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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 109 records · Page 6
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 NTRS1984

Abundances and spectra of superathermal H(+), He(++) and heavy ions in a fast moving plasma structure (plasmoid) in the distant geotail

An ISEE-3 Geotail Mission sensor has furnished data on a 16-min particle intensity increase in the distant magnetotail from which rest frame distribution functions have been deduced for 3-150 keV/amu H(+), He(++), and ions with a charge state greater than 3. The event was characterized by isotropic electron distributions and is identified as a tailward-moving plasmoid. These suprathermal ions are convected nearly tailward at an average speed of 1000 + or - 50 km/sec and have an energy density of 150 eV/cu cm. A crosstail expansion speed of about 80 km/sec is indicated.

Gloeckler, G.↗
NASA NTRS1984

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

First results of a systematic study of the helium ionic charge distribution in the energy range 0.4-0.62 MeV per nucleon in energetic particle events are reported. Large fluctuations of the He(+)/He(2+) ratios are found, especially at low interplanetary particle fluxes. The ratios exceeded a value of 0.3 for 41 days and a value of 1.0 for 11 days out of the 216 days analyzed. The median of the distribution is He(+)/He(2+) = 0.11. No obvious association with optical flare events could be observed for the events richest in He(+). No significant differences were found between the proton energy spectra and the elemental abundances of helium relative to hydrogen and heavy ions for He(+)-rich events versus events low in He(+). However, it has been found that generally He(+)-rich events are predominantly low in energetic particle intensity.

Hovestadt, D.↗
NASA NTRS1985

Channeled propagation of solar particles

Bartley (1966) and McCracken and Ness (1966) identified bundles of interplanetary magnetic field (IMF) lines that differed in direction from the interplanetary field lines in which they were imbedded. These bundles, called filaments differed in direction by as much as several tens of degrees from the surrounding field. The filaments werre first noticed due to the large and sudden change in flow direction of highly anisotropic solar flare protons in the energy range 1 to 13 MeV. Passage of the filaments over the spacecraft required a few hours, implying a diameter for the filaments of approximately 3 x 10 to the 6th power km at a distance of 1 AU from the Sun. In 1968, Jakipii and Parker used Leighton's hypothesis of random walk of magnetic field lines associated with granules and supergranules (1964) to develop a picture of an interplanetary medium composed of a tangle of field lines frozen into the solar wind, but whose feet were carried about by the random motions at the solar surface. Jakipii and Parker noted that using a correlation length of 15,000 km - about the radius of a supergranule - the magnetic structure would be 3 x 10 to the 6th power km in size of the filaments as determined by Bartley and McCracken and Ness. These workers did not find changes in the solar particle intensity, anisotropy ratio or energy spectrum as the spacecraft entered the filament.

Anderson, K. A.↗
NASA NTRS1985

Penetration of solar protons into the Earth's magnetosphere on November 22, 1977

The low polar-orbiting Cosmos-900 satellite carried a large geometric factor Cerenkov counter to study the particle anisotropy and spectrum near the proton increase peak in solar cosmic rays. The data help understand different temporal behavior of the increases detected at the stations because the whole set of data showed that the angular distribution of solar cosmic ray particles in interplanetary space was narrow throughout the observation time, resulting in a rapid variation of particle intensity near the poles. The power-law index of the solar cosmic ray integral spectrum varied from -2.4 to -5.2 in the 1 to 4 GV rigidity range from 10.31 to 11.25 UT on November 22, 1977. The flare-time data from all orbits indicate an increased radiation intensity on L=3.5 to 4.0.

Gorchakov, E. V.↗
NASA NTRS1987

Statistical analysis of secondary particle distributions in relativistic nucleus-nucleus collisions

The use is described of several statistical techniques to characterize structure in the angular distributions of secondary particles from nucleus-nucleus collisions in the energy range 24 to 61 GeV/nucleon. The objective of this work was to determine whether there are correlations between emitted particle intensity and angle that may be used to support the existence of the quark gluon plasma. The techniques include chi-square null hypothesis tests, the method of discrete Fourier transform analysis, and fluctuation analysis. We have also used the method of composite unit vectors to test for azimuthal asymmetry in a data set of 63 JACEE-3 events. Each method is presented in a manner that provides the reader with some practical detail regarding its application. Of those events with relatively high statistics, Fe approaches 0 at 55 GeV/nucleon was found to possess an azimuthal distribution with a highly non-random structure. No evidence of non-statistical fluctuations was found in the pseudo-rapidity distributions of the events studied. It is seen that the most effective application of these methods relies upon the availability of many events or single events that possess very high multiplicities.

