An analysis of polar coronal hole evolution: Relations to other solar phenomena and heliospheric consequences

We use observations of the green corona low-brightness regions to construct a time series of a polar coronal hole area from 1939 to 1996, covering 5 s olar cycles. We then perform a power-spectral analysis of the monthly data time series. Several persistent significant periodicities appear in the spe ctra, which are related with those found in solar magnetic flux emergence, geomagnetic storm sudden commencements and cosmic-ray flux at Earth. Of par ticular importance are the peak at around 1.6-1.8 yr recently found in cosm ic-ray intensity fluctuations, and the peak at around 1 yr, also identified in coronal hole magnetic flux variations. Additional interesting features are the peaks close to 5 yr, 3 yr and the possible peak at around 30 yr, th at were also found in other solar and interplanetary phenomena. Our results stress the physical connection between the solar magnetic flux emergence a nd the interplanetary medium dynamics, in particular the importance of coro nal hole evolution in the structuring of the heliosphere.