====== Sporadic E propagation ======

//Sporadic E// or //E<sub>s</sub>// is an unusual, sporadically occurring form of enhanced radio-wave propagation.

It was discovered in the early days of VHF radio transmissions, and greatly increases the long-distance propagation of radio waves in the region of 20 - 250 MHz.

It's known that the phenomenon is caused by radio-wave reflections from 'clouds' of highly ionised air in the Earth's //'E Region'// - an atmospheric layer in the Ionosphere also known as the //Heaviside layer//.

>__No conclusive theory has yet been formulated as to the origin of Sporadic E.__ Attempts to connect the incidence of Sporadic E with the eleven-year Sunspot cycle have provided tentative correlations. There seems to be a positive correlation between sunspot maximum and Es activity in Europe. Conversely, there seems to be a negative correlation between maximum sunspot activity and Es activity in Australasia.
>\\ Source [[https://en.wikipedia.org/wiki/Sporadic_E_propagation|Wikipedia]]