SM001-03
Concentrically expanding ring-shaped pulsating aurora: simultaneous observations with Arase and high-speed cameras in Scandinavia
Monday, 7 December 2020: 04:08
Virtual
Keisuke Hosokawa1, Satoshi Kurita2, Yoshizumi Miyoshi3, Shin-ichiro Oyama3, Yasunobu Ogawa4, Yoshiya Kasahara5, Yasumasa Kasaba6, Satoshi Yagitani5, Mitsunori Ozaki5, Fuminori Tsuchiya7, Atsushi Kumamoto6, Ayako Matsuoka8, Ryuho Kataoka4, Kazuo Shiokawa9, Masafumi Shoji3, Shun Imajo3, Takeshi Takashima10, Iku Shinohara10 and Ryoichi Fujii11, (1)University of Electro-Communications, Tokyo, Japan, (2)Kyoto University, Research Institute for Sustainable Humanosphere, Kyoto, Japan, (3)ISEE, Nagoya University, Nagoya, Japan, (4)NIPR National Institute of Polar Research, Tokyo, Japan, (5)Kanazawa University, Kanazawa, Japan, (6)Tohoku University, Sendai, Japan, (7)PPARC, Tohoku University, Sendai, Japan, (8)Kyoto University, Graduate School of Science, Kyoto, Japan, (9)ISEE, Nagoya Univ, Aichi, Japan, (10)JAXA Japan Aerospace Exploration Agency, ISAS, Sagamihara, Japan, (11)Research Organization of Information and Systems, Tokyo, Japan
Abstract:
During the coordinated campaign observation of pulsating aurora (PsA) with the Arase/ERG satellite in March 2017, we observed a peculiar PsA which expanded radially and eventually formed a concentric ring-shaped structure. Such a Concentrically Expanding ring-shaped PsA (CoE-PsA) was observed during a 5 min from 00:05 to 00:10 UT on March 29, 2017 by an all-sky camera located in Sodankylä, Finland. The CoE-PsA started from a small patch of diffuse aurora in a limited region. In the first several minutes, the small patch expanded radially in all the directions. Such a variation in the first stage is very similar to that of expansion type PsA reported in the past literature. Subsequently after the initial expansion, a small dark area appeared in the center of the initial patch and this dark region expanded radially too. Expansions of the first bright area and subsequent dark area formed a ring of diffuse aurora in the final stage. By mapping the traced outer/inner boundaries of CoE-PsA, we estimated the speed of the radial expansion of the corresponding structure in the equatorial plane of the magnetosphere. The speed actually varied, but it ranged from 500 to 3000 km/s in the radial direction. The expansion speed in the longitudinal direction was about an order smaller than that in the radial direction.
The magnetic footprint of the Arase satellite was located within the region of CoE-PsA. PWE/OFA onboard the satellite observed collective bursts of chorus whose intensity variation is very similar to that of CoE-PsA. A cross-correlation analysis indicates that the temporal variation of chorus has a delay of a few seconds from that of the optical intensity at the center of the CoE-PsA. In addition, a map of cross-correlation coefficient implies that the satellite footprint was situated in the southeastern part of the CoE-PsA at the time of expansion. In the presentation, we discuss the temporal variation of CoE-PsA by considering oblique propagation of chorus waves in all the azimuthal direction. In particular, we test the feasibility of the model by comparing the speed of the radial expansion of CoE-PsA with the propagation speed of chorus in the direction perpendicular to the ambient magnetic field.
