Geoelectric field evaluation during the September 2017 Geomagnetic Storm: MA.I.GIC. model.
IV - Geofisica e fisica dell'ambiente
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The impact of the interplanetary shock and of the Coronal Mass Ejections (CMEs) on the Earth's magnetosphere perturbs the geomagnetic field causing the occurrence of geomagnetic storms. Such extremely variable geomagnetic fields trigger geomagnetic effects measurable not only in the geospace but also in the ionosphere and at the ground. The rapid variations of the geomagnetic fields during geomagnetic storms generate intense geomagnetically induced currents (GICs). In recent years, the GIC impact on the power networks at middle and low latitudes has attracted attention due to the expansion of large-scale power networks into these regions. This work presents a new model, called MA.I.GIC. (Magnetosphere-Ionosphere-Ground Induced Current) model, to derive the geoelectric field used to determine the magnitude of GICs. In addition, the results of the MA.I.GIC. model applied to the September 2017 Geomagnetic Storm is discussed, with particular focus on the two sudden impulses occurring on September 6 and 7, 2017, and the two main phases on September 7 and 8, 2017. The study also indicates that the eastward component of the geoelectric field is dominant for low-latitude locations during the Storm Sudden Commencements related to the impact of the interplanetary shock preceding the interplanetary CME. For some magnetotelluric station the availability of the electric-field measurements allowed a direct comparison with the predicted geoelectric field. For these cases we obtain correlation coefficients as high as 0.92 and 0.95.