Distributions of the electron density (Ne) (a) and rate of change density index in 10 s (RODI) (b) measured by Swarm A in Northern (top) and Southern (bottom) hemispheres during the year with high (left) and low (right) solar activity levels. The red color shows the distribution in the low latitude region, green in the mid-latitude, blue in the high latitude, and purple in the polar cap regions.