[P-EM11] Dynamics of the Inner Magnetospheric System

[PEM11-P07] Characteristics of precipitating electrons of the omega band based on two wavelength optical measurement

*Yudai Morii¹, Satoshi Kurita², Yoshizumi Miyoshi¹, Kohei Toyama¹, Keisuke Hosokawa³, Shin-ichiro Oyama¹, Yasunobu Ogawa⁴, Shinji Saito⁵ (1.Institute for Space-Earth Environmental Reserch, 2.Research Institute for Sustainable Humanosphere, 3.The University of Electro-Communications, 4.National Institute of Polar Research, 5.National Institute of Information and Communications Technology)

The auroral omega band is found from midnight to dawn side during substorms and is characterized by a curved “Omega” structure that drifts to the east. The omega bands have a latitudinal structure, with discrete auroras on the polar side, while diffuse and pulsating auroras occur on the low-latitude side. It has been discussed that the omega-bands are related to fast plasma flow and shear motion in the magnetosphere, and the spatial structure and temporal variation of the omega-bands are important to understand the coupling between the magnetosphere and ionosphere. In this study, we investigate the two-dimensional spatial distribution of the characteristic energy and downward energy flux of the precipitating electrons in the omega-band using data from a multi-wavelength EMCCD camera in Tromsø, Norway. In this study, we estimate the characteristic energies of the omega-band events in the substorm recovery phase observed on February 3, 2017 from 1:30-2:30 UT, based on the ratio of emission intensities at two wavelengths, 427.8 nm and 844.6 nm. The east-west structure of the diffuse aurora on the low-latitude side of the omega band is found and the downward energy flux is approximately 2 times larger on the west side, although there is no difference in the downward electron characteristic energy. Discrete and diffuse auroras were observed from the polar to the low latitudes of the omega band, and black auroras were also observed inside the diffuse auroras. In the presentation, we will discuss the characteristics and temporal variations of the precipitating electron energy in each region of the omega band.