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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 199 records · Page 11
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NASA NTRS1974

The variation of solar proton energy spectra size distribution with heliolongitude

A statistical study of the initial phases of 185 solar particle events was carried out using the data from cosmic ray experiments on IMP 4 and IMP 5. Special emphasis was placed on the identification of the associated solar flare, as the parent flare can be determined for 68% of the events. It appears probable that most of the unidentified increases occur on the non-visible disc of the sun. The existence of a 'preferred-connection' longitude between 20 W and 80 W was established by examining the heliolongitude of all the flare associated events. It is demonstrated that the energy spectra determined at the time of maximum particle in the 20 to 80 MeV or 4 to 20 Mev interval range give results identical to that obtained by the 'distance-travelled' method.

Vanhollebeke, M. A. I.↗
NASA NTRS1974

Model of an anisotropy solar proton event

The anisotropy of the particle distribution and its variation with time at 1 AU early in a solar cosmic-ray event can provide information on the pitch-angle scattering of the particles in the interplanetary medium. One proton event (7.6-55 MeV) is described in which the anisotropy remained large well into the decay of the omnidirectional intensity. A Monte Carlo technique which gives the pitch-angle distribution is employed to investigate two models put forward to explain the sustained anisotropy. It is shown that the observed event is consistent with a model in which the injection of particles at the sun reaches a peak 1.5 hours after flare maximum before decaying with an e-folding time of 7 hours. The uniform diffusion coefficient in this model corresponds to a classical mean free path of 1.6 AU.

Palmer, I. D.↗
NASA NTRS1973

Propagation pattern of interplanetary shock waves associated with solar proton flares

The two dimensional pattern of interplanetary shock waves is deduced by taking into account the solar longitude dependence of the time intervals between SSC geomagnetic storms and responsible flares. This pattern near the earth's orbit is not symmetric with respect to the meridian plane which crosses the position of the flare, and the highest speed of this wave propagation is observed in the direction about 30 degrees east of this meridian plane. The magnitude of the Forbush decreases of galactic cosmic rays also varies with the longitude positions of those flares. This is used to estimate the distribution of magnetic fields behind the shock waves.

Sakurai, K.↗
NASA NTRS1975

The variation of solar proton energy spectra and size distribution with heliolongitude

A statistical study of the initial phases of a large number of solar particle events provides an approach for an investigation of the variability in the production process and coronal diffusion. A description is given of the procedures which are suitable for identifying the parent flare of an event, taking into account the heliocentric distribution of the flare-associated events. The determination of the proton energy spectrum at the sun is discussed along with the variation of the spectral index with the associated flare heliocentric longitude, questions concerning the source spectra and the acceleration process, and the size distribution of flare associated particle events.

Van Hollebeke, M. A. I.↗
NASA NTRS1972

Mariner Venus-Mercury 1973 mission solar proton environment: fluence and dose

A derivation is presented for proton fluence over the duration of the Mariner Venus-Mercury 1973 (MVM73) mission in terms of a relatively constant, low energy component, the solar wind, and a probabilistic high energy component from discrete solar events. An updated correlation of yearly energetic proton fluence with yearly average sunspot number is presented. This correlation and sunspot cycle forecasts for the period of the MVM73 mission (late 1973 through early 1975) form the basis for the high energy proton fluence estimates with various confidence levels. Uncertainties in the probability estimates and in calculation of the scaling with distance from the Sun are discussed. Selection of a particular 95-percentile model as the design constraint is recommended, and reasons are presented for not using the worst-case model. Interior fluences were calculated and expressed in terms useful for spacecraft design.

Thomas, J. R.↗
NASA NTRS1973

Nuclear microprobe analysis of solar proton implantation profiles in lunar rock surfaces

Discussion of the results of hydrogen (proton) depth profile concentration analyses conducted on selected Apollo 16 rocks. A modeling of solar particle implantation profiles in lunar rocks is shown to trace the evolvement of these profiles under the combined influence of diffusion of atomic particles implanted in the rock, and rock surface erosion. It is also demonstrated that such diffusion may have a significant effect on the shape of the implantation profiles in certain rock materials.

Stauber, M. C.↗
NASA NTRS1978

Rigidity-independent coronal propagation and escape of solar protons and alpha particles

In a study of rigidity-independent coronal propagation processes, data on the azimuthal variation of the solar proton/alpha-particle ratio were obtained. Sources for the data included a statistical analysis of events observed by Heos-2, a comparative study of events recorded by both Heos-2 and Pioneer-10 and -11, and a multiday survey of individual events observed by Heos-2 and Pioneer-10. The statistical investigation of Heos-2 events reveals an increase of the lower value of the proton/alpha-particle ratio away from the well-connected region. The data from one or two spacecraft connected at different heliolongitudes indicates no azimuthal dependence of the proton/alpha-particle ratio. All the data appear to suggest rigidity-independent propagation or escape processes.

