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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 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Early time interaction of lithium ions with the solar wind in the AMPTE mission

The early time interaction of an artifically injected lithium cloud with the solar wind is simulated with a one-dimensional hybrid code. Simulation results indicate that the lithium cloud presents an obstacle to the solar wind flow, forming a shock-like interaction region. Several notable features are found: (1) The magnetic field is enhanced up to a factor of about 6, followed by a magnetic cavity downstream. (2) Solar wind ions are slowed down inside the lithium cloud, with substantial upstream reflection. (3) Most of the lithium ions gradually pick up the velocity of the solar wind and move downstream. (4) Intense and short-wavelength electric fields exist ahead of the interaction region. (5) Strong electron heating occurs within the lithium cloud. (6) The convection electric field in the solar wind is modulated in the interaction region. The simulation results are in remarkable agreement with in situ spacecraft measurements made during lithium releases in the solar wind by the AMPTE (Active Magnetospheric Particle Tracer Explorers) Program.

Lui, A. T. Y.↗
NASA NTRS2008

Four Point Measurements of the Foreshock

Hybrid code numerical simulations accurately predict the properties of the Earth's foreshock, a region populated by solar wind particles heated and reflected by their interaction with the bow shock. The thermal pressures associated with the reflected population suffice to substantially modify the oncoming solar wind, substantially reducing densities, velocities, and magnetic field strengths, but enhance temperatures. Enhanced thermal pressures cause the foreshock to expand at the expense of the ambient solar wind, creating a boundary that extends approx.10 RE upstream which is marked by enhanced densities and magnetic field strengths, and flows deflected away from the foreshock. We present a case study of Cluster plasma and magnetic field observations of this boundary.

Sibeck, D. G.↗
DOE OSTI2017

Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A

Disk winds are thought to play a critical role in star birth. As winds extract excess angular momentum from accretion disks, matter in the disk can be transported inward to the star to fuel mass growth. However, observational evidence of wind carrying angular momentum has been very limited. We present Submillimeter Array (SMA) observations of the young star MWC 349A in the H26 α and H30 α recombination lines. The high signal-to-noise ratios made possible by the maser emission process allow us to constrain the relative astrometry of the maser spots to milli-arcsecond precision. Previous observations of the H30 α line with the SMA and the Plateau de Bure interferometer (PdBI) showed that masers are distributed in the disk and wind. Our new high-resolution observations of the H26 α line reveal differences in spatial distribution from that of the H30 α line. H26 α line masers in the disk are excited in a thin annulus with a radius of about 25 au, while the H30 α line masers are formed in a slightly larger annulus with a radius of 30 au. This is consistent with expectations for maser excitation in the presence of an electron density variation of approximately R {sup −4}. In addition, the H30 α and H26 α line masers arise from different parts in the wind. This difference is also expected from maser theory. The wind component of both masers exhibits line-of-sight velocities that closely follow a Keplerian law. This result provides strong evidence that the disk wind extracts significant angular momentum, thereby facilitating mass accretion in the young star.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1995

WIND measurements of proton and alpha particle flow and number density

We propose to review measurements of the solar wind proton and alpha particle flow velocities and densities made since launch with the WIND SWE instrument. The SWE Faraday cup ion sensors are designed to be able to determine accurately flow vector directions, and thus can be used to detect proton-alpha particle differential flow. Instances of differential flow, and the solar wind features with which they are associated will be discussed. Additionally, the variability of the percentage of alpha particles as a fraction of the total solar wind ion density will be presented.

