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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Titan's magnetospheric interaction

Voyager 1 encounter data are used to theoretically examine the interaction of Titan with the solar wind, the Saturn magnetosheath and the Saturn magnetosphere. The spacecraft data comprised magnetometer, plasma wave, radio signal and charged particle measurements. Attention is given to the Alfven (1.9) and Mach (0.57) numbers detected in the Saturn magnetosheath, along with a fast hydrodynamic Mach number of 0.55. Incident plasma interacted with the Titan atmosphere and produced a magnetosphere through mass capture and field-line draping. The tail region was loaded with N(+) and N2(+)/H2CN(+) ions instead of the strong H(+) signals typical of other regions. The magnetotail featured four lobes, and the Titan atmosphere was calculated to lose 10 to the 24th ions/sec. Finally, the Titan internal rotationally aligned magnetic field has an estimated strength of 7 x 10 to the 20th gauss/cu cm.

Neubauer, F. M.↗
NASA NTRS1994

Polar cap potential distributions during periods of positive IMF B(sub y) and B(sub z)

We compare the DE-2 electric field measurements used by HEPPNER and MAYNARD (1987) to illustrate strongly distorted, BC convection patterns for interplanetary magnetic field (IMF) B(sub z) greater than 0 and large absolute value of B(sub y), with simultaneous detections of particle spectra, plasma drifts and magnetic perturbations. Measured potentials greater than 50 keV, driven by the solar wind speeds exceeding 500 km/s, are greater than published correlation analysis predictions by up to 27%. The potential distributions show only two extrema and thus support the basic conclusion that under these conditions the solar wind/IMF drives two-rather than four-cell convection patterns. However, several aspects of the distorted two-cell convection pattern must be revised. In addition to the strong east-west convection in the vicinity of the cusp, indicated by Heppner and Maynard, we also detect comparable components of sunward (equatorward) plasma flow. Combined equipotential and particle precipitation distributions indicate the presence of a lobe cell embedded within the larger, afternoon reconnection cell. Both types rotate in the same sense, with the lobe cell carrying 20-40% of the total afternoon cell potential. We detected no lobe cell within morning convection cell.

Burke, William J.↗
DOE OSTI2024

Λ polarization from vortex rings as the medium response for jet thermalization

We performed a systematic study on the formation of vorticity rings as the process for jet thermalization in the medium created in high-energy nuclear collisions. In this work, we expanded our previous analysis to a more realistic framework by considering noncentral events and fluctuations in the initial condition. We simulate the formation and evolution of the flow vortex structure in a relativistic viscous hydrodynamic model and study the sensitivity of the proposed “ring observable” (ℛ$^{𝑡}_{Λ}$) that can be measured experimentally through the polarization of Λ hyperons. We show that this observable is robust with respect to fluctuating initial conditions to capture the jet-induced vortex flow signal and further study its dependence on different model parameters, such as the jet's velocity, position, the fluid's shear viscosity, and the collision centrality. The proposed observable is associated with the formation of vorticity in a quark-gluon plasma, showing that the measurement of particle polarization can be a powerful tool to probe different properties of jet-medium interactions and to understand better the polarization induced by the transverse and longitudinal expansions of the medium.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1974

Solar radio bursts at low frequencies

Properties of solar radio bursts observed by spacecraft at frequencies below several MHz are reviewed. In this frequency range most of the observed bursts are type III events (associated with particles) but several cases of type II emission (associated with shocks) have been reported. The analysis which lead to emission levels of type III solar bursts out to beyond 1 AU from the sun also indicate that the low frequency radiation is observed at the harmonic of the emission region plasma frequency. Simultaneous particle and radio measurements imply that the bursts are generated near the leading edge of impulsive streams of solar electrons with energies extending from several hundred keV to several keV. Recent experiments measuring the direction of arrival of the radio emission allow the exciter particles to be tracked along the interplanetary magnetic field from regions near the sun out to 1 AU.

Fainberg, J.↗
NASA NTRS1986

The joint NASA/Goddard-University of Maryland research program in charged particle and high energy photon detector technology

Progress made in the following areas is discussed: low energy ion and electron experiments; instrument design for current experiments; magnetospheric measurement of particles; ion measurement in the earth plasma sheet; abundance measurement; X-ray data acquisition; high energy physics; extragalactic astronomy; compact object astrophysics; planetology; and high energy photon detector technology.

Source record↗
NASA NTRS1985

The atmosphere of Venus: Recent findings; Proceedings of the Workshop III of the 25th COSPAR Plenary Meeting, Graz, Austria, June 25-July 7, 1984

Topics discussed include the structure and dynamics of the Venus atmosphere below 100 km, radiation and chemistry below 100 km, the neutral upper atmosphere, the ionosphere, and solar wind interaction. Papers are presented on infrared spectrometry of Venus from Venera 15 and Venera 16, recent results on the Venus atmosphere from Pioneer Venus radio occultations, absorption of solar energy and the heating rate in the atmosphere of Venus, long term changes in Venus sulfur dioxide, and mechanisms of cooling of the nightside thermosphere of Venus. Also considered are recent advances in model calculations of the Venus ionosphere, current-driven plasma instabilities and auroral-type particle acceleration at Venus, and plasma measurements in the Venus near wake.

