Relationship between the Magnetic Flux of Solar Eruptions and the Ap-Index of Geomagnetic Storms

          I.M. Chertok (1), M.A. Abunina (1) A.A. Abunin (1), A.V. Belov (1),  V.V. Grechnev (2),

(1) Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Troitsk, Moscow, Russia
(2)  Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia

Abstract.  Solar coronal mass ejections (CMEs) are main drivers of the most powerful non-recurrent geomagnetic storms. In the extreme-ultraviolent range, CMEs are accompanied by dimmings and bright post-eruption arcades. The analysis of events of the 23th solar cycle (Chertok et al. Solar Phys. 282, 175, 2013) revealed that the summarized unsigned magnetic flux of dimming and arcades at the photospheric level Φ is significantly related to the intensity (Dst-index) of geomagnetic storms. This provides the basis for the earliest diagnosis of geoefficiency of solar eruptions. In the present paper, by the same data set it is found that a noticeable correlation takes place also between the eruptive magnetic flux Φ and another geomagnetic index Ap. As the magnetic flux increases from tens to ≈500 (in 10²⁰ Mx units), the geomagnetic storm intensity measured by the 3-hour Ap –index, enhances in average from Ap ≈50 to a formally maximum value 400 (in 2 nT units). The established relationship shows that in fact the real value of the Ap-index is not limited and during the most severe magnetic storms may significantly exceed 400.

Figure 1: Dependence of the geomagnetic storm Ap-index on the magnetic flux of solar eruptions  

 

Table: parameters of GMSs, FDs and their solar eruptive sources