Category Archives: Solar

Solar Update March 2014 – ten charts by David Archibald

Solar Update March 2014 by David Archibald

With Solar Cycle 24 maximum in March 2013 (see the heliospheric current sheet tilt angle in Figure 5 below) and a one year lag between solar activity and neutron count, we have probably seen the minimum neutron count for this cycle. The minimum count is well above the minimum value for Solar Cycle 20.

In terms of neutron count, Solar Cycle 24 isn’t much weaker than the previous four cycles at a similar stage of development.

What is really interesting is what has happened to the solar wind flow pressure. Despite a high sunspot number and F10.7 flux for this cycle, in January 2014 the solar wind flow pressure fell to a new low of 1.2 nPa for the instrumental record. With another 10 years of solar cycle fall time ahead of us, this suggests that the neutron count is going to be impressive by the end of the decade.

Similarly, despite high sunspot numbers and F10.7 flux values, the Ap Index appears to be in a new regime with current values around the previous apparent floor level of activity for the instrumental record.

Based on the heliospheric tilt angle, Solar Cycle 24 maximum was in Carrington rotation 2134, which is March 2013. With the Solar cycle 23/24 minimum in December 2008, Solar Cycle 24 rise time was 4 years and three months.

The F10.7 flux is having a new peak of activity.

As with the solar wind flow pressure and Ap Index, the interplanetary magnetic field appears to be in a new regime in Solar Cycle 24 in which peak activity is at about the level of the previous floor of activity.

Solar Cycle 24 had been tracking Solar Cycle 5, the first half of the Dalton Minimum, quite closely in terms of monthly sunspot number. It is now somewhat stronger at the same stage of the cycle.

Livingstone and Penn’s forecast of a Solar Cycle 25 maximum amplitude of 7 is still the only prediction of the size of that cycle from the solar physics community. We are still a few years out before solar poloidal field strength can be used to estimate the size of the next cycle.

Of 54 predictions of Solar Cycle 24 peak amplitude, the six at the bottom of the range could be considered to be in the ball park of the achieved result. This suggests that the solar physics community’s understanding of the Sun, and thus climate, has the potential to evolve further. From: Pesnell, W.D., Predictions of Solar Cycle 24, Solar Phys., 252, 209-220, 2008
David Archibald