Topside ionosphere and plasmasphere: Use of NeQuick in connection with Gallagher plasmasphere model M. Cueto a, * , P. Coı ¨sson b , S.M. Radicella b , M. Herraiz a , L. Ciraolo c , C. Brunini d a Department of Geophysics and Meteorology, Universidad Complutense de Madrid, Avenida Complutense s/n 28040, Madrid, Spa b Aeronomy and Radiopropagation Laboratory, Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34014 Tries c Istituto di Fisica Applicata Carrara, CNR, Via Madonna del piano 10, 50019 Sesto Fiorentino (FI), Italy d Facultad de Ciencias Astrono ´micas y Geofı ´sicas, UNLP, Paseo del Bosque s/n, 1900, La Plata, Argentina Received 29 December 2005; received in revised form 16 October 2006; accepted 23 January 2007 Abstract The NeQuick ionospheric electron density model has a very simple topside formulation, which allows taking into accoun content up to 20,000 km. In the present work, the Gallagher model has been used in connection with NeQuick to provide a representation of the electron concentration distribution in the plasmasphere. An analysis of the impact of the proposed m low geomagnetic latitudes (±40°) on modeled vertical total electron content has been performed for different levels of sol son, and universal time. In addition, GPS vertical total electron content values obtained from seven IGS (International GPS Service) station data h compared with the NeQuick and NeQuick+Gallagher vertical total electron content values, confirming the importance of in plasmaspheric formulation in the NeQuick model. Ó 2007 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Ionosphere; Plasmasphere; Electron density; Total electron content; Ionospheric models 1. Introduction The NeQuick model is one of the three electron density models developed at the Abdus Salam International Centre for Theoretical Physics in Trieste (ICTP) and the Institute for Geophysics, Astrophysics, and Meteorology at the Uni- versity of Graz ( Hochegger et al., 2000; Radicella and Leit- inger,2001).All three are based on the DGR ‘‘profiler’’ concept (Di Giovanni and Radicella, 1990), further devel- oped by Radicella and Zhang (1995) and calculate electron density values as a function of solar activity, month,uni- versal time (UT), height,and geographiccoordinates. The ‘‘quick calculation’’ modelNeQuick usesa simple formulation for the topside F layer, which is essentially a semi-Epsteinlayer with a thicknessparameterthat increases linearly with height. The NeQuick model can be run online at http://arpl.ictp.it. In the presentwork, the Gallagher plasmasphere model(Gallagher etal., 1988)has been used in connec- tion with NeQuick to search for a more realistic repre- sentation of the electron concentration distribution in the plasmasphere. The Gallaghermodelis an empirical model of plasmaspheric low energy plasmaconsisting of H+. It was developed from a database derived from measurements taken by the Retarding Ion Mass Spec- trometer, RIMS (Chappellet al.,1981),on the Dynamics Explorer 1 satellite and represents the plasmasphere from 0 to 12 h magnetic local time and between ±40° of geo- magneticlatitude.TheGallagherplasmaspheremodel calculateselectron density values as a function of day of the year, universaltime, height, and geographic coordinates. 0273-1177/$30 Ó 2007 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2007.01.073 * Corresponding author. E-mail addresses: mcs@fis.ucm.es (M. Cueto), coissonp@ictp.it (P. Coı ¨sson), rsandro@ictp.it (S.M. Radicella), mherraiz@fis.ucm.es (M. Herraiz), l.ciraolo@ifac.cnr.it (L. Ciraolo), claudio@fcaglp.fcaglp. unlp.edu.ar (C. Brunini). www.elsevier.com/locate/asr Advances in Space Research 39 (2007) 739–743