... Data . ... Planetary perturbations during geomagnetic storms are measured by the Dst index, which is the deviation of variation of the magnetic field from the undisturbed level, averaged over the values measured at the control chain of magnetic stations located in the low latitudes. ... To predict the hourly values of the Dst index, artificial neural networks (ANN) of perceptron type are used. ... Loading of the data on the values of the Dst index and forecast update are performed twice per hour. ...