Interactions of solar wind streams and related small structures

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Abstract
Coronal holes produce high‐speed, low‐density, and high‐temperature streams that propagate into the interplanetary space. These streams interact with the slow‐speed, high‐density, and low‐temperature stream of the ambient solar wind. We investigate this problem using the time‐dependent, two‐dimensional hydrodynamic model in the spherical‐equatorial coordinate system. More accurate numerical methods and finer difference meshes used enable us to track the evolution of detailed features of the fast and slow stream interaction. An analysis of formation of shock pairs (forward and reverse shocks) is presented for both erupting and corotating parts of fast streams. Further, it is shown that the process of interaction of fast and slow solar wind streams may contain richer structures. Such structures may originate during the reconfinement process (internal shocks), spatial substructures (flux tubes), and small temporal modulations (shock wings). They may influence the global shape of stream interfaces and heating of the plasma. Finally, conclusion can be made that boundaries between the fast and slow coronal streams seem to be stable against small random fluctuations and against small introduced disturbances and the Kelvin‐Helmholtz instability is not initiated.