  Within the framework of the effective theory for ultrasoft field modes a
problem of interacting an energetic color particle with ultrasoft fluctuations
in hot gluon plasma is considered. The procedure of calculation of certain
effective current generating the process of interaction is proposed, and the
problem of its gauge independence is discussed. The application of the theory
developed to the problem of energy losses of the energetic color particle
propagating through hot QCD-medium is given. It is shown that the perturbation
approach for calculation of energy losses breaks down at the ultrasoft momentum
scale of plasma excitations.
