Figure 1. Dependence of the geomagnetic Ap-index on the total magnetic flux in dimmings and arcades Φ: (a) for GMSs reliably identified with a definite solar eruption (filled symbols); (b) for all considered events including ones with probable solar source identification (open symbols). Red diamonds denote eruptions in ARs, and blue triangles denote eruptions of filaments outside ARs. The dashed lines delimit the accepted 20% deviation band.