HST/STISでイオの大気の遠紫外線画像スペクトロスコピーを撮影しました
F L Roesler1, H W Moos, R J Oliversen
1Physics Department, University of Wisconsin, 1150 University Avenue, Madison, WI 53706, USA.
Science (New York, N.Y.)
|January 15, 1999
まとめ
遠紫外線画像は,木星の月イオのオーロラ放射に関する新しい詳細を明らかにしました. 酸素と硫黄の放出は木星の磁場に関連した明確なパターンを示し,水素の放出はユニークな行動を示しています.
科学分野:
- 惑星科学 惑星科学
- 宇宙物理学 宇宙物理学
- 天体物理学 天体物理学
背景:
- 木星の火山活動のある月イオは,薄い大気を持ち,木星の強烈な磁気圏に浸されています.
- 以前の観測では,Ioからの放射が検出されましたが,遠くの紫外線スペクトルの詳細な空間的および時間的な変動はよく理解されていません.
研究 の 目的:
- Io.からの遠紫外線放射の空間的分布と時間的変動性を調査する.
- ハイドロゲンライマン・アルファなどのこれまでに検出されていない排出量を特定し,特徴づけ,既知の酸素と硫黄の排出量と比較する.
主な方法:
- ハッブル宇宙望遠鏡の画像スペクトログラフ (STIS) を活用して,Ioの高解像度遠紫外線スペクトル画像を取得しました.
- 波長1250~1500アンストームの範囲の放射を分析し,OI,SI,Hライマン・アルファ線に焦点を当てた.
主要な成果:
- OIとSIの放射の明るい赤道点が検出され,木星の磁場方向に変化しています.
- 観測された四肢は,木星の磁界赤道と向き合う半球でより明るく輝き, ~20 Io 半径まで広がる拡散放射を観測した.
- OIとSIの特徴の ~50%の明るさが観測され,地上からの観測と一致し,イオゲン [OI] 6300-angstromの放出が増加しました.
- 特定されたHライマン-アルファ放射は,形状と時間的な変化が特徴的な小さな極点のパッチとして識別されました.
結論:
- イオのオーロラ放射は,木星の磁気圏に直接影響された複雑な空間構造を示しています.
- 観測された明るさは,磁気圏の条件とイオの大気/放出プロセスとの関連を示唆しています.
- 水素ライマンアルファ排出は,酸素と硫黄の排出とは異なる現象であり,さらなる調査が必要である.
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