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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Survey of He(+)/He(2+) abundance ratios in energetic particle events

The helium charge distribution in the energy range 0.4 to 0.62 MeV/nucleon in energetic particle events was studied. An average He+/He2+ ratio of 0.12 + or - 0.04 with ratios exceeding 0.3 for 41 out of 420 days events richest in He+ and no significant differences of the proton energy spectra, and the abundance of helium relative to protons and heavy ions for He+ rich events (He+/He2+ 0.3) and for events with He+/He2+ 0.3, respectively. It is also found that He+ rich events are predominantly low in energetic particle intensity.

Hovestadt, D.↗
NASA NTRS1999

CUSP Energetic Particles: Confinement, Acceleration and Implications

The cusp energetic particle (CEP) event is a new magnetospheric phenomenon. The events were detected in the dayside cusp for hours, in which the measured helium ions had energies up to 8 MeV. All of these events were associated with a dramatic decrease and large fluctuations in the local magnetic field strength. During January 1999 - December 1999 covered by this report, I have studied the CEP events by analyzing the POLAR, GEOTAIL, and WIND particle and magnetic field data measured during the geomagnetic quiet periods in 1996 and one geomagnetic storm period in 1998. The simultaneous observations indicated that the ion fluxes in the CEP events were higher than that in both the upstream and the downstream from the bow shock. The pitch angle distribution of the helium ions in the CEP events was found to peak around 90 deg. It was found that the mirror parameter, defined as the ratio of the square root of the integration of the parallel turbulent power spectral component over the ultra-low frequency (ULF) ranges to the mean field in the cusp, is correlated with the intensity of the cusp MeV helium flux, which is a measure of the influence of mirroring interactions and an indication of local effect. It was also found that the turbulent power of the local magnetic field in the ultra-low frequency (ULF) ranges is correlated with the intensity of the cusp energetic helium ions. Such ULF ranges correspond to periods of about 0.33-500 seconds that cover the gyroperiods, the bounce periods, and the drift periods of the tens keV to MeV charged particles when they are temporarily confined in the high-altitude dayside cusp. These observations represent a discovery that the high-altitude dayside cusp is a new acceleration and dynamic trapping region of the magnetosphere. The cusp geometry is connected via gradient and curvature drift of these energized ions to the equatorial plasma sheet as close as the geostationary orbit at local midnight. It implies that the dayside cusp is potentially an important source of magnetospheric particles. The discovery of the CEP events has been recognized as one of the most significant results from POLAR. I was invited to give a talk at 1999 IUGG meeting to interpret the CEP events. This discovery has also been written into the web-based Space Physics Text Book (http://www.oulu.fi/- spaceweb/textbook/cusp.html).

Chen, Jiasheng↗
NASA NTRS2021

Comparative Analysis of the 2020 November 29 Solar Energetic Particle Event Observed by Parker Solar Probe

We analyze two specific features of the intense solar energetic particle (SEP) event observed by Parker Solar Probe (PSP) between 2020 November 29 and 2020 December 2. The interplanetary counterpart of the coronal mass ejection (CME) on 2020 November 29 that generated the SEP event (hereafter ICME-2) arrived at PSP (located at 0.8 au from the Sun) on 2020 December 1. ICME-225 was preceded by the passage of an interplanetary shock at 18:35 UT on 2020 November 30 (hereafter26S2), that in turn was preceded by another ICME (i.e., ICME-1) observed in situ on 2020 November 30. The two interesting features of this SEP event at PSP are: First, the presence of the intervening ICME-1 affected the evolution of the.8 MeV proton intensity time profiles resulting in the observation of inverted energy spectra throughout the passage of ICME-1. Second, the sheath region preceding ICME-2 was characterized by weak magnetic fields compared to those measured immediately after the passage of the shock S2 and during the passage of ICME-2. Comparison with prior SEP events measured at 1 au but with similar characteristics indicates that (1) low-energy particles accelerated by S2 were excluded from propagating throughout ICME-1, and (2) the low magnetic fields measured in the sheath of ICME-2 resulted from the properties of the upstream solar wind encountered by ICME-2 that was propagated into the sheath; whereas the high energetic particle energy density in the sheath did not play a dominant role in the formation of these low magnetic fields.

