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A self-consistent Hamiltonian model based on equations describing the coupled dynamics of whistler and lower frequency waves in inhomogeneous plasmas is built. On this basis, different aspects of whistler turbulence are studied, concerning mainly the development of modulational instabilities and the dynamics of envelope solitons in irregular plasmas. Numerical simulations based on the model show that modulational instabilities can lead to the generation of a beating of stable nonlinear whistlers propagating with a speed near the group velocity. The whistler envelope soliton is determined analytically, and its propagation in plasmas presenting random density fluctuations and weakly irregular density structures of different scales and amplitudes is studied, showing that the envelope is very weakly affected by these inhomogeneities, whereas the wavelengths and the amplitudes of the phase oscillations strongly vary. Moreover, simulations show for the first time that two whistler solitons moving with different but close velocities and colliding one with the other remain unchanged after this collision, independently of their initial amplitudes and velocities. Finally, we study the dynamics of sonic whistler envelope solitons and show that the propagation of their lower frequency perturbation is governed by a KdV-type equation. [ABSTRACT FROM AUTHOR]

The combined effects of pulse slippage and the transverse magnetic field are studied on terahertz radiation excitation by nonlinear beating of two cosh-Gaussian (ChG) laser pulses propagating in a corrugated plasma. The beating lasers exert nonlinear ponderomotive force on plasma electrons. The oscillating electrons couple with corrugations present in the plasma and resonantly excite a nonlinear current (at different frequencies) which drive the terahertz wave at proper phase matching conditions. As the group velocity of THz radiation is higher than the group velocity of beating lasers, the THz pulse slips forward the pump lasers, and its saturation takes place. The effects of THz wave frequency, the decentred parameter (of beating lasers), the periodicity of the density structure, and the applied dc magnetic field are studied on THz emission. An efficiency of ~10-4 is achieved for a laser intensity of ~2×1015 W/cm2 (at a laser wavelength of ~10.6 μm for the CO2 laser). [ABSTRACT FROM AUTHOR]

The experimental observation of second order ion acoustic Peregrine breathers in multicomponent plasma with negative ions is reported. A long wavelength initial perturbation on a continuous carrier frequency ~0.5 ωpi (where ωpi is the ion plasma frequency) of finite amplitude is found to undergo self-modulation due to the interplay between nonlinear dispersive effect and group velocity dispersion because of modulational instability. Wave energy focusses to a smaller localized and isolated group of waves within the packet with amplitude amplification up to 5 times of the background carrier wave. The experimental results are compared with second order breather solution of nonlinear Schrodinger equation. The wavelet analysis and fast Fourier transform analysis of the experimental time series data indicate strong nonlinear evolution (wave energy focusing and spectral broadening) conforming to the formation of second order Peregrine solitons. [ABSTRACT FROM AUTHOR]