Longitudinal dependence of ionospheric irregularities to maximum ring current and PPEF sensed by GNSS and magnetometers during the storm of 4 November 2021

Abstract

We employ multi-instrumental data to investigate the behavior of equatorial and low latitude ionosphere during the geomagnetic storm of November 3-6, 2021. We used TEC data obtained from GPS receiver stations located in the equatorial and low-latitudes of the Asian, African, and American sectors. It is found that the storm-time ionization level varies significantly in the trough and crest of EIA region over the three longitudes. ROTI is used to estimate the occurrence of ionospheric plasma irregularities during the storm. Usually, the main phase of the geomagnetic storm triggers the equatorial plasma irregularities and the recovery phase suppresses the occurrence of them. Here, we observed inhibition of the plasma irregularities over the three sectors during the main phase of the storm. We suspect this may be due to the injection of the PEFs which occur between local midnight and around noon during the main phase. The PEFs restrict the diffusion of plasma and therefore, suppress the occurrence of plasma irregularities during the main phase. During the recovery phase, moderate ionospheric irregularities occurred at local midnight in the American sector. In the African sector, the occurrence of weak irregularities can be seen before midnight on November 5 and 6. However, the Asian sector does not exhibit noticeable ionospheric irregularities during the storm. We conclude that the longitudinal variation in the development of ionospheric irregularities can be influenced by factors such as local time occurrence of maximum ring current, PPEF, disturbance wind dynamo electric field, and shielding electric field.