Magnetotail Configuration Under Northward IMF Conditions

Due to the sparsity of space probes, it is still not clear on how the magnetic structure of the magnetotail looks like and how it evolves when the interplanetary magnetic field (IMF) directs northward. This simulation study uses two different global magnetosphere magnetohydrodynamics (MHD) models to simulate two northward IMF events and study the evolution of the magnetotail. Both models show that the magnetotail may form a structure that is composed of a dawnside tail lobe and a duskside tail lobe, under northward IMF conditions with significant By, instead of a northern tail lobe and a southern tail lobe under southward IMF conditions. In this magnetic configuration, a tail lobe extends a domain from northern (southern) cusp to southern (northern) IMF. The larger the magnitude of IMF clock angle, the longer and wider the magnetotail. Such magnetic configuration suggests that magnetotail reconnection is possible to occur when the dawnside tail lobe contacts with the duskside tail lobe and thus a substorm is also possible to occur under northward IMF conditions with significant By.

由于空间探测器数量稀少，当行星际磁场（IMF）向北时，磁尾的磁结构是什么样的以及它是如何演化的仍不清楚。这项模拟研究使用两种不同的全球磁层磁流体动力学（MHD）模型来模拟两个IMF向北的事件并研究磁尾的演化。两种模型都表明，在具有显著的By的IMF向北的条件下，磁尾可能形成由晨侧尾瓣和昏侧尾瓣组成的结构，而不是在IMF向南的条件下的北尾瓣和南尾瓣。在这种磁位形中，一个尾瓣从北（南）极尖区延伸到南（北）IMF区域。IMF时钟角的大小越大，磁尾就越长越宽。这种磁位形表明，当晨侧尾瓣与昏侧尾瓣接触时，磁尾可能发生重联，因此在具有显著By的IMF向北的条件下也可能发生亚暴。