Formation of three-dimensional Langmuir solitons by an intense radio wave in the ionosphere

The steady-state plasma-density wells which appear in the ionosphere an intense radio wave passes can turn out to be clusters of three-dimensional Langmuir (plasma-wave) solitons. These solitons can form during the final stage of the evolution of a thermal parametric instability caused by the plasma heating by the radio wave. Some of the plasma waves which arise as the result of this instability are trapped in the plasma-density wells and form, along with the help of the geomagnetic field, an equilibrium configuration: a soliton. A high-amplitude soliton can be maintained in a stable steady state if energy is pumped to the soliton from a radio wave. This pumping results from the dissipation of wave energy on the thermal motion of electrons induced by soliton waves. The amplitude of the waves in the soliton can exceed the amplitude of the radio wave under a certain condition involving the properties of the radio wave and the ionosphere. Because of the rf pressure which these waves exert on the plasma, the plasma density within the soliton can decrease significantly. When the radio wave is switched off (in a stable medium) the soliton collapses. (AIP)