An EXAMINATION OF THE SUNSPOT AREAL DATASET, 1875-2017

PAPER I, AN OVERVIEW

Abstract

Examined are annual values of sunspot number (SSN), corrected sunspot area (SSA), number of active region entries (NARE), largest-observed area active region (LAAR), mean area per entry (MAE), highest latitude spot (HLS), and inferred correlations between selected parameters based on the observed data for the years 1875–2017. A number of ±1 standard error of measurement prediction intervals are made regarding the size of the next sunspot cycle (SC) SC25. In particular, based on the even-odd cycle effect, SC25, the next solar cycle, should have maximum annual SSN = 170.4 ± 13.7, maximum annual SSA = 1,730.3 ± 180.0 millionths of a solar hemisphere, and maximum annual NARE = 3,775 ± 510, assuming that it is not a statistical outlier. Also, based on the observed annual minimum value of HLS for 2017 (= 19°), one predicts minimum annual SSN = 7.0 ± 3.2, minimum annual SSA = 41.5 ± 31.7 millionths of a solar hemisphere, minimum annual NARE = 155 ± 76, maximum annual SSN = 136.2 ± 14.8, maximum annual SSA = 1,461.5 ± 261.2 millionths of a solar hemisphere, and maximum annual NARE = 2,771 ± 330 for SC25. As of March 2019, there have been no occurrences of high-latitude new-cycle spots (≥30°) during the decline of ongoing SC24. Monthly values of SSN, SSA, and NARE are now well within the range of expected values indicative of the approaching SC24/25 cycle minimum, especially values since November 2017. Hence, another prolonged cycle-minimum period, as was experienced for SC23/24, may be underway for SC24/25.