D Lario↗
NASA NTRS1986

Manned Mars mission solar physics: Solar energetic particle prediction and warning

There are specific risks to the crew of the manned Mars mission from energetic particles generated by solar activity. Therefore, mission planning must provide for solar monitoring and solar activity forecasts. The main need is to be able to anticipate the energetic particle events associated with some solar flares and, occasionally, with erupting filaments. A second need may be for forecasts of solar interference with radio communication between the manned Mars mission (during any of its three phases) and Earth. These two tasks are compatible with a small solar observatory that would be used during the transit and orbital phases of the mission. Images of the Sun would be made several times per hour and, together with a solar X-ray detector, used to monitor for the occurrence of solar activity. The data would also provide a basis for research studies of the interplanetary medium utilizing observations covering more of the surface of the Sun than just the portion facing Earth.

Suess, S. T.↗
NASA NTRS1979

Prediction of energetic particle disturbances

The prediction of fluxes of energetic particles of solar or magnetospheric origin is addressed. Topics include the prediction of the properties of the particle populations generated by magnetospheric storms and substorms, and the prediction of long term variations in the populations of magnetospheric particles.

Paulikas, G. A.↗
NASA NTRS1982

An improved pulse-height analyzer for energetic particle measurements in the upper atmosphere

An energetic particle spectrometer for measurements in the upper atmosphere by rocket is described. The system has two methods of processing data. One is a staircase generator using threshold detectors; the other is a peak detector. The system incorporates a logarithmic converter for better resolution at low amplitudes and better use of telemetry channels. The circuits are described and calibration procedures are given. Modifications are recommended for high flux environments. Appendices cover sampling error in the peak detector and modifications made to the receiver of the propagation experiment.

Dean, L.↗
NASA NTRS1983

The delayed energetic particle event of June 6-10, 1979

Energetic particle observations carried out with the ISEE-3 Medium-Energy Cosmic Ray experiment during the flare event of June 6-10, 1979 are reported. An expanded time history of the He nuclei particle spectra is given, and particle trajectory angles are identified with respect to the earth-sun line. The backward flow of the particle stream following the shock was analyzed, and it is found that the shock continued to accelerate particles beyond 1 AU from the sun. Polar plots of the number of protons counted in each sector of observation are given with their corresponding magnetic field directions.

Von Rosenvinge, T. T.↗
NASA NTRS1996

Solar energetic particle events: Statistical modelling and prediction

Solar energetic particle events (SEPEs) can have a significant effect on the design and operation of earth orbiting and interplanetary spacecraft. In relation to this, the calculation of proton fluences and fluxes are considered, describing the current state of the art in statistical modeling. A statistical model that can be used for the estimation of integrated proton fluences for different mission durations of greater than one year is reviewed. The gaps in the modeling capabilities of the SEPE environment, such as a proton flux model, alpha particle and heavy ion models and solar cycle variations are described together with the prospects for the prediction of events using neural networks.

Gabriel, S. B.↗
NASA NTRS2003

Solar Energetic Particle Variations

In the largest solar energetic-particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). In fact, the highest proton intensities directly measured near Earth at energies up to approximately 1 GeV occur at the time of passage of shocks, which arrive about a day after the CMEs leave the Sun. CME-driven shocks expanding across magnetic fields can fill over half of the heliosphere with SEPs. Proton-generated Alfven waves trap particles near the shock for efficient acceleration but also throttle the intensities at Earth to the streaming limit early in the events. At high energies, particles begin to leak from the shock and the spectrum rolls downward to form an energy-spectral 'knee' that can vary in energy from approximately 1 MeV to approximately 1 GeV in different events. All of these factors affect the radiation dose as a function of depth and latitude in the Earth's atmosphere and the risk to astronauts and equipment in space. SEP ionization of the polar atmosphere produces nitrates that precipitate to become trapped in the polar ice. Observations of nitrate deposits in ice cores reveal individual large SEP events and extend back approximately 400 years. Unlike sunspots, SEP events follow the approximately 80-100-year Gleissberg cycle rather faithfully and are now at a minimum in that cycle. The largest SEP event in the last 400 years appears to be related to the flare observed by Carrington in 1859, but the probability of SEP events with such large fluences falls off sharply because of the streaming limit.

