Extending the IRI Topside Electron Density Profiles to Several Re using
IMAGE/RPI Measurements

P. Nsumei, B. W. Reinisch, X. Huang, P. Song, and J. Tu

Environmental, Earth, and Atmospheric Sciences Department,
Center for Atmospheric Research,
University of Massachusetts Lowell, USA


The radio plasma imager (RPI) onboard the IMAGE spacecraft measures electron
density distributions along the magnetic field; these density profiles can
be converted to the density distribution as a function of height. For many
individual events, the vertical profiles from the spacecraft down to about
2000 km were derived in the polar cap. These profiles were extrapolated
downward to join smoothly with the IRI profile at a few hundred km above the
F2 layer peak. We use Chapman functions [Reinisch and Huang, 2004], simple
exponential functions, and a power law [Nsumei et al., 2003] to test what
best describes the vertical profiles from the height of the F2 peak to ~4
Re. The resulting profiles are compared with the topside electron densities
computed with the international reference ionosphere (IRI) model. The
preliminary comparisons show considerable differences between the RPI driven
profiles and the topside IRI model. Although only individual RPI profiles
were used, the results confirm that the IRI topside model at high latitudes
may not be realistic above ~600 km. Our results demonstrate the potential
of using the RPI measurements, combined with the IRI model, to construct an
empirical electron model that covers the altitude range from the ionosphere
to several Re in the polar cap. A similar method can then be developed for
lower latitudes, i.e., the plasmasphere.

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Presentation, Fall A.G.U. Meeting, San Francisco, CA, 13-17 December 2004