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ARRL Special Bulletin ARLX012 (2019)

SB SPCL @ ARL $ARLX012
ARLX012 Two Solar Cycle 25 Sunspots Appear

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QST de W1AW  
Special Bulletin 12  ARLX012
From ARRL Headquarters  
Newington CT  December 30, 2019
To all radio amateurs 

SB SPCL ARL ARLX012
ARLX012 Two Solar Cycle 25 Sunspots Appear

New Solar Cycle 25 is on the way, but just when the transition from
Solar Cycle 24 to Solar Cycle 25 will take place is not entirely
clear.

On December 24, two new sunspots - one in each hemisphere - emerged
on the face of the Sun that exhibit the reversed magnetic polarity
marking them as belonging to Solar Cycle 25. According to Hale's
Law, sunspot polarities flip-flop from one solar cycle to the next,
the National Center for Atmospheric Research explains.

"The Sun is currently in solar minimum - the nadir of the 11-year
sunspot cycle," Tony Phillips said in his article, "Reversed
Polarity Sunspots Appear on the Sun" on the Spaceweather.com
website. "It's a deep minimum, century-class according to sunspot
counts." The remarkable sunspot scarcity has prompted discussion of
a possible "extended minimum" akin to the Maunder Minimum in the
17th century, when no sunspots appeared for decades, Phillips said.
"Such an event could have implications for terrestrial climate."

This article can be found online at,
https://spaceweatherarchive.com/2019/12/25/reversed-polarity-sunspots-appear-on-the-sun/
.

"Today's new-cycle sunspots (along with isolated new-cycle spots
earlier this year) suggest that the solar cycle is, in fact,
unfolding normally," Phillips wrote, adding that a new Maunder
Minimum does not appear to be in the offing.

Earlier this month, the NOAA/NASA-co-chaired international Solar
Cycle Prediction Panel released its latest forecast for Solar Cycle
25. The panel's consensus calls for a peak in July 2025 (+/- 8
months), with a smoothed sunspot number of 115 and the solar minimum
between Solar Cycles 24 and 25 occurring in April 2020 (+/- 6
months). If this solar minimum prediction is correct, it would make
Solar Cycle 24 the seventh longest on record at 11.4 years.

The forecast can be found online at,
https://www.swpc.noaa.gov/news/solar-cycle-25-forecast-update .

Climate scientist David Archibald speculates that the Solar Cycle
24/25 minimum could occur as late as March 2021, and that Solar
Cycle 25 maximum might not happen until 2027.

"We are well into the Solar Cycle 24/25 minimum but [Cycle] 24 may
not have ended yet," Archibald said in a December 22 update on the
"Watts Up With That?" website. "A solar cycle isn't over until the
heliospheric current sheet has flattened. And that could be as late
as March 2021. Solar cycle amplitude does matter with respect to
climate and the amplitude of Solar Cycle 25, from projecting trends
from the last three cycles, looks like being about 80 in 2027."

The Solar Cycle Prediction Panel agreed that Solar Cycle 25 will be
of average intensity and similar to Solar Cycle 24.

In an article posted on NOAA's Space Weather Prediction Center site,
Scott McIntosh, the Director of the High Altitude Observatory at
National Center for Atmospheric Research (NCAR -
https://ncar.ucar.edu/ ), stresses that Solar Cycle 25 will happen,
"but a sunspot cycle could be small."

Predictability comes with some physical understanding of the
underlying process, McIntosh asserts. "The sunspot cycle is
erratic," he said in his presentation, "provocative of a chaotic,
turbulent solar interior where sunspot progressions with time and
latitude are the only tracers..."
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