Direct observations of the full Dungey convection cycle in the polar ionosphere for southward interplanetary magnetic field conditions
Tracking the formation and full evolution of polar cap ionization patches in the polar ionosphere, we directly observe the full Dungey convection cycle for southward interplanetary magnetic field (IMF) conditions. This enables us to study how the Dungey cycle influences the patches\textquoteright evolution. The patches were initially segmented from the dayside storm enhanced density plume (SED) at the equatorward edge of the cusp, by the expansion and contraction of the polar cap boundary (PCB) due to pulsed dayside magnetopause reconnection, as indicated by in-situ THEMIS observations. Convection led to the patches entering the polar cap and being transported antisunward, whilst being continuously monitored by the globally distributed arrays of GPS receivers and SuperDARN radars. Changes in convection over time resulted in the patches following a range of trajectories, each of which differed somewhat from the classical twin-cell convection streamlines. Pulsed nightside reconnection, occurring as part of the magnetospheric substorm cycle, modulated the exit of the patches from the polar cap, as confirmed by coordinated observations of the magnetometer at Troms\o and EISCAT Troms\o UHF Radar. After exiting the polar cap, the patches broke up into a number of plasma blobs, and returned sunward in the auroral return flow of the dawn and/or dusk convection cell. The full circulation time was about three hours.
|Year of Publication||
Journal of Geophysical Research: Space Physics