Observations in the polar middle atmosphere by rocket-borne Rayleigh lidar: First results
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 1999
Received: 17 August 1998
Accepted: 24 May 1999
Published: 26 June 2014
We present a new rocket instrument which measures total atmospheric density with great precision and resolution by Rayleigh scattering of infrared light. Comparison with a ground-based lidar shows: (a) both instruments measure the same physical parameters, even though they have different integration times and volumes. (b) The observed density structures change little over the course of an hour and the horizontal distance of 14 km. The rocket instrument has a basic vertical resolution of approximately 8 m and a number density precision of 4.2 · 1019 m−3. Above 56 km we integrate over an increasing vertical range, reaching 80 m at 70 km. The measured number density profile shows remarkable alternations between very stable layering and metastable layering (adiabatic lapse rate) in the atmosphere between 52 km and 71 km. Comparison with the hodograph of the horizontal wind profile measured by a falling sphere 29 minutes later shows that the metastable height regions coincide with height regions where the hodograph deviates from an ideal spiral. The observation is tentatively interpreted as a gravity wave that is saturating (or encountering a critical level) in these height regions. The comparison of the fine-scale neutral number density observations with measurements of ion density by electrostatic skin probes on board the same vehicle shows a number of ion density enhancements in the stably-layered height regions. With one exception out of six cases, these enhancements occur where the vertical gradient of the meridional wind would collect positive ions as in sporadic E layers. This may be the first observation of such ion density enhancements in the height region 55 to 70 km.