Fig. 2From: Statistical analysis of ionospheric total electron content (TEC): long-term estimation of extreme TEC in JapanCDF of the daily foF2 occurrence from 1997 to 2018 at Kokubunji station, Tokyo. The occurrence rate, which is the number of days per 100 years, and the occurrence rate in percentage are shown on the left- and right-hand axes of the ordinate, respectively. Red, pink, blue, and light blue represent days of HSHG, HSLG, LSHG, and LSLG, respectively. The solid, dotted, and dashed horizontal lines represent occurrence rates of 0.3%, 0.03%, and 0.003%, which correspond to frequencies of once per year, 10 years, and 100 years, respectivelyBack to article page