noun
exosphere; outer atmosphere
Scientific term for the outermost layer of Earth's atmosphere, where particles can escape into space. Used in astronomy and earth science contexts.
外気圏は大気の最も外側の層です。
The exosphere is the outermost layer of the atmosphere.
人工衛星は外気圏を飛行している。
Artificial satellites fly in the exosphere.
熱圏 (thermosphere) is the layer directly below the exosphere.
Compound of 外気 (gaiki, 'outer air') + 圏 (ken, 'sphere, zone'). The term is a modern scientific coinage for the exosphere.