Possible use of (a) solar faculae and (b) the interplanetary magnetic field as heralds of a solar cycle peak

Two independent methods of predicting the magnitude of the peak of a forthcoming sunspot cycle are summarized. One is based on considerations of the development of spots relative to the area of the faculae within which they form during the early stages of the cycle in question, and gives a lead-time of about 2 years. The other uses measurements of the quiet-day variations of the Earth's magnetic field at the time of the preceding sunspot minimum and allows predictions to be made a half-cycle ahead. A possible extension of this technique to the use of data on the component of the interplanetary magnetic field normal to the ecliptic plane is suggested. References to fuller details of both methods are given. (orig.)