It would be interesting to see if any of the known solar cycles, especially those that coincide with the Earth's temperature cycles, also cause variations in solar cosmic ray production.
Carbon 14 & Beryllium 10 isotopes are generated in the atmosphere through nuclear interaction with cosmic rays in the atmosphere. Both show cycles in concentration in sync with solar cycles.
More directly the geomagnetic field varies with the solar cycle as it is modulated by the sun's magnetic field.
On top of that neutron counts vary with the solar cycle, as does the lower cloud levels.
Cosmic Rays & Climate
http://www.sciencebits.com/CosmicRaysClimate:
Clouds have been observed from space since the beginning of the 1980's. By the mid 1990's, enough cloud data accumulated to provide empirical evidence for a solar/cloud-cover link. Without the satellite data, it hard or probably impossible to get statistically meaningful results because of the large systematic errors plaguing ground based observations. Using the satellite data, Henrik Svensmark of the Danish National Space Center in Copenhagen has shown that cloud cover varies in sync with the variable cosmic ray flux reaching the Earth. Over the relevant time scale, the largest variations arise from the 11-yr solar cycle, and indeed, this cloud cover seemed to follow the cycle and a half of cosmic ray flux modulation. Later, Henrik Svensmark and his colleague Nigel Marsh, have shown that the correlation is primarily with low altitude cloud cover. This can be seen in fig. 3.
Figure 3: The correlation between cosmic ray flux (orange) as measured in Neutron count monitors in low magnetic latitudes, and the low altitude cloud cover (blue) using ISCCP satellite data set, following Marsh & Svensmark, 2003.
The solar-activity – cosmic-ray-flux – cloud-cover correlation is quite apparent.
