{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,23]],"date-time":"2026-02-23T23:54:12Z","timestamp":1771890852310,"version":"3.50.1"},"reference-count":32,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2021,4,17]],"date-time":"2021-04-17T00:00:00Z","timestamp":1618617600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["HO 6136\/1-1"],"award-info":[{"award-number":["HO 6136\/1-1"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["ZT-I-0022"],"award-info":[{"award-number":["ZT-I-0022"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>A 3D-model approach has been developed to describe the electron density of the topside ionosphere and plasmasphere based on Global Navigation Satellite System (GNSS) measurements onboard low Earth orbit satellites. Electron density profiles derived from ionospheric Radio Occultation (RO) data are extrapolated to the upper ionosphere and plasmasphere based on a linear Vary-Chap function and Total Electron Content (TEC) measurements. A final update is then obtained by applying tomographic algorithms to the slant TEC measurements. Since the background specification is created with RO data, the proposed approach does not require using any external ionospheric\/plasmaspheric model to adapt to the most recent data distributions. We assessed the model accuracy in 2013 and 2018 using independent TEC data, in situ electron density measurements, and ionosondes. A systematic better specification was obtained in comparison to NeQuick, with improvements around 15% in terms of electron density at 800 km, 26% at the top-most region (above 10,000 km) and 26% to 55% in terms of TEC, depending on the solar activity level. Our investigation shows that the developed model follows a known variation of electron density with respect to geographic\/geomagnetic latitude, altitude, solar activity level, season, and local time, revealing the approach as a practical and useful tool for describing topside ionosphere and plasmasphere using satellite-based GNSS data.<\/jats:p>","DOI":"10.3390\/rs13081559","type":"journal-article","created":{"date-parts":[[2021,4,19]],"date-time":"2021-04-19T06:35:53Z","timestamp":1618814153000},"page":"1559","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Topside Ionosphere and Plasmasphere Modelling Using GNSS Radio Occultation and POD Data"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7206-1705","authenticated-orcid":false,"given":"Fabricio S.","family":"Prol","sequence":"first","affiliation":[{"name":"German Aerospace Center (DLR), Institute for Solar-Terrestrial Physics, Kalkhorstweg 53, 17235 Neustrelitz, Germany"}]},{"given":"M. Mainul","family":"Hoque","sequence":"additional","affiliation":[{"name":"German Aerospace Center (DLR), Institute for Solar-Terrestrial Physics, Kalkhorstweg 53, 17235 Neustrelitz, Germany"}]}],"member":"1968","published-online":{"date-parts":[[2021,4,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1856","DOI":"10.1016\/j.jastp.2008.01.015","article-title":"A new version of the NeQuick ionosphere electron density model","volume":"70","author":"Nava","year":"2008","journal-title":"J. Atmos. Sol. Terr. Phys."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2587","DOI":"10.1016\/j.asr.2005.08.045","article-title":"Advanced specification of electron density and temperature in the IRI ionosphere\u2014Plasmasphere model","volume":"38","author":"Gulyaeva","year":"2006","journal-title":"Adv. Space Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"105055","DOI":"10.1016\/j.jastp.2019.06.002","article-title":"Validation of the IRI 2016, IRI-Plas 2017 and NeQuick 2 models over the West Pacific regions using the SSN and F10.7 solar indices as proxy","volume":"195","author":"Tariku","year":"2019","journal-title":"J. Atmos. Sol. Terr. Phys."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"752","DOI":"10.1002\/2015RS005905","article-title":"NeQuick and IRI-Plas model performance on topside electron content representation: Spaceborne GPS measurements","volume":"51","author":"Cherniak","year":"2016","journal-title":"Radio Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"913","DOI":"10.1016\/j.asr.2010.10.025","article-title":"Storm time behavior of topside scale height inferred from the ionosphere\u2014Plasmasphere model driven by the F2 layer peak and GPS-TEC observations","volume":"47","author":"Gulyaeva","year":"2011","journal-title":"Adv. Space Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2104","DOI":"10.1002\/2017JA024936","article-title":"Spatial and temporal features of the topside ionospheric electron density by a new model based on GPS radio occultation data","volume":"123","author":"Prol","year":"2018","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2083","DOI":"10.1029\/2018JA026286","article-title":"\u03b1-Chapman scale height: Longitudinal variation and global modeling","volume":"124","author":"Li","year":"2019","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"e2019JA027637","DOI":"10.1029\/2019JA027637","article-title":"New Vary-Chap scale height profile retrieved from COSMIC radio occultation data","volume":"125","author":"Wu","year":"2020","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1699","DOI":"10.1029\/2002GL014738","article-title":"Sounding of the topside ionosphere\/plasmasphere based on GPS measurements from CHAMP: Initial results","volume":"29","author":"Heise","year":"2002","journal-title":"Geophys. Res. Lett."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"RS0D04","DOI":"10.1029\/2010RS004565","article-title":"Imaging of 3D plasmaspheric electron density using GPS to LEO satellite differential phase observations","volume":"46","author":"Spencer","year":"2011","journal-title":"Radio Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1131","DOI":"10.1002\/2015RS005732","article-title":"Data assimilation of plasmasphere and upper ionosphere using COSMIC\/GPS slant TEC measurements","volume":"50","author":"Wu","year":"2015","journal-title":"Radio Sci."