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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Determining the solar wind speed above active regions using remote radio-wave observations

A new technique has made it possible to measure the velocity of portions of the solar wind during its flow outward from the sun. This analysis utilizes spacecraft (ISEE-3) observations of radio emission generated in regions of the solar wind associated with solar active regions. By tracking the source of these radio waves over periods of days, it is possible to measure the motion of the emission regions. Evidence of solar wind acceleration during this outward flow, consistent with theoretical models, has also been obtained.

Fainberg, J.↗
NASA NTRS1985

Measurements of distributed polarized radio sources from spinning spacecraft - Effect of a tilted axial antenna ISEE-3 application and results

An analysis is presented of the system response of a satellite receiver-antenna system to locate a radio source when the satellite is tilted on its axis. The satellite is spin stabilized but experiences a tilt due to either a mechanical misalignment or a shift in the electrical axis caused by parasitic currents in other spacecraft structures. The shorter the antenna, the more significant the effects. Numerical techniques are developed for obtaining the Stokes parameters and the angular parameters of a uniform conical source sensed by a linear antenna in order to derive the average power response of a synthesized dipole to a point on a distributed polarized source. Relative gains are calculated along the antenna at different angles to the source. The techniques are applied to sample ISEE-3 satellite data for Type III solar radio bursts which were sensed by an axial and an equatorial antenna. The two antennas permit localization of the source and quantification of the polarization and angular extent of the source. The resulting high precision in calculations of all three source parameters commends use of the model in analyses of data from the planned ULYSSES mission.

Fainberg, J.↗
NASA NTRS1988

Current sheet crossings in the distant magnetotail

A computer search of crossings of the field reversal region in the middle of the distant magnetotail has been done with ISEE-3 data. It is found that the instantaneous direction of the magnetic field at the crossings Bz is northward on average at a distance of 220 earth radii, with moderate values of the plasma flow. This result suggests that the magnetic field lines are closed; since the flow is tailward, the Dungey (1961) model with a steady state reconnection line across the magnetotail earthward of the spacecraft is invalidated. The present result gives strong support to a model in which tailward boundary layer flow provides the viscous interaction proposed by Axford and Hines (1961). At higher values of the plasma velocity, negative values of Bz are found.

Heikkila, W. J.↗
NASA NTRS1987

Bidirectional electron anisotropies in the distant tail - ISEE 3 observations of polar rain

A detailed observational treatment of bidirectional electrons (50 approx. 500 eV) in the distant magnetotail (or greater than or equal to 100 R sub E) is presented. It is found that electrons in this energy range commonly exhibit strong, field aligned anisotropies in the tail lobes. Because of large tail motions, the ISEE-3 data provide extensive sampling of both the north and south lobes in rapid succession, demonstrating directly the strong asymetries that exist between the north and south lobes at any one time. The bidirectional fluxes are found to occur predominantly in the lobe directy connected to the sunward IMF in the open magnetosphere model (north lobe for away sectors and south lobe for toward sectors). Electron anisotropy and magnetic field data are presented which show the transition from unidirectional (sheath) electron populations to bidirectional (lobe) populations. Taken together, the present evidence suggests that the bidirectional electrons that we observe in the distant tail are closely related to the Polar rain electrons observed previously at lower altitudes. Furthermore, these data provide strong evidence that the distant tail is comprised largely of open magnetic field lines in contra distinction to some recently advanced models.

Baker, D. N.↗
NASA NTRS1980

A cosmic-ray age based on the abundance of Be-10

The paper discusses a measurement of the isotopic composition of galactic cosmic-ray beryllium made with high resolution aboard the ISEE 3 spacecraft. The isotope fractions of Be-7, Be-9, and Be-10 were determined; the abundance of the radioactive isotope Be-10 is used to deduce the cosmic-ray confinement time of 8,400,000/yr and an interstellar gas density of 0.33 atoms/cu cm in the confinement volume. Errors in the propagation model parameters which result in comparable uncertainties are discussed.

