Update

Gamma-ray bursts are now known to originate from cosmological distances and represent the largest known explosions in the Universe. The observed characteristics of bursts in the gamma-ray region, primarily from data obtained with the BATSE experiment on the Compton Observatory, will be described. These include the temporal and spectral characteristic of bursts, and their intensity and sky distribution. A summary of recent discoveries and observations in other wavelength regions will also be presented, along with their implications for models of the burst emission mechanism. Various models for the energy source of gamma-ray bursts will be described.

Fishman, Gerald J.↗
NASA NTRS2009

The Orbiting Wide-Angle Light Collectors (OWL) Mission for Charged-Particle Astronomy

The space-based OWL mission is designed to perform high-statistics measurements of ultra-high-energy cosmic rays (UHECR) using the Earth's atmosphere as a vast particle calorimeter, furthering the field of charged-particle astronomy. OWL has been developed in formal NASA instrument and mission studies and is comprised of two large telescopes separated by approx.600 km in 1000 km, near-equatorial orbits to stereoscopically image the near-UV air fluorescence emitted by UHECR-induced particle cascades. The High Resolution Fly's Eye (HiRes) Collaboration, and subsequently the Pierre Auger Observatory, recently reported confirmation of the expected Greisen-Zatsepin-Kuzmin (GZK) suppression of the UHECR flux above a few times 10(exp 19) eV. This observation is consistent with the majority of UHECR originating in astrophysical objects and reduces the need to invoke exotic physical processes. Particles observed above the GZK threshold energy must have come from sources within about 100 Mpc from the Earth. The small particle deflection angles expected at UHECR energies, with standard assumptions of extragalactic magnetic fields, are on the order of 1 degree. Thus by observing particles above the GZK threshold with sufficient exposure, there is the potential of identifying and characterizing individual UHECR sources. Auger has reported significant anisotropy in the arrival directions of UHECR at energies above about 6 10(exp 19) eV observed in the South, and a correlation to AGN in the 12th VCV catalog, suggesting that the sources of UHECR are traced by the distribution of luminous matter in the Universe. However, with similar statistics and the same event selection criteria, HiRes observations in the North are consistent with isotropy. Extended observations by Auger-South, by Telescope Array in the North, and possibly by the proposed Auger-North, will further these investigations. However, much greater exposures will be required to fully identify individual sources and measure their cosmic ray spectra. A five-year OWL mission would deliver approximately 10(exp 6)sq km/sr/yr of exposure with full aperture reached at approx. 10(exp 19) eV. The baseline 3 m optical aperture OWL telescopes with 45 degree full field-of-view are easily accomodated on a single conventional launch vehicle. On orbit, the simultaneous viewing of the same volume of atmosphere allows for precise stereo event reconstruction, which is nearly independent of the inclination of the particle track and tolerant of atmospheric conditions. The availability of monocular operation provides increased reliability or can be employed to increase the instantaneous aperture. In stereo mode, OWL is also capable of fully reconstructing horizontal or upward-moving showers and so has unmatched sensitivity to neutrino-induced events. The details of the OWL mission will he presented and its science capabilities will be discussed.

Mitchell, John↗
NASA NTRS2013

The WIRED Survey. IV. New Dust Disks from the McCook & Sion White Dwarf Catalog

We have compiled photometric data from the Wide-field Infrared Survey Explorer All Sky Survey and other archival sources for the more than 2200 objects in the original McCook & Sion Catalog of Spectroscopically Identified White Dwarfs. We applied color-selection criteria to identify 28 targets whose infrared spectral energy distributions depart from the expectation for the white dwarf photosphere alone. Seven of these are previously known white dwarfs with circumstellar dust disks, five are known central stars of planetary nebulae, and six were excluded for being known binaries or having possible contamination of their infrared photometry. We fit white dwarf models to the spectral energy distributions of the remaining ten targets, and find seven new candidates with infrared excess suggesting the presence of a circumstellar dust disk. We compare the model dust disk properties for these new candidates with a comprehensive compilation of previously published parameters for known white dwarfs with dust disks. It is possible that the current census of white dwarfs with dust disks that produce an excess detectable at K-band and shorter wavelengths is close to complete for the entire sample of known WDs to the detection limits of existing near-IR all-sky surveys. The white dwarf dust disk candidates now being found using longer wavelength infrared data are drawn from a previously underrepresented region of parameter space, in which the dust disks are overall cooler, narrower in radial extent, and/or contain fewer emitting grains.

