We investigate the role of the coronal mass ejections (CMEs) (by using soft X ray solar emission as proxy data) in producing the nonrecurrent geomagnetic storms in the period 1969--1974. The linkage between these phenomena is confirmed: however, it turns out that CMEs associated with chromospheric flares, accompanied by type 4 radio emission, are the most effective in perturbing the geomagnetic field. ¿ 1998 American Geophysical Union