ヘリオシェアの移行層におけるプラズマの向外流速はゼロである
Stamatios M Krimigis1, Edmond C Roelof, Robert B Decker
1Applied Physics Laboratory, The Johns Hopkins University, Laurel, Maryland 20723, USA. tom.krimigis@jhuapl.edu
Nature
|June 17, 2011
まとめ
ヴォイジャー1号は,ヘリオシート内のゼロ速度プラズマ層に入り,ヘリオパウズに近いことを示唆しています. この発見は,ヘリオシート境界のモデルに異議を唱える.
科学分野:
- 宇宙物理学 宇宙物理学
- ヘリオフィジックス ヘリオフィジックス
- プラズマ物理学 プラズマ物理学
背景:
- ボイジャー1号は,2004年に太陽風の終結ショックを通過し,ヘリオシートに入りました.
- ヘリオシート (heliosheath) は,ターミネーションショックを超えたエネルギーイオンと電子の領域です.
- ボイジャー1号は現在,ターミネーション・ショック・クロースを過ぎて約22AUです.
研究 の 目的:
- ヘリオシート内のプラズマの大量速度を決定する.
- ボイジャー1号のヘリオパウズに対する位置を調査する.
- 観測されたプラズマフローを,ヘリオシート理論モデルと比較する.
主な方法:
- エネルギーイオン分布のアニソトロピーの測定を用いて.
- 半径横平面におけるプラズマの大量速度を分析する.
- プラズマ速度の半径成分の変化を時間とともに追跡する.
主要な成果:
- プラズマの放射速度は3年間で~70km/sから~0km/sに直線的に減少しています.
- ヴォイジャー1号は過去8ヶ月間,放射速度ゼロの領域に留まっていました.
- 宇宙船は,プラズマフローの有限の移行層に入ったようです.
結論:
- ボイジャー1号がゼロ速度層に入ったことは,それがヘリオパウズに近いことを示唆している.
- 観測されたフロー移行層は,鋭いヘリオパウスの不連続性を予測するモデルと矛盾しています.
- この発見は,ヘリオシェアの構造と星間空間との境界についての新しい洞察を提供します.
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