INTERACTIONS OF SOLAR-WIND STREAMS AND RELATED SMALL STRUCTURES

Coronal holes produce high-speed, low-density, and high-temperature st reams that propagate into the interplanetary space. These streams inte ract with the slow-speed, high-density, and low-temperature stream of the ambient solar wind. We investigate this problem using the time-dep endent, two-dimensional hydrodynamic model in the spherical-equatorial coordinate system. More accurate numerical methods and finer differen ce meshes used enable us to track the evolution of detailed features o f the fast and slow stream interaction. An analysis of formation of sh ock pairs (forward and reverse shocks) is presented for both erupting and corotating parts of fast streams. Further, it is shown that the pr ocess of interaction of fast and slow solar wind streams may contain r icher structures. Such structures may originate during the reconfineme nt process (internal shocks), spatial substructures (flux tubes), and small temporal modulations (shock wings). They may influence the globa l shape of stream interfaces and heating of the plasma. Finally, concl usion can be made that boundaries between the fast and slow coronal st reams seem to be stable against small random fluctuations and against small-introduced disturbances and the Kelvin-Helmholtz instability is not initiated.