Stream dynamics between 1 AU and 2 AU: A comparison of observations and theory

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Abstract
A radial alignment study of three solar wind stream structures observed by IMP 7 and 8 (at 1.0 AU) and Voyager 1 and 2 (in the range 1.4–1.8 AU) in late 1977 is presented. It is demonstrated that several important aspects of the observed dynamical evolution can be both qualitatively and quantitatively described with a single‐fluid two‐dimensional MHD numerical model of quasi‐steady corotating flow, including accurate prediction of (1) the formation of a corotating shock pair at 1.75 AU in the case of a simple, quasi‐steady stream, (2) the coalescence of the thermodynamic and magnetic structures associated with the compression regions of a fast corotating stream interacting with a slower corotating stream, and (3) the dynamical “destruction” of a “small” (i.e., low velocity‐amplitude, short spatial scale) stream by its overtaking of a slower‐moving, high‐density region associated with a preceding shock and transient flow. The evolution of these flow systems is discussed in terms of the concepts of “filtering” and “entrainment,” which have appeared in the literature. It is concluded that this study provides support at a detailed, quantitative level for our general conceptual notions of stream evolution in the inner solar system.