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Abstract

Two basic types of solar wind are usually distinguished: fast and slow. As the fast solar wind stream propagates through the interplanetary space, it interacts with the surrounding slow streams. This interaction creates stream interaction regions at the leading and trailing edges of the fast stream. These regions are filled with a solar wind of mixed properties that do not correspond to the standard classification of the solar wind. Moreover, the solar wind parameters change significantly with increasing radial distance from the Sun. We focus on the evolution of the fast solar wind streams and their surroundings throughout the heliosphere. We combine near-Sun observations made by the Parker Solar Probe (PSP) with Solar Orbiter measurements at intermediate distances and with near-Earth data (Wind, ACE) for study of the non-radial propagation of the fast solar wind. We investigate how this feature varies for different PSP encounters and how the corresponding processes contribute to the formation of the intermediate streams within the stream interaction regions.