Magnetospheric flux throughput in the Dungey cycle: identification of convection state during 2010

We quantify the contributions of different convection states to the magnetic flux throughput of the magnetosphere during 2010. To do this we provide a continuous classification of convection state for the duration of 2010 based upon observations of the solar wind and interplanetary magnetic field, geomagnetic indices, and field‐aligned currents measured by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). Convection states are defined as 1) quiet and 2) weak activity, substorm 3) growth, 4) expansion, and 5) recovery phases, 6) substorm driven phase (when relatively steady magnetospheric convection occurs), 7) recovery bays (when recovery phase is accompanied by a negative excursion of the AL electrojet index), and 8) periods of multiple intensifications (storm‐time periods when continuous short‐period AL activity occur). The magnetosphere is quiet for 46% of the time, when very little convection takes place. The majority of convection occurs during growth and driven phases (21% and 38%, respectively, of open magnetic flux accumulation by dayside reconnection). We discuss these results in the context of the expanding/contracting polar cap model of convection, and describe a framework within which isolated substorms and disturbances during periods of more continuous solar wind‐magnetosphere driving can be understood.

Plain Language Summary

Space weather within the Earth's geospace environment, including vivid auroral displays and geomagnetic activity that is damaging for satellites, telecommunications, global positioning systems, power distribution and pipelines, is caused by the interaction between the solar wind and the terrestrial magnetic field. We use observations of the solar wind, electric currents in the magnetosphere, and magnetic perturbations on the ground to analyse geomagnetic activity continuously for the whole of 2010. This allows us to determine that a range of responses are excited in the magnetosphere by different solar wind conditions, and to quantify the solar wind conditions that lead to most activity. These responses include substorms, geomagnetic storms, and periods of steady magnetospheric convection.