Recurrence - Implications for heliospheric cosmic ray transport

An analysis procedure is developed to quantify recurrence tendencies in lists of events. I apply this technique to 27-day recurrent variations in the intensity of the galactic cosmic radiation. Changes in the ground-level nucleonic intensity are significantly more recurrent than are intensity extrema. The recurrence periods of cosmic ray decreases do not respond to changes in the polarity of the heliospheric magnetic field. Corotation of quasi-static structures is a less important cause of recurrence than are the interplanetary disturbances responsible for abrupt cosmic ray changes.