Mcguire, Stephen C.↗
NASA NTRS1986

The recovery phase of galactic cosmic ray modulation in the outer heliosphere

Energetic hydrogen and helium nuclei from the galaxy (cosmic rays) enter the solar system with varying degrees of difficulty during the 11-year solar magnetic cycle, resulting in spatial and temporal variations of particle intensities in the heliosophere. Observations of these variations from the ISEE-3, Voyager 1 and 2, and Pioneer 10 spacecraft during the period from early 1981 to early 1986 and for heliocentric distances ranging from 1 to 37 AU are reported. During this time the high energy intensities in the outer heliosphere have been increasing exponentially at a rate of approximately 20 percent/year with occasional interruptions due to enhanced solar activity. The radial intensity gradients measured in the ecliptic plane are observed to remain constant or to decrease at the time of the reversal of the solar magnetic poles in 1980.

Mcdonald, F. B.↗
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 NTRS1988

Observations of a gradual transition between Ps 6 activity with auroral torches and surgelike pulsations during strong geomagnetic disturbances

This paper describes a long-lasting large-amplitude pulsation event, which occurred on January 10, 1983 in the ionosphere and magnetosphere and was characterized by Steen and Rees (1983). Over the 4-h period (0200-0600 UT), the characteristics of the pulsations in the ionosphere changed from being Ps 6 auroral torches toward substorms and back to Ps 6. At GEO, the corresponding characteristics were a modulation of the high-energy particle intensity and plasma dropouts. Based on the ideas presented by Rostoker and Samson (1984), an interpretation of the event is offered, according to which the pulsations are caused by the Kelvin-Helmholtz instability during an interval of strong magnetospheric convection. On the basis of this explanation, a new interpretation of the substorm time sequence is proposed.

Steen, A.↗
NASA NTRS1994

Diffusive shock acceleration in the presence of current sheets

We study the nature of diffusive shock acceleration in the presence of current sheets which are oriented normal to the shock, so that the drift along the sheets carries particles either away from or toward the shock plane. We consider a system with periodic regions of alternating magnetic field direction. This can be taken to be a very crude representation of the termination of the solar wind, with the equator being one sheet and the pole, with its rapid opposite drift, being another. We find very important effects of the current sheets. For example, particle intensities at the shock will be enhanced near one sheet and depressed at the other. Furthermore, the intensity at high energies (averaged over the shock plane) may in fact be considerably larger than in the standard one-dimensional infinite shock case. Implications of these results for the possible acceleration of cosmic electrons up to high energies at the solar-wind termination shock will briefly be discussed.

Kota, J.↗
NASA NTRS2002

The Living With a Star CDAW on the Solar and Geospace Connections of Solar Energetic Particles

The Living With a Star Program is sponsoring its first CDAW (Coordinated Data Analysis Workshop) to be held July 23-26, 2002 at a conference support location near the NASA Goddard Space Flight Center. This CDAW's topic is Solar Energetic Particle events. The topic was chosen due to the breadth of the impact of SEP's on the space environment and terrestrial climate. General goals of the LWS CDAW are a) Stimulate LWS Science on the near term, b) Facilitate cross-disciplinary interaction between the LWS scientific and space environment communities, c) Produce science products for all potential users, and d) Assist in the development of the LWS data system. The workshop will proceed similar to a previous CDAW held in 1999 on Interplanetary Type 11 Shocks. A list of target events has been compiled, which can be found at the workshop home page. The page lists all of the SEP events from 1996 January to 2001 December with energy > 10 MeV particle intensities exceeding 10 PFU. Preparation for the workshop consists of identifying relevant data from a wide variety of sources (solar, interplanetary, magnetospheric and climatary), accumulating the data (frequently this consists of both raw data, processed data and plots to ease perusal during the workshop) and gathering the software tools. Participants in the workshop are expected to complete their contributions of data or models prior to arriving at the workshop. Most of the CDAW consists of joint analysis of this data; only a few introductory talks are given at the beginning of the workshop, with the rest of the time being devoted to producing scientific results. Additional symposia may be scheduled at a later date, which will allow a venue for scientific talks on the CDAW results and associated science. The poster will list the scientific goals of the workshop, as well as a scientific discussion of the data which has been accumulated thus far.

