Electron density extrapolation above F2 peak by the linear Vary-Chap model supporting new Global Navigation Satellite Systems-LEO occultation missions

The new radio-occultation (RO) instrument on-board of the future EUMETSAT Polar System 2nd Generation (EPS-SG) satellites, flying at 820 km height, is primarily focusing on neutral atmospheric profiling. It will provide an opportunity for ionospheric sounding as well, but only below impact heights of 500 km. This will leave a gap of 320 km without occultation measurements, which impedes the application of the direct inversion techniques to retrieve the electron density profile. The challenge of looking for new ways (accurate and simple) of extrapolating the electron density (also applicable to other future and past Low-Earth Orbiting, (LEO), radio-occultation missions like CHAMP) has motivated this research. In this paper we propose a new Vary-Chap Extrapolation Technique (VCET) of the electron density. VCET is based on the scale height behavior, linearly dependent on the altitude above hmF2. This allows the electron density profile extrapolation for impact heights above its peak height (this is the case for EPS-SG), up to the satellite orbital height. VCET has been assessed with more than 3700 complete electron density profiles obtained in 4 representative scenarios of FORMOSAT-3/COSMIC occultations, in solar maximum and minimum conditions, and geomagnetically disturbed conditions, by applying an updated Improved Abel Transform Inversion technique to dual-frequency GPS measurements. It is shown that VCET performs much better than other classical Chapman models, with 60% of occultations showing relative extrapolation errors below 20%, in contrast with conventional Chapman model extrapolation approaches with 10% or less of the profiles with relative error below 20%.

HERNANDEZ-PAJARES Manuel;  GARCIA-FERNANDEZ Miguel;  RIUS Antonio;  NOTARPIETRO Riccardo;  VON ENGELN Axel;  OLIVEROS-PULIDO German;  ARAGON ANGEL Maria Angeles;  GARCIA RIGO Alberto; 

2017-09-19

AMER GEOPHYSICAL UNION

JRC107042

2169-9380,   

http://onlinelibrary.wiley.com/doi/10.1002/2017JA023876/abstract,    https://publications.jrc.ec.europa.eu/repository/handle/JRC107042,   

10.1002/2017JA023876,