Long‐term analysis between radio occultation and ionosonde peak electron density and height during geomagnetic storms

For the first time, a long‐term comparative analysis of radio occultation (RO) maximum electron density and peak height of the F 2 layer ( N m F 2 and h m F 2 ) with ionosonde data is presented during geomagnetic storm periods. Using the optimum spatial resolution of 4.5° × 4.5° in both latitude and longitude space over Grahamstown, GR13L(33.3°S, 26.5°E), South Africa, RO N m F 2 and h m F 2 (from CHAMP and COSMIC/FORMOSAT‐3) are directly compared to ionosonde values within 15 min of ionosonde observational data from 2003 to end of May 2015. This study provides for the first time the deviation of RO data from ionosonde data on a long‐term scale during disturbed conditions in a midlatitude region. We have found that maximum deviations between RO and ionosonde h m F 2 / N m F 2 occur during the high solar activity periods. For some storms, deviations between RO and ionosonde h m F 2 can reach values just over 30 km and 85 km during 2005–2010 and 2011–2015, respectively. Overall, statistical results show that h m F 2 and N m F 2 from these independent data sets agree to within ∼9% and 21% (1 standard deviation, 1 σ ) from 2003 to 2015. While the deviation can be large during some storm events, statistically and based on ionosonde data, RO F 2 peak parameters in midlatitudes are not degraded significantly during disturbed conditions and can therefore be reliably used to study ionospheric dynamics during extreme space weather events.