Comments on a formula describing the secular course of sunspot activity.
Abstract
A method proposed by Henkel for longterm forecasting of solar activity is discussed. The prediction formula is interpreted as the equation of an oscillatory motion of nonstationary character. Estimates of the predictive accuracy are given.
 Publication:

Solar Physics
 Pub Date:
 November 1976
 DOI:
 10.1007/BF00155311
 Bibcode:
 1976SoPh...50..501S
 Keywords:

 Prediction Analysis Techniques;
 Secular Variations;
 Solar Activity;
 Sunspots;
 Difference Equations;
 Harmonic Oscillators;
 Random Variables;
 Sine Waves;
 Sunspot Cycle;
 Solar Physics;
 Solar Activity;
 Predictive Accuracy;
 Oscillatory Motion;
 Sunspot Activity;
 Prediction Formula