First evidence of patchy flickering aurora modulated by multi‐ion electromagnetic ion cyclotron waves

Electromagnetic ion cyclotron (EMIC) waves, one of the possible origins of flickering aurora, have been thought to modulate the electron flux at a few thousand kilometers. In fact, flickering aurora with a frequency range of 3–15 Hz has often been identified by ground‐based optical observations and...

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Bibliographic Details
Published in:Geophysical research letters 2017-05, Vol.44 (9), p.3963-3970
Main Authors: Fukuda, Yoko, Kataoka, Ryuho, Uchida, Herbert Akihito, Miyoshi, Yoshizumi, Hampton, Donald, Shiokawa, Kazuo, Ebihara, Yusuke, Whiter, Daniel, Iwagami, Naomoto, Seki, Kanako
Format: Article
Language:English
Subjects:
aurora
Auroras
Cyclotrons
Data
Electron density
Flux
Frames per second
Ground-based observation
High speed
Hydrogen
Identification
Imaging
Imaging techniques
Ion cyclotron waves
Ions
M‐I coupling
Optical observations
Origins
Signatures
wave‐particle interaction
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Summary:Electromagnetic ion cyclotron (EMIC) waves, one of the possible origins of flickering aurora, have been thought to modulate the electron flux at a few thousand kilometers. In fact, flickering aurora with a frequency range of 3–15 Hz has often been identified by ground‐based optical observations and has been interpreted to be caused by O+‐band EMIC waves. However, extant research to date has not identified possible signatures of H+‐band EMIC waves due to technical limitations of ground‐based high‐speed imagers. The present study shows the first evidence that patchy flickering aurora could be modulated by H+‐band EMIC waves, based on the data obtained from imaging observations at 160 frames per second. The sporadic appearance of the flickering aurora in the frequency range of 50–80 Hz coexisted with typical flickering auroras of approximately 10 Hz. These results are consistent with the hypothesis that flickering auroras are generated by multi‐ion EMIC waves. Key Points Flickering aurora with a patchy structure varying every 1/160 s was detected by ground‐based high‐speed imaging observation The rapidly varying flickering aurora sporadically appeared on time scales of 0.1 s, with smaller patch structure than typical one Flickering auroras are likely to be generated by multi‐ion electromagnetic ion cyclotron waves
ISSN:0094-8276
1944-8007
DOI:10.1002/2017GL072956