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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Yet Another Stream Search Among 2401 Photographic Meteors

Two streams previously listed (one of them with a classification on Ceplecha's system in terms of beginning height) by Cook are shown probably not to exist, a possibility already pointed out by Cook. One stream that he questioned was revised as to membership and then classified. Four streams are added to the list and one of these is classified. Previous reports exist for three of these streams, while one is new. The two Piscid streams of Lindblad and his alpha Triangulid stream are regrouped into two streams, one already called the Andromedids by Cook and the other still called the Piscids; the alpha Triangulids are absorbed into the Andromedids. The Piscids are classified along with the iota Aquarids. The classifications of the Taurids and the Andromedids remain unchanged.

Cook, A. F., II↗
NASA NTRS1973

Origin and evolution of recent Leonid meteor showers

The four most prominent returns of the Leonid shower in the past decade fall into two broad classes. The 1966 and 1969 showers were of short duration, had a high proportion of small particles, and occured with the longest apparent delay after the perihelion passage of the parent comet Temple-Tuttle. By contrast, the 1961 and 1965 returns were of long duration, and had more large particles. The 1961 return preceded the comet. There are three major influences on particle orbits: ejection velocity, radiation pressure, and close encounters with planets. The observations are explainable in a qualitative way on the basis of the first two. But some speculation concerning the results of planetary perturbations are invoked.

Mcintosh, B. A.↗
NASA NTRS1977

Metal ions and isotopes in sporadic E-layers during the Perseid meteor shower

The electron density and positive-ion composition above Wallops Island were measured on August 12, 1976, about 12 hours after the maximum of the Perseid shower. At launch time, 4.5 MHz was recorded for fbEs, corresponding to an electron density of 2.4 x 10 to the 5th power per cu cm. Electron profile and ion composition measurements confirmed the presence of a sporadic E-layer with two maxima at 101.3 and 105.4 km. The electron density was measured with a pair of boom-mounted probes at fixed potential. The positive ion composition above 77 km was measured with a magnetic mass spectrometer employing a liquid He cryopump. Some of the salient results of the (still incomplete) analysis are discussed.

Herrmann, U.↗
NASA NTRS1978

Meteor ablation spheres from deep-sea sediments

Spheres from mid-Pacific abyssal clays (0 to 500,000 yrs old), formed from particles that completely melted and subsequently recrystallized as they separated from their meteoroid bodies, or containing relict grains of parent meteoroids that did not experience any melting were analyzed. The spheres were readily divided into three groups using their dominant mineralogy. The Fe-rich spheres were produced during ablation of Fe and metal-rich silicate meteoroids. The glassy spheres are considerably more Fe-rich than the silicate spheres. They consist of magnetite and an Fe glass which is relatively low in Si. Bulk compositions and relict grains are useful for determining the parent meteoroid types for the silicate spheres. Bulk analyses of recrystallized spheres show that nonvolatile elemental abundances are similar to chondrite abundances. Analysis of relict grains identified high temperature minerals associated with a fine-grained, low temperature, volatile-rich matrix. The obvious candidates for parent meteoroids of this type of silicate sphere is a carbonaceous chondrite.

Blanchard, M. B.↗
NASA NTRS1985

Mean Winds of the Upper Middle Atmosphere (60-110 Km): a Global Distribution from Radar Systems (MF, Meteor, VHF)

During the last decade a large number of radars have been developed, which have produced substantial quantities of tidally corrected mean winds data in the upper middle atmosphere. The distribution of the radars is not global, but many areas are well covered. Zonal and meridional wind height-time cross sections from 60 to 80 km (MF/meteor radar) to approx. 110 km were preared for the last 5 to 6 years. They are compared with cross sections from CIRA 1972 for zonal winds, and GROVES (1969) for meridional winds. It is shown that while CIRA 1972 is still a useful model for many purposes, significant differences exist between it and the new radar data. The latter demonstrate important seasonal, latitudinal, longitudinal and hemispheric variations. The new meridional cross sections are of great value. The common features with GROVES (1969) are the equatorward cells in summer near 85 km; however, their strength (approx. 10 m/s) and size are less. Systematic and somewhat different variations emerge at (higher 52 N) and lower (35 to 44 deg) latitudes.

Manson, A. H.↗
NASA NTRS1985

Results of the May 1982 ATMAP Campaign at the Meteor Wind Station Kuehlungsborn (54 Deg N, 12 Deg E), GDR

A sinusoisal least squares fit over the entire data of 1 to 6 May 1982 was computed. The results are shown. Wind results refere to an average height of 95 km (no height determination). The wind results correspond, in general, to the average behavior of early May. The zonal prevailing west wind, however, is stronger than the term mean value (-5 m/s). Also, the amplitude of the semidiurnal idal wind is larger (mean value 1977 to 1983: 8 m/s).

Greisiger, K. M.↗