Effects of solar flares on ionospheric TEC over Iceland before and during the geomagnetic storm of 8 September 2017

Abstract

The effects of solar flares on ionospheric total electron content (TEC) over Iceland before and during the geomagnetic storm of September 8, 2017 were studied. Global Positioning Syste (GPS)-TEC data were obtained from dual-frequency GPS sites operated by the University NAVSTAR Consortium at Dyna (65.06°N, −16.6°E) and Kisa (64.7°N, −17.6°E) stations. The findings of this study show that the enhancement of ionospheric TEC was more noticeable over the Kisa station than over the Dyna station during the coronal mass ejection day. However, during the geomagnetic storm day, maximum enhancement of TEC was observed over the Dyna station than over the Kisa station. The values of the ionospheric TEC during the initial phase of the storm were greater than during the main and recovery phases of the storm over both stations. This might be due to the effects of X-class solar flares and shock wave preceding the arriving of interplanetary coronal mass ejections plasma. The spatial gradients of TEC between two nearby stations are similar during the main phase of the storm, but slightly different during the initial and recovery phases of the storm. Finally, solar events have a favorable influence on geomagnetic storm indices and ionospheric observables.

Investigating the Potential of Vertical-TEC as an Earthquake Precursor: Haiti Major (ML 7) Earthquake Case Study

“…Spearman's rho (ρ) gauges the intensity and direction of a monotonic association between two variables [47] . Monotonicity entails a consistent ascending or descending pattern, not strictly linear.…”

Variation in Total Electron Content Over Ethiopia During the Solar Eclipse Events

“…But if the spatial gradient value (TEC in TECU/long) is high, the station with the greater geographic longitude is less affected by the solar eclipse than the station with the lower geographic longitude. The spatial gradient TEC is calculated using the formula expressed as (Idosa & Shogile, 2022), $$$Spatial\ Gradient=\frac{TE{C}_{A}-TE{C}_{B}}{{\Delta }L}$$$ where TEC A and TEC B are TEC over Addis Ababa and Bahir Dar stations, respectively. ΔL is the geographic longitudinal difference between the two stations.…”

“…The STEC between a GPS satellite (S) and a ground‐based receiver (R) can be expressed as (Sun et al., 2017), $$$STEC=\int \nolimits_{R}^{S}Ndl$$$ where l is the direction from the receiver to the satellite, and N is the location‐dependent electron density expressed in electron per meter cube. The STEC also can be computed using pseudo‐range and phase data as (Bagiya et al., 2009; Ghimire et al., 2022; Idosa et al., 2023), $$$STEC=\frac{1}{40.3}\times {\left(\frac{1}{L{1}^{2}}-\frac{1}{L{2}^{2}}\right)}^{-1}\times (P1-P2)+TE{C}_{\mathit{CAL}}$$$ where L1 and L2 are two L‐band frequencies, having respective frequencies of 1,575.42 MHz and 1,227.60 MHz, that are transmitted by each GPS satellite. A dual‐frequency GPS receiver examines the difference in ionospheric delay between the L1 and L2 signals as the GPS signal travels through the ionosphere to estimate the TEC value (Bagiya et al., 2009).…”

“…But if the spatial gradient value (TEC in TECU/long) is high, the station with the greater geographic longitude is less affected by the solar eclipse than the station with the lower geographic longitude. The spatial gradient TEC is calculated using the formula expressed as (Idosa & Shogile, 2022),…”