We know from the principles of physics concerning electromagnetic induction that an electrical current always has an associated magnetic field. 我们从有关电磁感应的物理学原理获知，电流总是要有一个相关的磁场的。
Because the core current is somewhat symmetrical around the axis of rotation, the associated magnetic field is similar to that of a bar magnet. 因为地核流在旋转轴周围存在着一些对称，所以相关的磁场与棒磁铁的磁场相似。