Perron, C.↗
NASA NTRS1971

Solar proton, helium, and medium nuclei (Z is equal to or greater than 6 and equal to or less than 9) observed from the IMP-6 satellite

Proton, helium, and medium nuclei energy spectra have been measured from the Explorer 35 satellite for a recent solar flare. Above 2 MeV/nucleon these spectra are based upon single and dual parameter pulse height analysis in addition to threshold rate counting. Pulse height analysis of medium nuclei is assigned a high priority for telemetry readout so that telemetry does not become saturated by the high proton intensity. In this manner the number of pulse height analyzed medium nuclei has been increased by a factor of approximately 200. Individual medium nuclei have been resolved in the energy interval 8 - 23 MeV/nucleon.

Vonrosenvinge, T. T.↗
NASA NTRS1972

Calculation of the lunar photon albedo from galactic and solar proton bombardment.

The lunar photon albedo due to cosmogenic and primordial photon sources has been calculated. The individual photon leakage spectra from prompt photons produced by galactic cosmic ray (GCR) and solar cosmic ray (SCR) induced nuclear interactions, from the decay of GCR- and SCR-induced radionuclides, and from the decay of naturally occurring radionuclides are given. An approximate estimate of the leakage from the photon-electron cascade initiated by the decay of neutral pions is also given. Monte Carlo methods have been used to determine the nucleon-meson cascade, and discrete-ordinates methods were used for the photon and low-energy neutron transport.

Armstrong, T. W.↗
NASA NTRS1995

Coronal Mass Ejections and Solar Proton Events During the Great March 1989 Disturbances

The great active region of March 1989 was the most prolific in X- rays in the preceding 15 years, and produced very large bright optical solar flares. The accompanying solar energetic particle event was one of the four most intense episodes since 1963. These increases in particle fluxes are compared to the major X-ray and optical flares and to the major coronal mass ejections in order to test hypothesis.

Corona Coronal Mass Ejections Solar Flares Sun↗
NASA NTRS1993

Solar-flare implanted He-4/He-3 and solar-proton-produced Ne and Ar concentration profiles preserved in lunar rock 61016

Depth profiles for Ne-21, Ne-22, and Ar-38 isotopes from oriented lunar rock 61016 are reported. Concentration profiles of cosmogenic GCR+SCR (Galactic cosmic ray and solar cosmic ray-produced) isotopes are determined, quantitatively resolving neon and argon produced by energetic solar flares from that produced by Galactic cosmic rays. The SCR component is resolved from the GCR component as a function of shielding, and excellent agreement is found between experimental SCR production profiles for the isotopes and theoretically calculated values. A characteristic SW He-4/He-3 ratio of 3450 +/- 81, representing energies down to as few keV/amu. In slightly deeper samples an SRF He-4/He-3 ratio of 3450 +/- 725 is found for He particles with E larger than about 1 MeV/amu. These results indicate that the isotopic composition of SF He, averaged over the long term, is energy-dependent. An implanted Ne-20/Ne-22 ratio of 12.4 is measured in unetched samples, representing E greater than 1 MeV/amu, and a ratio of 11.6 is inferred in the samples, representing E larger than about 5 MeV/amu.

Rao, M. N.↗
NASA NTRS1983

The sun-weather connection - Sudden stratospheric warmings correlated with sudden commencements and solar proton events

It has been found that a strong correlation exists between sudden stratospheric warmings and sudden commencements of geomagnetic activity. This correlation follows a 22-yr cycle. The sudden warmings of the lower stratosphere occur near the north magnetic pole over Siberia and the Pacific, although occasionally they do occur over North America. A mechanism explaining how the solar wind ultimately affects the surface weather through its selective interaction with the middle atmosphere is outlined.

Neubauer, L.↗
NASA NTRS1974

Low-energy protons of solar origin and investigation of the interplanetary medium

Experimental data on low energy solar protons are presented. A phenomenological classification of the fluxes of these particles is suggested. Contemporary model conceptions of the propagation of low energy proton fluxes are examined, along with information that has been obtained on the properties of the interplanetary medium from study of solar proton fluxes.

Lutsenko, V. N.↗