Research on the beaming structures of Jupiter's decametric radio emissions observed by Jovian polar orbiter Juno and LWA

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K05570
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Space and upper atmospheric physics
• Research Institution: Kochi National College of Technology
• Principal Investigator: IMAI Kazumasa 高知工業高等専門学校, ソーシャルデザイン工学科, 嘱託教授 (20132657)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 木星電波 / 放射機構 / 木星探査機 / 地上観測 / 電波源の位置 / ビーム構造 / モジュレーションレーン / 偏波特性

Outline of Final Research Achievements

Using Long Wavelength Array (LWA) data we analyzed the modulation lanes and the Riddle arcs and found that almost all of the Riddle arcs correspond to a zero-degree lead angle. This means that the radio sources related to the Riddle arcs are located along the instantaneous Io flux tube. This result is consistent with the conclusion of Riddle paper using Voyager data. With the advantage of Juno's unique polar orbit, the dynamic spectra recorded by the Waves instrument show the latitudinal dependence on the Riddle arcs, clearly. The appearance of these Riddle arcs remains isolated from the other groups of the radio arcs. The Riddle arcs occur during the time of positive Jovigraphic latitude, and their existence implies sharp beaming from the northern hemisphere radio source. We consider this finding of Riddle arcs recorded by Juno to be important because it would provide a direct link with the brightness of Io's footprint at the ultraviolet wavelength for a further study.

Free Research Field

宇宙電波工学

Academic Significance and Societal Importance of the Research Achievements

1955年に発見された木星からの短波帯の自然電波放射である木星デカメートル波は、地球上でも観測可能なほど強力な電波放射である。この放射機構を解明するためには、その３次元的なビーム構造を調べることが重要な鍵となると考えられている。本研究では木星探査機Junoと地上の低周波電波望遠鏡LWAの木星電波観測データを総合的に解析することにより、Riddle Arcと呼ばれる特徴的な電波放射の3次元的な木星電波放射ビーム構造を明らかにすることができた。