Modeling polar cap field-aligned electron density profiles measured with IMAGE Radio Plasma Imager J.-N. Tu (1), J. L. Horwitz (1), P. A. Nsumei (2), P. Song (2), X.-Q. Huang (2), B. W. Reinisch (2), W. Zeng (1) (1) Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville (2) Center for Atmospheric Research, University of Massachusetts Lowell A dynamic fluid semi-kinetic (DyFK) model is used to simulate the ion field-aligned flows within flux tubes drifting along a model specified convection line across the polar ionosphere. In this DyFK model, the collision dominated portion of the flux tube is treated with a moment-based fluid model for altitudes from 120 to 1100 km, while the generalized semi-kinetic model is used for 1100 km to 3 RE region. The effects of auroral soft electron precipitation, centrifugal acceleration, wave-driven transverse ion heating and parallel potentials are incorporated into the simulation of the ion field-aligned transport. The modeled field-aligned electron density profiles in the polar cap are compared with several field-aligned density profiles measured by the Radio Plasma Instrument (RPI) on the IMAGE satellite on March 4, 2003, in a weak magnetic storm (minimum Dst value of -58 nT). The electron densities were substantially elevated during the magnetic storm, with electron density reaching ~10 cm-3 at 2.8 RE altitude. It is found that reasonable parameters for the indicated aurora processes could raise the modeled electron densities to the level of the densities measured by the IMAGE/RPI. The simulation results indicate that the O+ becomes dominate ion species in the altitude range considered for high density cases. _______________ Presentation, Fall Meeting, American Geophysical Union, San Francisco, USA, 8-12 December 2003