A study of Solar Flares and Geomagnetic Storms Impact on Total Electron Content Over High-Latitude Region During July- November 2021: The Case of Tromso Station.

• Solar flare effect may suppress irregularities. • Positive ionospheric storm noticed during storm recovery phase. • Geomagnetic storm and solar flare impact affect TEC values. This study investigates the impact of geomagnetic storms and solar flares on total electron content (TEC) of the ionosphere of high-latitude auroral station at Tromso(Geog. Lat. 69.66 ° N, Geog.Long. 18.94 ° E, and Geomag.Lat. 66 °). The rate of increase or decrease in TEC value indicator ( ROTI ave ) are used as the ionospheric irregularities proxy to prob occurrence of TEC alteration during months of July, August, September, October and November 2021. The deviation of TEC (in percentage) denoted by Δ TEC (%) was utilized to examine the impact of geomagnetic storms and solar flares on the ionospheric storms over aurora region. The study finds that a remarkable boost of TEC values up to the order of about 7–10 TECU was noticed over Tromso station during moderate geomagnetic storms of 28 August 2021, 12 and 17 October 2021 and a strong geomagnetic storm of 4 November 2021. The investigation also finds suppression of ionospheric irregularities during peak of X-type solar flare of 28 October 2021. The suppression is probably attributed to effect of accelerated energetic particles associated to solar flare eruption and coronal mass ejection (CME). On the other hand, moderate occurrence of irregularity was observed during main and recovery storm phase of 4 November 2021 at 18:00–24:00 UT and 1:00 UT-3:00 UT. This article presents the consequence of geomagnetic storms and solar flare on characteristics evolution of phase fluctuations and ionospheric storm during July, August, September, October and November. [ABSTRACT FROM AUTHOR]