The alignment of 6300 A airglow isophotes in the Tropics

From the observations of a scanning photometer at Haleakala [Barbier et al., 1962] 6300 A airglow isophote maps have been produced. Figures 1 and 2 show sample maps. These isophote maps can be roughly classified into two types: (1) those that show a ‘spotty’ character, with at least some of the isophotes making closed loops, as in Figure 1, and (2) those that show a somewhat ‘aligned’ character with the isophotes roughly linear and parallel to each other, as in Figure 2. The spotty character is often associated with the localized tropical enhancements that have been discussed by a number of workers: Barbier [1964]; Barbier et al. [1962]; Carman and Gibson-Wilde [1964]; Davis and Smith [1965]; Delsemme and Delsemme [1960]; Saito [1962]; Silverman and Casaverde [1961]. Aligned isophotes are often associated with morning and evening twilight effects as evidenced by their orientation with respect to the sunset or sunrise directions, but also during the middle of the night isophote alignment of the nightglow is often evident.