Fast ionospheric response to enhanced activity in geospace: Ion feeding of the inner magnetotail

The role of the ionospheric particle source in the dynamic processes of the geospace was neglected, underestimated, or questioned for a long period. Recent studies have indicated a fast and effective feeding of the magnetosphere with energetic ionospheric-origin ions during periods of enhanced auroral electrojets, i.e., during the expansion and the late growth phase of substorms. Such a feeding with ionospheric ions can alter the plasma composition in the geospace system and thus influence its dynamics and evolution during substorms and magnetic storms. This paper addresses the issue of short-timescale (rather than long-term) feeding of the magnetosphere with ionospheric ions. We consider this feeding to be a result df the ionospheric response to increased auroral current dissipation due to increased solar wind - magnetosphere coupling or increased magnetospheric activity. Wk review and combine old and recent observations of both the ionospheric outflow and the ionospheric ions in the magnetosphere, along with transport and energization mechanisms for the relatively cold ionospheric outflowing ions and the potential implications of their enhanced presence in the magnetosphere for the dynamics of geospace processes (substorms/storms). We suggest that a fast feeding of the near magnetotail with ionospheric ions can lead to a transient localized dominance of heavy ionospheric ions (namely O+) and consequently to an ionospheric regulation of the evolution bf dynamic geospace processes. Accordingly, we suggest that the role of the ionosphere within the dynamic geospace coupling be given more emphasis: the ionosphere should be regarded not only as a material source for the magnetosphere but also as an active element in dynamic geospace processes.