Abstract
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 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.
Highlights
There is a specific need to develop methods for monitoring the thermosphere, in order to allow satellite systems to compensate for atmospheric drag effects if a booster is available
According to the results extracted from the analysis presented here, about half of COSMIC ionospheric radio occultation (IRO) electron density profiles (EDPs) observed under solar minimum (2007–2008) conditions gave neutral gas density with an inaccuracy close to the declared absolute inaccuracy ±(10–15)% of Challenging Minisatellite Payload (CHAMP) observations, with the results being better than the empirical models JB-2008 and MSISE-00 provide
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
Summary
There is a specific need to develop methods for monitoring the thermosphere, in order to allow satellite systems to compensate for atmospheric drag effects if a booster is available. In an attempt to assess the operational potential of the method, we have used as input Digisonde automatically scaled EDP, extrapolated with the NeQuick profiler As it was expected, because of the ionograms autoscaling errors reflected in the input EDP and the assumptions related to the topside extrapolation, the accuracy of the results is degraded comparing to what we got using ISR EDP, but there was a general agreement between CHAMP and the extracted neutral densities from M2012, especially under solar maximum conditions. Similar conclusions were obtained for the equatorial F2-region (Mikhailov et al 2013) where ISR and Digisonde EDP from Jicamarca Observatory were used for the retrieval of thermospheric parameters In this case, CHAMP and GRACE neutral gas density observations were used to evaluate the results of the method.
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