Ground-Based Observations of the Flux of Plasmaspheric Ions to the Dayside Magnetopause

J. Foster, A. Coster, B. Sandel, and F. Rich


Ionospheric storm-enhanced density (SED) and plumes of elevated total electron
content (TEC) have been shown to be signatures of the erosion of the outer
plasmasphere by disturbance electric fields. Boundaries of the SED/TEC plumes
identified at low altitude map directly onto the magnetospheric determination of the
boundaries of the plasmapause and plasmaspheric tail deter-mined by EUV imaging from
the IMAGE spacecraft. Low altitude observations are mapped into the magnetospheric
equatorial plane using Tsyganenko mapping. Looking upward with radio-propagation
techniques over North America, we use GPS/TEC map-ping to identify the
two-dimensional occurrence and evolution of the plasmaspheric erosion plumes.
Observations with the Millstone Hill incoherent scatter radar probe these regions
and determine the ion velocities and integrated total ion flux carried to the
dayside magnetopause in these events. We find flux rates in excess of 1026 ions/sec
and ionospheric electric fields >50 mV/ m associated with the plasmaspheric erosion
plumes. DMSP and radar observations of ionospheric ion EŽB convection are used to
investigate the SAPS (sub-auroral polarization stream) electric field structure,
which drives these events and connects the duskside plasmasphere to the dayside
magnetopause. Plasmaspheric exhaust plumes are formed where the SAPS overlaps the
corotating dusk-sector bulge of the plasmasphere.

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Presented at the Magnetospheric Imaging Workshop, 
Yosemite National Park, California, U.S.A., Feb. 9 - 13, 2003.