Alfven waves with the initial disturbance in the FMA-waveguide

We show that Fourier transform of fast magnetoacoustic (FMA) disturbance (in coordinates along which plasma is homogeneous) can be presented as the superposition of collective modes of the basic approximation of relation between FMA and Alfven waves since the initial moment of time. On the basis of this approximation of the FMA disturbance, we describe evolution of the Alfven disturbance into which waveguide mode packets (caused by the initial disturbance of random field-aligned structure) transform. The field-aligned structure of the Alfven disturbance generated by the packet of collective modes is shown to be determined by ratios between longitudinal scales of the initial disturbance and scales given by resonance conditions, resonant wave number and resonance width in longitudinal wave numbers. We describe Alfven disturbance structures, given different ratios.