Fig. 4From: High-latitude ionospheric irregularities: differences between ground- and space-based GPS measurements during the 2015 St. Patrick’s Day stormHourly rate of TEC (ionospheric total electron content) index (ROTI) maps over the Northern (left column) and Southern (right column) Hemispheres in geographical projections with superimposed Swarm pass (thin black line) and Swarm in situ electron density (Ne) values (thick black line) for selected time intervals on March 17, 2015. Geomagnetic poles are marked by black dots. SWA and SWB designate Swarm A and Swarm B satellites, respectively. All Swarm Ne data are plotted with the same linear scaleBack to article page