Prediction of quasi-stationary solar wind velocity based on image analysis of the Sun from the SDO / AIA space observatory
Recurrent high-speed solar wind streams are known to be long lived phenomena that result in substantial, particularly in high latitudes, but not very strong recurrent geomagnetic disturbances, which may span a few days or more up to a period of complete solar rotation. The source of recurrent high-speed solar wind streams is coronal holes (CH). The CHs are normally identified as regions of unipolar magnetic field, which appear as regions of decreased intensity in the ultraviolet and X-ray solar images owing to low plasma density. It is well known that there is a remarkable connection between the passage of the low latitude coronal holes across the solar disk and the recurrent high-speed solar wind streams recorded in Earth orbit. CH parameters are calculated for images obtained with SDO/AIA at wavelengths of 193 and 211Å. Algorithm of CH areas calculation is based on the classification of image points according to threshold intensity. For forecasting the solar wind velocities of recurrent high-speed streams a 3-4 days in advance from the parameters of the coronal holes empirical relations are used.