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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 163 records · Page 9
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NASA NTRS1977

Solar energetic particles below 10 MeV

The information on solar acceleration and coronal propagation contained in low energy solar particle observations must be extracted from the effects of propagation in a dynamic interplanetary medium and the proximity of the earth's magnetosphere. The resulting separation reveals long-lived coronal injection and strong spatial ordering of coronal propagation.

Roelof, E. C.↗
NASA NTRS1974

A solar energetic particle event with He-3/He-4 1

The solar event of 28 May 1968 is reported using the Goddard Cosmic Ray Telescope on OGO-5. The flare associated with the event occurred at 12:48 on 28 May and had importance 1B. About 600 He-3 were detected in the event and the He-3/He-4 equals 1.52 plus or minus 0.1 in the energy range 4-80 MeV/necleon. This is the highest ratio reported so far for any solar event.

Balasubrahmanyan, V. K.↗
NASA NTRS2002

Interplanetary Magnetic Field Control of the Entry of Solar Energetic Particles into the Magnetosphere

We have investigated the entry of energetic ions of solar origin into the magnetosphere as a function of the interplanetary magnetic field orientation. We have modeled this entry by following high energy particles (protons and 3 He ions) ranging from 0.1 to 50 MeV in electric and magnetic fields from a global magnetohydrodynamic (MHD) model of the magnetosphere and its interaction with the solar wind. For the most part these particles entered the magnetosphere on or near open field lines except for some above 10 MeV that could enter directly by crossing field lines due to their large gyroradii. The MHD simulation was driven by a series of idealized solar wind and interplanetary magnetic field (IMF) conditions. It was found that the flux of particles in the magnetosphere and transport into the inner magnetosphere varied widely according to the IMF orientation for a constant upstream particle source, with the most efficient entry occurring under southward IMF conditions. The flux inside the magnetosphere could approach that in the solar wind implying that SEPs can contribute significantly to the magnetospheric energetic particle population during typical SEP events depending on the state of the magnetosphere.

Richard, R. L.↗
NASA NTRS2002

Recent Solar Energetic Particles: Updates and Trends

The event-integrated fluences of solar protons >10 to >100 MeV were determined for 21 events since 1996. The Sun has been very active starting in July 2000. Trends in these data and possible trends in future solar particle events are discussed. Additional information is contained in the original extended abstract.

Reedy, R. C.↗
NASA NTRS2005

Solar Effects on Global Climate Due to Cosmic Rays and Solar Energetic Particles

Although the work reported here does not directly connect solar variability with global climate change, this research establishes a plausible quantitative causative link between observed solar activity and apparently correlated variations in terrestrial climate parameters. Specifically, we have demonstrated that ion-mediated nucleation of atmospheric particles is a likely, and likely widespread, phenomenon that relates solar variability to changes in the microphysical properties of clouds. To investigate this relationship, we have constructed and applied a new model describing the formation and evolution of ionic clusters under a range of atmospheric conditions throughout the lower atmosphere. The activation of large ionic clusters into cloud nuclei is predicted to be favorable in the upper troposphere and mesosphere, and possibly in the lower stratosphere. The model developed under this grant needs to be extended to include additional cluster families, and should be incorporated into microphysical models to further test the cause-and-effect linkages that may ultimately explain key aspects of the connections between solar variability and climate.

Turco, R. P.↗
NASA NTRS1990

Coronal mass ejections and the injection profiles of solar energetic particle events

Previous studies using Skylab and Solwind coronagraph observations have shown that almost all E greater than 10 MeV solar energetic proton (SEP) events are associated with the occurrence of a coronal mass ejection (CME). These earlier studies did not address the relationship between the position of the associated CME and the timing of the injection of particles into the interplanetary medium. Ten cases are selected in which a SEP event observed with the GSFC detectors on the IMP 8 or ISEE 3 spacecraft was correlated to a CME well observed by the Solwind coronagraph. The height of the leading edge of the CME is compared with the particle injection profiles for several energy ranges using the solar release times for the particles. The derived injection profiles are found to be increasing and sometimes reaching maximum while the associated CMEs are at heights of 2-10 Ro.

Kahler, S. W.↗
NASA NTRS1977

Simple analytical solutions for spherically symmetric production and modulation of energetic solar particles

Exact analytical solutions are presented for the standard time-independent spherically symmetric convection-diffusion-adiabatic deceleration equation governing the transport of cosmic rays in the interplanetary medium for the case in which particles are produced with spherical symmetry at the sun. It is assumed that the solar-wind speed is constant and radial, and that the spatial diffusion coefficient has a power-law dependence on momentum. The Green's function describing the modulation of a monoenergetic production of particles is presented. The solutions provide a useful basis for the study of time-integrated properties of energetic solar-flare particle spectra.