Keating, G. M.↗
NASA NTRS2014

MMS Observatory TV Results Contamination Summary

The Magnetospheric Multiscale (MMS) mission is a constellation of 4 observatories designed to investigate the fundamental plasma physics of reconnection in the Earth's magnetosphere. The various instrument suites measure electric and magnetic fields, energetic particles, and plasma composition. Each spacecraft has undergone extensive environmental testing to prepare it for its minimum 2 year mission. In this paper, we report on the extensive thermal vacuum testing campaign. The testing was performed at the Naval Research Laboratory utilizing the "Big Blue" vacuum chamber. A total of ten thermal vacuum tests were performed, including two chamber certifications, three dry runs, and five tests of the individual MMS observatories. During the test, the observatories were enclosed in a thermal enclosure known as the "hamster cage". The enclosure allowed for a detailed thermal control of various observatory zone, but at the same time, imposed additional contamination and system performance requirements. The environment inside the enclosure and the vacuum chamber was actively monitored by several QCMs, RGA, and up to 18 ion gauges. Each spacecraft underwent a bakeout phase, which was followed by 4 thermal cycles. Unique aspects of the TV campaign included slow pump downs with a partial represses, thruster firings, Helium identification, and monitoring pressure spikes with ion gauges. Selected data from these TV tests is presented along with lessons learned.

Pressure↗
NASA NTRS1995

Update on the Fire (solar probe) mission study

Since mid-1994 the U.S. and Russia have been studying the technical feasibility of a joint solar probe mission as part of the 'Fire and Ice' concept to explore close to the Sun, and Pluto, together. In the current concept of the 'Fire' mission, separate spacecraft built by each country would be launched together, fly by Jupiter to shed orbital angular momentum and achieve a solar polar orbit, and arrive 3.6 years later at 4 and 10 R(sub s). The Fire mission would measure basic parameters of the modes of energy and momentum flow and transfer to the coronal plasma that are not observable remotely. Specifically, measurement of magnetic fields, waves, suprathermal particles, and critical features of the plasma particle composition and distribution function would be made from 4 to 30 R(sub s) where the solar wind is known to be accelerated. In addition, the Fire spacecraft should image coronal structures unambiguously and relate the underlying and flown-through structures to plasma characteristics measured in situ. Each country is developing a backup plan to pursue the solar probe objectives alone if the other side is unable to carry out its mission.

Jones, W. Veron↗
DOE OSTI2020

Electron emission from particles strongly affects the electron energy distribution in dusty plasmas

The electron energy distribution of a low-temperature dusty plasma has been measured via a Langmuir probe. An unexpected broad peak at energy in the 2–4 V range has been observed. This can be theoretically reproduced for a sufficiently large electron emission rate from the nanoparticles dispersed in the plasma. A careful analysis of the nanoparticle energy balance, using measured values of nanoparticle concentration and plasma density, confirms that particles are sufficiently hot under the conditions of this study to rapidly inject electrons into the plasma via field-assisted thermionic emission. This work suggests that the presence of dust affects the plasma ionization balance more deeply than previously thought.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Magnetospheric plasma.

This paper reviews the principal features of the distribution of plasma in the magnetosphere as inferred from observations of particles with energies in the keV range and below. Low energy electrons are found within the equatorial region of the magnetotail, where they form the plasma sheet, and throughout the outer magnetosphere, where they envelop the earth with a complicated and as yet only partly explored structure. The sum of particle and magnetic pressures is roughly constant across the plasma sheet. The intense electron fluxes of the plasma sheet terminate at the so-called inner boundary of the plasma sheet, which is located at about 11 earth radii in the evening side of the magnetosphere and approaches the plasmapause near the midnight meridian. During substorms, the inner boundary moves closer to the earth, while deep in the magnetotail the plasma sheet first becomes thinner and then expands. Comparison between magnetotail electron densities and whistler measurements suggests that the observed plasma sheet particles may constitute the thermal particle population of the magnetotail.

Vasyliunas, V. M.↗
NASA NTRS2014

MMS Observatory Thermal Vacuum Results Contamination Summary

The MMS mission is a constellation of 4 observatories designed to investigate the fundamental plasma physics of reconnection in the Earths magnetosphere. Each spacecraft has undergone extensive environmental testing to prepare it for its minimum 2 year mission. The various instrument suites measure electric and magnetic fields, energetic particles, and plasma composition. Thermal vacuum testing was conducted at the Naval Research Laboratory (NRL) in their Big Blue vacuum chamber. The individual spacecraft were tested and enclosed in a cryopanel enclosure called a Hamster cage. Specific contamination control validations were actively monitored by several QCMs, a facility RGA, and at times, with 16 Ion Gauges. Each spacecraft underwent a bakeout phase, followed by 4 thermal cycles. Unique aspects of the TV environment included slow pump downs with represses, thruster firings, Helium identification, and monitoring pressure spikes with Ion gauges. Various data from these TV tests will be shown along with lessons learned.

