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Anisotropic crystals are shown to have three different mechanisms of the formation of breathers depending on the direction of the extraordinary wave propagation and on the symmetry of the medium. All uniaxial crystals with quadratic susceptibilities can be divided into three different groups, according to the crystal classes (CC). Each group is characterized by a universal structure of the breather zones (SBZ). The SBZ of the media with cubic susceptibilities does not depend neither on the crystal systems nor on the CC and coincides with the SBZ of the crystals with quadratic susceptibilities and the CC 3, 3m, 4, 4mm, 6, 6mm.

The possibility of mode-coupling, in a plasma, waves being in resonance with the sample particles is considered. The physical mechanism of this phenomenon is discussed, using as an example two monochromatic finite-amplitude waves: a Langmuir wave and an extraordinary wave. It is shown that the resonant electrons can be an effective channel for energy exchange between the waves.

Measurements of k ⊥ for an extraordinary wave near the lower hybrid frequency have been carried out by means of propagation between two dipole antennas into a plasma column. Resonance-like behavior have been observed when plasma parameters and frequency fulfil the condition ω ≈ ω LH .