Have we passed solar minimum?

Sunday, 31 May 2020 14:53 UTC

First of all... what is solar minimum and how do we decide when solar minimum took place? Solar minimum is the period of least solar activity in the 11-year solar cycle. The date of the minimum is described by a smoothed average over 13 months of sunspot activity (the sunspot number), from 6 months before to 6 months after a base month. That means we can not call solar minimum for sure until at least 6 months after the minimum takes place. For a more comprehensive explanation be sure to read the text below from the SIDC SILSO website:

While we decide when solar minimum took place with the help of the Smoothed Sunspot Number, there is another great benchmark which gives us an idea when solar minimum might have occurred and that is where friend of the website Christian Harris from Space Weather Trackers comes in. Christian is a space weather enthusiast like ourselves with an almost endless knowledge when it comes to space weather. He made a great post on his Space Weather Trackers page yesterday which he kindly shares with us. The latter half of his post is what we are going to focus on where he uses the sun's polar magnetic field strength (see the image below) to determine at what phase of the solar cycle we are currently in. Do read and fling a like at his post and of course follow his Space Weather Trackers page!

As Christian describes in his post on Space Weather Trackers:

The black line peaks during solar minimum, and goes to zero during solar maximum. The timing between these events are not perfectly aligned, generally once the magnetic field strength begins to drop, the effects are seen through the sunspot numbers beginning to increase months later.

Ignoring the sharp drop in the black line, which was due to the instrumentation being calibrated and no data being taken at the time, it is now clear the average field strength is dropping, and dropping considerably.

What can we take away from this? First of all if we take a look at the smoothed sunspot number, we first have to take a look at the sunspot number for each individual month. We can see here and on the image below that we had very low sunspot numbers between June and December of 2019. In January and April of this year the sunspot numbers were considerably higher. Based on the data available right now, we can estimate that December 2019 could have been the month of solar minimum. The graph of the Sun's polar magnetic field strength only fuels this theory as we could see earlier in this post how the sun's polar magnetic field strength has been dropping during the past few months indicating Solar Cycle 25 like already has begun. Two indicators pointing in the same direction: solar minimum has passed. Do not expect major solar activity in the months ahead, it is really still too early for that but there is light at the end of the tunnel. We cant wait to see what the years ahead will bring but we are glad you are following us along for the ride!