The electron density profile above the polar ionosphere

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


The plasma density above a few hundred kilometers to a couple of thousands
kilometers is important but less known because standard international
ionospheric (IRI) models are valid up only to 600 km. The extrapolations into
this region depend highly on the assumptions used for the extrapolations which
can vary a few orders of magnitude. The density radio plasma imager (RPI)
onboard the IMAGE spacecraft measures electron density distribution from the
satellite location to as low as 2000 km in altitude. The measured density
profiles not only provide the density at each height but also the trend which
may be used for extrapolations. In this preliminary report, we show examples
of extrapolations of the measured electron density profiles in the polar
region down to the ionospheric altitudes to connect to the topside electron
densities computed with the IRI models. It is found that while the IRI
(standard) model might have overestimated the density values above ~600 km,
the IRI (Reinisch-Huang) model might have underestimated the density values,
indicating possible improvement of the IRI topside models above ~600 km. An
attempt is also made to represent the extrapolated RPI density profiles with
Chapman distribution function. Our study shows that by assuming a linear
variation of the scale height with altitude, the extrapolated RPI electron
density profiles could be well represented with the Chapman function up to
about 1600 km above the F2 peak.

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2005 URSI National Meeting, Boulder, Colorado, U.S.A., 5-8 January 2005