Reames, D. V.↗
NASA NTRS2011

STEREO Observations of Solar Energetic Particles

We report on observations of Solar Energetic Particle (SEP) events as observed by instruments on the STEREO Ahead and Behind spacecraft and on the ACE spacecraft. We will show observations of an electron event observed by the STEREO Ahead spacecraft on June 12, 2010 located at W74 essentially simultaneously with electrons seen at STEREO Behind at E70. Some similar events observed by Helios were ascribed to fast electron propagation in longitude close to the sun. We will look for independent verification of this possibility. We will also show observations of what appears to be a single proton event with very similar time-history profiles at both of the STEREO spacecraft at a similar wide separation. This is unexpected. We will attempt to understand all of these events in terms of corresponding CME and radio burst observations.

vonRosenvinge, Tycho↗
NASA NTRS2017

Modeling Solar Energetic Particle Events Using ENLIL Heliosphere Simulations

Solar energetic particle (SEP) event modeling (SEPMOD) has gained renewed attention in part because of the availability of a decade of multipoint measurements from STEREO (Solar TErrestrial RElations Observatory) and L1 (Lagrangian point 1) spacecraft at 1 AU (Astronomical Unit). These observations are coupled with improving simulations of the geometry and strength of heliospheric shocks obtained by using coronagraph images to send erupted material into realistic solar wind backgrounds. The STEREO and ACE (Aerosol, Cloud systems, ocean Ecosystems) measurements in particular have highlighted the sometimes surprisingly widespread nature of SEP events. It is thus an opportune time for testing SEP models, which typically focus on protons approximately 1-100 megaelectronvolts, toward both physical insight to these observations and potentially useful space radiation environment forecasting tools. Some approaches emphasize the concept of particle acceleration and propagation from close to the Sun, while others emphasize the local field line connection to a traveling, evolving shock source. Among the latter is the previously introduced SEPMOD treatment, based on the widely accessible and well-exercised WSA-ENLIL (Wang-Sheeley-Arge-ENLIL)-cone model. SEPMOD produces SEP proton time profiles at any location within the ENLIL domain. Here we demonstrate a SEPMOD version that accommodates multiple, concurrent shock sources occurring over periods of several weeks. The results illustrate the importance of considering longer-duration time periods and multiple CME (Coronal Mass Ejection) contributions in analyzing, modeling, and forecasting SEP events.

Luhmann, J. G.↗
NASA NTRS1984

Association between energetic particle bursts and Birkeland currents in the geomagnetic tail

IMP 8 observations in the geomagnetic tail of energetic particles at hundreds of keV and of the magnetic field are examined for a substorm period from 1700 to 1800 UT on Mar. 3, 1976. For this interval, it is found that bursts of energetic protons detected at a downstream distance of about 37 earth radii in the midnight tail region are accompanied by east-west magnetic field perturbations indicative of Birkeland current sheets. The magnitude of the magnetic field perturbations range from about 1 to 12 nT, corresponding to current densities of 1 to 9 mA/m when integrated over the current sheet thickness. These values are comparable to previous observations of Birkeland currents in the near-earth tail (X greater than -20 earth radii) and with the auroral-arc-associated Birkeland current densities at low altitudes scaled out to the tail region. The favorable comparison suggests that the closure of small-scale Birkeland current systems, at least in these instances, lies tailward of about 40 earth radii. The observed Birkeland current system and the magnitude of current densities are found to be consistent with ion tearing instability in the tail. The inferred wavelength of the tearing mode along the tail axis is about 2 to 17 earth radii. In the context of the tearing model, the presence of Birkeland currents and the occasional isotropic distribution of energetic electrons (of more than 0.22 MeV) suggest that the energetic particle events in this study occur on closed magnetic field lines, even though strong tailward streaming dominates the particle anisotropy in these events.

