Ionospheric response to solar extreme ultraviolet radiation variations: comparison based on CTIPe model simulations and satellite measurements

Abstract

Abstract. The ionospheric total electron content (TEC) provided by the International GNSS Service (IGS) and the TEC simulated by the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model have been used to investigate the delayed ionospheric response against solar flux and its trend during the years 2011 to 2013. The analysis of the distinct low-latitude and midlatitude TEC response over 15∘ E shows a better correlation of observed TEC and the solar radio flux index F10.7 in the Southern Hemisphere compared to the Northern Hemisphere. Thus, a significant hemispheric asymmetry is observed. The ionospheric delay estimated using model-simulated TEC is in good agreement with the delay estimated for observed TEC against the flux measured by the Solar Dynamics Observatory (SDO) extreme ultraviolet (EUV) Variability Experiment (EVE). The average delay for the observed (modeled) TEC is 17(16) h. The average delay calculated for observed and modeled TEC is 1 and 2 h longer in the Southern Hemisphere compared to the Northern Hemisphere. Furthermore, the observed TEC is compared with the modeled TEC simulated using the SOLAR2000 and EUVAC flux models within CTIPe over northern and southern hemispheric grid points. The analysis suggests that TEC simulated using the SOLAR2000 flux model overestimates the observed TEC, which is not the case when using the EUVAC flux model.

Ionospheric Response to Solar EUV Radiation Variations Using GOLD Observations and the CTIPe Model

“…Furthermore, it is known from previous studies that the delayed ionospheric response is mainly related to the change in the O / N 2 ratio due to transport process (Vaishnav, Schmölter, et al., 2021). Considering this fact, we further investigate the delayed ionospheric response and examine the response of the O / N 2 ratio during the study period in Section 3.6.…”

“…Recently, Vaishnav, Schmölter, et al. (2021) conducted a comparative study of solar irradiance using observed irradiance and irradiance calculated from empirical models and found significant differences. Therefore, implementation of an improved solar EUV spectrum in the model needs to be considered.…”

“…Here we used the same model version as described in Vaishnav, Schmölter, et al. (2021) to study the TI parameters and simulate the neutral composition. In this version, F10.7 was used as the solar proxy.…”

“…(2020) reported that the delayed ionospheric response is influenced by geomagnetic activity. In addition, initial studies indicate that the delayed ionospheric response over Southern Hemisphere stations is greater than over Northern Hemisphere stations (e.g., Schmölter et al., 2020; Vaishnav, Schmölter, et al., 2021). Recently, Schmölter et al.…”

What to Do When the F10.7 Goes Out?

“…For NeQuick the response in the model is immediate with changes in F10.7, for example, between March 24 and 28. However the TIE‐GCM response to changes in F10.7 is delayed, by approximately 24–36 hr (Vaishnav, Jacobi, et al., 2021; Vaishnav, Schmölter, et al., 2021). Across the whole time period the model that uses either F15 alone (Equation ) or both F15 and F8 (Equation ) performs the best, slightly outperforming the Clette model at the beginning and end of the time period (with a similar performance between all three in the middle of the test period).…”