Two recent papers by Troshichev et al. (2023) and by Lockwood (2023) have presented different physical mechanisms that cause simultaneous polar cap indices, measured close to the geomagnetic poles in the north and south hemispheres, to differ even though their overall behaviour is very similar. Several effects are described but the two main mechanisms discussed are the effect of the dawn–dusk (Y) component of the Interplanetary Magnetic Field (IMF) and inductive decoupling of electric fields caused by changes in the magnetic fields in the magnetosheath and magnetospheric lobes. This paper shows that both papers are correct and that both of the two major mechanisms are active and cause differences between the northern and southern indices. The variations in the differences with fraction of the calendar year and Universal Time are described and explained.

Troshichev 等人最近发表的两篇论文。(2023) 和 Lockwood (2023) 提出了不同的物理机制，导致在北半球和南半球地磁极附近测量的同时极冠指数有所不同，尽管它们的总体行为非常相似。描述了几种效应，但讨论的两个主要机制是行星际磁场 (IMF) 的黎明-黄昏 (Y) 分量的效应以及磁鞘和磁层瓣中磁场变化引起的电场感应去耦。本文表明，这两篇论文都是正确的，并且这两个主要机制都是活跃的，导致了南北指数的差异。描述并解释了日历年和世界时间的部分差异的变化。