Solar cycles. You probably studied them in science class, boring! Something about 11 years blah, blah, blah, sunspots, yada, yada, yada, snore.
Solar cycles, boring as they may appear, help us understand the long-term impact our star the Sun has on the Earth. The challenge is we have been studying solar cycles only since they were recognized, in the mid-18th century by German astronomer Samuel Heinrich Schwabe. Sunspots however have been observed since the time of Galileo, the early 17th century and we now know sunspot numbers have a strong correlation with solar activity. That’s good but still presents us with a lack of data. In four centuries, 36 cycles can be extrapolated. I say extrapolated because sunspot counts in the 17th century were less reliable than later. Fewer astronomers did it and they had much cruder equipment to work with. Swiss astronomer Rudolf Wolf is credited with devising the Solar Cycle system, and to make it as accurate as possible the cycle period beginning in 1755 is traditionally named cycle 1. Since then, 24 solar cycles have occurred.
A solar cycle takes an average of 11 Earth years from minimum to maximum, back to minimum. We’re talking about solar activity and that correlates with sunspot counts. Solar activity includes sunspots, flares, prominences, even coronal mass ejections. More sunspots mean more activity and is the result of solar magnetic field interactions. You could say solar cycles are created by the Sun’s dynamic magnetic personality. The Sun’s magnetic poles perform a slow-motion flip-flop over an 11-year period, where north becomes south. During the pole reversal process solar activity fluctuates, producing 5.5-year run ups to maximums and run downs to minimums.
Before the past two cycles (23 & 24) we had been experiencing generally higher maximums than average. Solar activity from 1940-1960 had an upward trend with much higher maximums. The 1970s reversed that trend back to average or lower, then the 1980s and 1990s went back up higher than average. The late 1990s through 2020 show a general maximum decline. Cycle 25, which started in December 2019 is showing stronger sunspot activity than cycle 24, indicating an uptick in solar activity.
Is it a coincidence that a downturn in solar activity in the 1970s occurred and some were predicting global cooling? Was that a knee-jerk reaction? Maybe, but I believe concern about extended solar minimums is warranted. There have been several extended periods of low sunspot activity and some suggest an association with regional, if not global lower temperatures and shortened growing seasons. If true that can mean significant issues for agriculture. But the overall affect appears limited and other phenomenon such as high volcanic activity might have a stronger impact. Maybe the low solar activity is just coincidental.
Anyway, cycle 25 appears normal so far.
What’s in the Sky?
April 15-17; 45 minutes after sunset; west: A waxing crescent Moon is in Taurus with the Pleiades and Mars.