Transport of cold ions from the polar ionosphere to the plasma sheet

• Ionospheric outflow is believed to be a significant contribution to the magnetospheric plasma population. Ions are extracted from the ionosphere and transported downtail by the large-scale convection motion driven by dayside reconnection. In this paper, we use a comprehensive data set of cold ion (total energy less than 70 eV) measurements combined with simultaneous observations from the solar wind to investigate the fate of these ions. By tracing the trajectories of the ions, we are able to find out where in the magnetotail ions end up. By sorting the observation according to geomagnetic activity and solar wind parameters, we then generate maps of the fate regions in the magnetotail and investigate the effects of these drivers. Our results suggest that, on overall, for about 85% of the cases, the outflowing ions are transported to the plasma sheet. The region where the ions are deposited into the plasma sheet is larger during geomagnetic quiet time than during disturbed conditions. A persistent dawn-dusk asymmetry in the plasma sheet deposition is also observed.

Nyckelord

cold ion outflow

magnetotail

plasma sheet

polar ionosphere

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