Fig. 9
From: Effects of the postsunset vertical plasma drift on the generation of equatorial spread F
The longitude-month distributions of a the vertical ion drift at the PRE peak, b the occurrence probability of large amplitude ESF irregularities with ΔN > 2 × 1010 m−3, and c the occurrence probability of small-amplitude ESF irregularities with ΔN = 1–2 × 1010 m−3 measured by C/NOFS during moderate solar activity in 2011–2014, respectively