Surveys in Geophysics

, Volume 40, Issue 2, pp 277–293 | Cite as

Linear Vary-Chap Topside Electron Density Model with Topside Sounder and Radio-Occultation Data

  • Fabricio dos Santos ProlEmail author
  • David R. Themens
  • Manuel Hernández-Pajares
  • Paulo de Oliveira Camargo
  • Marcio Tadeu de Assis Honorato Muella


The Linear Vary-Chap function has received increased attention in describing the topside ionosphere due to its good performance for predicting and extrapolating radio-occultation (RO) electron density ionospheric profiles. The systematic increase in the scale height is consistent with first principles corresponding to the increase in the electron temperature; however, the altitude where the linear scale height approximation does not stay valid has not been explicitly discussed in the literature. In order to demonstrate up to what extent the linear behavior of the scale height is still valid, this work analyzes more than 50,000 manually scaled ionospheric profiles measured by topside sounders on board Alouette and International Satellites for Ionospheric Studies satellites. Based on this initial analysis, a new topside model is proposed to take into consideration the nonlinear behavior of the topside scale height. The proposed climatological model, a fit of spherical harmonics to parameters derived from topside RO profiles, is used to predict topside sounder measurements. An assessment of the predicted, RO-derived, topside is carried out and the experimental results are discussed in order to show the viability of extrapolating RO ionospheric profiles for altitudes above the low Earth orbit.


Chapman function Scale height Ionospheric profile ISIS Alouette COSMIC/FORMOSAT-3 



This work was jointly funded by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP Grants: 2015/15027-7 and 2016/22011-2) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq Grants: 429885/2016-4, 310829/2017-8 and 309832/2016-0). The authors are grateful to UCAR (USA) and NSPO (Taiwan) for providing FORMOSAT-3/COSMIC RO data.


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  • Fabricio dos Santos Prol
    • 1
    • 2
    Email author
  • David R. Themens
    • 3
  • Manuel Hernández-Pajares
    • 2
  • Paulo de Oliveira Camargo
    • 1
  • Marcio Tadeu de Assis Honorato Muella
    • 4
  1. 1.Department of CartographyUniversidade Estadual Paulista (UNESP)Presidente PrudenteBrazil
  2. 2.Department of MathematicsUniversitat Politècnica de Catalunya—IOnospheric Determination and Navigation Based on Satellite and Terrestrial Systems (UPC-IonSAT)BarcelonaSpain
  3. 3.Department of PhysicsUniversity of New BrunswickFrederictonCanada
  4. 4.Laboratório de Física e Astronomia, IP&DUniversidade do Vale do ParaíbaSão José dos CamposBrazil

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