Dwarf↗
NASA NTRS2024

Oblique Instability of Quasi-Parallel Whistler Waves in the Presence of Cold and Warm Electron Populations

Whistler waves propagating nearly parallel to the ambient magnetic field experience a nonlinear instability due to transverse currents when the background plasma has a population of sufficiently low energy electrons. Intriguingly, this nonlinear process may generate oblique electrostatic waves, including whistlers near the resonance cone with properties resembling oblique chorus waves in the Earth’s magnetosphere. Focusing on the generation of oblique whistlers, earlier analysis of the instability is extended here to the case where low-energy background plasma consists of both a “cold” population with energy of a few eV and a “warm” electron component with energy of the order of 100 eV. This is motivated by spacecraft observations in the Earth’s magnetosphere where oblique chorus waves were shown to interact resonantly with the warm electrons. The main new results are: 1) the instability producing oblique electrostatic waves is sensitive to the shape of the electron distribution at low energies. In the whistler range of frequencies, two distinct peaks in the growth rate are typically present for the model considered: a peak associated with the warm electron population at relatively low wavenumbers and a peak associated with the cold electron population at relatively high wavenumbers; 2) overall, the instability producing oblique whistler waves near the resonance cone persists (with a reduced growth rate) even in the cases where the temperature of the cold population is relatively high, including cases where cold population is absent and only the warm population is included; 3) particle-in-cell simulations show that the instability leads to heating of the background plasma and formation of characteristic plateau and beam features in the parallel electron distribution function in the range of energies resonant with the instability. The plateau/beam features have been previously detected in spacecraft observations of oblique chorus waves. However, they have been attributed to external sources and have been proposed to be the mechanism generating oblique chorus. In the present scenario, the causality link is reversed and the instability generating oblique whistler waves is shown to be a possible mechanism for formation of the plateau and beam features.

Vadim Roytershteyn↗
NASA NTRS1994

The continuum spectral characteristics of gamma-ray bursts observed by BATSE

Distributions of the continuum spectral characteristics of 260 bursts in the first Burst And Transient Source Experiement (BATSE) catalog are presented. The data are derived from flux calculated from BATSE Large Area Detector (LAD) four-channel discriminator data. The data are converted from counts to protons using a direct spectral inversion technique to remove the effects of atmospheric scattering and the energy dependence of the detector angular response. Although there are intriguing clusters of bursts in the spectral hardness ratio distributions, no evidence for the presence of distinct burst classes based in spectral hardness ratios alone is found. All subsets of bursts selected for their spectral characteristics in this analysis exhibit spatial distributions consistent with isotropy. The spectral diversity of the burst population appears to be caused largely by the highly variable nature of the burst production mechanisms themselves.

Pendleton, Geoffrey N.↗
NASA NTRS1974

Observation of a cosmic gamma-ray burst on Apollo 16. II - X-ray time profile and source location

A burst of X-rays was detected during the trans-earth coast phase of Apollo 16 on Apr. 27, 1972 at 10:68 UT, simultaneously with the observation of a transient event by a gamma-ray spectrometer aboard the same spacecraft. The two instruments provide a broad energy range of more than three orders of magnitude for describing the spectral distribution of this event. The conclusion that the incident flux was X-rays and not charged particles is based on the fact that the particle flux detectors in the Apollo gamma ray spectrometer and on the Vela 6A, which also observed the event, did not respond. The time variation of the total count rate in the X-ray range before and after corrections for detector geometry and the analysis for source direction is presented.

Trombka, J. I.↗
NASA NTRS1999

The Hyperluminous Infrared Quasar 3C 318 and Its Implications for Interpreting Sub-MM Detections of High-Redshift Radio Galaxies

