Fig. 7From: Effects of the postsunset vertical plasma drift on the generation of equatorial spread Fa The vertical ion drift at the PRE peak in the cases with plasma bubbles (red circles) and in the cases without plasma bubbles (blue circles) detected by C/NOFS during May 2008–June 2013. b The dependence of the plasma bubble occurrence probability on the vertical ion drift at the PRE peak. (After Huang and Hairston 2015)Back to article page