Mapping of the heavy ion outflows as seen by IMAGE and multifluid global 
modeling for the 17 April 2002 storm
 
R.M. Winglee, W. Lewis, Gang Lu 


Multifluid global modeling that includes both light and heavy ion dynamics is
used to investigate changes in magnetospheric dynamics produced by enhanced
ionospheric outflows for the 17 April 2002 storm. The predicted outflow rates
and their effects on the magnetosphere are compared with AMIE and IMAGE/HENA
data as a function of relative O+ concentration in the ionosphere. It is shown
that O+ can be the dominant species on the dusk side in the inner magnetosphere
during the periods of high activity even for ionospheric concentrations as low
as 5% as a result of differential heavy ion convection patterns. However, for
these low outflow conditions, the cross-polar cap potential is much larger than
that calculated by AMIE. As the O+ ionospheric concentration increases, the
heavy outflow rate approaches canonical values, and the effective ionospheric
resistivity falls in association with a decrease in cross-polar cap potential
and an increase in the auroral field aligned currents. Within the magnetosphere,
the region where the O+ concentration exceeds 50% expands toward the duskside
and down the tail. Pressures in excess of 1 nPa can be supported by the enhanced
O+ outflows. The presence of these enhanced outflows appears at about the same
time and over a similar region to enhancements seen in the HENA 51 Ð 180 keV
oxygen data. These results provide a direct tie between heavy ionospheric
outflows and their energization in the tail and suggest that during this period
the heavy ions provide a substantial amount of the plasma required to support
the magnetotail current sheet. The model results also show that the enhanced O+
outflow leads to the enhanced exclusion of light ions of both solar wind and
ionospheric origin in the plasma sheet, albeit with the light ions experiencing
enhanced heating in an O+ dominated current sheet. These results indicate that
observed heavy ionospheric outflows and their energetization in the tail have
global consequences for the magnetosphere including supporting the dynamics of
the tail current sheet during active times and in global circulation including
the cross-polar cap potential and the region 1 and 2 currents.

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Journal of Geophysical Research, 110, A12S24, doi:10.1029/2004JA010909, 2005