The PI proposes a thorough, five-part investigation of solar wind periodic structures. He plans to (1) determine the occurrence frequency of the periodic structures, and determine where in the overall heliospheric structure they are observed; (2) explore the possibility that the structures occur preferentially at certain scale-sizes, as opposed to discrete frequencies, and analyze the spatial structure of these convected structures relative to current sheets, shocks, stream interfaces, etc.; (3) study the magnetospheric response to external, periodic forcing using a combination of event studies and MHD simulations, with a primary goal the determination of the dayside magnetopause Q value; (4) examine the pressure balance of the periodic density structures to determine over which timescales they are stable, and use multi-point measurements from L1 and just upstream of the Earth to explore the evolution of such structures; and (5) explore the structure and evolution of periodic density structures that are observed in the downstream regions of shocks and discontinuities.