In the framework of the ideal MHD approximation, we shall discuss the dynamics of a 3-D expansion of a spherical cloud of rarefied plasma into a vacuum in the presence of a nonuniform external magnetic field of dipole structure. When the plasma expands rapidly, for example, as a result of the energy released by the explosion, at the stage of an expansion that is nearly radial, an effective retardation of the boundaries of the cloud takes place as a result of the interaction of induced surface currents with the magnetic field. It is necessary to find the configuration and location of the plasma front as a function of time, and also to determine the limits of its propagation, which are caused by the retardation effect. Interest in this problem is primarily due to the study of nonstationary processes of an explosive nature in the cosmic plasma [1], in particular, to the analysis of the global instability of the earth's magnetosphere in estimates of the effectiveness of explosive methods of its protection from collisions with asteroids and comets [2, 3]. The problem was studied in a similar formulation only in the simplest case, i.e., in a uniform external field [4]. The case with a dipole field was examined in [5] for comparatively low explosion energies and correspondingly small deviations of the shape of the plasma formation from a sphere. In [6], we estimated the size and configuration of the retardation region in the field of a point dipole. On the whole, the problem has been little-studied because of the absence of the necessary 3-D nonstationary numerical models owing to the complexity of creating them. The proposed study is based on some simple relationships for generalized characteristics of motion - energy and pressure - and does not allow for the role of magnetic diffusion, which makes it possible to find the basic principles of the 3-D dynamics of retardation with a minimum number of initial parameters. The calculation model is compared with the results of an experiment on the expansion of laser plasma clouds in a dipole field on a KI-1 stand [7]. This approach is aimed at estimating the possibilities of the hydrodynamic method and obtaining preliminary data necessary for constructing more rigorous models. 1. Analysis of the Retardation Model. As in [4], which discussed the problem of expansion of a superconducting sphere in a uniform external magnetic field, it can readily be shown that the work of ponderomotive forces A on particles of an ideally conducting plasma cloud of changing shape during its expansion time t in a field of arbitrary configuration is equal to the work of forces of magnetic pressure Bs2/87r on its surface S, written in the form t