Current ideas concerning the spectrum of the irregularities in the interplanetary plasma

The introduction contains a brief review of the study of interplanetary plasma by the “transillumination” method, with a summary of the development of the method and the results obtained with it during various stages. Principal attention is paid to the inhomogeneity spectrum, which plays an important role in the understanding of the physical processes that occur in solar wind. To this end, the experimental data obtained by the “scintillation” method are considered in detail. This is followed by an analysis of the theoretical conclusions that follow for two different models of the inhomogeneity spectrum, and by tests with which it is possible to choose between the two hypotheses. The results of the latest experiments and the difficulties connected with the available observed facts are discussed from this point of view.