[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-P03] Spatial distributions of precipitating electron energy of pulsating aurora using multi-wavelength cameras

遠山 航平¹、栗田 怜²、*三好 由純¹、細川 敬祐³、小川 泰信⁴、大山 伸一郎¹、齊藤 慎司⁵、浅村 和史⁶ (1.名古屋大学宇宙地球環境研究所、2.京都大学、3.電気通信大学、4.国立極地研究所、5.情報通信研究機構、6.宇宙航空研究開発機構)

キーワード：脈動オーロラ、多波長光学観測

Pulsating aurora (PsA) is characterized by quasi-periodic intensity modulations with a period of a few to tens of seconds which is known as the main modulation. Whistler-mode chorus waves play a crucial role in the pitch angle scattering of electrons to cause PsA, and the lower-band chorus causes precipitation of electrons whose energy is greater than several keV [Miyoshi et al., 2015]. The multi-wavelength optical measurements are useful to estimate the temporal-spatial variations of precipitating electron energy. In Tromsoe, Norway, we have operated highly-sensitive EMCCD cameras, which have simultaneously observed all-sky images of the emission intensity at the two wavelengths (427.8 and 844.6 nm) with a sampling frequency of 10 Hz. In this study, we investigate the spatio-temporal variations of precipitating electron energy using these EMCCD camera data. We estimated the precipitating electron energy of PsA by comparing the emission intensity ratio of the two emission lines using the all-sky image and the emission intensity by the GLobal airglOW (GLOW) model [Solomon, 2017]. We analyzed the events of March 6, 2017 at 2:15 UT. A moderate substorm occurred between 02:00 and 03:00 UTC on this day, and significant PsA emission was observed around 02:15 UTC during the substorm recovery phase. As a result of the case study, a few keV differences are found inside the patch, which suggests the spatial distributions of chorus-wave particle interactions in the magnetosphere. In addition to that, we developed auroral emission simulations combined with a test particle simulation and a two-fluid model to investigate relationship between the actual energy spectrum of precipitating electrons and the expected characteristic energy derived from the optical measurements. The result suggests that the energy estimated from optical observations is smaller than the energy with the largest downward energy flux. We also discussed the effect of the background emission on the estimated energy and found that the estimated energy may be underestimated if the background emission is not subtracted.