Side-viewing observations of OI(1D) and OH night airglows by ISUAL

Optical and side-viewing images obtained from airglow surveys by ISUAL/FORMOSAT-2 often showed local enhancements in the F region and in the 90 km OH-layer. Detailed inspection of the latitudinal distributions of airglows in these two layers indicates the enhancements may be correlated. In some cases, the enhancements fell on two sides of the magnetic equator and could have been invoked by the Equatorial Ionization Anomaly (EIA) effect with an additional displacement contributed by the wind field. However in most cases, the cause(s) are far from clear. In addition, nonuniform luminescence, called spread F, was often observed in the pre-midnight regions and appears to exhibit longitudinal and seasonal variations. In the paper, the possible mechanisms of the enhancements will be discussed systematically.