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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

A case study of magnetotail current sheet disruption and diversion

On June 1, 1985 the AMPTE/CCE spacecraft (at a geocentric distance of about 8.8 earth radii at the midnight neutral sheet region) observed a dispersionless energetic particle injection and an increase in magnetic field magnitude, which are features commonly attributed to disruption of the near-earth cross-tail current sheet during substorm expansion onsets. An analysis based on high time-resolution measurements from the magnetometer and the energetic particle detector indicates that the current sheet disruption region exhibited localized (less than 1 earth radius) and transient (less than 1 min) particle intensity enhancements, accompanied by complex magnetic field changes with occasional development of a southward magnetic field component. Similar features are seen in other current disruption/diversion events observed by the CCE. The present analysis suggests that the current disruption region is quite turbulent, similar to laboratory experiments on current sheet disruption, with signatures unlike those expected from an X-type neutral line configuration. No clear indication of periodicity in any magnetic field parameter is discernible for this current disruption event.

Lui, A. T. Y.↗
NASA NTRS1981

Rocket experiments

Payloads designed to study the ionization and the ionizing sources (energetic particles) during periods of auroral activity are described. These include a probe experiment to measure the variation in electron concentration, to measure electron temperature, and to measure the vehicle potential; a propagation experiment to obtain the electron concentration and the electron collision frequency; and an energetic particle experiment to measure particle energy spectra.

Source record↗
NASA NTRS1978

Coronal propagation and storage at energies approximately 1 MeV/nucleon

Energetic particle events relating to quasi-stationary particle populations, solar flare events, and solar composition are discussed in the context of similar observations likely to be made during solar probe encounter. Particlar emphasis is given to interrelationships with coronal magnetic structure and plasma processes. General instrumental requirements are listed, and it is concluded that energetic particle detectors meeting these requirements will successfully complement other essential experiments on the Solar Probe.

Roelof, E. C.↗
NASA NTRS1992

Particle acceleration in the heliosphere

This review presents an overview of the various populations of energetic particles accelerated in the heliosphere: energetic storm particles. corotating ion events, upstream ions at Earth's bow shock, the cosmic ray anomalous component, and interstellar and cometary pickup ions. In each case the review presents or describes original and/or key observations, the current understanding of its origin, and its particular impact on theoretical progress.

Lee, Martin A.↗
NASA NTRS1986

Observations of shock acceleration processes in the solar wind

Substantial evidence was accumulated over more than two decades that ion acceleration occurs at all collisionless shocks sampled directly in the solar system. The various shock waves in the heliosphere and the associated energetic particle phenomena are shown schematically. Three shocks have attracted considerable attention in recent years: corotating shocks due to the interaction of fast and slow solar wind streams during solar minimum, travelling interplanetary shocks due to coronal mass ejections, and planetary bow shocks. The signatures of these shocks and of their energetic particles are briefly reviewed. The most prominent theoretical models for shock acceleration are also reviewed. Recent observations at the earth's bow shock and at quasi-parallel interplanetary shocks are discussed in detail.

Scholer, M.↗
NASA NTRS2014

Influence of Dust Loading on Atmospheric Ionizing Radiation on Mars

Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

Norman, Ryan B.↗
DOE OSTI2022

Description of global EGAM in the maximum of local frequency during current ramp-up discharges in DIII-D

Energetic-particle-induced geodesic acoustic modes, EGAMs (Fu, Phys. Rev. Let., vol. 101, 2008, pp. 185002), driven by neutral beam injection (NBI), have been observed in many DIII-D tokamak experiments (Nazikian et al., Phys. Rev. Lett., vol. 101, 2008, pp. 185001). This mechanism has been theoretically investigated in (Qiu et al., Plasma Phys. Control. Fusion, vol. 52, 2010, pp. 095003), using a sharp energetic particle distribution function, and in (Qu et al., Plasma Phys. Control. Fusion, vol. 59, 2017, pp. 055018), where the dispersion relation and eigenmode behaviour were obtained for the situation of early beam scenario, that is, for times smaller than the beam slowing down time. In this work, we extend these studies determining the eigenmode for beyond the slowing down time, in a scenario with reverse safety factor q profile, where a small concentration of energetic ions can produce an off-axis maximum in the GAM dispersion relation. Here, the characteristics of EGAM are analytically studied with the drift kinetic equation together with the MHD code NOVA. The toroidal energetic ion transit frequency, coupled with the GAM frequency, produces the maximum in the dispersion relation where the eigenmode can be found. The quantitative correspondence of experimental results with the predictions of the proposed model is analysed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Design workflow of a symmetric traveling wave antenna for fast ion production on DD tokamaks

