SPORADIC ENHANCEMENT OF THE MESOSPHERIC SODIUM DURING THE PERSEIDS-GAMMA METEOR-SHOWER

Measurements of the night-time atmospheric sodium layer have been perf ormed intermittently since 1977, using a dye lidar at Fukuoka, Japan ( 33.4-degrees-N, 130.2-degrees-E). Sporadic enhancements of the total c olumn abundance of sodium during the Perseids gamma meteor showers wer e observed on the four sets of nights of August 12-14, 1978, 1979, 198 1 and 1983. The sodium abundance increased during nighttime of the sho wer period, but such correlative increase with permanent meteor shower has not been seen at low latitudes by lidar or twilight observations. Altitude profiles of the layer obtained during the shower show three interesting features. (1) The column abundance of sodium atoms increas ed with arising of the radiant point of the meteor shower. (2) The pea k height of the layer began to decrease slightly about two hours befor e dawn. (3) The column abundance drastically increased just before daw n.