Northern Light Now – The long absence of large solar flare activity may come to an end soon as solar cycle 25 active regions start to appear. The last C-class flare occurred on May 15, 2019 from active region 12741. In the 7 months since, there have been only 19 active regions numbered as the Sun has been in the depths of the cyclic solar minimum. For aurora hunters, the only source of activity has been from an occasional filament eruption and High Speed Streams originating at Coronal Holes. However, over the last several months there are indications that the next solar cycle is picking up and activity will return over the next year. Aurora hunters should start looking forward to the next season.
The Solar Cycle lasts about 11 years. During each cycle, activity increases for about five and a half years. The monthly count of active regions and sunspots visible on the Sun increases until Solar maximum. At maximum, the Sun’s polarity flips and activity slowly tapers back into solar minimum over the remaining five and a half years in the cycle. Currently, the Sun is in the least active part of this cycle and as a result there have been fewer and weaker aurora displays over the last year.
Solar Cycle 24 (SC24) started in January of 2008 and peaked in July of 2013 and is ending now. At peak, there were nearly 300 active regions numbered in 2013. There were only 22 new active regions numbered in 2019. There is normally an overlap between the end of one solar cycle and the beginning of the next. Of those 22 active regions numbered in 2019, only 17 actually belong to SC24, the other 5 are part of Solar Cycle 25.
When Will Solar Activity Increase?
By the start of the next northern hemisphere aurora season! Aurora hunters can expect the 6 to 9 months ahead to continue to have very low solar activity. During the minimum between SC23 and SC24 there were about 30 months with fewer than seven active regions numbered. In the current minimum, the last month with more than seven active regions identified was September of 2017 – or 27 months ago. This is an arbitrary threshold, but can prove useful when making an estimate. Projecting out and assuming the same length of solar minimum, May or June should be the first month with 7 newly numbered active regions of Solar Cycle 25.
While there won’t be much activity from CMEs originating at active regions, it will certainly be possible that there will be activity from coronal holes. Attentive space weather fans will have noticed over the last couple years that Coronal Holes are the primary driver behind aurora activity during solar minimum. It is possible there will also be activity from filament eruptions (link to what happened today). Overall, the frequency of storms should be about the same over the last 6 months as it will be over the next 6 months – that is to say, not much.
The frequency and magnetic complexity of SC25 regions will continue to increase. With each new region, the likelihood of the next C-class flare increases. Seasoned aurora hunters know that long duration C, M and X class flares are one of the keys to a good northern lights display. Of course, a more complex AR could develop at any time and produce an strong flare, it is just far less likely during solar minimum. So keep watching the data and keep watching the active regions.