We present near-infrared spectroscopy and imaging of the compact steep-spectrum radio source 3C 318 which shows it to be a quasar at redshift z = 1.574 (the z = 0.752 value previously reported is incorrect). 3C 318 is an IRAS, ISO and SCUBA source so its new redshift makes it the most intrinsically luminous far-infrared (FIR) source in the 3C catalogue (there is no evidence of strong gravitational lensing effects). Its bolometric luminosity greatly exceeds the 10(exp 13) solar luminosity level above which an object is said to be hyperluminous. Its spectral energy distribution (SED) requires that the quasar heats the dust responsible for the FIR flux, as is believed to be the case in other hyperluminous galaxies, and contributes (at the greater than 10% level) to the heating of the CIA dust responsible for the sub-mm emission. We cannot determine whether a starburst makes an important contribution to the heating of the coolest dust, so evidence for a high star-formation rate is circumstantial being based on the high dust, and hence gas, C-1 mass required by its sub-mm detection. We show that the current sub-mm and FIR data available for the highest-redshift radio galaxies are consistent with SEDs similar to that of 3C 318. This indicates that at least some of this population may be detected in the sub-mm because of dust heated by the quasar nucleus, and that interpreting sub-mm detection as evidence for very high (approx. less than 1000 solar mass/yr) star-formation rates may not always be valid. We show that the 3C318 quasar is slightly reddened (A(sub v) approx. = 0.5), the most likely cause of which is SMC-type dust in the host galaxy. If very distant radio galaxies are reddened in a similar way then we show that only slightly greater amounts of dust could obscure the quasars in these sources. We speculate that the low fraction of quasars amongst the very high redshift (z approx. greater than 3) objects in low-frequency radio-selected samples is the result of such obscuration. The highest-z objects might be preferentially obscured because like 3C318 they are inevitably observed very shortly after the jet-triggering event, or because their host galaxies are richer in dust and gas at earlier cosmic epochs, or because of some combination of these two effects.

Willott, Chris J.↗
NASA NTRS1979

Evidence for the deficiency of short cosmic ray pathlengths and a physically realistic explanation - The no-near-sources model

Recent observations of the charge and energy spectra of cosmic-ray nuclei are used to construct secondary-to-primary charge ratios at the two ends of the charge spectrum. These ratios are found to be inconsistent with the ad hoc leaky-box model of cosmic-ray propagation which leads to an exponential pathlength distribution. Models for which the pathlength distribution function is deficient in short pathlengths provide a more consistent picture. Several of these models, both ad hoc and physical, are investigated. The physical model considered is one for which detailed galactic propagation parameters and boundary conditions are used and for which there exist no near sources of cosmic rays over a time interval corresponding to a few times the cosmic-ray age.

Lezniak, J. A.↗
NASA NTRS1994

The continuum spectral characteristics of gamma ray bursts observed by BATSE

Distributions of the continuum spectral characteristics of 260 bursts in the first Burst and Transient Source Experiment (BATSE) catalog are presented. The data are derived from flux ratios calculated from the BATSE Large Area Detector (LAD) four channel discriminator data. The data are converted from counts to photons using a direct spectral inversion technique to remove the effects of atmospheric scattering and the energy dependence of the detector angular response. Although there are intriguing clusterings of bursts in the spectral hardness ratio distributions, no evidence for the presence of distinct burst classes based on spectral hardness ratios alone is found. All subsets of bursts selected for their spectral characteristics in this analysis exhibit spatial distributions consistent with isotropy. The spectral diversity of the burst population appears to be caused largely by the highly variable nature of the burst production mechanisms themselves.

Pendleton, Geoffrey N.↗
NASA NTRS1972

The plasma physics of the Jovian decameter radiation.

We have assumed that the decameter radiation from Jupiter is produced near the local electron gyrofrequency and is amplified as it propagates out of the Jovian magnetosphere. We have derived the growth rate for radiation that propagates almost perpendicular to the direction of the magnetic field. When the electrons are described by a loss-cone distribution function, the growth rate is large enough to lead to a large amplification factor over a source of 100-4000 km, depending on the choice of parameters. Because we expect low-energy electrons to be trapped in the Jovian dipole field regardless of the position of the satellite Io, we maintain that this model provides a plausible mechanism for the decametric radiation not associated with Io.

Goldstein, M. L.↗
NASA NTRS1975

X-ray astronomy

Various experiments in X-ray astronomy are described. The occurrence of lunar occultations of the Crab Nebula were utilized to determine the spatial distribution of X-ray emitting regions in the nebula. Study of the Cygnus Loop included a search for a central X-ray point source for the area and measurement of the energy spectrum of the flux from the supernova remnant. The X-ray morphology of the Perseus cluster of galaxies was studied. X-ray spectra of different points in the cluster were also obtained. In addition, the construction of a high resolution gas fluorescence proportional counter for application to X-ray astronomy is discussed.

