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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Impulsive acceleration and scatter-free transport of about 1 MeV per nucleon ions in (He-3)-rich solar particle events

Impulsive solar energetic particle (SEP) events are studied to: (1) describe a distinct class of SEP ion events observed in interplanetary space, and (2) test models of focused transport through detailed comparisons of numerical model prediction with the data. An attempt will also be made to describe the transport and scattering properties of the interplanetary medium during the times these events are observed and to derive source injection profiles in these events. ISEE 3 and Helios 1 magnetic field and plasma data are used to locate the approximate coronal connection points of the spacecraft to organize the particle anisotropy data and to constrain some free parameters in the modeling of flare events.

Mason, G. M.↗
NASA NTRS1981

Interplanetary propagation of less than 1-MeV protons in nonimpulsive energetic particle events

An investigation is conducted regarding the existence of measurable transverse diffusive transport for 0.3- to 0.5 MeV protons. The study focuses on 1-hour averaged proton anisotropy data measured by detectors on board the earth-orbiting IMP 7 and 8 spacecraft. The data is restricted to nonimpulsive energetic particle events which are not explicitly associated with solar flares. It is established to within the limits of the measurements using 1-hour averages, that in nonimpulsive 0.3- to 0.5-MeV proton events as measured in the Newtonian inertial frame of the solar system, the anisotropy is predominantly transverse to the magnetic field and most hourly averages of the transverse component are essentially due to the particles' E x B drift.

Zwickl, R. D.↗
NASA NTRS1989

Plasma and energetic electron flux variations in the Mercury 1 C event - Evidence for a magnetospheric boundary layer

Charge-particle and magnetic-field data obtained during the first encounter (on March 29, 1974) of Mariner 10 with the planet Mercury are reexamined, and a new interpretation of the Mariner 10 energetic electron, plasma electron, and magnetic field data near the outbound magnetopause at Mercury is presented. It is shown that Mariner 10 sampled the hot substorm energized magnetospheric plasma sheet for the first 36 sec of the C event and, for the next 48 sec, alternatively sampled hot (plasma sheet) and cold (boundary-layer magnetosheathlike) plasma regions. It is argued that the counting rate of the ID1 event (i.e., a particle event triggering detector D1 but not the D2, D3, or D7 detectors) throughout the C event most probably represents a pulse pileup response to about 35-175 keV electrons, rather than the nominal above-175 keV electrons presumed in the earlier interpretations.

Christon, S. P.↗
NASA NTRS1994

Features of steady magnetospheric convection

The large-scale patterns of ionospheric convection and particle precipitation are described during two intervals of steady magnetospheric convection (SMC) on November 24, 1981. The unique data set used in the analysis includes recordings from the worldwide network of magnetometers and all-sky cameras, global auroral images from the Dynamics Explorer (DE) 1 spacecraft, and particle precipitation data from low-altitude National Oceanic and Atmospheric Administration (NOAA) 6 and NOAA 7 spacecraft. The data show that intense magnetospheric convection continued during more than 10 hours under the steady southward interplanetary magnetic field without any distinct substorm signatures. All data sets available confirmed the stable character of the large-scale magnetospheric configuration during this period. In particular, the magnetic flux threading the polar cap was stable (within 10%) during 3.5 hours of continued DE 1 observations. The dayside cusp was located at an unusually low latitude (70 deg CGL). The nightside auroral pattern consisted of two distinct regions. The diffuse aurora in the equatorward half of the expanded (10 deg wide) auroral oval was well-separated from the bright, active auroral forms found in the vicinity of the poleward boundary of the oval. The twin-vortex convection pattern had no signature of the Harang discontinuity; its nightside 'convection throat' was spatially coincident with the poleward active auroras. This region of the auroral oval was identified as the primary site of the short-lived transient activations during the SMC intervals. The energetic particle observations show that the auroral precipitation up to its high-latitude limit is on closed field lines and that particle acceleration up to greater than 30-keV energy starts close to this limit. The isotropic boundaries of the greater than 30-keV protons and electrons were found close to each other, separating regions of discrete and diffuse precipitation. This suggests that these precipitation types originate on the very taillike and very dipolelike field lines, respectively.

