Question

Why are the D, E, and F regions of the ionosphere called that? And why is the F-layer further divided into F1 and F2?

Answer 1

Various types of cosmic rays ionize different molecules in the air atmosphere.This stratifies the ionosphere at different heights into different sub-layers.The plasma density has usually a considerable value in the range of 10⁹el/m² at heights from 50 to 70 km above the earth surface which is called D-layer.At the altitudes between 70 to 100 km which is called E-layer.The plasma density reaches its relative maximum value,and after that,it start to decrease,and again,it reaches its absolute maximum value at height uptown 1000 km which is called F-layer.

The ionosphere can be divided into two parts
according to the F2 layer peak; altitudes higher than the F2 peak are considered the topside ionosphere, and altitudes lower than the F2 peak are considered the bottomside iono-sphere.