Spectroscopic Study of the Nitrogen Airglow

概要

論文の詳細を見る
Four rocket observations of the NO γ(1, 0) 2148 Å band airglow and ground observations of the NI 5200 Å emission in the auroral zone are presented. A radiometer was developed to measure the NO γ(1, 0) band airglow in the mesosphere and thermosphere. It can extract the γ(1, 0) band airglow from intense background radiations by making use of a self-absorbing gas cell. NO density profiles were deduced from the γ(1, 0) band emission rates measured at Uchinoura (31°N), Thumba (9°N) and Syowa Station (69°S). The NO densities in the thermosphere obtained at middle and low latitudes are found to vary with solar activity. In view of a considerable temperature dependence of the production rate of NO in the thermosphere, the variation may be attributed to change in thermospheric temperature, which is closely related to solar activity. Change in the solar extreme ultraviolet radiation flux may also be responsible for the variation. The NO density in the mesosphere and the lower thermosphere obtained in the auroral zone is found to be larger than those obtained at middle and low latitudes under the conditions of similar solar activity. Because of a long life time of NO in the altitude region, the observed enhancement may be due to the after-effect of a particle precipitation event which occurred within a day before in despite of no polar disturbance during the flight. The emission rate of the NI 5200 Å doublet in the aurora was measured with a tilting-filter photometer at Syowa Station from March to September 1977. The N_2^+ 1NG(0, 1) 4278 Å band emission was measured simultaneously with the 5200 Å emission for comparison. Examining nighttime variations of the emissions obtained in thirteen clear and moonless nights, the 5200 Å emission is found to be one of the common spectral features of the aurora. A simple model calculation is performed to investigate the excitation mechanism for the 5200 Å emission in the aurora, and dissociative recombination of NO^+ is found to be insufficient to explain the observations. Alternatively, impact dissociation and excitation of N_2 by auroral electrons may be the major excitation process. The ratio of measured 5200 Å emission rate to the 4278 Å emission rate decreases as the 4278 Å emission rate increases. This tendency may be qualitatively explained by the combined effect due to the highly forbidden nature of the 5200 Å emission and the characteristics of the precipitating particles in that their mean energy generally increases with their total energy.
国立極地研究所の論文

Spectroscopic Study of the Nitrogen Airglow

スポンサーリンク

概要

著者

関連論文

スポンサーリンク