Ion upflow enhanced by drifting F-region plasma structure along the nightside 
polar cap boundary

J. Semeter, C.J. Heinselman, J.P. Thayer, R.A. Doe, and H.U. Frey


Conjugate observations by the incoherent scatter radar at Sondrestrom,
Greenland, and the Wideband Imaging Camera (WIC) on the IMAGE satellite have
been used to establish a causal relationship between drifting F-region plasma
structure in the polar ionosphere and upward ion number flux near the poleward
edge of the auroral oval. A longitudinally extended patch of enhanced F-region
density was observed as it advected equatorward across the openclosed field line
boundary and into a region of discrete auroral rays and strong ion upflow (Vi >
800 m/s at 900 km altitude). Upward velocities within the upflow region remained
constant during the patch transit, such that the upflowing number flux was
directly controlled by F-region density (both increased by a factor of 2 within
the patch). Because polar cap patches and ion upflows are both longitudinally
extended, quasi-stable features of the nightside polar cap boundary, the
observed interaction can produce a global-scale increase in plasma density at
higher altitudes where suprathermal outflows are initiated. 

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Geophysical Research Letters, 30(22), 2139, doi:10.1029/2003GL017747, 2003.