冷たいヘリオシートプラズマと,上流の太陽風の減速が,終結ショックで起こる

John D Richardson¹, Justin C Kasper, Chi Wang

¹Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 37-655, Cambridge, Massachusetts 02139, USA. jdr@space.mit.edu

Nature

|July 4, 2008

まとめ

ヴォイジャー2号のデータは,ヘリオスフィアは非対称であることを明らかにしています. ターミネーションショックはプラズマを弱く加熱し,太陽風のエネルギーはエネルギー粒子に転送されます.

科学分野:

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
星間媒介は,星間媒介である.

背景:

太陽風によって作られたバブルであるヘリオスフィアは,太陽系の内部をシールドしています.
ターミネーションショックは,太陽風が超音速から亜音速に減速する境界をマークします.
ボイジャー1号は2004年にターミネーションショックを横断し,ボイジャー2号は2007年に横断した.

研究の目的:

終止ショック時のおよびその近くのプラズマ観測を分析する.
ボイジャー2号のデータを用いてヘリオシート領域を調査する.
ヘリオスフィアの構造と終結ショックの性質を理解するために.

主な方法:

"ボイジャー2"宇宙船からのインシットプラズマ測定
太陽風の速度,イオン行動,エネルギー粒子相互作用の分析.
異なる方向におけるヘリオスフィアの条件の比較.

主要な成果:

ヘリオスフィアはアシンメトリーを示し,ターミネーションショックはボイジャー2の方向に近づいている.
終結ショックは,熱プラズマを最小限に加熱する弱い準垂直ショックです.
衝撃の下流にある熱イオンに関して,フローは超音速であり,エネルギーがピックアップイオンに転送されます.

結論:

ヘリオスフィアの非対称な構造は,ターミネーションショック時のプラズマの振る舞いに影響を与えます.
ピックアップイオンへのエネルギー転送は,ターミネーションショックで支配的なプロセスです.
ヘリオスフィアの動力学と粒子加速を完全に理解するためには,さらなる研究が必要である.

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