Eleven year cycle. If that means something to you, you must be an amateur radio operator, or some other student of the Sun. Here’s an older NASA video that’s still interesting.
Despite the wishes of medieval philosophers, the Sun is not a perfect disk. Sunspots are
regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection… may last anywhere from a few days to a few months…. [and affect] space weather, the state of Earth’s ionosphere, and hence the conditions of short-wave radio propagation or satellite communications. wikipedia
We’ve known for a long time that the frequency of sunspots roughly follows an eleven year cycle, with a lot of variation in intensities and somewhat in durations, but it’s been hard to explain why. A recent study (in Solar Physics, which looks like a real journal – you gotta be careful now-a-days) found a “high level of concordance” between the positions of three planets in their orbits and sunspot activity.
The study examined 90 cycles, which means almost 1,000 years of records. That’s a lot of history and the article I read doesn’t say how reliable ancient records are. But for the last two dozen cycles, we have pretty good data. The cycle seems to align with movements of Venus, Earth, and Jupiter in an 11.07 year cycle.
There are some problems. Sunspot cycles have varied from eight to fourteen years in length, so explaining the average by itself isn’t enough. What about the other planets? When you have a bunch to choose from, any correlation may simply be fortuitous. But I’m curious to know if adding more planets to the model will help or hurt the correlations.
By what mechanism could such a relatively small gravitational force impact our star? Perhaps plasma stability analyses can explain it? The math needs to be done.
My spouse, the ham radio operator in the family, is skeptical. There have been other attempts to explain the sunspot cycle that didn’t pan out. Of course, this hypothesis must be examined further.
But every discovery starts with an observation.
Thanks to newsweek.com for their article.