[P-EM09] Space Weather and Space Climate

[PEM09-13] Optical observations of polar cap aurora: continuous measurements with an EMCCD all-sky imager in Longyearbyen, Norway

★Invited Papers

*Keisuke Hosokawa¹, Satoshi Taguchi², Yasunobu Ogawa³, Takuo T. Tsuda¹, Ryuho Kataoka³ (1.Department of Communication Engineering and Informatics, University of Electro-Communications, 2.Graduate School of Science, Kyoto University, 3.National Institute of Polar Research)

An all-sky optical imager has been operational in Longyearbyen, Norway since October 2011 (Taguchi et al., 2012). The all-sky imager is equipped with an EMCCD camera, which has allowed us to observe various auroral and airglow phenomena at the polar cap latitudes for more than one solar cycle. The all-sky imager data have been extensively used for high temporal resolution measurements of polar cap patches, which are regions of enhanced electron density in the polar cap propagating along the anti-sunward convection (e.g. Hosokawa et al., 2013a; 2013b; 2014; 2016a; 2016b). In addition, the all-sky imager has been used to detect weak auroral phenomena in the polar cap, which are usually observed during northward IMF conditions (Hosokawa et al., 2020 and references therein). Such aurorae in the polar cap are often called Sun-aligned arcs and represent complicated structures at the interface between the solar wind, the magnetospheric lobe and the boundary plasma sheet. In this talk we will show several case examples of such faint auroral emission obtained with the all-sky Imager during the last solar cycle, in particular during the solar minimum period from 2018 to 2021. In addition, we will present a unique case of diffuse auroral emission that has only recently been identified.