Covariation of 6300 A and 5577 A emissions in subtropical nightglow arc

Motions of OI 6300 A Subtropical arc from observations in February, 1978 at Iriomote, Okinawa are analysed. Usually. arc comes in sight of observation area from southernedge in the early evening, moves northward with enhancement of emission at the speed of some tens meter per second, then turn to the southward at its northernmost location of 12 - 13 geomagnetic latitude. The maximum emission is observed during its southward motion about 15 minute after turning. The speed is same order to that of northward motion. Moving speed changes nightly within a factor of 2 refrecting the variation of plasma diffusion above the equator. OI 5577 A arc was observed simultaneously, and the correlations between intensities of 6300 A and 5577 A emission is as high as 0.9 for both time variation and spatial distribution. The 5577 A arc always locate some tenth km north and somewhat lower altitude from the 6300 A arc. This seems to be the effect of deactivatio of O('D). (author)