Initial computational plasma physics scoping and a finite element method antenna modeling design workflow for a symmetric center-fed high-field side high harmonic fast wave traveling wave array (TWA) antenna are reported here. The TWA is designed to generate a test population of fast deuterium ions in an existing D–D tokamak by heating neutral beam deuterium ions, accelerating them from 80 keV to several hundred keV. The resulting fast particles are tailored to mimic key reactor energetic particle parameters with regards to exciting Alfven eigenmode instabilities, allowing for a D–D tokamak like DIII-D or ASDEX-U to replicate reactor-relevant conditions experimentally. Initial scenario scoping for high single-pass absorption as well as good preferential fast ion damping relative to electron damping was completed using the ray-tracing/Fokker–Planck codes GENRAY and CQL3D. Python RF network analysis packages were used to create a custom TWA optimization tool to inform a COMSOL flat antenna design, and Petra-M was used to study cold plasma effects. The TWA produced by this workflow has several novel features when compared to previous TWA studies, including symmetric center feeding, and passive end straps for image current cancellation for reduced impurity production. We show here that the antenna design workflow can readily produce TWA antennas optimized for reflection coefficient, image current cancellation, and launched power spectrum shape; and that a population of fast ions can be generated in the correct region of parameter space, warranting future more detailed studies.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1978

Radiation damage of germanium detectors

Energetic particles can produce interstitial-vacancy pairs in a crystal by knocking the atoms from their normal positions. Detectors are unique among semiconductor devices in depending on very low concentrations of electrically active impurities, and also on efficient transport of holes and electrons over relatively large distances. Because the dense regions of damage produced by energetic particles may result in donors and/or acceptors, and also provide trapping sites for holes and electrons, detectors are very sensitive to radiation damage. In addition to these effects occurring within the detector, radiation may also change the characteristics of the exposed surfaces causing unpredictable effects on the detector leakage current. Radiation-induced surface degradation has rarely, if ever, been observed for germanium detectors. The possibility of minimizing hole trapping in charge collection by the use of a high-purity germanium coaxial detector configured with the p (+) contact on the coaxial periphery is discussed.

Pehl, R. H.↗
NASA NTRS1976

A review of the Jovian magnetosphere based upon Pioneer 10 and 11

A review and analysis are presented of data derived from the Pioneer 10 and Pioneer 11 flybys of Jupiter on the Jovian plasma, magnetic field, and energetic particles in circumjovian space. The design of the space probes is described along with the principal experiments flown. Overall features of the Jovian magnetosphere are drawn and contrasted with the earth's magnetosphere. The trajectories of the two space probes are contrasted and their data on Jupiter's plasmasphere are correlated. Isointensity contours and count rates of energetic particles are plotted, flux tubes within the Jovian magnetosphere are mapped, the ring current (plasma torus) encircling the planet is described, and possible effects of solar wind and of the moons immersed in Jupiter's magnetosphere are considered.

Trainor, J. H.↗
NASA NTRS1990

Rocket studies of the lower ionosphere

The earth's ionosphere in the altitude range of 50 to 200 km was investigated by rocket-borne sensors, supplemented by ground-based measurement. The rocket payloads included mass spectrometers, energetic particle detectors, Langmuir probes and radio propagation experiments. Where possible, rocket flights were included in studies of specific phenomena, and the availability of data from other experiments greatly increased the significance of the results. The principal ionospheric phenomena studied were: winter anomaly in radiowave absorption, ozone and molecular oxygen densities, mid-latitude sporadic-E layers, energetic particle precipitation at middle and low latitudes, ionospheric instabilities and turbulence, and solar eclipse effects in the D and E regions. This document lists personnel who worked on the project, and provides a bibliography of resultant publications.

