Statistical behavior of the longitudinal variations of daytime electron density in the topside ionosphere at middle latitudes

Around March equinox (ME), June solstice (JS), and September equinox (SE) in the Northern Hemisphere and around ME, SE, and DS in the Southern Hemisphere, the longitudinal variations of topside Ne have similar patterns to h(m)F(2). Around JS in the Southern Hemisphere (winter), the topside Ne has similar patterns to NmF2 and h(m)F(2) does not change much with longitude. Thus, the topside variations may be explained intuitively in terms of h(m)F(2) and NmF2.

This approach works reasonably well in most of the situations except in the northern winter in the topside not too far from the F-2 peak. In this sense, understanding variations in h(m)F(2) and NmF2 becomes an important and relevant subject for this topside ionospheric study.