[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-P14] Characteristic of the precipitating electron of the Omega band aurora by two-wavelength auroral observations.

*Naganawa Itsuki¹, Satoshi Kurita², Keisuke Hosokawa³, Yasunobu Ogawa⁴ (1.Nagoya University, 2.Kyoto University, 3.The University of Electro-Communications, 4.National Institute of Polar Research)

Keywords:Aurora, Omega band, Two-wavelength obeservation

The Omega band aurora is characterized by a structure resembling an inverted Ω and typically, occurs immediately after auroral break-up, drifting eastward from midnight to early morning. Previous studies on the Omega band aurora have reported that the Omega band aurora consists of a discrete aurora on the polar side and a diffuse aurora on the equator side. Our previous studies have shown a stronger downward energy flux on the western side. However, the origin of the Omega band aurora structure and its generation mechanism remain unclear. The purpose of this study is to elucidate the common features of the Omega band aurora based on observations at two wavelengths (427.8 nm and 844.6 nm) using the two EMCCD cameras in Tromsø, Norway. The analyzed event corresponds to five days from 15 to 20 February 2018 when a CIR-driven magnetic storm occurred. Prolonged substorms were observed over several days, during which three Omega band auroras were identified. All three Omega band auroras had a stronger emission intensity inside the torch and westside at the equator side. Two events on 17 February at 00:09 UT and 00:22 UT consisted of diffuse auroras, with a notable difference of about 500-1000 R between inside and outside the eastern side of the torch structure. The average precipitating electron energy of the Omega band aurora at 00:09 UT was about 1.8 keV and 3.6 keV inside and outside the torch structure, respectively. However, the average precipitating electron energy of the Omega band aurora at 00:22 UT is 2keV and did not show a significant difference between inside and outside the torch structure. The third event at 01:01 UT on 19 February consisted of a discrete aurora and a pulsating aurora, with a difference of about 5.5 kR at 427.8 nm and 800 R at 844.6 nm between the inside and outside the eastern side of the torch structure. The average energies were about 6 keV and 3.5 keV for the inside and outside the eastern side of the torch structure at 01:01 UT, respectively. In this presentation, we report on these three events, especially for, focus on the spatial distribution of the downward energy flux and characteristics energy of precipitating electrons.