[S-IT25] Planetary cores: Structure, formation, and evolution

[SIT25-05] レーザー衝撃実験によるFe-Si融体の重力不安定性成長のその場観察

*寺崎 英紀¹、境家 達弘¹、重森 啓介²、加藤 弘樹²、弘中 陽一郎²、近藤 忠¹ (1.大阪大学大学院理学研究科、2.大阪大学レーザー科学研究所)

キーワード：核形成、レイリー・テーラー型重力不安定、鉄合金融体

Rayleigh–Taylor instability occurs at the interface between two fluids with different densities when a heavy fluid overlies a light one in a gravitational field. The RT instability is considered as one of the important core formation mechanism beneath the magma ocean. This mechanism has been discussed from simulations (e.g., Honda et al. 1993, Ricard et al. 2009) and analog experiment (e.g., Olson and Weeraratne, 2008). However, experimental approach using liquid Fe-alloys for this mechanism has never been performed under high pressure. In this study, we applied the laser-shock technique to observe in situ the Rayleigh–Taylor instability of liquid Fe-Si alloy under high pressure. The growth of the Rayleigh–Taylor instability was successfully observed using in situ x-ray radiography under shock compression. The growth rate of the Rayleigh–Taylor instability was estimated to 0.3 ns⁻¹. The present results provide useful information to constrain the time scale of the Earth’s and planetary core formation.