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"18819","DOI":"10.1029\/1999JA000241","article-title":"Global core plasma model","volume":"105","author":"Gallagher","year":"2000","journal-title":"J. Geophys. Res."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"e2019GL086841","DOI":"10.1029\/2019GL086841","article-title":"COSMIC-2 radio occultation constellation: First results","volume":"47","author":"Schreiner","year":"2020","journal-title":"Geophys. Res. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"e2019RS006953","DOI":"10.1029\/2019RS006953","article-title":"Validation of ionospheric electron density measurements derived from Spire CubeSat constellation","volume":"55","author":"Forsythe","year":"2020","journal-title":"Radio Sci."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"S09001","DOI":"10.1029\/2011SW000687","article-title":"Quantitative evaluation of the low Earth orbit satellite based slant total electron content determination","volume":"9","author":"Yue","year":"2011","journal-title":"Space Weather"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"377","DOI":"10.5047\/eps.2011.03.001","article-title":"Global ionospheric radio observatory (GIRO)","volume":"63","author":"Reinisch","year":"2011","journal-title":"Earth Planets Space"},{"key":"ref_17","first-page":"A07306","article-title":"Statistical behavior of the topside electron density as determined from DMSP observations: A probabilistic climatology","volume":"115","author":"Garner","year":"2010","journal-title":"J. Geophys. Res."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"4611","DOI":"10.1002\/2015JA022132","article-title":"Automated determination of electron density from electric field measurements on the Van Allen Probes spacecraft","volume":"121","author":"Zhelavskaya","year":"2016","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1007\/s10712-019-09521-3","article-title":"Linear Vary-Chap Topside Electron Density Model with Topside Sounder and Radio-Occultation Data","volume":"40","author":"Prol","year":"2019","journal-title":"Surv. Geophys."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1473","DOI":"10.1029\/2001GL013744","article-title":"A simple \u201cgeometric\u201d mapping function for the hydrostatic delay at radio frequencies and assessment of its performance","volume":"29","author":"Foelsche","year":"2002","journal-title":"Geophys. Res. Lett."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"353","DOI":"10.1007\/s10291-015-0444-6","article-title":"Assessment of vertical TEC mapping functions for space-based GNSS observations","volume":"20","author":"Zhong","year":"2016","journal-title":"GPS Solut."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"9156","DOI":"10.1002\/2015GL066093","article-title":"Vertical structure of medium-scale traveling ionospheric disturbances","volume":"42","author":"Ssessanga","year":"2015","journal-title":"Geophys. Res. Lett."},{"key":"ref_23","first-page":"7932","article-title":"A linear scale height Chapman model supported by GNSS occultation measurements","volume":"121","year":"2008","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"11227","DOI":"10.1002\/2017JA024406","article-title":"Empirical Modeling of the Plasmasphere Dynamics Using Neural Networks","volume":"122","author":"Zhelavskaya","year":"2017","journal-title":"J. Geophys. Res."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"299","DOI":"10.1029\/RS023i003p00299","article-title":"Ionospheric imaging using computerized tomography","volume":"23","author":"Austen","year":"1988","journal-title":"Radio Sci."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"41","DOI":"10.3724\/SP.J.1246.2013.01041","article-title":"Application of a simultaneous iterations reconstruction technique for a 3D water vapor tomography system","volume":"4","author":"Wei","year":"2013","journal-title":"Geod. Geodyn."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1007","DOI":"10.1016\/0021-9169(92)90067-U","article-title":"A preliminary experimental test of ionospheric tomography","volume":"54","author":"Pryse","year":"1992","journal-title":"J. Atmos. Sol. Terr. Phys."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1051\/swsc\/2020076","article-title":"Plasmasphere and topside ionosphere reconstruction using METOP satellite data during geomagnetic storms","volume":"11","author":"Prol","year":"2021","journal-title":"J. Space Weather Space Clim."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2571","DOI":"10.1109\/TGRS.2018.2874974","article-title":"A New Method for Ionospheric Tomography and its Assessment by Ionosonde Electron Density, GPS TEC, and Single-Frequency PPP","volume":"57","author":"Prol","year":"2019","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"9525","DOI":"10.1029\/2019JA026971","article-title":"Validation of NeQuick 2 model topside ionosphere and plasmasphere electron content using COSMIC POD TEC","volume":"124","author":"Kashcheyev","year":"2019","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"12253","DOI":"10.1038\/s41598-019-48440-6","article-title":"The ESA Swarm mission to help ionospheric modeling: A new NeQuick topside formulation for mid-latitude regions","volume":"9","author":"Pezzopane","year":"2019","journal-title":"Sci. Rep."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"17541","DOI":"10.1038\/s41598-020-73886-4","article-title":"On the link between the topside ionospheric effective scale height and the plasma ambipolar diffusion, theory and preliminary results","volume":"10","author":"Pignalberi","year":"2020","journal-title":"Sci. Rep."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/8\/1559\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:49:11Z","timestamp":1760161751000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/8\/1559"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,4,17]]},"references-count":32,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2021,4]]}},"alternative-id":["rs13081559"],"URL":"https:\/\/doi.org\/10.3390\/rs13081559","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,4,17]]}}}