Steinberg, J. T.↗
DOE OSTI2017

The Spectrum of SS 433 in the H and K Bands

SS 433 is an X-ray binary and the source of sub-relativistic, precessing, baryonic jets. We present high-resolution spectrograms of SS 433 in the infrared H and K bands. The spectrum is dominated by hydrogen and helium emission lines. The precession phase of the emission lines from the jet continues to be described by a constant period, P{sub jet}=162.375 days. The limit on any secularly changing period is | P-dot |≲10{sup −5}. The He i λ2.0587 μm line has complex and variable P-Cygni absorption features produced by an inhomogeneous wind with a maximum outflow velocity near 900 km s{sup −1}. The He ii emission lines in the spectrum also arise in this wind. The higher members of the hydrogen Brackett lines show a double-peaked profile with symmetric wings extending more than ±1500 km s{sup −1} from the line center. The lines display radial velocity variations in phase with the radial velocity variation expected of the compact star, and they show a distortion during disk eclipse that we interpret as a rotational distortion. We fit the line profiles with a model in which the emission comes from the surface of a symmetric, Keplerian accretion disk around the compact object. The outer edge of the disk has velocities that vary from 110 to 190 km s{sup −1}. These comparatively low velocities place an important constraint on the mass of the compact star: its mass must be less than 2.2 M{sub ⊙} and is probably less than 1.6 M{sub ⊙}.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1977

Wake characteristics of an eight-leg tower for a MOD-0 type wind turbine

Low speed wind tunnel tests were conducted to determine the flow characteristics of the wake downwind of a 1/25th scale, all tubular eight leg tower concept suitable for application to the DOE-NASA MOD-0 wind power turbine. Measurements were made of wind speed profiles, and from these were determined the wake local minimum velocity, average velocity, and width for several wind approach angles. These data are presented herein along with tower shadow photographs and comparisons with data from an earlier lattice type, four leg tower model constructed of tubular members. Values of average wake velocity defect ratio and average ratio of wake width to blade radius for the eight leg model were estimated to be around 0.17 and 0.30, respectively, at the plane of the rotor blade. These characteristics suggest that the tower wake of the eight leg concept is slightly less than that of the four leg design.

Savino, J. M.↗
NASA NTRS1988

Horizontal plasma flow velocities in the ionosphere of Mars - A test case for the solar wind interaction

On the apparently nonmagnetic planets Mars and Venus, ionospheric plasma can be driven from the day to the nightside by two different mechanisms: (1) the pressure gradient force across the terminator, and (2) a solar wind-induced force via a viscous boundary layer interaction. Calculations of the horizontal flow velocities in the ionosphere of Mars using the two mechanisms produce results differing by an order of magnitude. It is pointed out that the detailed observations of the horizontal flow velocity in the ionosphere of Mars may provide a test case for the resolution of some problems relating to the interaction of the solar wind with the planets Mars and Venus.

Singhal, R. P.↗
NASA NTRS1967

Jet engine powers large, high-temperature wind tunnel

Wind tunnel for large component testing uses a jet engine with afterburner to provide high temperatures /1200 degrees to 2000 degrees F/ and controlled high velocity gas. This economical wind tunnel can accommodate parts ten feet by ten feet or larger, and is a useful technique for qualitative information.

Benham, T. F.↗
NASA NTRS1976

Wind estimates from cloud motions - Preliminary results from phases I, II and III of an in situ aircraft verification experiment

The accuracy of wind estimates derived from cloud motion is under investigation. Aircraft measurements of the ambient wind field have been compared with simultaneous inertial navigation system descriptions of the extent and motion of 40 tropical cumulus and 5 cirrus clouds. Preliminary results indicate that cloud-motion wind estimates are sufficiently accurate to be used in sensitive divergence, vorticity, and vertical motion calculations. The magnitude of the vector difference between the cirrus cloud velocity and the mean wind of the cloud layer was found to be about 1.6 m/sec. The major source of error is thought to be in determination of the position of the cloud. In the case of cumulus clouds, the magnitude of the vector difference between the aircraft-measured cloud motion and the cloud-base wind is less than 1.3 m/sec.

Hasler, A. F.↗
NASA NTRS1972

Interstellar helium in interplanetary space

The velocity distribution function of He(+) in the solar wind at 1 AU is calculated with the assumption that the source is photoionization of a cold (T = 100 K), neutral interstellar wind. If the spiral magnetic field is noise free, the velocity distribution is diffuse and would not produce a peak at 4(E over Q) sub H in an E over Q particle spectrum. If the velocity of the interstellar wind with respect to the sun lies in the ecliptic, a large variation of the He(+) number density with respect to ecliptic longitude is expected.

