Interplanetary Origin of Geomagnetic Activity in the Declining Phase of the Solar Cycle

Interplanetary magnetic field and plasma data are compared with ground-based geomagnetic Dst and AE indices to determine the causes of magnetic storms, substorms, and quiet during the descending phase of the solar cycle. The primary focus is on 1974 data characterized by the presence of two long-lasting corotating streams associated with coronal holes.