The interchange cycle: A fundamental mode of magnetic flux circulation for northward interplanetary magnetic field

The interchange cycle is a mode of magnetic flux circulation that dominates when the interplanetary magnetic field (IMF) clock angle (theta(c) atan2(B(Y), B(Z))) lies in the range of vertical bar theta(c)vertical bar <= 30 degrees. It consists of IMF-lobe reconnection in one hemisphere and lobe-closed reconnection in the other hemisphere, producing in the ionosphere an interchange-type merging cell in the former hemisphere and a reciprocal cell in the latter hemisphere. For a given IMF clock angle and a given dipole tilt angle, there usually exist two independent interchange cycles. Thus the two interchange cycles drive twin reverse cells in both hemispheres, but the category of each reverse cell ( either an interchange-type merging cell or a reciprocal cell) depends on the given conditions. In this paper, we demonstrate how the reverse cell pattern changes systematically depending on the IMF orientation and the dipole tilt. Citation: Watanabe, M., and G. J. Sofko ( 2009), The interchange cycle: A fundamental mode of magnetic flux circulation for northward interplanetary magnetic field, Geophys. Res. Lett., 36, L03107, doi: 10.1029/2008GL036682.