Sunspot update for April 2017

My annual birthday-month fund-raising drive for Behind the Black is now on-going. Not only do your donations help pay my bills, they give me the freedom to speak honestly about science and culture, instead of being forced to write it as others demand.


Please consider donating by giving either a one-time contribution or a regular subscription, as outlined in the tip jar below.


Regular readers can support Behind The Black with a contribution via paypal:

Or with a subscription with regular donations from your Paypal or credit card account:

If Paypal doesn't work for you, you can support Behind The Black directly by sending your donation by check, payable to Robert Zimmerman, to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652


You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage. And if you buy the books through the ebookit links, I get a larger cut and I get it sooner.

Today NOAA posted its monthly update of the solar cycle, covering sunspot activity for April. It is posted below, with annotations, as I have done now every month since 2010.

April 2017 Solar Cycle graph

The graph above has been modified to show the predictions of the solar science community. The green curves show the community’s two original predictions from April 2007, with half the scientists predicting a very strong maximum and half predicting a weak one. The red curve is their revised May 2009 prediction.

April showed an uptick in sunspot activity, enough to move the numbers back up above the 2007 low prediction. Nonetheless, activity as the cycle has been ramping down has consistently and generally remained below expectation, and does seem heading to an early arrival of solar minimum, sometime in late 2019 or early 2020, about a year early.

I don’t want to sound like a broken record, as I have written this practically every month since I started these updates in 2010, but this short and weak solar maximum suggests the possibility that we might be facing a grand minimum, where there are no significant sunspots for decades. Some solar scientists think this is coming. Others are much more doubtful. Regardless, we can only wait and watch, while also recognizing that weak solar maximums and grand minimums have in the past consistently coincided with global cool weather. The reasons why this has happened are not yet known, but it has happened nonetheless.


One comment

  • LocalFluff

    Here’s an interesting effect of Solar activity:

    This weeks FISO telecon mentions how the Sun spot cycle affects space debris. During the Sun spot peaks, Earth’s upper atmosphere is heated and expanded. This helps deorbit debris in LEO, as they encounter more drag. And the effect is very substantial, a few times more debris objects are deorbited during sun spot peaks. An average object in the ISS’ orbit would stay up 22 years longer if the next Sun spot cycle is “anemic”.

    I note that altitudes between 1,100 and 1,400 km are relatively empty. That’s where thousands of space based internet satellites would be launched to. That’s good news. If there’s hardly anything there to impact, and all satellites are launched in a controlled manner, there would be near zero chance of any impact happening. On the other hand, the atmospheric drag is tiny up there. It would take centuries for those satellites to come down naturally.

Leave a Reply

Your email address will not be published. Required fields are marked *