[FARC_list] Newer Solar Cycle 25 Forecast Runs Counter to Consensus

[ai2n at twcny.rr.com]

FROM: THE ARRL LETTER FOR JULY 9, 2020 

	 Scientists associated with the National Center for Atmospheric
Research, the University of Maryland, NASA Goddard Space Flight
Center, and other institutions are offering a "bold prediction" on how
Solar Cycle 25 will play out. In a  paper [1] , "Overlapping Magnetic
Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25
Amplitude," they assert that the next sunspot cycle will be of major
proportions. The forecast stands in stark contrast to the consensus of
forecasters who predict that the magnitude of the nascent Cycle 25 may
not be much different from the current unremarkable solar cycle, which
appears to have reach its low point. 

	 "From the dawn of modern observational astronomy, sunspots have
presented a challenge to understanding -- their quasi-periodic
variation in number, first noted 160 years ago, stimulates
community-wide interest to this day," the abstract points out. "A
large number of techniques are able to explain the temporal landmarks,
(geometric) shape, and amplitude of sunspot 'cycles,' however,
forecasting these features accurately in advance remains elusive." 

	 The paper notes that recent studies have illustrated a relationship
between the sun's 22-year Hale magnetic cycle and the production of
sunspot cycle landmarks and patterns, but not the amplitude of the
cycle. 

	 "Using discrete Hilbert transforms on 270 years of monthly sunspot
numbers to robustly identify the so-called 'termination' events --
landmarks marking the start and end of sunspot and magnetic activity
cycles -- we extract a relationship between the temporal spacing of
terminators and the magnitude of sunspot cycles," the abstract
explains. "Given this relationship and our prediction of a terminator
event in 2020, we deduce that Sunspot Cycle 25 will have a magnitude
that rivals the top few since records began. This outcome would be in
stark contrast to the community consensus estimate of Sunspot Cycle 25
magnitude." 

	 According to the paper, low-amplitude solar cycles appear to
correspond with widely separated terminators, while larger-amplitude
cycles correspond to more narrowly separated terminators. 

	 "[O]ur best estimate for the [sunspot number] amplitude of Solar
Cycle 25 is 233 spots, with a 68% confidence that the amplitude will
fall between 204 and 254 spots," the paper posits. "We predict with
95% confidence that the Cycle 25 amplitude will fall between 153 and
305 spots." 

	 The researchers concede that their forecast is outside of the
scientific consensus, based on different paradigms. "Over the coming
months, as [Solar Cycle] 25 matures, it will become evident which of
these paradigms is most relevant," the paper says. "Very early
indications of the spot pattern are appearing at higher-than-average
latitudes (∼40°). Historically, high-latitude spot emergence has
been associated with the development of large amplitude sunspot cycles
-- only time will tell."

Links:
------
[1] https://arxiv.org/pdf/2006.15263.pdf

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