Overview of the Problem

The upper part of the Earth’s atmosphere, beginning at an altitude z ∼ 60 km, is ionized. The ionization results from the action of the Sun’s ultraviolet radiation. This creates a plasma layer surrounding the Earth, called the ionosphere. The electron and ion densities N in the ionosphere increase up to altitudes z ∼ 300 km, where they reach values N _max ∼ 10⁵ − 10⁶ cm⁻³; at higher altitudes N falls off slowly.