Paper#: 74
Poster #:
Session Name: Workshop 6B: Inonspheric Process
Room: 200ABC
Day: Thursday
Time: 4:10-4:30 p.m.
Abstract Title: Auroral Ionospheric Ion Outflow and Circulation of Plasma during Magnetic Storms and Substorms
PresentSurname: McFadden, J.P.
All Authors: J.P. McFadden
Abstract : Observations from the FAST mission are used to develop a picture of ionospheric outflow and the subsequent circulation of this plasma through the plasma sheet and inner magnetosphere during magnetic storms and substorms. Active periods are characterized by intense auroral outflows near midnight on newly reconnected field lines, with the largest outflow observed during a magnetic storm. Changes in plasmasheet composition demonstrate these outflows are preloading the plasmasheet with O+. If the outflows occur prior to storm main phase, the ions are subsequently injected into the inner magnetosphere near midnight, with the inner edge of the plasmasheet shifting Earthward to as close as L=2.5. These ions subsequently drift through the inner magnetosphere and are observed at local times that depend upon ion energy and phase of the storm. The energetic ions (>10 keV), which contain the bulk of the energy density, are observed to drift to the dusk side as indicated by the asymmetry in Dst. However, the lower energy (<5 keV) ions primarily convect through the dawn side at velocities several times the co-rotation speed. These ions can contain a significant energy density (~100 keV/cc) and may represent as much as ~25% of the ring current. This asymmetry in drift changes during the recovery phase where storm driven convection is replaced by co-rotation which carries the lowest energy ions (<1 keV) to dusk. These observations suggest that the enhanced pressure on the dusk side, due to gradient B drift of the energetic ring current, may result in pressure gradients that drive the convection flows to the dawn side during the storm main phase.