Wiedenbeck, M. E.↗
NASA NTRS1987

A comparative study of plasma heating by ion acoustic and modified two-stream instabilities at subcritical quasi-perpendicular shocks

Plasma heating due to the ion acoustic instability and the modified two-stream instability is examined for quasi-perpendicular subcritical shocks. Electron and ion heating is investigated as a function of upstream electron to ion temperature ratio and plasma beta using second-order heating rates. A simple shock model is employed in which the cross-field electron-ion drift speed is adjusted until the total (adiabatic plus anomalous) heating matches that required by the Rankine-Hugoniot relations. Quantities such as the width of the shock and the maximum electric field fluctuations are also calculated, and the results are compared with the ISEE data set of subcritical bow shock crossings. The observed width of the shock, the amount of plasma heating, and the low-frequency electric field intensity are in reasonably good agreement with the calculations for the modified two-stream instability. On the other hand, the wave intensities at higher frequency are about 4 orders of magnitude smaller than those predicted for the ion acoustic instability at saturation, consistent with the fact that the measured shock widths imply cross-field drift speeds that are below threshold for this instability. It is therefore concluded that the dissipation at these shocks is most likely due to the lowest frequency, modified two-stream instability.

Winske, D.↗
NASA NTRS1987

Magnetic configuration of the distant plasma sheet - ISEE 3 observations

The influence of the IMF orientation and magnitude and substorm activity on the magnetic configuration of the central plasma sheet at 20-240 earth radii down the geomagnetic tail is investigated on the basis of ISEE-3 data. The results are presented graphically, and high-speed antisolar bulk flows threaded by southward magnetic fields are shown to be present in the distant plasma sheet after periods of substorm activity and southward IMF Bz. The effective dayside reconnection efficiency is estimated as 25 + or - 4 percent, in good agreement with theoretical models.

Slavin, J. A.↗
NASA NTRS1986

Gyrating and intermediate ion distributions upstream from the earth's bow shock

Study of ISEE 2 fast plasma data reveals that many suprathermal ion events that in previous studies would have been identified as intermediate ion events are actually gyrating ion events. Of 190 apparently intermediate ion events selected on the basis of their signature in energy-time spectrograms, half are actually found to be gyrating ion events. Using a model bow shock, the shock geometries and spacecraft locations for the observed gyrating and intermediate ion events are compared and found to be quite similar. Both gyrating and intermediate ion events are found to be associated with upstream MHD-like wave activity. Most gyrating ion events are associated with large-amplitude, monochromatic, weakly compressive waves, whereas many intermediate ion events are associated with smaller-amplitude, nonmonochromatic, weakly compressive waves. Some intermediate ion events are found to have no associated waves. Detailed study of the gyrating ion distributions reveals that the distributions are typically gyrotropic within about 4 earth radii of the bow shock, whereas at larger distances (up to about 10 earth radii) upstream from the shock the distributions are frequently 'gyrophase bunched'. In light of these observational characteristics, it is concluded that gyrating ion distributions are most likely generated both through coherent wave disruption of field-aligned beams and through reflection of solar wind ions off the shock.

Fuselier, S. A.↗
DOE OSTI2021

Using Machine Learning for Quantum Annealing Accuracy Prediction

Quantum annealers, such as the device built by D-Wave Systems, Inc., offer a way to compute solutions of NP-hard problems that can be expressed in Ising or quadratic unconstrained binary optimization (QUBO) form. Although such solutions are typically of very high quality, problem instances are usually not solved to optimality due to imperfections of the current generations quantum annealers. In this contribution, we aim to understand some of the factors contributing to the hardness of a problem instance, and to use machine learning models to predict the accuracy of the D-Wave 2000Q annealer for solving specific problems. We focus on the maximum clique problem, a classic NP-hard problem with important applications in network analysis, bioinformatics, and computational chemistry. By training a machine learning classification model on basic problem characteristics such as the number of edges in the graph, or annealing parameters, such as the D-Wave’s chain strength, we are able to rank certain features in the order of their contribution to the solution hardness, and present a simple decision tree which allows to predict whether a problem will be solvable to optimality with the D-Wave 2000Q. We extend these results by training a machine learning regression model that predicts the clique size found by D-Wave.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1986

Strong electron bidirectional anisotropies in the distant tail - ISEE 3 observations of polar rain

A detailed observational treatment of bidirectional electrons (about 50 to 500 eV) in the distant magnetotail (r not below 100 earth radii) is presented. It is found that electrons in this energy range commonly exhibit strong, field-aligned anisotropies in the tail lobes. Because of large tail motions, the ISEE 3 data provide extensive sampling of both the north and south lobes in rapid succession. These data directly demonstrate the strong asymmetries that exist between the north and south lobes at any one time. The bidirectional fluxes are found to occur predominantly in the lobe directly connected to the sunward interplanetary magnetic field in the open magnetosphere model (north lobe for away sectors and south lobe for toward sectors). Electron anisotropy and magnetic field data are presented which show the transition from unidirectional (sheath) electron populations to bidirectional (lobe) populations. The open nature of the distant magnetopause is demonstrated and it is shown that the source of the higher-energy, bidirectional lobe electrons is the tailward directed electron heat flux population in the distant magnetosheath. Taken together, the present evidence suggests that the bidirectional electrons that were observed in the distant tail are closely related to the polar rain electrons observed previously at lower altitudes. Furthermore, these data provide strong evidence that the distant tail is composed largely of open magnetic field lines in contradistinction to some recently advanced models.

