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

[PEM13-P14] Observations of the ionosphere by the imager onboard the Antarctic research vessel "Shirase"

*Saki Yamashina¹, Akinori Saito¹, Takeshi Sakanoi², Takuo T. Tsuda³, Takeshi Aoki³, Mitsumu K. Ejiri⁴, Takanori Nishiyama⁴, Yuta Hozumi⁵, Takahiro Naoi⁵, Masato Nagahara⁵ (1.Graduate School of Science, Kyoto University, 2.Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, 3.Graduate School of Informatics and Engineering, The University of Electro-Communications, 4.National Institute of Polar Research, 5.National Institute of Information and Communications Technology)

Keywords:airglow, aurora

Ionospheric phenomena such as aurora and airglow have been observed by ground-based imager networks [e.g., Shiokawa et al.,1999]. The ionosphere over the ocean has not been observed sufficiently and there are observational gaps. Especially the southern hemisphere, where the ocean dominates a large proportion, has large gaps. If these gaps are filled, there will be more opportunities to observe the differences in phenomena between the northern and southern hemispheres [e.g., Fukushima et al., 2017] and the influence of land and sea on the mesosphere [e.g., Hozumi et al., 2019] and the ionosphere. There are previous cases of 630.0-nm airglow observations from the International Space Station (ISS) [e.g., Nakata et al., 2018]. However, only ultraviolet airglow has been observed for satellite-based observations [e.g., Immel et al., 2003]. We conducted observations of the ionosphere from the ocean with a vessel-borne imager to fill these gaps. From the 61st to 63rd Japanese Antarctic Research Expedition (JARE 61-63), the all-sky imager was installed on the Antarctic research vessel "Shirase" and multi-wavelength observations were conducted between Japan and Syowa station. The observation periods were from November 2019 to March 2020 for JARE61, from November 2020 to February 2021 for JARE62, and from November 2021 to March 2022 for JARE63. The OI 630.0-nm airglow was observed with an exposure time of 19s for JARE61, the OI 630.0-nm and 670.0-nm airglow were observed with an exposure time of 9s for JARE62, and the OI 630.0-nm and 760.0-nm airglow were observed with an exposure time of 18s for JARE63. The 670.0-nm and 760.0-nm airglow both attribute to the N₂ 1PG aurora and OH airglow in the E-region of the ionosphere. The imager was mounted on a 3-axis attitude stabilized gimbal which cancels the vessel's vibration to take images with little vibration. The observed images were corrected and converted into geographical images by assuming emission altitudes (250 km for 630.0-nm airglow, and 100 km for 670.0-nm and 760.0-nm airglow) to identify observed phenomena. The aurora and airglow were successfully observed during JARE61, and airglow was observed during JARE62. Aurora was also observed during JARE63, although it is still in the initial analysis. These phenomena are compared with data of total electron content observed by the GNSS receiver, which was installed in our system from JARE62, and other data of satellite-based or ground-based observations. The accuracy of the ionospheric observation from the vessel is evaluated and traveling ionospheric disturbances (TID) and other phenomena are analyzed.

References
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