2003 Fiscal Year Final Research Report Summary
Energy coupling between atmosphere and inosphere via electrical descharge
| Project/Area Number |
13304037
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 | Tohoku University |
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Principal Investigator |
FUKUNISHI Hiroshi Tohoku University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (90099937)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIWARA Hitoshi Tohoku University, Graduate School of Environmental Studies, Research Associate, 大学院・理学研究科, 助手 (50298741)
MURATA Isao Tohoku University, Graduate School of Science, Associate Professor, 大学院・環境科学研究科, 助教授 (00291245)
TAKAHASI Yukihiro Tohoku University, Graduate School of Science, Lector, 大学院・理学研究科, 講師 (50236329)
YUMOTO Kiyofumi Kyushu University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (20125686)
SAKANOI Takeshi Tohoku University, Graduate School of Science, Research Associate, 大学院・理学研究科, 助手 (80271857)
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| Project Period (FY) |
2001 – 2003
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| Keywords | sprite / elves / lightning / thundercloud / ELF / VLF / Solar activity / Schumann resonance |
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| Research Abstract |
In order to investigate the generation mechanisms of luminous events in the middle and upper atmosphere induced by lightning discharge and their relationship to the parental thunderstorm activity, some observation campaigns and continuous measurements have been carried out using a multipoint observation system composed of several optical instruments and VLF-ELF radio wave sensors. Detail analysis and computer simulations based on the observation data clarified following issues : (1) Thunderclouds producing sprites around Japan in wintertime are classified into 4 types and the apparent feature of sprites depends on the geographic location. (2) Cloud to ground discharge generating winter sprites in Japan occurs in the most active convective region of the thundercloud. (3) Considering the appearance of intermittent radio wave in VLF range just after sprite optical emissions, it is suggested that hybrid type discharge consisting of cloud-to-ground and intra-cloud discharges is relating to sprite generation. (4) Number of columns in a sprite event well correlates to the peak current of the parent lightning while the vertical length of column shows good correlation with charge moment of the cloud to ground lightning. (5) The average upper and bottom heights and the horizontal extent of sprite halo are 88 km, 73 km and 86 km, respectively. The estimated electron energy is 6 ?23 eV. (6) The average number of sprite evens for a day is estimated to be 720 based on the ELF measurements. (7) The lightning energy shows variation with a time period of 27.9 days, which may be caused by solar activity. (8) Sprites and sprite halo could be major sources of O(D) in the nighttime mesosphere.
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