Accepted author manuscript, 3.13 MB, PDF document
Available under license: CC BY: Creative Commons Attribution 4.0 International License
Final published version
Licence: CC BY: Creative Commons Attribution 4.0 International License
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Simultaneous observation of auroral substorm onset in Polar satellite global images and ground-based all-sky images
AU - Ieda, Akimasa
AU - Kauristie, K.
AU - Nishimura, Yukitoshi
AU - Miyashita, Yukinaga
AU - Frey, Harald
AU - Juusola, L.
AU - Whiter, Daniel
AU - Nosé, Masahito
AU - Fillingim, Matt
AU - Honary, Farideh
AU - Rogers, Neil Christopher
AU - Miyoshi, Yoshizumi
AU - Miura, Tsubasa
AU - Kawashima, Takahiro
AU - Machida, Shinobu
N1 - Conference code: 13
PY - 2018/5/4
Y1 - 2018/5/4
N2 - 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.
AB - 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.
KW - substorm
KW - auroral breakup
KW - aurora
KW - SUBSTORM ONSET
KW - global images
KW - all-sky images
U2 - 10.1186/s40623-018-0843-3
DO - 10.1186/s40623-018-0843-3
M3 - Journal article
VL - 70
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
M1 - 73
T2 - 13th International Conference on Substorms
Y2 - 25 September 2017 through 29 September 2017
ER -