Birkeland current

例句：

1. 1. The Birkeland current is responsible for the formation of the polar ice caps.
   北极洋流是形成极地冰盖的原因。
2. 2. The Birkeland current plays a crucial role in the global climate system.
   北极洋流在地球气候系统中起着至关重要的作用。
3. 3.The Birkeland current has been studied extensively to understand its impact on marine life.
   对北极洋流的研究非常广泛，以了解其对海洋生物的影响。