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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Effect of small flares in the neutral component of secondary cosmic radiation

The results are presented of an investigation of the effect of small flares, scale divisions 1 and 1(+), in the neutron component of secondary cosmic radiation from the data of neutron supermonitors at the stations of Kiev, Bukhta Tiksi, and Deep River. It is shown that flares of scale divisions 1 and 1(+) are accompanied by an effect in the neutron component amounting to about 0.4%. A mechanism is presented for calculating the outflow of particles accelerated in small flares, owing to diffusion across the magnetic field of a trap.

Bondarenko, V. I.↗
NASA NTRS1974

Recent improvements in our knowledge of neutral atmosphere structure from satellite drag measurements

Observational results on the density in the thermosphere and lower exosphere (i.e., within the altitude range from about 150 to about 1000 km) are discussed in this paper. Most observational results on total gas density were obtained from orbital drag and more recently also from in-situ drag analysis. The primary parameter measured is atmospheric density, with temperature as a secondary structural parameter deduced with the help of theory and/or atmospheric models. Both the merits and shortcomings of the drag analysis method are outlined in view of a comparison of temperature deduced from total density and kinetic gas temperature measured by incoherent scatter. Recent improvements of our knowledge of the known density variations are presented.

Roemer, M.↗
NASA NTRS1974

Absorption of infrared radiation by electrons in the field of a neutral hydrogen atom

An analytical expression for the absorption coefficient is developed from a relationship between the cross-section for inverse bremsstrahlung absorption and the cross-section for electron-atom momentum transfer; it is accurate for those photon frequencies v and temperatures such that hv/kT is small. The determination of the absorption of infrared radiation by free-free transitions of the negative hydrogen ion has been extended to higher temperatures. A simple analytical expression for the absorption coefficient has been derived.

Stallcop, J. R.↗
NASA NTRS1974

Oscillator strengths for neutral sodium and the interstellar sodium abundance in zeta Ophiuchi

Use of the high-frequency deflection technique to measure radiative lifetimes for the 4p and 5p upper states in Na I, along with relative populations of a number of ns and nd states. These data have been used to obtain f-values for the corresponding resonance transitions in Na I, which proved to be in reasonable agreement with previous oscillator strengths. From the theoretical curve of growth for pure Doppler broadening, revised line ratios for D1/3303 are given and are compared with observations of Na I in zeta Oph.

Erman, P.↗
NASA NTRS1975

Plasma phenomena at magnetic neutral points

A model of the plasma focus is considered, in which large axial electric fields are induced by the imploding current sheet during the final few nanoseconds of the collapse phase. This field provides a mechanism for creation of a beam of electrons of highly suprathermal energies. For this beam, the bremsstrahlung radiation is calculated, which is expected either from electron-deuteron collisions in the focused plasma itself or from the beam as it reaches the walls of the device. Comparison with experimental results indicates that the walls are the more likely source of these hard X-rays and also find qualitative agreement of the expected angular distribution of X-rays with experiment.

Sturrock, P. A.↗
NASA NTRS1976

The neutral coma of comets: A review

The hypothesis that water snow controls the vaporization of the nucleus of some comets seems verified from the general order of magnitude of the size of their nucleus and of their nuclear albedo; the largest observed production rates are H and OH which both seem to originate from the photodissociation of H2O, as also confirmed by the scale length of the invisible parent molecule producing OH. However, comet Encke is not uniformly covered by water snow, as it produces only one tenth of the expected vaporization. Early results on comet Kohoutek suggest that the conclusions could be slightly different for some of the new comets in Oort's sense. If the far ultraviolet observations confirm the early assessments of the production rates of C, O and H, then at least another major constituent competing with water has not yet been detected. Such a major constituent is suggested by the ratios C/O = 0.24 and H/O = 2.5.

Delsemme, A. H.↗
NASA NTRS1976

Neutral temperature of cometary atmospheres

Spectral analyses of the coma and type I tails of a comet indicate that the main constituent of a cometary atmosphere is H2O and that cometary nuclei are composed of dirty ice containing mainly CO and N2. Thermochemical calculations on strong infrared coupling between H2O and dust grains explain the dependence of atmospheric temperature on the distance of the comet from the sun considering the strong cooling effect of H2O. It is concluded that atmospheric temperatures of comets cannot be so high as 1500 K.

Shimizu, M.↗