Identification of the sources of the high-speed and...

3. Conclusion

[24] In conclusion, one should note that the performed study confirms the assumption that high-speed and low-speed solar wind streams are formed in different regions of the solar atmosphere. The deepest layers of the solar atmosphere down to the photosphere are involved into formation of high-speed streams. The presence of the adjoining active regions is of a great importance for their formation. At the same time, low-speed streams are formed high in the corona in the top parts of arch structures.

[25] 1. Coronal holes registered in the He I 10830 Å line always are located in unipolar magnetic regions. They may cover both the entire unipolar region of the magnetic field in the photosphere or only part of it. The area of the coronal holes in the He I line is, as a rule, less than or equal to the area of the coronal holes observed by Yohkoh. The shape and area of coronal holes in the He I line vary considerably from one day to another. However, they do not go outside the boundaries of the coronal holes registered by Yohkoh and stay all the time within the same unipolar region. Often coronal holes are observed first only in the Yohkoh data and only some time later they are registered in the He I line. Within one coronal hole observed in the X-ray range several coronal holes may be observed in the He I line. The regions of the coronal holes coinciding according to the data in X-ray and He I line observations may be located in different parts of the coronal holes registered in X ray. Therefore high-speed streams of the solar wind do not concentrate to the centers of the coronal holes registered in X ray but correspond to the regions of coincidence.

[26] 2. In the regions at the boundaries of coronal holes to active regions, an increase of the solar wind speed up to values of 700 km s ^-1 and a sharp increase of the flux density and magnetic field strength are observed. For the regions with diffusion boundaries, smooth rise and decrease of the solar wind speed and its lower values are typical. For loop-like boundaries speed values of 300-500 km s^-1 and increased values of the flux density are typical. The high-speed streams are observed outside arch structures, whereas a decrease in the speed and some increase in the density are observed within the arch zone. At the passage of all coronal holes an increase in the mean value of the magnetic field strength in the solar wind is observed.

[27] 3. It is found that the regions of the coronal holes registered in the He I 10830 Å line correspond to the zones with increased value of the magnetic field strength of the dominant polarity on the photosphere for the given coronal hole. For the regions of the coronal holes registered only by Yohkoh the disbalance of positive and negative polarity photospheric magnetic fields is either less pronounced or is not pronounced at all. In the region of the coronal holes registered in the He I 10830 Å line the structure of the photosphere magnetic field differs strongly from the structure of quiet regions outside coronal holes.

[28] 4. The maximum values of the solar wind speed are observed in the cases when the regions of the coronal holes registered in the He I 10830 Å line and by Yohkoh coincide. In these cases during the whole period of the coronal hole passage an increase in the solar wind speed up to the maximum values and a decrease of the density are observed. The maximum value of the solar wind velocity is also observed when the coronal hole adjoins an active region. This fact confirms the conclusion of Mustel [1980] and Kuklin and Plyusnina [1979] that high-speed solar wind streams are not formed in active regions but also do not avoid them. Their source is located near active regions.