The use of abnormal quiet days in Sq(H) for predicting the magnitude of sunspot maximum at the time of preceding sunspot minimum

The previously established connection between the occurrence of AQDs (abnormal quiet days when the phase of the solar diurnal variation of horizontal magnetic field, Sq(H), at a mid-latitude northern hemisphere station is anomalous) at sunspot minimum and the magnitude of the following sunspot maximum is examined in the light of recent improved understanding of the nature and cause of AQDs. A small contribution to the relationship is found to arise from variations from cycle to cycle in the additional northward field which is characteristic of AQDs and leads to a reduced Sq(H) amplitude at stations poleward of the Sq focus. However, the main factor which determines the connection is a variation from one sunspot minimum to another of the amplitude of the small southward bay-like field perturbations which constitute the AQD events, and evidence is presented which suggests that this parameter may be quantitatively related to the extent of southward swing of the Bsub(z) component of the interplanetary magnetic field which determines the energy transfer from the solar wind into the magnetospheric tail. It thus appears that the magnitude of southward swing in Bsub(z) might be another solar parameter which anticipates the size of a forthcoming sunspot cycle during its build-up over the declining phase of the previous cycle and at the minimum. (author)