Schematic illustrating inductive decoupling of solar wind and ionospheric electric field and flows that is a key part of the Expanding-Contracting Polar Cap (ECPC) model of non-steady convection. In (a), the X, Y, and Z axes of the Geocentric Solar Equatorial frame are shown. The points a, b, c, d, e and f are the ionospheric field line footpoints of the points on the magnetopause or cross tail current sheet A, B, C, D, E and F, respectively and all lie on the open-closed field line boundary, bounding the green area showing the open field line polar cap. AB is the dayside magnetopause reconnection X-line (across which the voltage Φ_AB is applied by the magnetic reconnection that opens field lines) and DE is the reconnection X-line in the cross tail current sheet (where the voltage Φ_DE is caused by reconnection that recloses open field lines). FC is the “Stern Gap” in interplanetary space, the ionospheric footprint of which is the polar cap of diameter, fc, and in which the open field lines are frozen-in to the solar wind flow, V_SW. (b) A view of the ionospheric polar cap (with noon at the top), with the green area again showing the open field line region, the blue lines showing “adiaroic” (non-reconnecting) segments of the open-closed boundary and red segments being “merging gaps” that map to the reconnection X-lines (from Lockwood & Morley, 2004).