Feldman, W. C.↗
NASA NTRS2024

The Martian Ionospheric Response to the Co-Rotating Interaction Region That Caused the Disappearing Solar Wind Event at Mars

An unusually low density solar wind event was observed in December 2022 moving past both Earth and Mars. The source was traced back to a coronal hole and active region on the Sun's surface. The resulting solar wind lead to the development of a co-rotating interaction region (CIR) and trailing rarefaction region that lasted for multiple solar rotations. Within this structure, the solar wind conditions, including density, velocity, and magnetic field magnitude and orientation drastically changed. In this study we analyze the response of the Martian ionosphere using MAVEN data to these changing solar wind conditions. The low density solar wind region associated with the December event resulted in the expansion of the Martian ionospheric boundaries. We show that the ion composition boundary (ICB) is located at extreme altitudes that are beyond previously observed locations from the MAVEN mission between 2015 and 2018. Furthermore, the boundary between shocked solar wind and the Martian ionosphere identified using electron and ion data moved together on the dayside of the planet with the changing solar wind conditions. However, at the flank region these boundaries do not move together, and we show here that the decoupling of the two boundaries may be the result of a change in the interplanetary magnetic field azimuthal angle.

S. R. Shaver↗
DOE OSTI2025

Gaussian FLOWERS: Wind-rose-based analytical integration of Gaussian wake model for extremely fast AEP estimation

A major cost in the study of wind farm layout optimization is the repeated evaluation of the annual energy production (AEP). The current approach to estimating AEP requires a large set of flow simulations to be performed that cover each discrete wind speed and direction combination contained within the wind rose, followed by a probability-weighted sum of the power production resulting from each simulation. Even with inexpensive engineering wake models, this numerical integration scheme can lead to high computational costs. In this paper, we derive an analytical formulation for estimating farm AEP across every wind direction, based on a Gaussian wake velocity model, which reduces the number of wind farm simulations to a single function evaluation. As a result, we find that the Gaussian-FLOWERS approach reduces the time for AEP calculations by more than two orders of magnitude with a small trade-off in accuracy when compared to a conventional approach. This massive reduction in computation cost is useful to reduce overall costs in wind farm layout optimization studies.

17 WIND ENERGY↗
DOE OSTI2014

HIGH-RESOLUTION X-RAY SPECTROSCOPY OF THE BURSTING PULSAR GRO J1744-28

The bursting pulsar GRO J1744-28 is a Galactic low-mass X-ray binary that distinguishes itself by displaying type-II X-ray bursts: brief, bright flashes of X-ray emission that likely arise from spasmodic accretion. Combined with its coherent 2.1 Hz X-ray pulsations and relatively high estimated magnetic field, it is a particularly interesting source to study the physics of accretion flows around neutron stars. Here we report on Chandra/High Energy Transmission Grating observations obtained near the peak of its bright 2014 accretion outburst. Spectral analysis suggests the presence of a broad iron emission line centered at E {sub l} ≅ 6.7 keV. Fits with a disk reflection model yield an inclination angle of i ≅ 52° and an inner disk radius of R {sub in} ≅ 85 GM/c {sup 2}, which is much further out than typically found for neutron star low-mass X-ray binaries. Assuming that the disk is truncated at the magnetospheric radius of the neutron star, we estimate a magnetic field strength of B ≅ (2-6) × 10{sup 10} G. Furthermore, we identify an absorption feature near ≅ 6.85 keV that could correspond to blue-shifted Fe XXV and point to a fast disk wind with an outflow velocity of v {sub out} ≅ (7.5-8.2) × 10{sup 3} km s{sup –1} (≅ 0.025c-0.027c). If the covering fraction and filling factor are large, this wind could be energetically important and perhaps account for the fact that the companion star lost significant mass while the magnetic field of the neutron star remained strong.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1989

An Exosat X-ray observation of one orbital cycle of 4U 1700-37/HD 153919

Exosat observations of close to one complete binary cycle of 4U 1700-37/HD 153919 are presented, and X-ray absorption variations are determined as a function of orbital phase in order to study the properties of the stellar wind of the companion HD 153919. The decrease noted in absorption between eclipse egress and phase 0.5 may be due to X-rays from a neutron star being absorbed by an inner wind with a radial velocity law close to that predicted by Castor et al. (1975). Under the assumption that the X-ray source is powered by material captured from the steller wind, the absorption variations with orbital phase and the time-average luminosity have been modeled to investigate the suppression of the radiative acceleration of the wind via the ionization of the wind by the X-ray source.

