линия раздела
• There is no sharp line of demarcation (or demarcation line) between the atmosphere and space.
• The two parts are separated by a dividing line.
Источник:
Русско-английский научно-технический словарь
на Gufo.me
• There is no sharp line of demarcation (or demarcation line) between the atmosphere and space.
• The two parts are separated by a dividing line.