Hydromagnetic Waves in Interplanetary Space

Review of recent theoretical and observational work attempting to explain the origin and nonlinear properties of interplanetary hydromagnetic waves and the role played by these waves in modifying the thermal and dynamic characteristics of the solar wind. Attention is restricted to propagating hydromagnetic waves which are intrinsic to the solar wind itself. An initial straightforward analysis of small-amplitude hydromagnetic waves serves as a guide for interpreting the data and as a reference point for examining the more complex nonlinear phenomena. Representative data illustrate the appearance of the various hydromagnetic wave modes in the solar wind. The various effects which the waves may have on the solar wind itself are finally discussed.