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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

On the acceleration of thermal coronal ions by flare induced shock waves

The energy spectra of solar flare ions are calculated by assuming that the process which accelerates solar wind ions to MeV/ nucleon energies in the interplanetary corotating interaction region (CIR) also occurs in flare induced magnetosonic fast-mode (MFM) shocks in the corona. Solar wind ions are considered to be accelerated to MeV/nucleon energies by wave-particle interactions in the shock front and the downstream flow, being compressed between upstream and downstream magnetic field irregularities, and then accelerated by the shock drift acceleration mechanism. The energy spectra of the accelerated ions is calculated from the number of shock encounters as a function of the post- and preacceleration energies. A best fit by an exponential in momentum is determined for ions in the 50 MeV to a few GeV range, and from 20-80 MeV by a suitable power law in kinetic energy with a mean spectral index. Comparisons with observed solar protons show good agreement.

Decker, R. B.↗
NASA NTRS2016

Inverse Energy Dispersion of Energetic Ions Observed in the Magnetosheath

We present a case study of energetic ions observed by the Energetic Particle Detector (EPD) on the Magnetospheric Multiscale spacecraft in the magnetosheath just outside the subsolar magnetopause that occurred at 1000 UT on 8 December 2015. As the magnetopause receded inward, the EPD observed a burst of energetic (approximately 50-1000 keV) proton, helium, and oxygen ions that exhibited an inverse dispersion, with the lowest energy ions appearing first. The prolonged interval of fast antisunward flow observed in the magnetosheath and transient increases in the H components of global ground magnetograms demonstrate that the burst appeared at a time when the magnetosphere was rapidly compressed. We attribute the inverse energy dispersion to the leakage along reconnected magnetic field lines of betatron-accelerated energetic ions in the magnetosheath, and a burst of reconnection has an extent of about 1.5 R(sub E) using combined Super Dual Auroral Radar Network radar and EPD observations.

Lee, S. H.↗
NASA NTRS2002

Comparison of the Effects of Wave-Particle Interactions and the Kinetic Suprathermal Electron Population on the Acceleration of the Solar Wind

Kinetic effects due to wave-particle interactions and suprathermal electrons have been suggested in the literature as possible solar wind acceleration mechanisms. Ion cyclotron resonant heating, in particular, has been associated with some qualitative features observed in the solar wind. In terms of solar wind acceleration, however, it is interesting to compare the kinetic effects of suprathermal electrons with those due to the wave-particle interactions. The combined effects of the two acceleration mechanisms on the fast solar wind have been studied by Tam and Chang (1999a,b). In this study. we investigate the role of the suprathermal electron population in the acceleration of the solar wind. Our model follows the global kinetic evolution of the fast solar wind under the influence of ion cyclotron resonant heating, while taking into account Coulomb collisions, and the ambipolar electric field that is consistent with the particle distributions themselves. The kinetic effects due to the suprathermal electrons, which we define to be the tail of the electron distributions, can be included in the model as an option. By comparing the results with and without the inclusion of the suprathermal electron effects, we determine the relative importance of suprathermal electrons and wave-particle interactions in driving the solar wind. We find that although suprathermal electrons enhance the ambipolar electric potential in the solar wind considerably, their overall influence as an acceleration mechanism is relatively insignificant in a wave-driven solar wind.

Tam, S. W. Y.↗
NASA NTRS1980

Solar wind ions accelerated to 40 keV by shock wave disturbances

Observations in the solar wind with the LASL/MPI fast plasma experiment on ISEE 1 and 2 reveal the common presence of ions with energies extending from 100 eV up to at least 40 keV in a broad region, typically 10 million kilometers wide, following interplanetary shocks. Peak differential fluxes up to 5000/sq cm s sr keV at 28 keV are observed either at the shock or within the first 1.5 hours following shock passage. In the solar wind frame the distribution function of these ions is roughly isotropic, peaks near zero velocity, and above 5 keV can adequately be characterized as power law in energy with a spectral index of 2.7. The effective 'temperature' of these ions generally exceeds 100 million K. These suprathermal interplanetary ions are almost certainly solar wind ions which have been accelerated by some mechanism associated with the shock wave disturbance. Present evidence leads the authors to favor stochastic particle acceleration involving electrostatic and/or electromagnetic turbulence in the postshock flow.

