地球からの酸素イオンが,磁気圏のプロセスを経て大気中に失われていること
K Seki1, R C Elphic, M Hirahara
1Department of Earth and Planetary Sciences, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan. seki@space.eps.s.u-tokyo.ac.jp
まとめ
地球 地球 地球 地球 地球 地球
科学分野:
- 惑星科学は惑星科学である.
- 大気科学 大気科学
- 宇宙物理学 宇宙物理学
背景:
- 酸素イオン (O+) は大気組成に不可欠である.
- 極外流は大気逃亡の重要な経路である.
- 酸素の損失に関する以前の推定では,戻り流が無視されていた可能性がある.
研究 の 目的:
- 地質学的時間尺度における地球の大気からの純酸素損失を定量化するために.
- 観測された極流出と推定された全酸素損失率の間の不一致を調整する.
- 大気中の酸素保持における磁気圏の逆流の役割を調査する.
主な方法:
- 高地からの宇宙船観測の分析.
- 4つの異なる大気逃避路の調査.
- イオン流出と潜在的帰流のメカニズムのモデリング.
主要な成果:
- 観測された極性O+の流出は,大気中の酸素の有意な損失を示唆している (約. 30億年にわたって18%).
- 既知の脱出ルートを考慮すると,酸素の総損失は,極地からの流出よりも大きさの順序が低い.
- 大量の磁気圏からイオノスフィアへの帰還流が,この不一致を説明するために推論されている.
結論:
- 30億年にわたる地球の大気からの純酸素の損失は,以前に推定されたものより大幅に低く,約2%です.
- 磁気圏のプロセス,特に帰流は,大気中の酸素を保持する上で重要な役割を果たします.
- 大気圏の脱出と保持に関する我々の理解を修正することは,惑星の居住可能性の研究にとって不可欠である.
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