ON THE USE OF FIRST SPOTLESS DAY AS A PREDICTOR FOR SUNSPOT MINIMUM

Defining the 'first spotless day' of a sunspot cycle as the first day Without spots relative to sunspot maximum during the decline of the so lar cycle, one finds that the timing of that occurrence can be used as a predictor for the occurrence of solar minimum of the following cycl e. For cycle 22, the first spotless day occurred in April 1994, based on the International sunspot number index, although other indices (Bou lder and American) indicated the first spotless day to have occurred e arlier (September 1993). For cycles 9-14, sunspot minimum followed the first spotless day by about 72 months, having a range of 62-82 months ; for cycles 15-21, sunspot minimum followed the first spotless day by about 35 months, having a range of 27-40 months. Similarly, the timin g of first spotless day relative to sunspot minimum and maximum for th e same cycle reveals that it followed minimum(maximum) by about 69 (18 ) months during cycles 9-14 and by about 90 (44) months during cycles 15-21. Accepting April 1994 as the month of first spotless day occurre nce for cycle 22, one finds that it occurred 91 months into the cycle and 57 months following sunspot maximum. Such values indicate that its behavior more closely matches that found for cycles 15-21 rather than for cycles 9-14. Therefore, one infers that sunspot minimum for cycle 23 will occur in about 2-3 years, or about April 1996 to April 1997. Accepting the earlier date of first spotless day occurrence indicates that sunspot minimum for cycle 23 could come several months earlier, p erhaps late 1995.