[P-EM14] Study of coupling processes in solar-terrestrial system

[PEM14-P03] Resonance-scattering Ca/Ca⁺ lidar precisely observing the upper atmosphere: simultaneous observation of Ca and Ca⁺ layers and measurement of Ca⁺ temperature

*Masayuki Katsuragawa^1,2, Mutsumi K Ejiri^2,3, Ayaka Hashimoto¹, Sota Kobayashi¹, Sayako Miyoshi¹, Hikaru Miyagi¹, Ken'ichi Nakagawa¹, Takuo T Tsuda¹, Chiaki Ohae¹, Takuji Nakamura^2,3 (1.University of Electro-Communications, 2.National institute of Polar Research, 3.The Grad. Univ. for Advanced Studies)

Keywords:Resonance Scattering Lidar, Ca, Ca+ ion, Ti:sapphire laser

To observe the upper atmosphere from the ground with a high temporal and spatial resolution, we have developed a resonant-scattering Ca/Ca⁺ lidar that can simultaneously observe both meteoric Ca and Ca⁺. The system is based on a solid-state laser (the dual-wavelength injection-locked nanosecond pulsed Ti:sapphire laser), providing a major benefit of operating stably for long periods. As the development of this lidar system has reached a practically applicable stage and a preliminary operation has been also tested, the simultaneous observation of Ca and Ca⁺ over a long time has been attempted. We could successfully conduct the simultaneous observation of Ca and Ca⁺ for an entire night (December 24, 2024). We found that the complex spatio-temporal behaviors of Ca and Ca⁺ were very similar to each other although their detailed density-distributions were different. We also observed a relatively dense Ca⁺ layer a few kilometers deep that appeared at the uppermost altitude in the observed range of 80 – 105 km, being recognized as a formation of a sporadic E layer.

The developed resonant-scattering Ca/Ca⁺ lidar has a high frequency-purity and a high frequency-accuracy, thereby, giving it the ability to also measure temperature and wind/drift of the target atoms/ions in the observed altitude range by measuring the Doppler broadened resonance profile. In fact, we conducted a preliminary test of Ca⁺ temperature observation continuously for one hour. In the presentation, in addition to the details of the Ca⁺ temperature measurements, we will also discuss what new insights we have gained from this new lidar, including comparisons with data from the ionosonde observation, and etc.