Tuesday, September 15, 2020

Solar Minimum "Probably" Occurred Last December

The Royal Observatory of Belgium reports that the solar minimum marking the end
of Cycle 24 and the beginning of Cycle 25 "most probably" occurred in December 2019. The ARRL Letter reports that the observatory's Sunspot Index and Long-Term Solar Observations branch, or SILSO, based its call on this past January's increase in the 13-month smoothed sunspot number, the first time that number has increased since the last solar maximum in April 2014. SILSO also reported that since last November, more new-cycle sunspots have been observed than old-cycle spots. They are differentiated by their location on the sun's surface and their magnetic polarity.