Internal reconnection for northward interplanetary magnetic field

[ 1] On the basis of magnetohydrodynamic simulation results for northward interplanetary magnetic field ( IMF) and significant dipole tilt, we describe internal reconnection processes that occur earthward of the magnetopause subsequent to magnetopause reconnection. We discuss the associated ionospheric signatures and show that the internal reconnection occurs not only between a summer lobe and a winter lobe field line but also between a summer lobe field line and a closed field line. The latter internal reconnection drives a pair of convection cells circulating outside the polar cap in the winter ionosphere. In this paper, we refer to these convection cells as "reciprocal cells'' and the corresponding reconnection as reciprocal cell reconnection. The reciprocal cells are coupled to the so-called lobe cells that are driven by magnetopause reconnection between an IMF line and a summer lobe field line ( lobe cell reconnection); these lobe cells circulate inside the polar cap in the summer ionosphere. The reciprocal cell reconnection converts an overdraped lobe field line to a relaxed lobe field line, while the lobe cell reconnection converts a relaxed lobe field line to an overdraped lobe field line. Thus the reciprocal cell reconnection reciprocates with the lobe cell reconnection through the exchange of magnetic flux.