Novick, R.↗
NASA NTRS1983

Decimetric gyrosynchrotron emission during a solar flare

A decimetric, microwave, and hard X-ray burst was observed during a solar flare in which the radio spectrum below peak flux fits an f+2 power law over more than a decade in frequency. The spectrum is interpreted to mean that the radio emission originated in a homogeneous, thermal, gyrosynchrotron source. This is the first time that gyrosynchrotron radiation has been identified at such low decimetric frequencies (900-998) MHz). The radio emission was cotemporal with the largest single hard X-ray spike burst ever reported. The spectrum of the hard X-ray burst can be well represented by a thermal bremsstrahlung function over the energy range from 30 to 463 keV at the time of maximum flux. The temporal coincidence and thermal form of both the X-ray and radio spectra suggest a common source electron distribution. The unusual low-frequency extent of the single-temperature thermal radio spectrum and its association with the hard X-ray burst imply that the source had an area approx. 10(18) sq cm a temperature approx 5x10(8) K, an electron density approx. 7.10(9) cu cm and a magnetic field of approx. 120 G. H(alpha) and 400-800 MHz evidence suggest that a loop structure of length 10,000 km existed in the flare active region which could have been the common, thermal source of the observed impulsive emissions.

Batchelor, D. A.↗
NASA NTRS1985

The planetary distribution of heat sources and sinks during FGGE

Heating distributions from analysis of the National Meteorological Center and European Center for Medium Range Weather Forecasts data sets; methods used and problems involved in the inference of diabatic heating; the relationship between differential heating and energy transport; and recommendations on the inference of heat soruces and heat sinks for the planetary show are discussed.

Johnson, D. R.↗
NASA NTRS2005

Thermal and Kinetic Properties of Motions in a Prominence Activation and Nearby Loop

We perform a quantitative analysis of the thermal properties of a prominence activation and motions in a nearby loop. In order to make measurements of the quickly moving features seen in prominences in the UV we use the SOHO/SUMER spectrograph to take a time series of exposures from a single pointing position, providing a measurement of spectral line properties as a function of time and position along the slit. The lines observed cover a broad range of temperatures from 80,000 - 1.6 million K. These measurements are combined with TRACE movies in transition region and coronal temperature bands to obtain more complete information concerning prominence structure and motions. The resulting observations allow us to analyze the thermal and kinetic energy of the moving sources as functions of time. The loop and prominence are most apparent in lines formed at temperatures below 250,000 K. We find that in most cases the temperature distribution of plasma in a moving feature changes relatively little over time periods of about 20 minutes.

Kucera, Therese↗
NASA NTRS2015

3D Photocatalytic Air Processor for Dramatic Reduction of Life Support Mass and Complexity

To dramatically reduce the cost and risk of CO2 management systems in future extended missions, we have conducted preliminary studies on the materials and device development for advanced "artificial photosynthesis" reaction systems termed the High Tortuosity PhotoElectroChemical (HTPEC) system. Our Phase I studies have demonstrated that HTPEC operates in much the same way a tree would function, namely directly contacting the cabin air with a photocatalyst in the presence of light and water (as humidity) to immediately conduct the process of CO2 reduction to O2 and useful, "tunable" carbon products. This eliminates many of the inefficiencies associated with current ISS CO2 management systems. We have laid the solid foundation for Phase II work to employ novel and efficient reactor geometries, lighting approaches, 3D manufacturing methods and in-house grown novel catalytic materials.The primary objective of the proposed work is to demonstrate the scientific and engineering foundation for light-activated, compact devices capable of converting CO2 to O2 and mission-relevant carbon compounds. The proposed HTPEC CO2 management system will demonstrate a novel pathway with high efficiency and reliability in a compact, lightweight reactor architecture. The proposed HTPEC air processing concept can be developed in multiple architectures, such as centralized processing as well as "artificial leaves" distributed throughout the cabin that utilize pre-existing cabin ventilation (wind). Additionally, HTPEC can be deployed with spectrally tunable collection channels for selectable product generation. HTPEC employs light as its only energy source to remove and convert waste CO2 using a non-toxic composite catalyst.We have demonstrated in the Phase I studies the production, tunability and robustness of the novel composite catalysts following the preliminary work in the Chen laboratory. Additionally, we have designed, fabricated and tested all components of HTPEC device with active materials, including flow modeling to optimize flow mixing and pressure drop as well as the production of ethylene and other larger hydrocarbons. To best determine how this technology could be implemented, we also performed system integration optimization and trade studies. This includes parameters such as mass, volume, power in relation to selected mission configurations, CO2 delivery methods and light source/delivery approaches.

Artificial Photosynthesis↗