Ogo-4 observations of the Lyman-Birge-Hopfield emission in the day airglow
Abstract
The results of measurements of the day airglow in the wavelength interval 1356-1600 A from detectors aboard the polar-orbiting satellite Ogo 4 are reported for the period August 1967 through July 1968. The columnar emission rates for the total Lyman-Birge-Hopfield system of molecular nitrogen (implied by assuming a relative spectral composition for the incident radiation) for a solar zenith angle of 0° were of the order of 6.5 kR, with variations that tended to follow the 10.7-cm flux; however, the magnitudes of the variations of the two were not always the same. The emission rate at night has an upper limit of 25 R (determined by the data noise level). The dependence of the emission on solar zenith angle is shown to be approximately proportional to the reciprocal of the Chapman function; i.e., the local intensity can be expressed as the product of the reciprocal of the Chapman function, the subsolar point intensity, and a global distribution function that has a value close to one. This global distribution function is approximately related to the atmospheric composition and has a latitude and local-time dependence similar to that of the exospheric temperature. Using an expression for the diurnal variation of the exospheric temperature developed by Jacchia (1965), the relation implies that the global distribution function maximum (at 70° solar zenith angle) follows the latitude of the subsolar point with a lag of 5.3 hours. The magnitude of the observed columnar emission rate for the LBH band system agrees well with recent calculations that assume that the excitation mechanism is photoelectron impact.
- Publication:
-
Journal of Geophysical Research
- Pub Date:
- 1971
- DOI:
- 10.1029/JA076i025p06146
- Bibcode:
- 1971JGR....76.6146P
- Keywords:
-
- Particles and Fields in the Ionosphere: Airglow;
- Aeronomy: Atmospheric absorption and scattering of radiation (particles or waves)