Guest essay by David Archibald
The sun today – spotless
Image from the Solar Dynamics Observatory HMI Continuum
Solar Update October 2017
Solar activity continues to look weak. If the 23/24 solar minimum was the end of the Modern Warm Period, it does not look like it will be followed by a compensating period of especially low solar activity.
Figure 1: F10.7 Flux 2014 – 2017
Figure 2: Heliospheric Current Sheet Tilt Angle 1976 – 2017
The solar cycle isn’t over until the heliospheric current sheet flattens. It is now in striking distance of flattening.
Figure 3: Aligned on minimum by solar cycle
Aligned on solar minimum, Solar Cycle 24 plots on top of Solar Cycle 22 at the same time elapsed from cycle start. If it followed 22 from here, it would be another 15 months long with the minimum in December 2018.
Figure 4: Solar Polar Field Strength
After timing, the next consideration is solar cycle amplitude. The best indication of that comes from the solar polar field strength at minimum. While that is at least a year away, current indications are that Solar Cycle 25 will be of an amplitude similar to that of 24.
Figure 5: Oulu Neutron Count 1964 – 2017
Neutron count has fallen over the last few months in reponse to the higher solar activity evident in Figure 1.
Figure 6: Ap Index 1932 – 2017
The Ap Index during this cycle has remained around the previous floor of activity.
Figure 7: Interplanetary Magnetic Field 1966 – 2017
The IMF has not weakened despite being late in the cycle.
Figure 8: Solar Wind Flow Pressure 1971 – 2017
David Archibald is an independent researcher based in Perth, Western Australia. He is author of American Gripen: The Solution to the F-35 Nightmare