Irregular Variation of Ionosphere.
a. In addition to the regular variation of the ionosphere, there
are temporary effects.
Some of these are Sporadic E, sudden
ionospheric disturbance (Dellinger fade), ionosphere storms and
b. Sporadic E.
consists of an ionized cloud at a slightly higher height than the
normal E layer.
Why it appears and what causes it to move is
It will reflect frequencies from 1.5 to 15 MHz.
appearance is frequent, especially in the middle latitudes. Not all
stations in a net may experience the Sporadic E reflection.