2018 Fiscal Year Final Research Report
Identification of Generation/Driving Mechanisms of Upper-Atmospheric Discharges and Global Electric Circuit Using Satellite Data and Numerical Simulation
| Project/Area Number |
16H04055
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Hokkaido University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
平木 康隆 電気通信大学, 大学院情報理工学研究科, 研究員 (80514843)
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| Research Collaborator |
BANDHOLNOPPARAT kittanapat
SHIMIZU chiharu
SATO tsuyoshi
KIKUCHI hiroshi
MINAMOTO yasuhiro
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | 雷放電 / 高高度放電発光現象 / スプライト / 全球電流回路 / 国際宇宙ステーション |
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| Outline of Final Research Achievements |
The main objectives of this research are (1) to identify the generation mechanism of the horizontal distribution of sprites, and (2) to estimate the Z-value (occurrence ratio of intra-cloud to cloud-to-ground discharges) and to evaluate the contribution of the global lightning activities to the global electrical circuit (GEC) as the electrical current generator. For these purposes, JEM-GLIMS optical data, ground-based lightning and atmospheric electric field data are analyzed. From the JEM-GLIMS and ground-based lightning data, the latitudinal/seasonal/regional dependences of the Z-value are quantitatively and first estimated in the world. In addition, the 3-dimensional GEC model with the spatial and temporal resolution of 0.2x0.2 deg and 5 min in the 0-80km altitude range is newly developed. The quantitative comparison between the model results and observational data revealed that the global lightning activities contribute only ~20% of the total electrical current to the GEC.
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| Free Research Field |
超高層物理学，大気電気学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究によって明らかとなったZ値の緯度分布と季節・地域依存性は，過去の研究とは比較にならないほど圧倒的な統計量と定量性の観点から世界トップと言え，世界標準となり得る重要な成果である。また，新規に開発した三次元全球電流回路モデルは，雷放電のみならず衛星観測に基づく世界降水量分布・雲分布も初期値に組み込み，高い時間・空間分解能で世界のあらゆる点の大気電場強度を算出できる点で画期的である。本研究で明らかとなった，雷放電が全球電流系の電流駆動源として約20%しか担っていないという事実は，革新的な成果といえる。
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