Ionospheric irregularities in low-mid latitudes and effects over Japanese ionosphere

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K17814
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Space and upper atmospheric physics
• Research Institution: Kyoto University (2018-2019); National Institute of Information and Communications Technology (2016-2017)
• Principal Investigator: Yokoyama Tatsuhiro 京都大学, 生存圏研究所, 准教授 (30397525)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 電離圏 / プラズマバブル / MSTID / シミュレーション

Outline of Final Research Achievements

Equatorial plasma bubble (EPB) is a well-known phenomenon in the equatorial ionosphere. As it causes severe scintillation in the amplitude and phase of radio signals, it is important to understand and forecast the occurrence of EPB from a space weather point of view. In order to simulate the instability in the equatorial ionosphere, a 3D high-resolution bubble (HIRB) model with a grid spacing of as small as 200 m has been developed. It provides a unique opportunity to characterize intermediate-scale EPB structure, which was not well resolved until very recently. Ahievements of the HIRB model are as follows: (1) Vertical wind perturbation with an amplitude of a few meters per second can work as a seeding of EPBs.(2) Developed structure is characterized by a two-component power law spectral density which fully supports the reported EPB diagnostics from previous in situ measurements.

Free Research Field

超高層物理学

Academic Significance and Societal Importance of the Research Achievements

GPS等を用いた精密航法、測位のためには、電離圏の影響による誤差を正しく推定することが必要である。その誤差の最大の要因の1つである赤道プラズマバブルに関して、数値モデルを用いた研究を行った。従来は衛星・ロケット観測に頼らざるを得なかった微細な構造がモデルにより再現され、実際の電波伝搬に及ぼす影響の評価が可能となった。今後、電波伝搬モデルと組み合わせることで、GPSの精度向上や自動運転の実用化に向けた研究へと発展することが期待できる。