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2019 Fiscal Year Final Research Report

Role of non-uniform ionosphere in the formation of auroral vortices revealed by tomography method

Research Project

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Project/Area Number 17K05672
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Research Field Space and upper atmospheric physics
Research InstitutionNational Institute of Polar Research

Principal Investigator

Tanaka Yoshimasa  国立極地研究所, 研究教育系, 特任准教授 (50425766)

Project Period (FY) 2017-04-01 – 2020-03-31
Keywordsオーロラ / 磁気圏電離圏結合 / トモグラフィ解析 / 電離圏電気伝導度 / 3次元電流系 / 電離圏カウリング効果
Outline of Final Research Achievements

We established a new method based on the auroral tomography to retrieve various physical quantities of mesoscale aurora, such as three-dimensional (3D) distribution of volume emission rate, energy distribution of precipitating electrons, and electrical conductivity, electric field, and 3D electric current system in the ionosphere, with a time resolution less than 10s. We applied this method to data obtained with multi-point imager network, magnetometer network, and incoherent scatter radar in the northern Scandinavia. We succeeded to obtain 3D current system of auroral vortices in the discrete aurora, which change their form quickly, and further to extract the component due to the ionospheric Cowling effect included in the current system.

Free Research Field

超高層大気物理学

Academic Significance and Societal Importance of the Research Achievements

これまで水平2次元の研究が主だったオーロラ研究を3次元に拡張し、イメージャや磁力計等の地上多点観測網のデータを最大限活用することで、電離圏磁気圏結合過程における様々な物理量を10秒以下の高い時間分解能で導出できること、電離圏の能動的役割を抽出できることを示したという点で本研究の学術的意義は大きい。開発した手法は、2022年頃から観測が始まる国際共同プロジェクトEISCAT_3Dと組み合わせることで、新しい極域電離圏3次元観測・研究に寄与する。本成果は、地上総合観測によって地球近傍宇宙空間と極域超高層大気の結合過程を時々刻々とモニターできる可能性を示しており、宇宙天気研究の発展に貢献する。

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Published: 2021-02-19  

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