Yahnin, A.↗
NASA NTRS1973

Tracking and data system support for the Pioneer project. Volume 1: Pioneer 10-prelaunch planning through second trajectory correction, 4 December 1969 - 1 April 1972

The tracking and data system support of the launch, near-earth, and deep space phases of the Pioneer 10 mission, which sent a Pioneer spacecraft into a flyby of Jupiter that would eventually allow the spacecraft to escape the solar system is discussed. The support through the spacecraft's second trajectory correction is reported. During this period, scientific instruments aboard the spacecraft registered information relative to interplanetary particles and fields, and radiometric data generated by the network continued to improve knowledge of the celestial mechanics of the solar system. In addition to network support activity detail, network performance and special support activities are covered.

Siegmeth, A. J.↗
NASA NTRS1995

Fuzzy inference enhanced information recovery from digital PIV using cross-correlation combined with particle tracking

Particle Image Velocimetry provides a means of measuring the instantaneous 2-component velocity field across a planar region of a seeded flowfield. In this work only two camera, single exposure images are considered where both cameras have the same view of the illumination plane. Two competing techniques which yield unambiguous velocity vector direction information have been widely used for reducing the single exposure, multiple image data: cross-correlation and particle tracking. Correlation techniques yield averaged velocity estimates over subregions of the flow, whereas particle tracking techniques give individual particle velocity estimates. The correlation technique requires identification of the correlation peak on the correlation plane corresponding to the average displacement of particles across the subregion. Noise on the images and particle dropout contribute to spurious peaks on the correlation plane, leading to misidentification of the true correlation peak. The subsequent velocity vector maps contain spurious vectors where the displacement peaks have been improperly identified. Typically these spurious vectors are replaced by a weighted average of the neighboring vectors, thereby decreasing the independence of the measurements. In this work fuzzy logic techniques are used to determine the true correlation displacement peak even when it is not the maximum peak on the correlation plane, hence maximizing the information recovery from the correlation operation, maintaining the number of independent measurements and minimizing the number of spurious velocity vectors. Correlation peaks are correctly identified in both high and low seed density cases. The correlation velocity vector map can then be used as a guide for the particle tracking operation. Again fuzzy logic techniques are used, this time to identify the correct particle image pairings between exposures to determine particle displacements, and thus velocity. The advantage of this technique is the improved spatial resolution which is available from the particle tracking operation. Particle tracking alone may not be possible in the high seed density images typically required for achieving good results from the correlation technique. This two staged approach offers a velocimetric technique capable of measuring particle velocities with high spatial resolution over a broad range of seeding densities.

Wernet, Mark P.↗
NASA NTRS1991

LDEF contaminants analysis data

Modification of surface texture for Ram Facing FEP Teflon on the Long Duration Exposure Facility (LDEF) satellite is documented. Photos of changes in surface texture if thermal blanket material with position on tray C-08 are presented. Infrared spectra and photographic documentation of molecular film deposits on LDEF surfaces by location is reported. Results of a survey of the functional groups and elemental composition of the brown film found widely distributed on the surface of LDEF is shown. A partial photographic catalog of LDEF particulate contaminants is included. A set of photos of particles collected or photographed in place on the surface of LDEF is shown. Particle counts and surface obscuration data for the LDEF satellite are reported. The surface data in tables and charts is presented for the LDEF satellite by location.

Crutcher, E. Russ↗
NASA NTRS2023

Updated Observations of Clouds By MODIS for Global Model Assessment

This paper describes a new global dataset of cloud properties observed by MODIS relying on the current (collection 6.1) processing of MODIS data and produced to facilitate comparison with results from the MODIS observational proxy used in climate models. The dataset merges observations from the two MODIS instruments into a single netCDF file. Statistics (mean, standard deviation, and number of observations) are accumulated over daily and monthly timescales on an equal-angle grid for viewing and illumination geometry, cloud detection, cloud-top pressure, and cloud properties (optical thickness, effective particle size, and water path) partitioned by thermodynamic phase and an assessment as to whether the underlying observations come from fully or partly cloudy pixels. Similarly partitioned joint histograms are available for (1) optical thickness and cloud-top pressure, (2) optical thickness and particle size, and (3) cloud water path and particle size. Differences with standard data products, caveats for data use, and guidelines for comparison to the MODIS simulator are described.

