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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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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

Asteroid size distribution - Implications for the origin of stony-iron and iron meteorites

The diameter-frequency distribution of large asteroids is analyzed, based on polarimetric and radiometric albedo data. The population of carbonaceous objects shows a high degree of fragmentation. But a class of apparently stony-iron asteroids shows a relative excess frequency between diameters of 100 to 200 km. It is proposed that the latter objects are predominantly metallic cores of a group of chemically differentiated planetesimals all of which (except Vesta) have suffered catastrophic collisions. Collision frequencies in the asteroid belt may have been much greater than previously supposed.

Chapman, C. R.↗
NASA NTRS1978

Albedos and size distribution of meteoroids from 0.3 to 4.8 AU

Observational data are compared on the distribution of very small micrometeoroids (1 billionth to 1 hundred-millionth g), the scattering source function of the zodiacal light, the distribution of larger micrometeoroids (at least 1 hundred-thousandth g) as observed from Helios A and Pioneer 10, and the distribution of meteoroids from the sample seen from earth. The experiments, analyses, and simulations involved in obtaining these data are described in detail. It is shown that the various groups of data can be reconciled only by small albedos that decrease outward from 0.1 to at least about 3.3 AU for the particles which produce both the zodiacal light and the observed meteors. The results also indicate that there must be a maximum in the distribution of the larger particles somewhere between the orbits of earth and Jupiter. It is suggested that a search for fireballs in Jupiter's atmosphere by the television cameras of the MJS 77 mission should aid in locating this maximum.

Cook, A. F.↗