Gosling, J. T.↗
NASA NTRS1990

Particle acceleration at shocks with surface ripples

The present treatment of superthermal-ion acceleration on the surface of a fast-mode hydromagnetic shock gives attention to (1) small-amplitude surface ripples characterized by width L and amplitude A that are large relative to the energetic-ion gyroradius, and (2) shocks which are on average quasi-perpendicular. An investigation is made of the effects of the confinement, evolving geometry, and finite shock curvature associated with the ripple, by integrating along the orbits of the proton test particles. As an upstream magnetic field line convects through the surface ripple, it intersects the shock at two points, thereby forming a temporary magnetic trap. Flux-line profiles and angular distributions in a given ripple differ substantially, depending on the path it takes through the ripple and its distance from the shock.

Decker, R. B.↗
NASA NTRS2013

Faster Heavy Ion Transport for HZETRN

The deterministic particle transport code HZETRN was developed to enable fast and accurate space radiation transport through materials. As more complex transport solutions are implemented for neutrons, light ions (Z < 2), mesons, and leptons, it is important to maintain overall computational efficiency. In this work, the heavy ion (Z > 2) transport algorithm in HZETRN is reviewed, and a simple modification is shown to provide an approximate 5x decrease in execution time for galactic cosmic ray transport. Convergence tests and other comparisons are carried out to verify that numerical accuracy is maintained in the new algorithm.

Slaba, Tony C.↗
NASA NTRS1970

Dispersion discontinuities of strong collisionless shocks

Linear fluid equations are used to estimate wave train properties of strong collisionless shocks. Fast shocks exhibit several dispersion changes with increasing Mach number. For perpendicular propagation into a finite-beta plasma, an ion cyclotron radius trailing wave train exists only for (M sub F)2 is smaller than 2. Oblique fast shocks have a leading ion inertia wave train if M sub A is smaller than root of M(+)/M(-) cos theta/2 and a trailing electron inertia train if M sub A is greater than root of M(+)/M(-) cos theta/2. If the downstream sound speed exceeds the flow speed, linear wave theory predicts a trailing ion acoustic structure which probably resides within the magnetic shock. For a turbulent shock model in which an effective electron-ion collision frequency exceeds the lower hybrid frequency, ions decouple from the magnetic field; the shock wave train now trails with electron inertia and electron gyroradius lengths. Comparisons of this turbulent model and observations on the earth's bow shock are made.

Coroniti, F. V.↗
NASA NTRS1984

The ion cyclotron dispersion relation in a proton-alpha solar wind

Solutions to the WKB warm plasma dispersion relation are investigated for the case of a proton-alpha plasma, to determine when parallel ion cyclotron waves can propagate at the alpha particle gyrofrequency. Examples are given of the behavior of the dispersion curves in this resonant regime, for several types of plasma states that are appropriate to the fast solar wind. It is found that while ion cyclotron waves can propagate at the alpha particle gyrofrequency for a bounded set of plasma parameters, use of the correct dispersion relation will probably make resonant cyclotron acceleration of solar wind plasma particles less feasible as a mechanism for the generation of the observed preferential effects.

Isenberg, P. A.↗
NASA NTRS2001

Fast prototyping of high-aspect ratio, high-resolution x-ray masks by gas-assisted focused ion beam

The capacity of chemically-assisted focused ion beam (fib) etching systems to undertake direct and highly anisotropic erosion of thin and thick gold (or other high atomic number [Z])coatings on x-ray mask membranes/substrates provides new levels of precision, flexibility, simplification and rapidity in the manufacture of mask absorber patterns, allowing the fast prototyping of high aspect ratio, high-resolution masks for deep x-ray lithography.

fast prototyping of high-aspect ratio high-resolut↗
NASA NTRS1990

Radial diffusion of low-energy plasma ions in Saturn's magnetosphere

Radial diffusion of low-energy plasma ions in Saturn's magnetosphere is investigated using a comprehensive set of equations for radial diffusion that incorporate distributed sources and sinks of ions. The results of calculations indicate that the radial-diffusion transport of low-energy O(+) ions with a source in the neutral H2O cloud of the satellites Dione and Tethys can account for Voyager observations of thermal heavy ions in Saturn's magnetosphere. The source rate was calculated to be about 10 to the 26th O(+) ions/sec, in good agreement with the sputtering calculations of Johnson et al. (1989). It is estimated that, due to fast radial diffusion, the residence time of O(+) ions in the Dione-Tethys torus is about 30 days, sufficiently short to account for the plasma density observed there. The densities of hot H(+) and N(+) resulting from the ionization and pickup of Titan's neutral clouds in the outer magnetosphere can also be accounted for within the framework of diffusive ion transport.