Haberl, F.↗
DOE OSTI2021

Comparison of Infrasound Wind Noise Reduction Systems for Use in Temporary Deployments

Infrasound, or low frequency sound 20 Hz, is produced by a variety of natural and anthropogenic sources. Wind also generates signals within this frequency band and serves as a persistent source of infrasonic noise. Infrasound sensors measure pressure fluctuations, which scale with the ambient density and velocity fluctuations of ground winds. Here we compare four different wind noise reduction systems, or "filters", and make recommendations for their use in temporary infrasound deployments. Our results show that there are two filters that are especially effective at reducing wind noise: (1) a Hyperion high frequency (HF) shroud with a 1 m diameter metal mesh dome placed on top and (2) a Hyperion Four Port Garden Hose shroud with 4 Miracle-Gro Soaker System garden hoses. We also find that placing a 5-gallon bucket over the HF wind shroud should not be done as it provides a negligible decrease in noise up to ~ 1 Hz and then an increase in noise. We conclude that it is up to the researcher to determine which of the other filters is best for their needs based on location and expense. We anticipate this study will be used as a resource for future deployments when a wind noise reduction method is necessary but only needed for a limited time period.

58 GEOSCIENCES↗
NASA NTRS1990

Mesospheric momentum fluxes observed by the MST radar at Poker Flat, Alaska

An analysis of the wave motions observed with the Poker Flat MST radar during the winter, summer, and fall of 1986 is presented. Monthly and daily mean winds, momentum fluxes, and velocity variances are investigated in detail. While several features are in agreement with previous measurements, some significant differences also are found to exist in the observations. Monthly mean horizontal winds between 82 and 89 km have amplitudes of 20-40 m/s westward and 10-25 m/s southward in July and August. In fall and winter, the horizontal winds between 58 and 75 km are weaker and essentially eastward.

Wang, Ding-Yi↗
DOE OSTI2018

AIMMS 20 Hz ACE-ENA

The AIMMS-20 probe is manufactured by Aventech Research Inc. (http://www.aventech.com) and measures platform position, velocity, attitude, and ambient temperature, static pressure, and the differential pressures from a 5-port hemispheric gust probe, and combines all these measured data into a calculation of the ambient winds. A detailed description of the AIMMS-20 specifications is available on (http://aventech.com/documents/PMS%20CANISTER/PMS%20Canister%20Technical%20Specifications.pdf). The data provided here are originally communicated as raw measurements over the CAN bus to the ODMS data module and stored in flight in binary .rXX files. These files are combined in post processing using the Aventech program asmbl.exe in to .raw files, one for each flight. The .raw files are subsequently processed using the Aventech program ekf553_oemv.exe, which regenerates the wind estimates, in this case at an output rate of 20 Hz.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1984

Aeolian processes on Venus

Many of the questions regarding aeolian processes on Venus and the subsequent implications for surface history involve understanding the physics of particle motion in the venusian environment. The surface environment of Venus is simulated as closely as practicable using the Venus Wind Tunnel and to determine threshold wind speeds, particle flux, particle velocities, and the characteristics of various aeolian bedforms. Despite the relatively low wind speeds on Venus, the flux of windblown material on Venus is potentially high. A high fraction of material is transported as surface creep by rolling, estimates yield rates up to 100 kg per cm lane width per year depending upon the availability of material and wind frequency, suggesting that the formation of lowland plains by aeolian processes and the burial of various landforms such as impact craters could occur on short geological time-scales. Wind tunnel simulations demonstrate that aeolian processes may be very effective in modifying the surface through erosion and deposited and may have an important influence on the composition of the atmosphere.

Greeley, R.↗