Tag Archives: sunspot activity

Ramp down to solar minimum continues

On Sunday NOAA posted its monthly update of the solar cycle, showing the Sun’s sunspot activity in May. As I have done since 2010, I am posting it here, with annotations to give it context.

May 2015 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.

Sunspot activity once again increased in May, though it continues to remain below the 2009 prediction of activity. Though it is still early in the ramp down, a look at the present pattern suggests that (as I also noted last month) sunspot activity is declining much faster than normal. In the past, the ramp down after solar maximum was long and drawn out, while ramp up was much faster. This ramp down seems much more precipitous than past solar cycles.

I should add that in early April Sunspot Index and Long-term Solar Observations (SILSO) had declared that the peak of the solar maximum had occurred in April 2014, and that they could now sum up the overall weakness of this maximum.

Cycle 24 proves to be 30% weaker than the previous solar cycle, which reached 119.7 in July 2000, and thus belongs to the category of moderate cycles, like cycles 12 to 15, which were the norm in the late 19th and early 20th century. Compared to strong cycles, such cycles typically feature a broader maximum, with a 3-year plateau on top of which two or more surges of activity can produce sharp peaks of similar height.

I had missed this announcement when it was first posted. It is worth noting however, especially since their discussion in April is interesting to read in the context of what has happened since.

Sunspot activity tracks prediction

On Monday NOAA posted its monthly update of the solar cycle, showing the sunspot activity for the Sun in January. As I do every month, I am posting it here below the fold, with annotations to give it context.

As I have noted previously, the ramp down from solar maximum continues to track the 2009 prediction of the solar scientist community (indicated by the red curve) quite closely. As NOAA also notes,

While awaiting final confirmation, all evidence points to the most recent solar maximum having peaked at 82 in April, 2014. This was within the expected range for the peak, but occurred significantly later than predicted.

Since their graph doesn’t show the entire curves for their predictions, the above statement seems reasonable. However, looking at the graph with those curves inserted (see my annotated graph below the fold), it becomes clear that not only did the peak occur much later than predicted, the maximum’s overall activity was also generally less than predicted.
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