Predicting Sunspot Numbers for Solar Cycles 25 and 26. (arXiv:2102.06001v2 [astro-ph.SR] UPDATED)

Predicting Sunspot Numbers for Solar Cycles 25 and 26. (arXiv:2102.06001v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Wu_S/0/1/0/all/0/1">S.-S. Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Qin_G/0/1/0/all/0/1">G. Qin</a>

The prediction of solar activity is important for advanced technologies and
space activities. The peak sunspot number (SSN), which can represent the solar
activity, has declined continuously in the past four solar cycles (21$-$24),
and the Sun would experience a Dalton-like minimum, or even the Maunder-like
minimum, if the declining trend continues in the following several cycles, so
that the predictions of solar activity for cycles 25 and 26 are crucial. In Qin
& Wu, 2018, ApJ, we established an SSN prediction model denoted as
two-parameter modified logistic prediction (TMLP) model, which can predict the
variation of SSNs in a solar cycle if the start time of the cycle has been
determined. In this work, we obtain a new model denoted as TMLP-extension
(TMLP-E). If the start time of a cycle $n$ is already known, TMLP-E can predict
the variation of SSNs in the cycle $n+1$. Cycle 25 is believed to start in
December 2019, so that the predictions of cycles 25 and 26 can be made with our
models. It is found that the predicted solar maximum, ascent time, and cycle
length are 115.1, 4.84 yr, and 11.06 yr, respectively, for cycle 25, and 107.3,
4.80 yr, and 10.97 yr, respectively, for cycle 26. The solar activities of
cycles 25 and 26 are predicted to be at the same level as that of cycle 24, but
will not decrease further. We therefore suggest that the cycles 24$-$26 are at
a minimum of Gleissberg cycle.

The prediction of solar activity is important for advanced technologies and
space activities. The peak sunspot number (SSN), which can represent the solar
activity, has declined continuously in the past four solar cycles (21$-$24),
and the Sun would experience a Dalton-like minimum, or even the Maunder-like
minimum, if the declining trend continues in the following several cycles, so
that the predictions of solar activity for cycles 25 and 26 are crucial. In Qin
& Wu, 2018, ApJ, we established an SSN prediction model denoted as
two-parameter modified logistic prediction (TMLP) model, which can predict the
variation of SSNs in a solar cycle if the start time of the cycle has been
determined. In this work, we obtain a new model denoted as TMLP-extension
(TMLP-E). If the start time of a cycle $n$ is already known, TMLP-E can predict
the variation of SSNs in the cycle $n+1$. Cycle 25 is believed to start in
December 2019, so that the predictions of cycles 25 and 26 can be made with our
models. It is found that the predicted solar maximum, ascent time, and cycle
length are 115.1, 4.84 yr, and 11.06 yr, respectively, for cycle 25, and 107.3,
4.80 yr, and 10.97 yr, respectively, for cycle 26. The solar activities of
cycles 25 and 26 are predicted to be at the same level as that of cycle 24, but
will not decrease further. We therefore suggest that the cycles 24$-$26 are at
a minimum of Gleissberg cycle.

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