| Summary: | 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 northern 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 of 2017 and 2018. The averaged Ca + layer observed at Syowa were with a FWHM of ~7 km, peak altitude of ~94 km, and peak density of ~10 cm -3 . The Ca + layers were observed in the main supply height region by meteor, however the layer was not always existing but sometimes disappeared. Temporal variation of Ca + density is compared with meteoric, geomagnetic, and gravity wave activities. In this presentation, we will discuss a main reason of Ca + layer disappearance with considering chemical lifetime of Ca + below 100 km.
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