Decay Process in an Active Medium. An Example

In the background of many plasma phenomena are wave-wave interactions, wave-particle interactions, energy transfers, and so on. In natural and laboratory plasma, very often there are situations when a plasma is weakly unstable, that is not far above a threshold of instability. In these cases, we can describe a perturbed state in terms of a small finite number of plasma waves. In the present work, we will consider non-linear stabilization of the current instability in isothermal magnetized plasma by a three-wave decay process. This problem was studied in the many works, but some questions remain unclear, e.g. the existence and properties of chaotic regimes for certain parameters. We will consider an interesting, realistic plasma system with current instability in isothermal plasmas. To assume that only three waves are involved in the process of stabilization we have to consider instability in the conditions very close to the threshold, when only one low hybrid mode is unstable. This wave decays on two other strongly damped low hybrids waves. The dynamic stabilization of instability and swapping of energy from a radiant in area of damping (heat of plasma) thus happens. This example shows a common situation and that represents practical interest at the analysis of natural processes in ionosphere. (author)