Fine structure of sporadic sodium layer observed with a sodium lidar at Tromsø, Norway

We report a sporadic sodium layer (SSL), in particular its fine structure, observed at 92-98 km between 20:00 and 23:30 UT (21:00-24:30 LT) on 11 January 2011 using a sodium lidar, which was installed in the European incoherent scatter (EISCAT) radar site at Tromso, Norway (69.6 degrees N, 19.2 degrees E) in early 2010. The sodium lidar measurement with 5-sec time-resolution reveals the details of dramatic sodium-density increase as well as short-period wavelike structure in the SSL. The rate of increase of height-integrated sodium density at the beginning of the SSL event was 6.4-9.6 x 10(10) m(-2) s(-1). Dominant oscillation periods in the wave-like structures were 7-11 min at 95-98 km and 3 min at 92-95 km. The calculated power spectral densities are well represented by power laws, implying the presence of the short-period waves and turbulence in the frequency range of 10(-4)-10(-1) Hz. Citation: Tsuda, T. T., et al. (2011), Fine structure of sporadic sodium layer observed with a sodium lidar at Tromso, Norway, Geophys. Res. Lett., 38, L18102, doi:10.1029/2011GL048685.