Noctilucent Clouds

Soberman, R. K.

doi:10.1038/scientificamerican0663-50

Cited by 16 publications

(6 citation statements)

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“…These, of course, are in addition to the small particles of approximately normal distribution in speed reported by Eshlernan and Gallagher [1962]. Their existence and field patterns might be important in discussions of (1) the zodiacal light [James, 1963], (2) the concentration of fine Ni particles within noctilucent clouds where densities relative to space outside the cloud are greater by orders of magnitude [Soberman, 1963;Wittet al, 1963], (3) the concentration of condensation nuclei for ordinary rain clouds, and (4) the variation of concentration of dust responsible for the radiance [Barber, 1962] of twilight sky. This last phenomenon (4) apparently is influenced by the position of the moon --an effect formerly thought impossible through the influence of the lunar gravitational field, but which, now viewed in terms of the field patterns for very slow particles (predicted by the theory to follow), may be a significant factor.…”

mentioning

confidence: 87%

Meteoric flux and density fields about an infinitesimal attractive center generated by a stream monoenergetic and monodirectional at infinity

Hale¹,

Wright²

1964

J. Geophys. Res.

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The meteoric field structure theory previously developed for meteoric streams monoenergetic and monodirectional at infinity is applied to the problem of a meteoric stream incident upon an infinitesimal attractive center. Flux and density contours about the center are explicitly obtained for a particle speed at infinity of 2 km/sec as an example of a method developed to provide flux and density contours for any speed. An incident stream five to ten earth diameters in width results in an order of magnitude enhancement of flux at points downstream from the attractive center. The flux patterns for any energy can be derived from a universal flux plot in terms of a dimensionless parameter λ = yr, where y = V∞2/γM, and γ is distance in earth (or center) radii. This universal flux plot is shown.

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mentioning

confidence: 87%

Meteoric flux and density fields about an infinitesimal attractive center generated by a stream monoenergetic and monodirectional at infinity

Hale¹,

Wright²

1964

J. Geophys. Res.

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“…OZ + e--> 0* + 0 0* } 0 + hv (18) Airglow radiations from nitrogen, the most abundant gas of the terrestrial atmosphere, are sparse except for some atomic lines. The neutral nitrogen molecule in the electronic ground state has no dipole moment and therefore is a poor radiator.…”

Section: Airglowmentioning

confidence: 99%

<title>Optical Radiation From The Atmosphere</title>

Baker

Pendleton

1976

SPIE Proceedings

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The interface region which lies between the meteorological atmosphere of the Earth and "outer" space is a source of abundant optical radiation. The purpose of this paper is to provide the optical instrumentation engineer with a generalized understanding and a summary reference of naturally-occurring aerospace radiation phenomena. The colors of the radiation extend over the full optical spectrum from ultraviolet through the infrared. The emissions, observed during both day and night times, are rich in line and band spectra. The parameterization of atmospheric light by frequency (or photon energy) and by spectral radiance is discussed. The sources of the natural light from the gases of the atmosphere are grouped into four categories: (1) airglow mechanisms, (2) thermal processes, (3) scattering phenomena, and (4) auroral excitations. An overview of the characteristic spectral occurrences and intensities is given.

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“…is not present. The clouds are optically thin enough for bright stars to shine through them [Soberman, 1963]. Unfortunately, the actual mechanism of formation of noctilucent clouds is unknown, i.e., whether it depends on the number of condensation nuclei available or on the local temperature, air pressure, and vapor pressure.…”

Section: One Salient Point Remains In the Analysis Of The Spectrum Ofmentioning

confidence: 99%

On the composition of the Venus clouds

Rea¹,

O'Leary²

1968

J. Geophys. Res.

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Recently, using near‐infrared spectra of Venus obtained from a high‐altitude balloon, Bottema, Plummer, Strong, and Zander have concluded that the Venus clouds are composed of H2O ice. This conclusion was supported by Sagan and Pollack, who, moreover, bracketed the particle radii between 7.5 and 10 μ. Because it contradicts previous statements by Kuiper and Moroz that H2O ice is not present, we decided to re‐examine the relevant spectroscopic data and their interpretations. To assist us, Miller and Boese recorded long path absorption spectra of pure CO2 gas. Two salient features emerge from our study: the absence of any absorption other than CO2 both at 1.5 μ and at 2.0 μ. Since cirrus and laboratory ice clouds both exhibit strong absorptions centered at these wavelengths, it is clear that the Venus clouds cannot be similar to these. There remains a possibility that the major scatterers could be H2O ice—if the particle sizes are submicron, the absorption bands would diminish in intensity. It is argued, however, that the existence of the required abundance of such particles on a planet‐wide basis is improbable. Accordingly the major scatterers of radiation are almost certainly not composed of H2O ice. Various candidates for the particles are mentioned, but no positive spectroscopic evidence to support a particular one is advanced.

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Noctilucent Clouds

Cited by 16 publications

References 0 publications

Meteoric flux and density fields about an infinitesimal attractive center generated by a stream monoenergetic and monodirectional at infinity

Meteoric flux and density fields about an infinitesimal attractive center generated by a stream monoenergetic and monodirectional at infinity

<title>Optical Radiation From The Atmosphere</title>

On the composition of the Venus clouds

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