Populating the plasma sheet with ionospheric and solar plasmas, one 
particle at a time

We have implemented a 3D description of the solar wind - ionosphere 
interaction based on a magnetohydrodynamic calculation of the 
magnetosphere using the Lyon-Fedder-Mobarry code, and the full particle 
motion code of Delcourt, adapted by M-C Fok. We examine the kinetic 
behavior of proton test particles released in the upstream solar wind 
and in the topside ionosphere as polar wind. We find that the solar 
wind particles are largely precluded from entering the polar lobes, 
leaving them empty apart from polar wind ions flowing into the center 
of the plasma sheet and subsequently into the inner magnetosphere, 
forming a ring current population. Solar wind protons leak in through 
the dawn flank and drift into the inner magnetosphere, contributing to 
the ring current, without visiting the plasma sheet, suggesting that 
solar wind particles do not much participate in substorm phenomena of 
the midnight and evening plasma sheet. The surprising result is that 
the polar wind protons contribute substantially to the quiet time ring 
current both for northward and southward IMF.