Slant TEC data ingestion in the Modified NeQuick ionosphere electron density model

1. Slant TEC data ingestion in theModified NeQuickionosphere electron density model • B. Nava, S.M. Radicella, R. Leitinger and P.Coïsson • The Abdus Salam ICTP, Trieste, Italy • IGAM, Graz, Austria • XXVIII General Assembly of International Union of Radio Science • New Delhi, India October 23-29, 2005

2. Outline • Introduction • NeQuick model and Modified NeQuick model description • Slant TEC data ingestion • Electron density reconstruction technique (concepts) • The Modified NeQuick performance • Evaluation criteria • Data used • Data analysis • Conclusions

3. Introduction (NeQuick) • NeQuick is an ionospheric electron concentration model able to give the electron density distribution on both the bottomside and topside of the ionosphere. • The model formulation includes 6 semi-Epstein layers with modeled thickness parameters and is based on anchor points defined by foE, foF1, foF2 and M(3000)F2 values. • These values can be modeled (e.g. ITU-R coefficients for foF2, M(3000)F2) or experimentally derived. • The NeQuick topside formulation is based on an empirical k parameter, that controls the topside profile shape and depends on the month of the year. • NeQuick inputs are: position, time and solar flux; the output is the electron concentration at the given location and time.

4. Introduction (modified NeQuick) • The Modified NeQuick topside formulation is based on an empirical k’ parameter that does not depend on the month of the year and therefore it is a simplification of the previous one (ICTP). • foF2 and hmF2 (instead of foF2 and M(3000)F2) are modeled using a new mapping procedure, based on simplified ITU-R maps “CCsim” (IGAM University of Graz). • M(3000)F2 is recovered “inverting” the Dudeney formula for hmF2 and it is used only as internal parameter.

5. Slant TEC data ingestion NeQuick + ITU-R [or “CCsim”] coefficients + F10.7 Climate representation of the ionosphere NeQuick + ITU-R [or “CCsim”] coefficients + effective ionization level Weather specification of the ionosphere

6. Az j Slant TEC data ingestion At a given epoch m sTECexp (several stations & satellites) Minimize each mismodeling Scattered Interpolate to get regularly spaced grid Use NeQuick to reconstruct the 3D electron density of the ionosphere Reconstruct TEC along any given ray-path Reconstruct any foF2 value (foF2 map)

7. Model performance evaluation Criteria: comparison between experimental and reconstructed sTEC (self consistency of the reconstruction method) comparison between experimental and reconstructed foF2 (independent crosscheck with ionosonde data) Data used: Super-truth sTEC data from 25 ground stations & foF2 data from 6 ionosondes at 15 min. time interval for the days 27 March, 5 April, 6 June 2000 (undisturbed days in high solar activity) Data analysis: cumulative distributions of the absolute values of the differences between experimental and reconstructed sTEC data and foF2 data

8. Stations & ionosondes locations Super-truth stations Modip isolines Ionosondes

9. Results: sTEC & foF2, day 000327 NeQuick Modified NeQuick NeQuick Modified NeQuick

10. Results: NmF2, day 000327 NeQuick Modified NeQuick

11. Results: sTEC & foF2, day 000405 NeQuick Modified NeQuick NeQuick Modified NeQuick

12. Results: NmF2, day 000405 NeQuick Modified NeQuick

13. Results: sTEC & foF2, day 000607 NeQuick Modified NeQuick NeQuick Modified NeQuick

14. Results: NmF2, day 000607 NeQuick Modified NeQuick

15. Conclusions • NeQuick model has been modified. The impact of the changes has been tested using an electron density reconstruction technique previously developed by the authors. This technique, based on slant TEC data ingestion, has been applied to NeQuick and Modified NeQuick models. • The results obtained show that the Modified NeQuick model allows a better reconstruction of the ionosphere in terms of TEC, if compared with NeQuick model. Not substantial changes are observed in terms of foF2. • Since NeQuick has been developed to be used in single frequency positioning applications, where TEC is the most important parameter to be modeled, the Modified NeQuick model can be considered an improvement with respect to Nequick.

16. Acknowledgments The authors are grateful to the WAAS community from whom they received the “Supertruth” data used for the present study and to the Center for Atmospheric Research of the University of Massachusetts at Lowell, for providing access to the digital ionogram data base (DIDBase).

17. Thank you for your attention