Bowhill, Sidney A.↗
NASA NTRS1991

Near-Mars space

The prevalent attributes of near-Mars space are described: the ambient interplanetary environment, the ionosphere, the upper atmosphere, and more remote regions that are affected by the presence of Mars. The descriptions are based on existing Martian data and/or models constructed from measurements made near Venus. Specific attention is given to the features of solar wind interaction with magnetospheric and ionospheric obstacles. The high-altitude plasma and field environment, the energetic particle environment, the ionosphere environment, and the neutral upper atmosphere environment are described with extensive graphic information, based on existing measurements collected from nine Martian missions. The ionospheric obstacle is assumed to prevail as a mechanism for describing the scenario. Martian perturbation of solar wind is theorized to be of a relatively small order. A distinctive local energetic particle population of planetary origin is shown to result from the direct interaction of solar wind plasma. This phenomenon is considered evidence of the important scavenging of planetary elements from Mars. The absence of a planetary dipole field around Mars, like its low gravity and distance from the sun, is considered important in determining the environment of this earthlike laboratory.

Luhmann, J. G.↗
NASA NTRS1986

Interplanetary shocks preceded by solar filament eruptions

The solar and interplanetary characteristics of six interplanetary shock and energetic particle events associated with the eruptions of solar filaments lying outside active regions are discussed. The events are characterized by the familiar double-ribbon H-alpha brightenings observed with large flares, but only very weak soft X-ray and microwave bursts. Both impulsive phases and metric type II bursts are absent in all six events. The energetic particles observed near the earth appear to be accelerated predominantly in the interplanetary shocks. The interplanetary shock speeds are lower and the longitudinal extents considerably less than those of flare-associated shocks. Three of the events were associated with unusual enhancements of singly-ionized helium in the solar wind following the shocks. These enhancements appear to be direct detections of the cool filament material expelled from the corona. It is suggested that these events are part of a spectrum of solar eruptive events which include both weaker events and the large flares. Despite their unimpressive and unreported solar signatures, the quiescent filament eruptions can result in substantial space and geophysical disturbances.

Cane, H. V.↗
NASA NTRS2019

Full Inversion of Solar Relativistic Electron Events Measured by the Helios Spacecraft

The Parker Solar Probe and the incoming Solar Orbiter mission will provide measurements of solar energetic particle (SEP) events at close heliocentric distances from the Sun. Up to present, the largest data set of SEP events in the inner heliosphere are the observations by the two Helios spacecraft. Aims.We re-visit a sample of 15 solar relativistic electron events measured by the Helios mission with the goal of better characterizing the injection histories of solar energetic particles and their interplanetary transport conditions at heliocentric distances <1AU. Methods. The measurements provided by the E6 instrument on board Helios provide us with the electron directional distributionsin eight di erent sectors that we use to infer the detailed evolution of the electron pitch-angle distributions. The results of a Monte Carlo interplanetary transport model, combined with a full inversion procedure, were used to fit the observed directional intensities in the 300–800 keV nominal energy channel. Unlike previous studies, we have considered both the energy and angular responses of the detector. This method allowed us to infer the electron release time profile at the source and determine the electron interplanetary transport conditions. Results. We discuss the duration of the release time profiles and the values of the radial mean free path, and compare them with thevalues reported previously in the literature using earlier approaches. Five of the events show short injection histories (<30 min) at the Sun and ten events show long-lasting (>30 min) injections. The values of mean free path range from 0.02AU to 0.27AU.Conclusions. The inferred injection histories match with the radio and soft X-ray emissions found in literature.We find no dependence of the radial mean free path on the radial distance. In addition, we find no apparent relation between the strength of interplanetary scattering and the size of the solar particle release.

