On the possible use of radio occultation middle latitude electron density profiles to retrieve thermospheric parameters

This paper investigates possible use of middle latitude daytime COSMIC and CHAMP ionospheric radio occultation (IRO)
electron density profiles (EDPs) to retrieve thermospheric parameters, based on the Mikhailov et al. (2012) method. The aim of
this investigation is to assess the applicability of this type of observations for the routine implementation of the method. According
to the results extracted from the analysis presented here, about half of COSMIC IRO EDP observed under solar minimum
(2007–2008) conditions gave neutral gas density with an inaccuracy close to the declared absolute inaccuracy ±(10–15)% of
CHAMP observations, with the results being better than the empirical models JB-2008 and MSISE-00 provide. For the other half
of IRO EDP, either the solution provided by the method had to be rejected due to insufficient accuracy or no solution could be
obtained. For these cases, the parameters foF2 and hmF2 extracted from the corresponding IRO profiles have been found to be
inconsistent with the classic mid-latitude daytime F2-layer formalism that the method relies on, and they are incompatible with
the general trend provided by the IRI model. For solar maximum conditions (2002) the method was tested with IRO EDP from
CHAMP and it is indicated that its performance is quite stable in the sense that a solution could be obtained for all the cases
analyzed here. However available CHAMP EDP are confined by ~ 400 km in altitude and this might be the reason for the
20% bias of the retrieved densities toward larger values in respect to the observed densities. IRO observations up to 600 km under
solar maximum are required to confirm the exact performance of the method.