Baker, D. N.↗
NASA NTRS1993

Space and Earth Sciences, Computer Systems, and Scientific Data Analysis Support, Volume 1

This Final Progress Report covers the specific technical activities of Hughes STX Corporation for the last contract triannual period of 1 June through 30 Sep. 1993, in support of assigned task activities at Goddard Space Flight Center (GSFC). It also provides a brief summary of work throughout the contract period of performance on each active task. Technical activity is presented in Volume 1, while financial and level-of-effort data is presented in Volume 2. Technical support was provided to all Division and Laboratories of Goddard's Space Sciences and Earth Sciences Directorates. Types of support include: scientific programming, systems programming, computer management, mission planning, scientific investigation, data analysis, data processing, data base creation and maintenance, instrumentation development, and management services. Mission and instruments supported include: ROSAT, Astro-D, BBXRT, XTE, AXAF, GRO, COBE, WIND, UIT, SMM, STIS, HEIDI, DE, URAP, CRRES, Voyagers, ISEE, San Marco, LAGEOS, TOPEX/Poseidon, Pioneer-Venus, Galileo, Cassini, Nimbus-7/TOMS, Meteor-3/TOMS, FIFE, BOREAS, TRMM, AVHRR, and Landsat. Accomplishments include: development of computing programs for mission science and data analysis, supercomputer applications support, computer network support, computational upgrades for data archival and analysis centers, end-to-end management for mission data flow, scientific modeling and results in the fields of space and Earth physics, planning and design of GSFC VO DAAC and VO IMS, fabrication, assembly, and testing of mission instrumentation, and design of mission operations center.

Estes, Ronald H.↗
NASA NTRS1986

Magnetospheric origin of energetic (at least 50 keV) ions upstream of the bow shock - The October 31, 1977, event

Energetic particle data gathered by the ISEE-1 and IMP-7 and -8 spacecraft on Oct. 31, 1977 while travelling inside the plasma sheet upstream of the earth's bow shock are analyzed for an indication of the source of the 30 keV-1 MeV particles observed. The IMP spacecraft also travelled through the magnetosphere and the dawn bow shock during the measurement data. The data included records of magnetospheric bursts of energetic protons, which had intensities about 2-8 times higher inside the plasma sheet than did the proton intensities. The magnetospheric bursts began about 40 min before the ISEE recorded an upstream ion event and 2 hr before its cutoff. Other data indicated that the appearance of upstream ions was controlled by the interplanetary magnetic field. The ions arose in the plasma sheet of the magnetosphere and in 'leaking' upstream experienced a separation of ions from electrons, a condition caused by the interplanetary magnetic field. A phenomenological model is developed for the process of injection of energetic particles upstream of the bow shock in a manner that is not commensurate with Fermi acceleration.

Anagnostopoulos, G. C.↗
DOE OSTI2023

Artificial Magnetic Tripod Ice

We study the collective behavior of interacting arrays of nanomagnetic tripods. These objects have six discrete moment states, in contrast to the usual two states of an Ising-like moment. Our experimental data demonstrate that triangular lattice arrays form a “tripod ice” that exhibits charge ordering among the effective vertex magnetic charges, in direct analogy to artificial kagome spin ice. The results indicate that the interacting tripods have effective moments that act as emergent local variables, with strong connections to the well-studied Potts and clock models. In addition, the tripod moments display a tendency toward a nearest neighbor alignment in our thermalized samples that separates this system from kagome spin ice. In conclusion, our results open a path toward the study of the collective behavior of nonbinary moments that is unavailable in other physical systems.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Wave mode identification of electrostatic noise observed with ISEE 3 in the deep tail boundary layer

The characteristics of the VLF electrostatic noise observed with ISEE 3 in the low-latitude boundary layer of distant geomagnetic tail are examined using a display format for the wave dynamic spectra different from that used by Scarf et al. (1984). It is shown that the observed noise is composed of impulsive bursts. The results of the detailed analysis of the noise parameters are used to develop a model of plasma wave behavior in the plasma rest frame. A hypothesis is proposed that the wide frequency extent of the noise spectra is composed of Doppler effects of waves propagating nearly omnidirectionally within the plasma rest frame, which is moving with the electron bulk speed. On the basis of this hypothesis, the wavelength of the observed waves were determined from the width of the frequency extent and the measured electron bulk speed. It is shown that the wavelength ranges from 2 to 8 times the plasma Debye length.

