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Hall, L. A.

Publications and source records attributed to Hall, L. A..

16 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Ultraviolet O2 transmittance - AURIC implementation

A new spectrally precise approach to Schumann-Runge synthesis has been devised, employing nine (9) different spectral arrays containing polynomial coefficients. The coefficients were fit to calculated cross sections obtained from a detailed Schumann-Runge model that incorporates the most recent high resolution spectroscopic data for a temperature range between 130 and 500K. This large data base is being used to reexamine the existing parameterizations of UV transmission and photolysis. In addition, it is now possible to extend atmospheric radiance codes further into the ultraviolet. Initial implementation has been accomplished for the MODTRAN code as part of the eventual development of AURIC, the Atmospheric Ultraviolet Radiance Integrated Code.

Anderson, G. P.↗
NASA NTRS1992

Polynomial coefficients for calculating O2 Schumann-Runge cross sections at 0.5/cm resolution

O2 cross sections from 49,000 to 57,000/cm have been fitted with temperature dependent polynomial expressions, providing an accurate and efficient means of determining Schumann-Runge band cross sections for temperatures between 130 and 500 K. The least squares fits were carried out on a 0.5/cm spectral grid, using cross sections obtained from a Schumann-Runge line-by-line model that incorporates the most recent spectroscopic data. The O2 cross sections do not include the underlying Herzberg continuum, but they do contain contributions from the temperature dependent Schumann-Runge continuum. The cross sections are suitable for use in UV transmission calculations at high spectral resolution. They should also prove useful for updating existing parameterizations of ultraviolet transmission and O2 photolysis.

Minschwaner, K.↗
NASA NTRS1985

Radiative processes

Solar radiation and the processes that control its deposition in the Earth atmosphere are considered. The published data obtained since 1978 define a reference solar spectral irradiance for use in atmospheric chemical and dynamical studies, while long term satellite measurements are now providing information on variations in the output of the Sun over a range of time scales. As concerns absorption of solar radiation in the atmosphere, new cross section data for molecular oxygen and ozone are now available. Line-by-line calculations used to predict infrared flux divergences, both as regards assumptions made in radiative transfer calculations and in the spectroscopic parameters used as inputs are examined. Also examined are the influence of radiative processes on planetary scale wave activity, photochemical acceleration of radiative damping, and the breakdown of local thermodynamic equilibrium at mesospheric altitudes.

Frederick, J. E.↗
NASA NTRS1971

Solar flares in the extreme ultraviolet.

Measurements of flare-related impulsive enhancements in solar emission lines in the extreme ultraviolet, observed from the satellite OSO-III, are reported. The enhancement of a line, expressed in percent of the total disk intensity in the line, is of the same order of magnitude as the flare area, expressed in heliocentric square degrees. Rise-times and decay-times of impulsive enhancements average about 2 min and 5 min, respectively. The maximum enhancements of radiation from ions in the chromosphere-corona transition region precede the H-alpha maximum by an average of 2 min, and occur in the same period of time as the hard component of solar X rays and the impulsive microwave bursts. Coronal lines in the extreme ultraviolet are less impulsive than the transition region lines in flare-related enhancements and their maxima follow the H-alpha maximum.

Hall, L. A.↗