The highest part of the Earth’s ionosphere. The F layer is split into two regions: a lower F1 layer around 170 km altitude, and an upper F2 layer at 250 km. The F2 layer disappears at night, and may occasionally be absent during daytime.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。