Robert Pincus↗
NASA NTRS1987

Performance of laminar-flow leading-edge test articles in cloud encounters

An extensive data bank of concurrent measurements of laminar flow (LF), particle concentration, and aircraft charging state was gathered for the first time. From this data bank, 13 flights in the simulated airline service (SAS) portion were analyzed to date. A total of 6.86 hours of data at one-second resolution were analyzed. An extensive statistical analysis, for both leading-edge test articles, shows that there is a significant effect of cloud and haze particles on the extent of laminar flow obtained. Approximately 93 percent of data points simulating LFC flight were obtained in clear air conditions; approximately 7 percent were obtained in cloud and haze. These percentages are consistent with earlier USAF and NASA estimates and results. The Hall laminar flow loss criteria was verified qualitatively. Larger particles and higher particle concentrations have a more marked effect on LF than do small particles. A particle spectrometer of a charging patch are both acceptable as diagnostic indicators of the presence of particles detrimental to laminar flow.

Davis, Richard E.↗
NASA NTRS1984

The dust around R Coronae Borealis type stars

Measurements taken by the International Ultraviolet Explorer spacecraft of the stars RY Sgr and R CrB have been analyzed using Mie theory. The extinction data, which show a 2400-2500 A peak, are consistent with a distribution of 5-60 nm glassy or amorphous carbon particles obscuring the stellar flux. The data are also fairly consistent with a cloud ejection model. Since the extinction data lack the commonly observed peak at 2170 A, it is proposed that this difference is due to the conditions present when the dust condenses. Interstellar carbon grains appear to originate in normal carbon stars which are carbon and hydrogen rich. In contrast, the grains around R CrB type stars seem to condense from a carbon-rich and hydrogen-poor vapor.

Hecht, J. H.↗
NASA NTRS1984

Plasma and energetic particle structure upstream of a quasi-parallel interplanetary shock

ISEE 1, 2 and 3 data from 1978 on interplanetary magnetic fields, shock waves and particle energetics are examined to characterize a quasi-parallel shock. The intense shock studied exhibited a 640 km/sec velocity. The data covered 1-147 keV protons and electrons and ions with energies exceeding 30 keV in regions both upstream and downstream of the shock, and also the magnitudes of ion-acoustic and MHD waves. The energetic particles and MHD waves began being detected 5 hr before the shock. Intense halo electron fluxes appeared ahead of the shock. A closed magnetic field structure was produced with a front end 700 earth radii from the shock. The energetic protons were cut off from the interior of the magnetic bubble, which contained a markedly increased density of 2-6 keV protons as well as the shock itself.

Kennel, C. F.↗
NASA NTRS2001

Microphysical Interpretation of Cirrus Measurements With Lidar

Cirrus measurements obtained with a ground-based polarization Raman lidar at 67.9 N in January 1997 reveal a strong correlation between the particle optical properties, specifically depolarization ratio delta and extinct ion-to-backscatter ratio S, for ambient cloud temperatures above approximately -45 C (delta less than approximately 40%), and an anti-correlation for colder temperatures (delta greater than approximately 40%). Over the length of the measurements (4-7.5 hours) the particle properties vary systematically: Initially, delta approximately equal to 60% and S approximately equal to 10sr are observed. Then, with decreasing delta, S first increases to approximately 27 sr(delta approximately equal to 40%) before decreasing to values around 10 sr again (delta approximately equal to 20%). The particle optical properties distinctly depend on the ambient temperature. For the microphysical analysis of the lidar observations. ray-tracing computations of particle scattering properties and a size-distribution resolving cirrus model with explicit microphysics have been used. The theoretical studies show that the optical properties and their temporal evolution can be interpreted in terms of size, shape, and growth of the cirrus particles: Near the cloud top in the early stage of the cirrus development, light scattering by small hexagonal columns with aspect ratios close to one is dominant. Over time the cloud base height extends to lower altitudes with warmer temperatures, the ice particles grow and get morphologically diverse (the scattering contributions of hexagonal columns and plates are roughly the same for large S and depolarization values of approximately 40%). In the lower ranges of the cirrus clouds, light scattering is predominantly by plate-like or complex ice particles. Mid-latitude cirrus data measured with the same instrument at 53.4 N between 1994 and 1996 follow closely the correlation between delta and S found in the warmer regions of the Arctic cirrus clouds (delta less than approximately 40%). Cirrus clouds with higher depolarization ratios are rarely observed, even for very cold ambient temperatures. Atmospheric parameters other than temperature, e.g., the availability of water vapor, are also important for the growth and the morphology of cirrus particles.