Barbosa, D. D.↗
NASA NTRS2015

Improved Detection System Description and New Method for Accurate Calibration of Micro-Channel Plate Based Instruments and Its Use in the Fast Plasma Investigation on NASA's Magnetospheric MultiScale Mission

The Fast Plasma Investigation (FPI) on NASAs Magnetospheric MultiScale (MMS) mission employs 16 Dual Electron Spectrometers (DESs) and 16 Dual Ion Spectrometers (DISs) with 4 of each type on each of 4 spacecraft to enable fast (30 ms for electrons; 150 ms for ions) and spatially differentiated measurements of the full 3D particle velocity distributions. This approach presents a new and challenging aspect to the calibration and operation of these instruments on ground and in flight. The response uniformity, the reliability of their calibration and the approach to handling any temporal evolution of these calibrated characteristics all assume enhanced importance in this application, where we attempt to understand the meaning of particle distributions within the ion and electron diffusion regions of magnetically reconnecting plasmas. Traditionally, the micro-channel plate (MCP) based detection systems for electrostatic particle spectrometers have been calibrated using the plateau curve technique. In this, a fixed detection threshold is set. The detection system count rate is then measured as a function of MCP voltage to determine the MCP voltage that ensures the count rate has reached a constant value independent of further variation in the MCP voltage. This is achieved when most of the MCP pulse height distribution (PHD) is located at higher values (larger pulses) than the detection system discrimination threshold. This method is adequate in single-channel detection systems and in multi-channel detection systems with very low crosstalk between channels. However, in dense multi-channel systems, it can be inadequate. Furthermore, it fails to fully describe the behavior of the detection system and individually characterize each of its fundamental parameters. To improve this situation, we have developed a detailed phenomenological description of the detection system, its behavior and its signal, crosstalk and noise sources. Based on this, we have devised a new detection system calibration method that enables accurate and repeatable measurement and calibration of MCP gain, MCP efficiency, signal loss due to variation in gain and efficiency, crosstalk from effects both above and below the MCP, noise margin, and stability margin in one single measurement. More precise calibration is highly desirable as the instruments will produce higher quality raw data that will require less post-acquisition data correction using results from in-flight pitch angle distribution measurements and ground calibration measurements. The detection system description and the fundamental concepts of this new calibration method, named threshold scan, will be presented. It will be shown how to derive all the individual detection system parameters and how to choose the optimum detection system operating point. This new method has been successfully applied to achieve a highly accurate calibration of the DESs and DISs of the MMS mission. The practical application of the method will be presented together with the achieved calibration results and their significance. Finally, it will be shown that, with further detailed modeling, this method can be extended for use in flight to achieve and maintain a highly accurate detection system calibration across a large number of instruments during the mission.

detection system↗
NASA NTRS1988

Excitations of low-frequency hydromagnetic waves by freshly created ions in the solar wind

Low-frequency hydromagnetic waves excited by newborn ions in the solar wind plasma are studied. The freshly created ions appear in the solar wind frame with a ring beam distribution. Both Alfven and fast magnetosonic waves are made unstable by the presence of the newborn ions. The dependence of the growth rate of both waves on the newborn ion density, the angle between the interplanetary magnetic field (IMF) and solar wind flow, and the angle of wave propagation relative to the IMF is investigated. Analytic approximations for the growth rates are presented, and numerical solutions of the dispersion equation are shown. The approximations are quite close to the numerically determined growth rates. It is found that the waves grow preferentially in the direction parallel to the IMF, and that the growth rates increase with both newborn ion density and the angle between the IMF and the solar wind flow.

Price, C. P.↗
NASA NTRS1994

Studies for the loss of atomic and molecular species from Io

The general objective of this project is to advance theoretical understanding of Io's atmosphere and how various atomic and molecular species are lost from this atmosphere and are distributed in the circumplanetary environment of Jupiter. The major task for the University of Michigan portion of this work is the generalization of the Io sodium cloud model to simulate the ion-precursor of sodium that is the apparent source of the fast sodium jet observed by Schneider et al. (1991). The goal is a quantitative test of the molecular ion hypothesis with a model that is comparable to a general sodium cloud model published previously. A detailed comparison of observations with such a model will help to probe the feasibility of such a source and to examine the rates and scale lengths associated with the decay of the ion precursor so as to possibly uncover the identity of the parent ion. Another important task to be performed at Michigan is more support of AER in the general area of modeling the Na and SO2-family clouds.