Gross, M. W.↗
NASA NTRS1974

Solar energetic particle event with He-3/He-4 greater than 1

An unusual solar event involving the detection of a He-3/He-4 ratio of about 1.5 was observed with the aid of the cosmic-ray telescopes of OGO-V on May 28, 1969. A theory dealing with the production of H-2, H-3, and He-3 in solar events is considered together with the conditions which would have to be satisfied in order to explain the observed very high helium isotope ratio in terms of the theory.

Balasubrahmanyan, V. K.↗
NASA NTRS1980

The effect of coronal transport of energetic solar particles

A single active center was the origin of several solar flares observed in September, 1977. The longitude of the flares ranged from approximately 115 deg E to approximately 117 deg W. During this period Helios 1, Helios 2, Voyager 1 and Voyager 2 were extended over a range of approximately 120 deg in longitude, thus providing an opportunity to study the coronal transport of energetic solar flare particles. The result of a detailed study of the relative intensity and spectral shape of approximately 2-200 MeV protons and alphas at several solar longitudes has enabled the imposition of some criteria on models of coronal transport.

Conlon, T. F.↗
NASA NTRS1991

Focused interplanetary transport of solar energetic particles through self-generated Alfven waves

The coupled evolution of solar-flare protons and interplanetary Alfven waves based on the quasi-linear theory implies an order of magnitude amplification (damping) in the outward (inward) propagating left helical resonant Alfven waves at less than 0.4-AU helioradius, if the proton intensity at 1 AU exceeds 300 particles/(sq cm s sr MeV) at 1 MeV, and the initial wave intensities give mean free paths of more than 0.5 AU. The wave growth significantly retards solar-particle transport, and has implications on the nature of solar-wind turbulence.

Ng, C. K.↗
NASA NTRS1985

The mean ionic charges of N, Ne, MG, SI and S in solar energetic particle events

The mean ionic charges of nitrogen, neon, magnesium, silicon, and sulfur in solar flare particle events were determined for 12 flares during the time interval from September 1978 to September 1979. The observations were carried out with the MPI/UoMd ULEZEQ Sensor on the ISEE-3 satellite comparing the results with mean charge states established in a hot coronal plasma under equilibrium conditions, different temperatures for different elements are discussed. These range from approx. 2 million K to 7 million K in a single flare. From flare to flare the variation in temperature for each element is less than the variation between different ion species.

Luhn, A.↗
NASA NTRS1979

Elemental composition of solar energetic particles in 1977 and 1978

The elemental composition of energetic nuclei from seven major solar flare events were measured wit the cosmic ray detector systems aboard the Voyager 1 and 2 spacecraft. The energetic nuclei abundances differ significantly from those of photospheric material. They are enhanced relative to the photonsphere by a factor which is the ratio of abundance of an energetic nuclei species (relative to oxygen) over the corresponding abundance of photospheric material. This factor is common to all events and has a nonmonochromatic characteristic dependence on nuclear charge. This factor is roughly ordered by first ionization potential into two groups of elements, metallics and volatiles.

Cook, W. R.↗
NASA NTRS1986

Two classes of solar energetic particle events associated with impulsive and long-duration soft X-ray flares

For the period 1978 September to 1983 December, 67 solar particle events have been identified for which the instruments detected electrons above 3 MeV and for which there are soft X-ray observations. The events are divided into two classes impulsive and long-duration - based on their signature in soft X-rays, and it is found that they have different properties. The events originating with impulsive flares are associated with intensed meter-wavelength type III bursts with associated type V continuum. The events associated with long-duration flares can originate anywhere on the solar disk, extend to much higher proton energies, and are well associated with coronal and interplanetary shocks; for about half of the long-duration events, the associated meter-wavelength events do not include type III bursts. The results discovered by Evenson et al. (1984) and by Kahler et al. (1984) are extended.

Cane, H. V.↗
NASA NTRS1985

The Propagation of Solar Energetic Particles in Magnetic Channels

The existence of interplanetary flow systems produced by the entrainment of interplanetary transients, consisting of flare produced shocks, high speed solar wind streams and coronal mass ejection, has been established. This entrainment process produces enhanced regions of the interplanetary magnetic field that should be connected back to the solar corona. These compressed regions can provide a preferred magnetic channel for the propagation of solar cosmic rays. The characteristics of these events appear to be different from those previously reported by the NASA/University of New Hampshire team and the University of Chicago in their study of a large number of events in the region beyond 1 AU. These new events have a very flat energy spectra (with gamma = approx. 1.5) that frequently extend to energies above 100 MeV and have a significant enhancement of MeV electrons.

Mcdonald, F. B.↗