Analysis of the spatial distribution of dayside cleft optical emissions

An analysis of measurements of the 4278-A, 5200-A, 5577-A and 6300 A emissions obtained from a rocket launch through the postnoon dayside cleft into the polar cap ionosphere is reported. The 4278-A and 5577-A emission show a clearly defined decrease in intensity at the poleward edge of the dayside particle precipatation, while the 5200-A emission extends well into the polar cap with only a slight decrease in intensity. The 6300-A emission displays a behavior intermediate between these extremes. The optical data are analyzed by using a dynamical model of dayside cleft auroral processes incorporating transport by ion and neutral winds. It is concluded that neutral winds are responsible for modifying the spatial distribution of the 5200-A and 6300-A emission while the ion drift component is negligible. In addition, it is found that (1) 80% of the 4278-A emission intensity is due to resonance fluorescence in the sunlit cleft ionosphere, (2) the reaction O2(c1Σ/sub u/-)+O→ O2+O(1S) is consistent with the 5577-A data if the yield of O(1S) from the dissociative recombination of O2+ is about 2%, and (3) the rate of the reaction N2++O→NO++N is apparently higher in the ionosphere than indicated by the laboratory measurements