Barbara Bell

Geomagnetism and the emission-line corona, 1950-1953

107

Lunar eclipses and the forecasting of solar minima

Abstract It is shown that an equation, derived by Danjon from a study of the variation in brightness of the eclipsed Moon with phase of the sunspot cycle, predicts dates in good agreement with observed sunspot minima in 1923, 1933, 1944, 1954, and 1964, and for all minima back to 1823. Even better agreement is obtained by the addition of 0.4 yr to the constant term of Danjons equation, from which it is inferred that the discontinuity in eclipse brightness occurs on the average 4–5 months before sunspot minimum. Predictions of future minima are given, the next one being 1974.9 ± 0.3.