TV↗
NASA NTRS1994

Formation and eruption of Sun-aligned arcs at the polar cap-auroral oval boundary

This paper reports on results from a study of the poleward edge of the auroral oval in the morning sector using a comprehensive blend of in-situ and ground-based measurements. Three rockets, equipped to measure electric and magnetic fields, energetic particles, and plasma density flew into an auroral display whose dynamical features were reorded with a digital image into an auroral display intensified all-sky camera as well as with an incoherent scatter radar. In addition, a number of DMSP satellite measurements bracketed the launch time. Evidence is presented here that in a condition of declining magnetic activity Sun-aligned arcs are injected into the polar cap at velocities approximately 7 km/s from locations of periodic brightening along the morningside of the auroral oval. The multipoint in situ measurements allow some separation of temporal and spatial effects and strongly suggest a poleward contraction of the convention pattern of about 0.25 deg INVL in 70 s. The most equatorward of the two brightest arcs studied erupted into a region which already was characterized by strong sunward convection. The most poleward, however, pushed into a region that had been convecting in an antisunward direction at velocities exceeding 1 km/s less than 2 min earlier, and it is likely that sunward convection subsequently pertained poleward of that arc as well. We believe that these events mark the reconfiguration of the magnetosphere into a system characterized by a smaller polar cap.

Berg, G. A.↗
DOE OSTI2022

Spatiotemporal Plasma-Particle Characterization of Dry Aerosols Using Nanosecond, Femtosecond, and Filament Laser-Produced Plasmas

The ability to rapidly characterize dry aerosols in air using laser-induced breakdown spectroscopy (LIBS) with femtosecond laser pulses promises advancement towards real-time atmospheric sampling and standoff capabilities. Of particular interest is the ability to apply LIBS in the context of low-particle loaded environments where discrete particle interactions must be observed within the sampling volume of the laser-produced plasma (LPP). In this study, dry nanoparticles in suspension are generated from a standard solution and sampled in air using Q-switched nanosecond (ns-) pulses, short-focus (SF) femtosecond (fs-) pulses, and filaments. Short time-gated plasma images are captured to observe spatially and temporally varying discrete plasma-particle interactions, which is shown to influence early air breakdown behavior and subsequent plasma evolution. Along with images, photo-multiplier tube (PMT) measurements are conducted where strong spatiotemporal dependencies are exhibited by the collected emission signal on particle proximity and plasma expansion behavior. Finally, conditional analysis is performed on LIBS measurements to determine associated sampling probabilities and filter out spectra with poor or absent emission peaks with an adaptive threshold algorithm.

42 ENGINEERING↗
DOE OSTI2023

A flexible proton beam imaging energy spectrometer (PROBIES) for high repetition rate or single-shot high energy density (HED) experiments (invited)

The PROBIES diagnostic is a new, highly flexible, imaging and energy spectrometer designed for laser-accelerated protons. The diagnostic can detect low-mode spatial variations in the proton beam profile while resolving multiple energies on a single detector or more. When a radiochromic film stack is employed for “single-shot mode,” the energy resolution of the stack can be greatly increased while reducing the need for large numbers of films; for example, a recently deployed version allowed for 180 unique energy measurements spanning ~3 to 75 MeV with <0.4 MeV resolution using just 20 films vs 180 for a comparable traditional film and filter stack. When utilized with a scintillator, the diagnostic can be run in high-rep-rate (>Hz rate) mode to recover nine proton energy bins. Here, we also demonstrate a deep learning-based method to analyze data from synthetic PROBIES images with greater than 95% accuracy on sub-millisecond timescales and retrained with experimental data to analyze real-world images on sub-millisecond time-scales with comparable accuracy.

3D printing↗
NASA NTRS1973

Planetary, lunar, and cometary studies, overview

Recent lunar and planetary oriented satellite missions are reviewed as are in situ measurements of magnetic fields, plasmas, and energetic particles in the earth's environment and in the sun's environment in heliocentric space. The detection of a planetary magnetic field on Mars is reported.

Ness, N. F.↗
NASA NTRS1985

Wave observations in outer planet magnetospheres

The first measurements of plasma waves and wave-particle interactions in the magnetospheres of the outer planets were provided by instruments on Voyager 1 and 2. At Jupiter, the observations yielded new information on upstream electrons and ions, bow shock dissipation processes, trapped radio waves in the magnetospheres and extended Jovian magnetotail, pitch angle diffusion mechanisms and whistlers from atmospheric lightning. Many of these same emissions were detected at Saturn. In addition, the Voyager plasma wave instruments detected dust particles associated with the tenuous outer rings of Saturn as they impacted the spacecraft. Most of the plasma wave activity at Jupiter and Saturn is in the audio range, and recordings of the wave observations have been useful for analysis.

Scarf, F. L.↗