Non-recurrent geomagnetic disturbances from high-speed streams

It is shown that at any phase of solar activity cycle the Earth is circumflown mainly by high-speed solar wind streams (M-streams). The attention is called to the fact that M-streams cause not only the wellknown recurrent geomagnetic disturbances (at the declining phase of solar cycle) but also numerous nonrecurrent disturbances (at all the other phases). The intensity and duration of a typical non-recurrent M-disturbance are less than those of a recurrent one.