Tsutsui, M.↗
NASA NTRS2001

International Space Station Radiation Shielding Model Development

The projected radiation levels within the International Space Station (ISS) have been criticized by the Aerospace Safety Advisory Panel in their report to the NASA Administrator. Methods for optimal reconfiguration and augmentation of the ISS shielding are now being developed. The initial steps are to develop reconfigurable and realistic radiation shield models of the ISS modules, develop computational procedures for the highly anisotropic radiation environment, and implement parametric and organizational optimization procedures. The targets of the redesign process are the crew quarters where the astronauts sleep and determining the effects of ISS shadow shielding of an astronaut in a spacesuit. The ISS model as developed will be reconfigurable to follow the ISS. Swapping internal equipment rack assemblies via location mapping tables will be one option for shield optimization. Lightweight shield augmentation materials will be optimally fit to crew quarter areas using parametric optimization procedures to minimize the augmentation shield mass. The optimization process is being integrated into the Intelligence Synthesis Environment s (ISE s) immersive simulation facility at the Langley Research Center and will rely on High Performance Computing and Communication (HPCC) for rapid evaluation of shield parameter gradients.

Qualls, G. D.↗
DOE OSTI2023

Critical behavior in a chiral molecular model

Understanding the condensed-phase behavior of chiral molecules is important in biology as well as in a range of technological applications, such as the manufacture of pharmaceuticals. Here, we use molecular dynamics simulations to study a chiral four-site molecular model that exhibits a second-order symmetry-breaking phase transition from a supercritical racemic liquid into subcritical D-rich and L-rich liquids. We determine the infinite-size critical temperature using the fourth-order Binder cumulant, and we show that the finite-size scaling behavior of the order parameter is compatible with the 3D Ising universality class. We also study the spontaneous D-rich to L-rich transition at a slightly subcritical temperature of T = 0.985Tc, and our findings indicate that the free energy barrier for this transformation increases with system size as N2/3, where N is the number of molecules, consistent with a surface-dominated phenomenon. The critical behavior observed herein suggests a mechanism for chirality selection in which a liquid of chiral molecules spontaneously forms a phase enriched in one of the two enantiomers as the temperature is lowered below the critical point. Furthermore, the increasing free energy barrier with system size indicates that fluctuations between the L-rich and D-rich phases are suppressed as the size of the system increases, trapping it in one of the two enantiomerically enriched phases. Such a process could provide the basis for an alternative explanation for the origin of biological homochirality. We also conjecture the possibility of observing nucleation at subcritical temperatures under the action of a suitable chiral external field.

Chemistry↗
NASA NTRS1980

Observations of a nonthermal ion layer at the plasma sheet boundary during substorm recovery

Measurements of the energy and angular distributions of energetic protons and alpha particles (not less than 30 keV/charge) in the geomagnetic tail are presented. The measurements were made during the recovery phase of a geomagnetic substorm on Apr. 19, 1978, with the Max-Planck-Institut/University of Maryland sensor system on the Isee 1 satellite. The measurements were also correlated with plasma observations made by the LASL/MPE instrument on Isee 1. The data reveal the presence of a thin nonthermal layer of protons and alpha particles at the plasma sheet boundary. The particles have their maximum flux at 60 keV/charge and are streaming highly collimated in the earthward direction. The alpha particle layer is confined within the proton layer. Many aspects of the observations are in agreement with an acceleration model near the neutral line proposed by Jaeger and Speiser (1974)

Moebius, E.↗
NASA NTRS1980

Magnetospheric observation of large sub-auroral electric fields

An example of large subauroral poleward electric fields similar to those observed on OGO-6, S3-2 and AE-C (SAID) has been found in the magnetosphere near L = 4 and 2300 MLT using ISEE-1 electric field data. The event is located adjacent to and outside the plasmapause and occurs 1 1/2 hours into a substorm. The event is accompaned by a significant penetration of the convection electric field inside the plasmasphere. Data from similar regions on the next orbit occurring near the beginning of a substorm did not exhibit these effects. Recent theoretical models predict SAID to occur in the trough regions, where substorm dynamics force currents to flow in regions of low conductivity. These models provide a first-order interpretation of this phenomena; however, the overal picture is more complex.

Maynard, N. C.↗