Lidar observations of sporadic Na layers over Gadanki (13.50 N, 79.20 E)

We present in this paper sporadic sodium layers (SSLs), which we observe with a Resonance Lidar at Gadanki, India (13.5(0) N, 79.2(0) E). The SSLs were observed on a total of 63 occasions during 464 hours of Na lidar observations from January 2005 to February 2006. The SSL occurrence rate of I event/7 h at Gadanki was obtained. These results show that the rate of occurrence of SSLs fall between 20 (0) N and 2 S-0. The most prominent sporadic layer, which formed on the night of Feb'12, 2005 exhibited a peak density of 60722 c.m(-3) near 92 km. At our Gadanki site, SSLs have the following properties (1) they develop between 88 and 98 km with average height of 94 kin (2) they develop maximum in the early morning between 0200 and 0500 LT (3) The ratio of the maximum peak density to the average Na density is normally 3 to 5, but values as high as 11 have been observed in the most outstanding cases (4) The events last from a few minutes to several hours. Most of the Sporadic Sodium layer events were downward phase.