Although its peak is still four years away, a new active period of Earth-threatening solar storms will be the weakest since 1928, predicts an international panel of experts led by NOAA’s Space Weather Prediction Center and funded by NASA. Despite the prediction, Earth is still vulnerable to a severe solar storm.
The panel predicts the upcoming Solar Cycle 24 will peak in May 2013 with 90 sunspots per day on average. If the prediction proves true, Solar Cycle 24 will be the weakest cycle since No. 16, which peaked at 78 daily sunspots in 1928, and ninth weakest since the 1750s, when numbered cycles began.
The panel also predicted that the lowest sunspot number between cycles – or solar minimum – occurred in December 2008, marking the end of Cycle 23 and the start of Cycle 24. If the December prediction holds up, at 12 years and seven months Solar Cycle 23 will be the longest since 1823 and the third longest since 1755. Solar cycles span 11 years on average, from minimum to minimum.
An unusually long, deep lull in sunspots led the panel to revise its 2007 prediction that the next cycle of solar storms would start in March 2008 and peak in late 2011 or mid-2012. The persistence of a quiet sun also led the panel to a consensus that the next cycle will be "moderately weak."