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

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Abstract

[1] 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 Tromsø, Norway (69.6°N, 19.2°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 × 1010 m−2 s−1. Dominant oscillation periods in the wavelike 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.

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