  During southward interplanetary magnetic field, dayside reconnection will
drive the Dungey cycle in the magnetosphere, which is manifested as a two-cell
convection pattern in the ionosphere. We address the response of the
ionospheric convection to changes in the dayside reconnection rate by examining
magnetic field perturbations at 780 km altitude. The Active Magnetosphere and
Planetary Electrodynamics Response Experiment data products derived from the
Iridium constellation provide global maps of the magnetic field perturbations.
Cluster data just upstream of the Earth's bow shock have been used to estimate
the dayside reconnection rate. By using a statistical model where the magnetic
field can respond on several time scales, we confirm previous reports of an
almost immediate response both near noon and near midnight combined with a
10-20 min reconfiguration time of the two-cell convection pattern. The response
of the ionospheric convection has been associated with the expansion of the
polar cap boundary in the Cowley-Lockwood paradigm. In the original formulation
of this paradigm the expansion spreads from noon to midnight in 15-20 min.
However, also an immediate global response has been shown to be consistent with
the paradigm when the previous dayside reconnection history is considered. In
this paper we present a new explanation for how the immediate response can be
accommodated in the Cowley-Lockwood paradigm. The new explanation is based on
how MHD waves propagate in the magnetospheric lobes when newly reconnected open
flux tubes are added to the lobes, and the magnetopause flaring angle
increases.
