A lot has been made about the relative quietness of solar cycle 24. For those who do not know about the solar cycle, let me give you a brief introductory course. The Sun has a cycle of activity that runs about 11 years between times of peak to peak and valley to valley. Probably the easiest way to see how busy the Sun is to keep track of the number of sunspots (the more sunspots, the busier the Sun is). Let's take a look at the graph below:
Notice the approximate 11-year period between peaks in activity (roughly 2001-2002 to 2012-2013). This solar cycle is called 24 because it is the 24th recorded solar cycle. According to wikipedia:
"The solar cycle was discovered in 1843 by Samuel Heinrich Schwabe, who after 17 years of observations noticed a periodic variation in the average number of sunspots seen from year to year on the solar disk. Rudolf Wolf compiled and studied these and other observations, reconstructing the cycle back to 1745, eventually pushing these reconstructions to the earliest observations of sunspots by Galileo and contemporaries in the early seventeenth century."
OK, back to our original point. We can certainly see the peak of solar cycle 24 is nowhere near the peak of solar cycle 23 and going back farther in times, previous cycles.
This was expected.... but maybe not to the extreme we had seen up to October 2013.
Notice how the actual sunspot numbers, besides a few spikes, were below the projection (middle dashed line). Also notice how the projected maximum (top dashed line) was much lower than the peak of solar cycle 23.
NASA released to the public, "May 8, 2009 -- Solar Cycle 24 Prediction Update The Solar Cycle 24 Prediction Panel has reached a consensus decision on the prediction of the next solar cycle (Cycle 24). First, the panel has agreed that solar minimum occurred in December, 2008. This still qualifies as a prediction since the smoothed sunspot number is only valid through September, 2008. The panel has decided that the next solar cycle will be below average in intensity, with a maximum sunspot number of 90. Given the predicted date of solar minimum and the predicted maximum intensity, solar maximum is now expected to occur in May, 2013. Note, this is a consensus opinion, not a unanimous decision. A supermajority of the panel did agree to this prediction."
So, the point of this post? To point out that October 2013 was basically the only time period where solar cycle 24 has met expectations besides a few exceptions.
Well, all fine and good! This leads to two questions in my mind: Well, we see how solar cycle 24 is playing out... what do we expect for solar cycle 25? And what does this all mean for the average person on Earth?
Well, first question can be answered in this graph from NASA:
So you can see they are expecting solar cycle 25 to be weak as well, even weaker than solar cycle 24. However, also notice how bad their forecast for solar cycle 24 was. They expected it to be less than solar cycle 23, but not this much less.
Finally, what does this mean on Earth? Well, a less active sun means fewer CMEs (coronal mass ejections), fewer solar flares and fewer sunspots. There will be some... and some may be strong. There just will not likely be as many. This means that there is less chances for northern lights and communications disruptions; both things occurring when the sun is busy.
Also related to us here on Earth, a less active Sun means that it is putting out slightly lower amounts of energy. This could mean a slight cooling effect here on Earth. Look at the graph below and notice how when the Sun has less sunspots, it appears to have a correlation to cooling on Earth.
A couple of things to get out of this graph... the warming of the late 1800s and 1900s also coincided with a rather active solar period as a whole. The Dalton Minimum, basically the late 1700s and early 1800s, was a time with a less active Sun and generally cooler temperatures on the Earth (by an average of 1 degree C, though recent evidence also points it was a time with more volcanism than normal, which also could be responsible for the cooling).
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