Pacheco, D.↗
NASA NTRS1995

Cosmic ray decreases and solar wind disturbances during late October 1989

We describe the interplanetary phenomena (energetic particles, solar wind plasma, and magnetic field) seen at Interplanetary Monitoring Platform 8 (IMP 8) and at International Cometary Explorer (ICE), located 65 deg west of IMP 8, during the period October 19-31, 1989, when neutron monitors observed three ground level events originating in one active region when it was in the longitude range E09 deg to W57 deg. At least four shocks, associated with energetic particle enhancements, which can be attributed to a sequence of coronal mass ejections from the same active region, were seen at both spacecraft. An additional shock was observed only at ICE late in this period when the active region was behind the west limb. Considering all the data (which unfortunately suffer from large gaps), it appears that the ejecta associated with the shocks were detected only when the spacecraft and solar source longitude were separated by less than 50 deg. The shocks extended over a greater range of longitudes. The cosmic ray record at Earth is consistent with this picture such that only the first two shock-associated cosmic ray decreases had the signature expected for intercepting ejecta material. This same time period was also examined by Bavassano et al. (1994). However, we do not agree with their conclusion that 'magnetic clouds' extending at least 75 deg from the source longitude were present.

Cane, H. V.↗
DOE OSTI2022

Hybrid-gyrokinetic simulations of low- n toroidal Alfvén eigenmodes using gKPSP

Here, we report a benchmark study of toroidal Alfvén eigenmode (TAE) simulation using the hybrid-gyrokinetic code GyroKinetic Plasma Simulation Program (gKPSP). A simulation capability for energetic particles based on the gyrokinetic δf method has been newly implemented in the gKPSP code. Benchmark simulations have been performed in both circular and realistic tokamak geometries. Good agreement has been found with previously reported results, demonstrating the new capability of the gKPSP code. We have investigated the effects of the distribution function on TAE stability by examining both isotropic and anisotropic slowing-down distributions of energetic particles. The slowing-down distribution produces a higher linear growth rate than a Maxwellian distribution, while a growth rate scan with the anisotropy shows an opposite trend. This can be attributed to competition between Landau damping and the linear drive, which are correlated with the fraction of resonant passing particles and their distribution in phase space.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Modeling of the ECCD injection effect on the Heliotron J and LHD plasma stability

The aim of the study is to analyze the stability of the energetic particle modes (EPM) and Alfven Eigenmodes (AE) in Helitron J and LHD plasma if the electron cyclotron current drive (ECCD) is applied. Additionally, the analysis is performed using the code FAR3d that solves the reduced MHD equations describing the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moments for the energetic particle (EP) species, including the effect of the acoustic modes. The Landau damping and resonant destabilization effects are added via the closure relation. The simulation results show that the n = 1 EPM and n = 2 global AE (GAE) in Heliotron J plasma can be stabilized if the magnetic shear is enhanced at the plasma periphery by an increase (co-ECCD injection) or decrease (ctr-ECCD injection) of the rotational transform at the magnetic axis ($\rlap{-} \iota_{0}$). In the ctr-ECCD simulations, the EPM/AE growth rate decreases only below a given $\rlap{-} \iota_{0}$, similar to the ECCD intensity threshold observed in the experiments. In addition, ctr-ECCD simulations show an enhancement of the continuum damping. The simulations of the LHD discharges with ctr-ECCD injection indicate the stabilization of the n = 1 EPM, n = 2 toroidal AE (TAE) and n = 3 TAE, caused by an enhancement of the continuum damping in the inner plasma leading to a higher EP β threshold with respect to the co- and no-ECCD simulations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1973

Solar radio bursts at kilometer wavelengths

The potential value of traveling solar radio bursts for investigating energetic particle propagation, and for probing the interplanetary medium is discussed. A general survey of the characteristics of type 3 radio phenomena observed at hectometer and kilometer wavelengths is presented along with a brief discussion of the relationships among type 1 meter noise storms, decametric continuum, and type 3 hectometric storms. Type 3 bursts are analyzed to show how these data provide information about the average energy, dispersion, and trajectory of energetic particles, the interplanetary scale, and magnetic field configuration. The recent observations of type 2 shock wave phenomena at kilometer wavelengths are described, and current research and the direction of future observation are outlined.

Stone, R. G.↗