英语语法分析

Geomagnetic activity, the natural variations in Earth's magnetic field, it fluctuates in 11-year cycles.

地磁活动是地球磁场的自然变化，其波动周期为11年。

Oh yes, and there's geomagnetic reversal.

噢对了。还有地磁反转呢。

In a infinite and empty space the geomagnetic field falls off in strength with the third power of distance.

在无限和真空的空间中，地磁场在强度上随距离3次方而衰减。