A model of solar wind–magnetosphere–ionosphere coupling for due northward IMF

Abstract

A solar wind–magnetosphere–ionosphere coupling model for due northward IMF is proposed. The magnetosphere couples with the solar wind through reconnection nightside of the cusps. Other than the two small regions where reconnection takes place, the magnetosphere is closed. There are three plasma regions in the magnetosphere. The inner core is dominated by corotation. The outer magnetosphere contains two convection cells, and maps to the ionospheric viscous cells and Region I currents. The boundary layer and magnetotail region consists of a pair of flow channels, and maps to the ionospheric reverse cells. The three regions are separated by separatrix surfaces. Energy coupling across the surfaces can be facilitated by non-ideal-MHD processes such as ionospheric coupling, viscous and diffusive interactions, and waves and instabilities, although only the ionospheric coupling is essential to the model. This model is consistent with most established characteristics from observations and MHD computer simulations in both the ionosphere and magnetosphere. There are two specific features that need to be further confirmed from observations. The model expects that the ionospheric NBZ currents and reverse cells are maximized in the region sunward of the pole near the dayside cusps, and that in the tail there is a region which separates the earthward and tailward flows although the field and plasma characteristics are magnetospheric on both sides.