Reichardt, Jens↗
NASA NTRS1984

Ionic charge state measurements during He(+)-rich solar particle events

Ionic charge state measurements of carbon, oxygen, and iron in He(+)-rich energetic particle events are presented. The data have been obtained with the Max-Planck-Institut/University of Maryland sensor system on the ISEE 3 spacecraft. The ionic charge states cannot be explained in terms of a model in which the coronal temperature determines a charge equilibrium which is subsequently frozen-in nor in terms of charge exchange during transition through coronal matter after acceleration. It is concluded that the acceleration and probably also the injection process is biased against particles with high mass-to-charge ratios. The plasma injected into the acceleration process must consist of material of cold (not greater than 8.5 x 10 to the 4th K) as well as hot (2.5 x 10 to the 6th K) origin. The cold material must be more abundant than the hot material.

Hovestadt, D.↗
NASA NTRS1988

Observational test of shock drift and Fermi acceleration on a seed particle population upstream of earth's bow shock

The efficiency of proposed shock acceleration mechanisms as they operate at the bow shock in the presence of a seed energetic particle population was examined using data from simultaneous observations of energetic solar-origin protons, carried out by the IMP 7 and 8 spacecraft in the vicinity of the quasi-parallel (dawn) and quasi-perpendicular (dusk) regions of the earth's bow shock, respectively. The results of observations (which include acceleration effects in the intensities of the energetic protons with energies as high as 4 MeV observed at the vicinity of the dusk bow shock, but no evidence for any particle acceleration at the energy equal to or above 50 keV at the dawn side of the bow shock) indicate that the acceleration of a seed particle population occurs only at the quasi-perpendicular bow shock through shock drift acceleration and that the major source of observed upstream ion populations is the leakage of magnetospheric ions of energies not less than 50 keV, rather than in situ acceleration.

Anagnostopoulos, G. C.↗
NASA NTRS1994

Statistical characteristics of bursty bulk flow events

Using a common methodology to analyze data from the Active Magnetospheric Particle Tracer Explorer/Ion Release Module (AMPTE/IRM) and International Sun-Earth Explorer 2 (ISEE 2) satellites we report on the statistical properties of bursty bulk flow events (BBFs) in the inner plasma sheet (IPS). A positive correlation between BBFs and the AE index suggests that BBFs are predominantly geomagnetically active time phenomena. Earthward BBFs are more frequent close to midnight and away from Earth, up to a distance of approximately 19 R(sub E). Tailward BBFs are very infrequent in the IRM data set and somewhat less infrequent in the ISEE 2 data set in the region of the satellites' spatial overlap, possibly due to the more active conditions prevailing during the ISEE 2 mission in that region. However, in both data sets the ratio of tailward to earthward BBFs increases with distance from Earth; more than 20% of all BBFs are anti-sunward tailward of X = -19 R(sub E) in the ISEE 2 data set. BBFs are responsible for 60-100% of the measured earthward transport of mass, energy and magnetic flux past the satellite in the regions of maximum occurrence rate, even though they last approximately 10-15% of the IPS observation time there. Thus BBFs represent the primary transport mechanism at those regions. The one-to-one correspondence between BBFs and substorm phase, as well as the relative contribution of BBFs to the total transport observed during substorms are questions that await further investigation based on multi instrument studies of individual events.

Angelopoulos, V.↗
NASA NTRS1993

The wavelength dependence of Martian atmospheric dust radiative properties

One of the key radiative agents in the atmosphere of Mars is the suspended dust particles. A new analysis of two data sets of the Martian atmosphere is being carried out in order to better evaluate the radiative properties of the atmospheric dust particles. The properties of interest are the size distribution, optical constants, and other radiative properties, such as the single-scattering albedo and phase function. Of prime importance is the wavelength dependence of these radiative properties throughout the visible and near-infrared wavelengths. Understanding the wavelength dependence of absorption and scattering characteristics will provide a good definition of the influence that the atmospheric dust has on heating of the atmosphere.

Pollack, J. B.↗
NASA NTRS2016

More Than the Sum of the Parts: Satellite Aerosol Remote Sensing, and Its Relationship to Sub-Orbital Measurements and Models

Space-borne instruments are providing increasing amounts of data relating to global aerosol spectral optical depth, horizontal and vertical distribution, and very loose, but spatially and temporally extensive, constraints on particle micro-physical properties. The data sets, and many of the underlying techniques, are evolving rapidly. They represent a vast amount of information, potentially useful to the AAAR community. However, there are also issues, some quite subtle, that scientific users must take into consideration. This tutorial will provide one view of the answers to the following four questions: 1) What satellite-derived aerosol products are available? 2) What are their strengths and limitations? 3) How are they being used now? 4) How might they be used in conjunction with each other, with sub-orbital measurements, and with models to address cutting-edge aerosol questions?

satellite remote sensing↗