When I last wrote about the solar activity situation, things were (as Jack Horkheimer used to say) “looking up”. Now, well, the news is a downer. From the Space Weather Prediction Center (SWPC) all solar indices are down, across the board:
The radio activity of the sun has been quieter:
And the Ap Geomagnetic Index has taken a drop after peaking last month:
WUWT contributor Paul Stanko writes:
As has been its pattern, Solar Cycle 24 has managed to snatch defeat from the jaws of victory. The last few months of raw monthly sunspot numbers from the Solar Influences Data Analysis Center (SIDC) in Belgium are: January = 12.613, February = 18.5, March = 15.452, April = 7.000 and May = 8.484. After spending 3 months above the criteria for deep solar minimum, we’re now back in the thick of it.
The 13 month smoothed numbers, forecast values and implication for the magnitude of the cycle peak are as follows:
- June 2009 had a forecast of 5.5, actual of 2.801, implied peak of 45.83
- July 2009 had a forecast of 6.7, actual of 3.707, implied peak of 49.79
- August 2009 had a forecast of 8.1, actual of 5.010, implied peak of 55.67
- September 2009 had a forecast of 9.7, actual of 6.094, implied peak of 56.55
- October 2009 had a forecast of 11.5, actual of 6.576, implied peak of 51.46
- November 2009 had a forecast of 12.6, actual of 7.190, implied peak of 51.36
- December 2009 had a forecast of 14.6, actual would require data from June.
Solar Cycle 24 now has accumulated 810 spotless days. 820, which would require only 10 more spotless days, would mean that Cycle 24 was one standard deviation above the mean excluding the Dalton and Maunder Grand Minima.
One standard deviation is often an accepted criteria for considering an occurrence ‘unusual’.
Here are the latest plots from Paul Stanko: