| Project/Area Number |
14540418
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | National Institute of Polar Research |
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Principal Investigator |
MIYAOKA Hiroshi National Institute of Polar Research, Division for Research and Education, Associate Professor, 研究教育系, 助教授 (10150046)
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| Co-Investigator(Kenkyū-buntansha) |
OKADA Masaki National Institute of Polar Research, Division for Research and Education, Assistant Professor, 研究教育系, 助手 (40270425)
TAKESHITA Shu Tokai University, Research Institute of Science and Technology, Lecturer, 総合科学技術研究所, 講師 (80366046)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2002: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | aurora / small-scale structure / electric field / EISCAT radar / optical-flow |
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| Research Abstract |
Small-scale structures and dynamics of aurora are expected to contain essential clues relevant to the generation mechanisms of auroral particles in the coupling region of the topside polar ionosphere and the magnetosphere. Based on this perspective, in this project we have developed a computer program to derive the velocity vector of small-scale auroras directly from the sequential video frames using the gradient method optical flow algorism. We thereafter applied this technique to investigate the characteristics of a variety of micro/small-scale auroras; curls, flickering and black auroras, so on. It is confirmed that this method is quite useful to deduce and describe auroral dynamics, except in the case that the auroral intensity changes so rapidly.
We also made simultaneous EISCAT radar and optical imager observations for small-scale auroras in Tromso, Norway, in order to clarify the condition of plasma and electric field in the vicinity of small-scale auroras. The following feature became evident in this study.
1. The thickness of a discrete arc which forms into a curl is the thinnest, 〜100m approximately.
2. The anti-clockwise fast motion with several 100m/sec is apparent during a curl formation.
3. A small-scale(2-3km) structure is superposed in the 10-20km medium-scale structure in a flickering aurora.
4. The ion temperature is elevated at both side regions(10km scale) of an intensive auroral arc.
5. The electron density in a black aurora decreases to 30-50% level of the background diffuse aurora, but still keeps much higher than that of no auroral emission region.
These results have been presented in several science meetings and are now in preparation for publication. The optical images acquired in the EISCAT campaign were also used in the work for master's theses at Nagoya University.
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