Overlapping Magnetic Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25 Amplitude. (arXiv:2006.15263v1 [astro-ph.SR])

Overlapping Magnetic Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25 Amplitude. (arXiv:2006.15263v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+McIntosh_S/0/1/0/all/0/1">Scott W. McIntosh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chapman_S/0/1/0/all/0/1">Sandra C. Chapman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leamon_R/0/1/0/all/0/1">Robert J. Leamon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Egeland_R/0/1/0/all/0/1">Ricky Egeland</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Watkins_N/0/1/0/all/0/1">Nicholas W. Watkins</a>

The Sun exhibits a well-observed modulation in the number of sunspots over a
period of about 11 years. 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. 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.
Recent observationally-motivated studies have illustrated a relationship
between the Sun’s 22-year (Hale) magnetic cycle and the production of the
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. 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.

The Sun exhibits a well-observed modulation in the number of sunspots over a
period of about 11 years. 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. 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.
Recent observationally-motivated studies have illustrated a relationship
between the Sun’s 22-year (Hale) magnetic cycle and the production of the
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. 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.

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