论文标题：A silicate dynamo in the early Earth

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作者：Lars Stixrude, Roberto Scipioni et.al

发表时间：2020/02/25

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发表的一项模型研究A silicate dynamo in the early Earth详细分析了地球早期磁场是如何产生的。

电导率

图片来源：Stixrude, L., Scipioni, R. & Desjarlais, M.P.

地球的磁场已经运行了至少34亿年，而它的起源一直未知。如今的磁场是由富含金属铁的液态地核外核中的发电机产生的，但这一过程在地球早期应该较难维持，因为地核的冷却速度并不够快。早期地核周围有一层熔融硅酸盐（一种基底的岩浆海洋）；不过，此前对硅酸盐液体的导电率测量显示，这些化合物无法形成发电机。

美国加州大学洛杉矶分校的Lars Stixrude和同事进行了一系列模拟，对条件近似早期地球基底岩浆海洋的硅酸盐液体的导电率进行了预测。作者发现，在该海洋的预测温度和压强下，硅酸盐的导电率足够维持发电机的运转。基于这些结果，他们计算了磁场强度，发现其与太古宙（约40-25亿年前）古地磁记录中的磁场强度相似。作者的结论是，早期磁场是由基底岩浆海洋产生的，并认为宇宙中其它类地天体可能也存在硅酸盐发电机。

摘要：The Earth’s magnetic field has operated for at least 3.4 billion years, yet how the ancient field was produced is still unknown. The core in the early Earth was surrounded by a molten silicate layer, a basal magma ocean that may have survived for more than one billion years. Here we use density functional theory-based molecular dynamics simulations to predict the electrical conductivity of silicate liquid at the conditions of the basal magma ocean: 100–140 GPa, and 4000–6000 K. We find that the electrical conductivity exceeds 10,000 S/m, more than 100 times that measured in silicate liquids at low pressure and temperature. The magnetic Reynolds number computed from our results exceeds the threshold for dynamo activity and the magnetic field strength is similar to that observed in the Archean paleomagnetic record. We therefore conclude that the Archean field was produced by the basal magma ocean.

（来源：明升手机版(明升中国)）