Discussion: Solar Cycle 24 is ending as a new solar minimum arrives as of late 2018 and 2019. Interestingly, NASA forecasts an unusually lengthy solar minimum extending through 2022 and into 2023. Solar minimum usually lasts less than 2 years as part of the complete 11-year solar cycle. The previous solar minimum occurring 2006-2009 was also unusually lengthy and was followed by a solar maximum in 2012-2014 which was about 60% the intensity of previous solar maximum dating back over 100 years. While the influence of the solar cycle on earth’s climate is not well understood the Space Weather Prediction Center (SWPC) has made a comment on their web site that presence of long duration solar minimum as implied by the current NASA forecast for the next several years occurs when there is a “maximum amount of cosmic rays, high energy particles whose source is outside our Solar System, reaching earth. There is a theory that cosmic rays can create nucleation sites in the atmosphere which seed cloud formation and create cloudier conditions. If true, there would be a significant impact on climate”.
Fig. 1: SWPC plot of solar cycle 24 which is ending as a new solar minimum has arrived. The NASA solar cycle forecast indicates an unusually lengthy solar minima ahead.