Solar cycle 24 contines to be lower than the vast majority of predictions that came out during the waning years of solar cycle 23. David Archibald gives an update on the current progress of solar cycle 24, showing that it remains quite low, and under-performs almost all of the “official”predictions based on models and other forecasting tools, some of which claimed as late as 2006 that cycle 24 would be 30-50% stronger that cycle 23. So far, solar Cycle 24 has been most like Solar Cycles 10 to 15 which started in 1855 and ended in 1923. It is noteworthy that solar cycle 10 produced the famed Carrington event, which if it occurred today, would likely wreak havoc with our sensitive electric grid and electronics.
Guest essay by David Archibald.
Figure 1: Sunspot Number
Source: SILSO data/image, Royal Observatory of Belgium, Brussels
Solar Cycle 24 has been stronger for longer for about a year now. This plot of sunspot number that decline from the second peak is underway.
Figure 2: AP Index 1932 – 2015
The Ap Index, a geomagnetic index driven by the Sun’s magnetism and the solar wind, remains at levels of previous solar cycle minima.
Figure 3: Sunspot Area versus Ap Index 1932 – 2105
From Jan Janssens’ website Solaemon, this graph plots the Ap Index with sunspot area from 1932. Absolute lows in the Ap Index correspond to solar cycle minima but the peak in the Ap Index can be much later than peaks in the solar cycle. Note that the Ap Index was quite strong during the 1970s cooling period up to the Solar Cycles 20/21 minimum.
Figure 4: Monthly F10.7 Flux 1948 – 2015
The F10.7 flux is not subject to observer bias and thus many prefer it to the sunspot number. This chart confirms a second peak in Solar Cycle 24 over the last year. A F10.7 flux above 100 is warming, below 100 is cooling. So the last few years have put a little pulse of warming into the climate system.
Figure 5: Heliospheric Current Sheet Tilt Angle 1976 – 2015
The heliospheric current sheet tilt angle flattens at solar minimum. For the Solar Cycle 23/24 minimum, that occurred in October 2009. From that minimum, the tilt angle had the fastest ascent of the instrument record which happens to be only three and a half cycles. The peak in the tilt angle this cycle is also the broadest in the instrument record. If that means anything, it possibly means that there is not much drive behind it.
Figure 6: Solar Wind Flow Pressure 1967 – 2015
This graph shows a rise from the low in the late 1960s to the peak at Solar Cycle 22 maximum and then the 23 year decline from that peak. It is this flow that modulates the flow of galactic cosmic rays in the inner planets of the solar system.
Figure 7: Oulu Neutron Count 1964 – 2015
Galactic cosmic rays produce a continuous shower of neutrons in the lower atmosphere. The climatic significance of these neutrons is that they provide nucleation sites for cloud droplets. Clouds in turn reflect more sunlight than land or open ocean, cooling the planet. The neutron count follows solar activity with a lag of about a year, reflecting the time the solar wind takes to get to the outer parts of the solar system.
Figure 8: Sum of Solar Polar Field Strengths 1976 – 2015
This data is from the Wilson Solar Observatory and thanks to Dr Hoeksma for updating the data. As with the broad top in the heliospheric current sheet tilt angle, there appears to be a broad top and not much energy in the system.
Figure 9: Smoothed Sunpost Number in months from minimum
Also from Jan Janssens, this figure shows Solar Cycle 24 (green line) compared to the averages of Solar Cycles 10 to 15 (solid blue line) and Solar Cycles 16 to 23 (solid red line). In terms of analogue cycles, Solar Cycle 24 has been most like Solar Cycles 10 to 15.
Figure 10: Sunspot Latitude
Yet again from Jan Janssens, this figure shows the sunspot latitude of Solar Cycle 24 (green line) compared to the average of Solar Cycles 19 to 23. Note for the purpose of this graph, a different month of minimum is used. In this case it is August 2007. This graph is important in that it shows that Solar Cycle 24 is no faster or slower than the previous five cycles. That does not preclude Solar Cycle 24 from becoming a very long cycle if the tail includes a period of no sunspots.
David Archibald is a visiting fellow at the Institute of World Politics in Washington.
His most recent book is Twilight of Abundance (Regnery, 2014).