Thompson, Barbara J.↗
NASA NTRS2008

CME Initiation

One of the most challenging problems in solar physics is understanding the processes responsible for giant magnetic disruptions such as the event of July 14, 2000, which consisted of a massive filament ejection, a fast coronal mass ejection (CME), prolonged X-class flaring, and an intense particle storm. These major events are of critical importance because they drive the most destructive forms of space weather and they provide a unique opportunity to study, in revealing detail, MHD instability and nonequilibrium -- processes that are at the heart of plasma astrophysics. It is now widely accepted that CMEs/eruptive flares represent the explosive release of magnetic energy stored in the corona. Therefore, in order to understand the phenomenon, we must answer the following questions: What is the field structure responsible for the disruption and why is the energy released explosively? In this talk we address these two questions using the latest theories and numerical models for CMEs/eruptive flares.

Antiochos, Spiro K.↗
NASA NTRS2018

Flat Proton Spectra in Large Solar Energetic Particle Events

We present solar energetic particle events observed at 1 AU from the Sun for which the proton energy spectra at energies between ~50 keV to ~1 MeV flatten during a period of at least ~12 hours prior to the passage of the associated interplanetary shock. The flattening of the proton energy spectra occurs when the source of the particles (presumably the traveling interplanetary shock) is still downwind from the spacecraft and particle intensities are still continuously increasing. The arrival of the shock at the spacecraft is then characterized by a steepening of the spectra, where low-energy proton intensities show a more pronounced enhancement than the high-energy proton intensities. We discuss the mechanisms that may result in this flattening of the spectra in terms of current models presented in the literature.

Lario, D.↗
NASA NTRS2011

Factors Affecting the Intensity of Solar Energetic Particle Events

This paper updates the influence of environmental and source factors of shocks driven by coronal mass ejections (CMEs) that are likely to influence the solar energetic particle (SEP) events. The intensity variation due to CME interaction reported that is confirmed by expanding the investigation to all the large SEP events of solar cycle 23. The large SEP events are separated into two groups, one associated with CMEs running into other CMEs, and the other with CMEs running into the ambient solar wind. SEP events with CME interaction generally have a higher intensity. New possibilities such as the influence of coronal holes on the SEP intensity are also discussed. For example, the presence of a large coronal hole between a well-connected eruption and the solar disk center may render the shock poorly connected because of the interaction between the CME and the coronal hole. This point is illustrated using the 2004 December 3 SEP event delayed by about 12 hours from the onset of the associated CME. There is no other event at the Sun that can be associated with the SEP onset. This event is consistent with the possibility that the coronal hole interaction influences the connectivity of the CMEs that produce SEPs, and hence the intensity of the SEP event.

Coronal mass ejections↗
NASA NTRS1973

Measurements of geomagnetically trapped alpha particles, 1968-1970. I - Quiet time distributions

Results of observations of geomagnetically trapped alpha particles over the energy range from 1.18 to 8 MeV performed with the aid of the Injun 5 polar-orbiting satellite during the period from September 1968 to May 1970. Following a presentation of a time history covering this entire period, a detailed analysis is made of the magnetically quiet period from Feb. 11 to 28, 1970. During this period the alpha particle fluxes and the intensity ratio of alpha particles to protons attained their lowest values in approximately 20 months; the alpha particle intensity versus L profile was most similar to the proton profile at the same energy per nucleon interval; the intensity ratio was nearly constant as a function of L in the same energy per nucleon representation, but rose sharply with L when computed in the same total energy interval; the variation of alpha particle intensity with B suggested a steep angular distribution at small equatorial pitch angles, while the intensity ratio showed little dependence on B; and the alpha particle spectral parameter showed a markedly different dependence on L from the equivalent one for protons.

Krimigis, S. M.↗
NASA NTRS1990

Particle acceleration by intense auroral VLF turbulence

Broadband turbulence in the lower-hybrid to plasma frequency range is found in a variety of forms in the suprauroral region, most notably as auroral hiss and VLF saucers. When the turbulence is intense, it is observed to be associated with ion conics (ions heated transverse to the geomagnetic field) and 'counter-streaming' electron fluxes (heated in both directions parallel to the field). A review is presented of the dispersion and propagation characteristics of whistler resonance-cone waves, which comprise the turbulence. Plasma simulation and mesoscale (Monte Carlo) simulation techniques are used to illustrate the interaction of the ambient plasma with the turbulence. These calculations demonstrate how this interaction results in transverse heating of the ions and parallel heating of the electrons of the plasma, leading to the formation of the observed heated and accelerated particle fluxes.

Retterer, John M.↗