Fig. 8From: Ionospheric irregularity behavior during the September 6–10, 2017 magnetic storm over Brazilian equatorial–low latitudesSão Luís PolaRx5 GPS receiver S4 parameters for the frequencies L1, L2C and L5 during the storm period. The green line is the noise threshold, i.e., we consider ionospheric scintillation when S4 > 0.15. The vertical dashed red lines represent the 2 SSCs, the first one at 23:43 UT on day 06 and the second one 23:00 UT on day 07Back to article page