英语语法分析

Thermosphere: Heating, density increase, expansion at high latitude.

热层：加热过程，密度增长，在高纬的扩张。

This is the biggest contraction of the thermosphere in at least 43 years.

这是至少在43年中最大的热大气层收缩。

When solar activity is high, solar extreme ultraviolet rays warm and expand the thermosphere.

当太阳活动剧烈时，太阳极端的紫外线会加热并使热大气层扩张。