Spatial and seasonal effects on the delayed ionospheric response to solar EUV changes

Abstract

This study correlates different ionospheric parameters with the integrated solar extreme ultraviolet radiation (EUV) radiation to analyze the delayed ionospheric response, testing and improving upon previous studies on the ionospheric delay. Several time series of correlation coefficients and delays are presented to characterize the trend of the ionospheric delay from January 2011 to December 2013. The impact of the diurnal variations of ionospheric parameters in the analysis at an hourly resolution for fixed locations are discussed and specified with calculations in different timescales and with comparison to solar and geomagnetic activity. An average delay for the total electron content (TEC) of ≈ 18.7 h and for foF2 of ≈ 18.6 h is calculated at four European stations. The difference between the Northern and Southern hemispheres is analyzed by comparisons with the Australian region. A seasonal variation of the delay between the Northern and Southern hemispheres is calculated for TEC with ≈ 5 ± 0.7 h and foF2 with ≈ 8 ± 0.8 h. The latitudinal and longitudinal variability of the delay is analyzed for the European region, and found to be characterized by a decrease in the delay from ≈ 21.5 h at 30 • N to ≈ 19.0 h at 70 • N for summer months. For winter months, a roughly constant delay of ≈ 19.5 h is calculated. The results based on solar and ionospheric data at an hourly resolution and the analysis of the delayed ionospheric response to solar EUV show seasonal and latitudinal variations. Results also indicate a relationship of the ionospheric delay with geomagnetic activity and a possible correlation with the 11-year solar cycle in the analyzed time period.

The Delayed Ionospheric Response to the 27‐day Solar Rotation Period Analyzed With GOLD and IGS TEC Data

“…Q EUV and corresponding TEC are in good agreement (correlation coefficient of 0.69). The estimated delays based on Q EUV and TEC are similar to the results of studies using actual EUV measurements and TEC, for example, Schmölter et al (2020) 3. N Max and corresponding TEC are in good agreement (correlation coefficient of 0.59).…”

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

“…Past studies on the effect of solar radiation variations at different timescales have been based on the total electron content (TEC, frequently given in TECU; 1 TECU= 10 16 electrons m −2 ), peak electron density (NmF2, cm −3 ), and the corresponding height (HmF2, km) (e.g., Jakowski et al, 1991;Afraimovich et al, 2008;Lee et al, 2012; Published by Copernicus Publications on behalf of the European Geosciences Union. et al, 2016;Schmölter et al, , 2020Vaishnav et al, 2018Vaishnav et al, , 2019Ren et al, 2018, and references therein).…”

“…Using a more precise and higher temporal resolution solar flux, an ionospheric delay of about 17-19 h has been reported by . The spatial and seasonal effects on the ionospheric delay have been further investigated in detail by Schmölter et al (2020) using European and Australian locations. Their study highlighted the role of geomagnetic activity in the ionospheric delay.…”

Ionospheric Response to Solar EUV Radiation Variations: Comparison based on CTIPe Model Simulations and Satellite Measurements

“…To estimate the ionospheric delay, different ionospheric parameters have been considered using daily resolution data, an ionospheric delay of about 1-2 d against solar proxies has been reported (Jakowski et al, 1991;Jacobi et al, 2016;Vaishnav et al, 2019). Only recently, Schmölter et al (2020) used SDO EVE and GOES EUV fluxes to calculate the ionospheric delay of about 17 h as a mean value based on hourly time resolution data. This observed delay was also confirmed by numerical physics based models (Ren et al, 2018;Vaishnav et al, 2018).…”

“…Profiles of the delayed ionospheric response dependent on latitude have been calculated in previous studies (Lee et al, 2012;Ren et al, 2018) and the influence of seasonal variations and geomagnetic activity on both hemispheres has also been characterized (Schmölter et al, 2020). The complexity of the seasonal variations and associated anomalies has been investigated in other studies for ionospheric parameters like TEC (Romero-Hernandez et al, 2018).…”