We present a theory for the generation of mesoscale (k rgT1, where rg is the cosmic-ray gyroradius) magnetic fields during diffusive shock acceleration. The decay or modulational instability of resonantly excited Alfvén waves scattering off ambient density perturbations in the shock environment naturally generates larger scale fields. For a broad spectrum of perturbations, the physical mechanis...

In this paper the wave breaking induced by modulational instability is investigated numerically. The wave train is composed by a fundamental component with two sideband disturbances and the analysis is performed for those conditions in which the instability leads the limiting steepness to be exceeded. Due to the different speeds characterizing individual waves and the peak of the envelope, the ...

We study the dynamics of discrete vector solitons in arrays of weakly coupled birefringent optical waveguides with cubic nonlinear response. We start with a modulational instability analysis, followed by approximate analytical solutions in the form of strongly localized modes. Next, we compute the effective Peierls-Nabarro potential for these modes and obtain the spatial average of the power tr...