Effects of Version 2 of the International Sunspot Number on Naïve Predictions of Solar Cycle 25

Abstract

The recalibration of the International Sunspot Number brings new challenges to predictions of Solar Cycle 25. One is that the list of extrema for the original series is no longer usable because the values of all maxima and minima are different for the new version of the sunspot number. Timings of extrema are less sensitive to the recalibration but are a natural result of the calculation. Predictions of Solar Cycle 25 published before 2016 must be converted to the new version of the sunspot number. Any prediction method that looks across the entire time span will have to be reconsidered because values in the nineteenth century were corrected by a larger factor than those in the twentieth century. We report a list of solar maxima and minima values and timings based on the recalibrated sunspot number. Naïve forecasts that depend only on the current values of the time series are common in economic studies. Several naïve predictions of Solar Cycle 25, the climatological average (180 ± 60), two versions of the inertial forecast, and two versions of the even‐odd forecast, are derived from that table. The climatological average forecast is the baseline for more accurate predictions and the initial forecast in assimilative models of the Sun. It also provides the error estimate for Monte Carlo techniques that anticipate the long‐term effects on the terrestrial environment. The other four predictions are shown to be statistically insignificant.

Lessons learned from predictions of Solar Cycle 24

“…The values were clustered near the climatological average rather than the actual, belowaverage, value. Pesnell (2018) found that the climatological predictions of Solar Cycle 24 were less accurate than those in the precursor category. This agrees with Brown (1986) and Li et al (2001), who concluded that methods using a single source of information gave more widely varying predictions for Solar Cycles 21-24.…”

“…The use of a function that resembles a Debye function to represent S can be traced to a Poisson distribution that omitted the c from the denominator (Stewart and Panofsky, 1938;Cook, 1949). It is timely to do this for S as the recalibration changed the shape of several of the double-peaked cycles (Pesnell, 2018). The discrepancy in shape also reduced the agreement between the shape of R Z and F10.7.…”

“…1. The times of solar minimum listed in Pesnell (2018) were used as the starting time of each cycle. An error of 2.6 √ S was used in the fits.…”

Another Mini Solar Maximum in the Offing: A Prediction for the Amplitude of Solar Cycle 25

“…This unusual behavior has drawn the attention of researchers worldwide who have attempted to predict the amplitude of solar cycle 25 (Bhowmik & Nandy, 2018;Cameron et al, 2016;Gopalswamy et al, 2018;Hathaway & Upton, 2016;Iijima et al, 2017;Janardhan et al, 2015;Jiang et al, 2018;Kakad et al, 2017;Kirov et al, 2018;Macario-Rojas et al, 2018;Pesnell & Schatten, 2018;Petrovay et al, 2018;Sarp et al, 2018;Upton & Hathaway, 2014, 2018. The different estimates of SSN in V1.0 and V2.0 for the amplitude of cycle 25 by different researchers along with the ratio of peak SSN of cycle 25 to cycle 24 are summarized in Table 1.…”

“…We therefore revisit, in this paper, our earlier prediction in order to update the amplitude of solar cycle 25 using the revised SSN V2.0 observations available after July 2015 and to find out the nature of solar cycle 25. Pesnell (2018) also suggested that the solar cycle 25 predictions which used the SSN V1.0 observations need to be revisited as he showed that the revised SSN V2.0 observations have different values of SSN for the solar maxima and minima compared to the original SSN V1.0 observations. Further, we primarily claimed, in our earlier prediction (JBA15), a possible continuation of a steady declining trend observed in unsigned solar polar fields above latitudes of ≥45°starting from ∼1995 until the minimum of cycle 24.…”