The Tenth Symposium on Polar Science/Ordinary sessions: [OS] Space and upper atmospheric sciences, Wed. 4 Dec. /Entrance Hall (1st floor) at National Institute of Polar Research (NIPR

Akira Mizuno

Chengyu Li

Junichi Kurihara

Keisuke Hosokawa

Satonori Nozawa

Shin-ichiro Oyama

Takuo Tsuda

Tetsuya Kawabata

National Institute of Polar Research Repository

Spectra of pulsating aurora emissions observed by an optical spectrograph at Tromsø, NorwayChengyu Li1, Takuo Tsuda1, Keisuke Hosokawa1, Satonori Nozawa2, Tetsuya Kawabata2, Akira Mizuno2, Shin-ichiro Oyama2,and Junichi Kurihara31The University of Electro-Communicaitons2Nagoya University3Hokkaido UniversityPulsating auroras are a diffuse-type aurora, and are characterized by a repetition of brighter (on-phase) and darker (off-phase)auroral emissions with periods of a few to a few tens of seconds. Optical observations for pulsating auroras have been widelyperformed for many years. Recent major activities in the optical imaging observation would be, for example, high-speedobservations for faster modulations (3-Hz or higher) in the emission intensity during on-phases of pulsating auroras andground network observations in association with satellites in the magnetosphere for source regions of pulsating auroras. Whilesuch imaging observations equipped with bandpass or cutoff filters are useful for observing several auroral emission lines andbands of specific atoms and molecules, there is relatively less information on optical spectra of pulsating auroras.We have been investigating optical spectra of pulsating auroras observed by an optical spectrograph at Tromsø, Norway(69.6°N, 19.2°E). Our spectrograph is capable of measuring optical emission intensity in mainly visible range from 480 to 880nm with a resolution of 1.6 nm. The aperture, i.e. F-number, is 4. The field-of-view (FOV) is 0.03°x2°, which is pointed atmagnetic field-aligned direction. The time resolution is 1 second, and thus it can observe pulsating auroras, which have periodsfrom a few to a few tens of seconds.In this presentation, we show a pulsating aurora event occurred in morning hours on 6 March 2017. The event was a relativelylong-lasting event within the FOV of spectrograph, and it allows us to make more data integrations to enhance signal-to-noiseratios. According to a time-series of observed auroral emission data, we integrated spectral data for on- and off-phasesseparately. After such data integrations, auroral emission lines, such as OI 557.7 nm, OI 630 nm, and OI 844.6 nm, as well asemission bands, such as N2 1PG, were clearly found in both integrated-optical spectra of on- and off-phases. Then, wecalculated a difference spectrum between the optical spectra of on- and off-phases. In the difference spectrum, clear line-likeshapes were found for the emission lines of OI 557.7 nm and OI 844.6 nm. On the other hand, a shape of the differencespectrum around 630 nm does not seem to be a line-like shape due to OI 630 nm, and it seems to be a part of band-like shapeof the emission band of N2 1PG. These results would suggest an importance of spectral observations of pulsating auroras, inaddition to imaging observations.

Spectra of pulsating aurora emissions observed by an optical spectrograph at Tromso, Norway

https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=15869&item_no=1&attribute_id=16&file_no=1

Spectra of pulsating aurora emissions observed by an optical spectrograph at Tromso, Norway

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