[P-EM13] Coupling Processes in the Atmosphere-Ionosphere System

[PEM13-04] Comparing Ca⁺ density variation over Syowa with background wind, geomagnetic activity and number of meteors

*Mitsumu K. Ejiri^1,2、Takanori Nishiyama^1,2、Takuo T. Tsuda³、Masaki Tsutsumi^1,2、Katsuhiko Tsuno⁴、Makoto Abo⁵、Takuya Kawahara⁶、Takayo Ogawa⁴、Satoshi Wada⁴、Takuji Nakamura^1,2 (1.National Institute of Polar Research、2.The Graduate University for Advanced Studies, SOKENDAI、3.The University of Electro-Communications、4.RIKEN,RAP、5.Tokyo Metropolitan Univ.、6.Shinshu Univ.)

キーワード：Ca+ layer, Lidar observation, Antarctic

Layers of metal ions in the mesosphere and lower-thermosphere (MLT) are produced by meteoric ablation. The meteoric metal ions have relatively long chemical lifetime in the MLT region and behave as plasma affected by neutral atmosphere dynamics. Ca⁺ is one of meteoric metal ion and only one ion, which can be measured its vertical profile from the ground by a lidar sounding. Ca⁺ lidar observations have been conducted at the low and mid latitudes in the nothern hemisphere only. A resonance scattering lidar developed by the National Institute of Polar Research (NIPR) was installed at Syowa (69S, 40E), Antarctic in 2017 and successfully obtained Ca⁺ density profiles 6 nights in total in Spring in 2017 and 2018. The averaged Ca⁺ layer observed at Syowa were with a width of ~7 km, peak altitude of ~94 km, and peak density of ~10 cm^-3. In the most of nights, the Ca⁺ layers were lasting several hours around 90-100 km with density variation while the lifetimes derived based on steady state chemistry with chemical reactions and rate coefficients listed in Plane et al. (2018) were less than 15 minutes. In this presentation, we will investigate a major reason of Ca⁺ density variation by comparing the temporal variation of Ca⁺ density with background neutral wind, geomagnetic activity, and meteor activity.