Combi, Michael R.↗
NASA NTRS1980

Thermal iron ions in high speed solar wind streams Detection by the IMP 7/8 energetic particle experiments

The first measurements of the abundance of iron ions in high speed (greater than 600 km/s) solar wind streams have been made with the NOAA/JHU energetic particles experiments (EPE) on IMP 7/8. The identification of iron ions is quantitatively established using 4 years of observations and heavy ion accelerator calibrations of detectors similar to those flown on the spacecraft. Preliminary estimates of the Fe/H ratio are within a factor of 2 of the adopted coronal abundance (0.00005), and there is some evidence that Fe/H may remain approximately constant within a given stream. In the peaks of fast streams (700-800 km/s), about 50 iron ion counts are obtained every 20 s, offering the possibility of studying the Fe/H ratio with approximately 1 m time resolution in high speed streams throughout the decline of Solar Cycle 20 and the rise of Solar Cycle 21.

Mitchell, D. G.↗
NASA NTRS1972

Design, fabrication, assembly and delivery of a laboratory prototype of a residual gas analyzer

The design, development, and testing of a wide mass range residual gas analyzer which will be one component of an integrated real time contamination monitor system are described. The instrument has been developed and tested to the laboratory prototype phase, demonstrating the performance that can be expected from a flight instrument of similar design. The instrument's analyzer is of the quadrupole type and a cold cathode ion source is employed as the ionizer. The associated electronics supply all necessary operating and mass sweep voltages for the ionizer, analyzer and electron multiplier ion detector. The instrument features a very fast linear electrometer with automatic range changing. The full mass range of 2 to 300 amu is automatically and repetitively scanned every sixty seconds and suitable telemetry outputs are provided for intensity and mass identification as well as a digital identification of the electrometer range.

Kreisman, W. S.↗
NASA NTRS1984

Electron precipitation in solar flares - Collisionless effects

A large fraction of the electrons which are accelerated during the impulsive phase of solar flares stream towards the chromosphere and are unstable to the growth of plasma waves. The linear and nonlinear evolution of plasma waves as a function of time is analyzed with a set of rate equations that follows, in time, the nonlinearly coupled system of plasma waves-ion fluctuations. As an outcome of the fast transfer of wave energy from the beam to the ambient plasma, nonthermal electron tails are formed which can stabilize the anomalous Doppler resonance instability responsible for the pitch angle scattering of the beam electrons. The non-collisional losses of the precipitating electrons are estimated, and the observational implication of these results are discussed.

Vlahos, L.↗
NASA NTRS1995

The mean ionic charge state of solar energetic Fe ions above 200 MeV per nucleon

We have analyzed the geomagnetic transmission of solar energetic Fe ions at approximately 200-600 MeV per nucleon during the great solar energetic particle (SEP) events of 1989 September-October. By comparing fluences from the Chicago charged-particle telescope on IMP-8 in interplanetary space and from NRL's Heavy Ions in Space (HIIS) experiment aboard the Long Duration Exposure Facility (LDEF) in low-Earth orbit, we obtain a mean ionic charge (Q(sub 3)) = 14.2 +/- 1.4. This result is significantly lower than (Q) observed at approximately 1 MeV per nucleon in impulsive, He-3 rich SEP events, indicating that neither acceleration at the flare site nor flare-heated plasma significantly contributes to the high-energy Fe ions we observe. But it agrees well with the (Q) observed in gradual SEP events at approximately 1 MeV per nucleon, in which ions are accelerated by shocks driven by fast coronal mass ejections, and hence shows that particles are accelerated to very high energies in this way. We also note apparent differences between solar wind and SEP charge state distributions, which may favor a coronal (rather than solar wind) seed population or may suggest additional ionization in the ambient shock-region plasma.

Tylka, A. J.↗
NASA NTRS1996

Analysis of Supercritical-Extracted Chelated Metal Ions From Mixed Organic-Inorganic Samples

Organic and inorganic contaminants of an environmental sample are analyzed by the same GC-MS instrument by adding an oxidizing agent to the sample to oxidize metal or metal compounds to form metal ions. The metal ions are converted to chelate complexes and the chelate complexes are extracted into a supercritical fluid such as CO2. The metal chelate extract after flowing through a restrictor tube is directly injected into the ionization chamber of a mass spectrometer, preferably containing a refractory metal filament such as rhenium to fragment the complex to release metal ions which are detected. This provides a fast, economical method for the analysis of metal contaminants in a sample and can be automated. An organic extract of the sample in conventional or supercritical fluid solvents can be detected in the same mass spectrometer, preferably after separation in a supercritical fluid chromatograph.

Sinha, Mahadeva P.↗