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Ieda A, Kauristie K, Nishimura Y, Miyashita Y, Frey HU, Juusola L, Whiter D, Nosé M, Fillingim MO, Honary F, Rogers NC, Miyoshi Y, Miura T, Kawashima T, Machida S. Simultaneous observation of auroral substorm onset in Polar satellite global images and ground-based all-sky images. EARTH, PLANETS, AND SPACE : EPS 2018; 70:73. [PMID: 31258378 PMCID: PMC6560699 DOI: 10.1186/s40623-018-0843-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 04/17/2018] [Indexed: 06/09/2023]
Abstract
Substorm onset has originally been defined as a longitudinally extended sudden auroral brightening (Akasofu initial brightening: AIB) followed a few minutes later by an auroral poleward expansion in ground-based all-sky images (ASIs). In contrast, such clearly marked two-stage development has not been evident in satellite-based global images (GIs). Instead, substorm onsets have been identified as localized sudden brightenings that expand immediately poleward. To resolve these differences, optical substorm onset signatures in GIs and ASIs are compared in this study for a substorm that occurred on December 7, 1999. For this substorm, the Polar satellite ultraviolet global imager was operated with a fixed-filter (170 nm) mode, enabling a higher time resolution (37 s) than usual to resolve the possible two-stage development. These data were compared with 20-s resolution green-line (557.7 nm) ASIs at Muonio in Finland. The ASIs revealed the AIB at 2124:50 UT and the subsequent poleward expansion at 2127:50 UT, whereas the GIs revealed only an onset brightening that started at 2127:49 UT. Thus, the onset in the GIs was delayed relative to the AIB and in fact agreed with the poleward expansion in the ASIs. The fact that the AIB was not evident in the GIs may be attributed to the limited spatial resolution of GIs for thin auroral arc brightenings. The implications of these results for the definition of substorm onset are discussed herein.
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Affiliation(s)
- Akimasa Ieda
- Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Aichi Japan
| | | | - Yukitoshi Nishimura
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA USA
- Department of Electrical and Computer Engineering and Center for Space Physics, Boston University, Boston, MA USA
| | | | - Harald U. Frey
- Space Sciences Laboratory, University of California, Berkeley, CA USA
| | | | - Daniel Whiter
- School of Physics and Astronomy, University of Southampton, Highfield, Southampton UK
| | - Masahito Nosé
- Data Analysis Center for Geomagnetism and Space Magnetism, Graduate School of Science, Kyoto University, Kyoto, Japan
| | | | - Farideh Honary
- Space and Planetary Physics, Lancaster University, Bailrigg, Lancaster UK
| | - Neil C. Rogers
- Space and Planetary Physics, Lancaster University, Bailrigg, Lancaster UK
| | - Yoshizumi Miyoshi
- Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Aichi Japan
| | - Tsubasa Miura
- Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Aichi Japan
| | - Takahiro Kawashima
- Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Aichi Japan
| | - Shinobu Machida
- Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Aichi Japan
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