地球の両極の静電場と,イオンが宇宙に逃げるための役割
Glyn A Collinson1,2,3, Alex Glocer4, Robert Pfaff4
1Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA. glyn.a.collinson@nasa.gov.
Nature
|August 28, 2024
まとめ
地球のイオン圏の電子は強力な電場を生成し,磁気圏への冷たいイオン流出を大幅に増加させます. この発見は 宇宙のプラズマと磁気圏の動力学に対する理解を 変えてくれます
科学分野:
- 宇宙物理学
- 大気科学
- プラズマ物理学
背景:
- イオノスフィアのプラズマは地球の磁気圏に大きく貢献している.
- これまでのイオン脱出の理論には 波粒子の相互作用と グローバルな静電場が含まれていました
- 寒い極風のイオンの観測は 静電場の存在を示唆した.
研究 の 目的:
- イオノスフィアの電子によって生成される惑星の静電場の存在と影響を調査する.
- このフィールドのイオン流出と磁気圏のプラズマ供給への貢献を定量化する.
主な方法:
- 高度250kmから768kmまでの電位下落の実験測定
- 惑星の静電場の定量化 (E).
- 極のイオノスフィアの構造とスケールの高さに対するアンビポラーフィールドの効果の実証.
主要な成果:
- 静電場 (E = 1.09 ± 0.17 μV m−1) に起因する +0.55 ± 0.09 V の電位下落の発見.
- 実験的な証拠によると,両極のフィールドは,極のイオノスフィアのスケールの高さを271%増加させる.
- 磁気圏への冷たいO+イオンの供給が3800%以上増加した.
結論:
- 地球の静電場は,イオノスフィアの電子によって駆動され,極風を駆動するのに十分です.
- このフィールドは,磁気圏に存在する冷たいH+イオンの主要な源である可能性が高い.
- 静電場は,極のイオノスフィアの構造とイオノスフィアと磁気圏の結合を制御する上で重要な役割を果たします.
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