Ion Outflow and Lobe Density: Interhemispheric Asymmetries

As an important supplier of plasma, the ionosphere possesses a significant influence on magnetospheric properties and processes. Ions escaping from the polar ionosphere transit through the magnetotail lobes before being convected to the plasma sheet or escaping along the open field lines into the solar wind. Variations in plasma density in the lobes can therefore be regarded as a proxy for variations of ionospheric outflow and plasma supply to the magnetosphere. In this chapter, we address the connection between ion outflow and lobe density. In particular, we review recent results based on an extensive set of measurements from the Cluster mission indicating persistent interhemispheric asymmetries in ion outflow and lobe density. We outline the experimental support and discuss possible mechanisms for this asymmetry.