Solar cycle 24 has seen very low solar activity thus far, likely the lowest in 100 years.
Guest essay by David Archibald
Figure 1: F10.7 Flux 2014 – 2017
The F10.7 flux shows that over the last three and a half years the Sun has gone from solar maximum through a bounded decline to the current stage of the trail to minimum. Solar minimum is likely to be still three years away.
Solar Cycle 24 is sitting at the lower bound of activity for solar cycles back to 1964, the start of Solar Cycle 19. From here to minimum though, it looks like Solar Cycle 24 will have much lower volatility than the solar cycles that preceded it.
Figure 3: Oulu Neutron Count 1964 – 2017
According to Svensmark’s theory, the neutron flux, with its effect on cloud cover and thus the Earth’s albedo, is one of the bigger climate drivers. For Solar Cycle 24, the neutron flux duly turned around and starting rising again in 2015, one year after solar maximum. It is a safe bet that the neutron flux is heading for a record high at solar minimum (+ one year) relative to the instrumental record.
The last weak solar cycle was Solar Cycle 20 which caused the 1970s Cooling Period. From the same stage in that cycle the neutron count flattened out to minimum. That could happen for Solar Cycle 24 but it is more likely to keep rising to minimum as 23 did and thus we can expect a count, at the end, of over 7,000.
If we conflate the F10.7 flux and the Oulu neutron count inverted, that shows they tracked each other closely up to 2004. Something changed in 2004 and since then the neutron count has been higher relative to its previously established correlation with the F10.7 flux.