Solar activity and the variations of the geomagnetic Kp-index

A careful correlation analysis is made between various types of solar activity as observed at photospheric levels and the daily variations of the geomagnetic K_p-index which, in turn, is a measure of the solar wind speed. We find that in no case does a significant enough correlation exist to pin-point a physical relation between some aspect of photospheric activity and the solar wind speed. It is concluded that the physical processes that do determine the wind speed occur at coronal heights.