The Northward IMF Magnetosphere

The manner in which the Earth s magnetosphere responds to the solar wind is highly dependent upon the orientation of the interplanetary magnetic field (IMF), particularly the north–south (B Z ) component. As most auroral and geomagnetic activity occurs when the IMF is southward (or weakly northward, but dominated by the dawn–dusk [B Y ] component), it is perhaps unsurprising that these conditions have received the most attention. However, when the IMF is more strongly northward (B Z \textgreater 0 and B Z \textgreater \textbarB Y \textbar), magnetospheric dynamics (e.g. magnetic reconnection and auroral activity) move to higher latitudes; certain aspects of this activity are much more poorly understood than their southward IMF counterparts. In this chapter, we provide a review of the historical context and current understanding of the behavior of the Earth s magnetosphere during periods of northward IMF, and outline some current controversies and future directions of research.