Ionosphere over Eastern North Atlantic Midlatitudinal Zone during Geomagnetic Storms

Abstract

The ionospheric response at middle latitudes to geomagnetic storms is not yet very well understood. Total electron content (TEC) variations associated with eight strong geomagnetic storms between 2015 and 2022 obtained from GNSS receivers in the eastern area of the North Atlantic (Portuguese continental and insular territory) are studied in an attempt to fill this gap. It was found that for most of the studied geomagnetic storms, TEC variations are synchronous for the longitudinal ranges from 27° W and 9° W. In the southern part of the studied region (around 32° N), the amplitude of TEC variations is, in general, significantly higher than in the northern part (around 39° N). Some of the studied geomagnetic storms were associated with TEC variations that we interpret as effects of post-sunset equatorial plasma bubbles that travelled well north from their habitual region. Additionally, though most of the studied storms were accompanied by reports on different kinds of malfunction of GNSS systems (GPS; GALILEO and other), there is no clear pattern in their appearance in dependence on the geomagnetic/ionospheric storms’ strength, commencement time, and its characteristics, in general.

Total Electron Content PCA-NN Prediction Model for South-European Middle Latitudes

“…On the other hand, two other locations, Furnas (Azores) and Funchal (Madeira), are at different longitudes (Furnas, difference in longitude of ~16 • ) or latitudes and longitudes (Funchal, differences in latitude of ~6• and longitude of ~7.5 • ). A recent study [32] of TEC variations during geomagnetic storms at these three locations showed that in most cases, TEC variations at the Lisbon area, Azores, and Madeira are very similar, with higher amplitude observed for the southernmost location (Madeira). Furthermore, it seems that the Funchal TEC series shows variability that can be attributed to the effect of the equatorial electrojet (EEJ).…”

“…This can also be deduced from the width of histograms shown in Figure 6. We interpret this difference as the influence (unaccounted by used input SWp) of EEJ and events related to the equatorial ionosphere (as, for example, equatorial plasma bubbles that in some regions and under certain conditions can reach Madeira longitude and latitude [32,33]).…”