Lui, A. T. Y.↗
NASA NTRS1976

Location of the source of magnetospheric energetic particle bursts by multispacecraft observations

During a magnetic substorm on Oct. 16, 1973 a number of magnetospheric bursts of energetic particles were observed simultaneously by IMP-6 and IMP-7 in the magnetotail. Detailed anisotropy measurements of 210 and 290 keV protons provide for the first time an indication of the location of the source of the energetic magnetospheric particles as well as evidence for its movement with speeds from 30 to more than 80 km/sec, in association with the intensification of the westward auroral electrojet during a magnetic bay at the station closest to the local time of the spacecraft (also local midnight). The observations indicate that energetic particles are accelerated to greater than 1.85 MeV in a moving and localized region in the geomagnetotail.

Sarris, E. T.↗
NASA NTRS2022

Impulsive Solar Energetic Particle Events: Extreme-Ultraviolet Waves and Jets

Impulsive solar energetic particle (ISEP) events show peculiar elemental composition, with enhanced 3 He and heavy-ion abundances, markedly different from our Solar System composition. Furthermore, the events are characterized by a wide variety of energy spectral shapes from power laws to rounded spectra toward the low energies. Solar sources of the events have been firmly associated with coronal jets. Surprisingly, new observations have shown that events are often accompanied by so-called extremeultraviolet (EUV) coronal waves–a large-scale phenomenon compared to jets. This paper outlines the current understanding of the linkage of EUV waves with jets and energetic ions in ISEP events.

solar energetic particles↗
NASA NTRS1989

On the relationship between the energetic particle flux morphology and the change in the magnetic field magnitude during substorms

The relationship between the morphology of energetic particle substorm injections and the change in the magnetic field magnitude over the course of the event is examined. Using the statistical relationships between the magnetic field during the growth phase and the change in the field magnitude during substorms calculated by Lopez et al. (1988), a limited number of dispersionless ion injections observed by AMPTE CCE are selected. It is argued that this limited set is representative of a large set of events and that the conclusions drawn from examining those events are valid for substorms in general in the inner magnetosphere. It is demonstrated that in an event when CCE directly observed the disruption of the current sheet, the particle and field data show that the region of particle acceleration was highly turbulent and was temporally, and perhaps spatially, limited and that the high fluxes of energetic particles are qualitatively associated with intense inductive electric fields.

Lopez, R. E.↗
DOE OSTI2021

Nonlinear dynamics and transport driven by energetic particle instabilities using a gyro-Landau closure model *

Abstract Energetic particle (EP) destabilized Alfvén eigenmode (AE) instabilities are simulated for a DIII-D experimental case with a pulsed neutral beam using a gyro-Landau moments model which introduces EP phase-mixing effects through closure relations. This provides a computationally efficient reduced model which is applied here in the nonlinear regime over timescales that would be difficult to address with more complete models. The long timescale nonlinear evolution and related collective transport losses are examined including the effects of zonal flow/current generation, nonlinear energy cascades, and EP profile flattening. The model predicts frequencies and mode structures that are consistent with experimental observations. These calculations address issues that have not been considered in previous modelling: the EP critical gradient profile evolution in the presence of zonal flows/currents, and the dynamical nature of the saturated state. A strong level of intermittency is present in the predicted instability-driven transport; this is connected to the zonal flow growth and decay cycles and nonlinear energy transfers. Simulation of intermittent AE-enhanced EP transport will be an important issue for the protection of plasma facing components in the next generation of fusion devices.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1987

Solar energetic particles events observed by Prognoz-10 Intercosmos (May-October 1985)

On 26 April 1985, Intershock began observation of a solar energetic particle (SEP) event, resulting from a 3B solar flare which originated on 24 April. The following observation period was quiet with only a few weak increases of low-energy protons of several days duration. Two prominent SEP events occurred on 9 July 1985 (start 0133 UT, position S13, W25) and 17 July (no optical data, type II radio burst from 0333 to 0348 UT). These mass ejection and particle propagation episodes were studied on the basis of X-ray, radio, and energetic particle emissions.

Lutserko, V.↗