Study of the solar wind coupling to the time difference horizontal geomagnetic field

The local ground geomagnetic field fluctuations (AB) are dominated by high frequencies and 83% of the power is located at periods of 32 min or less. By forming 10-min root-mean-square (RMS) of A B a major part of this variation is captured. Using measured geomagnetic induced currents (GIC), from a power grid transformer in Southern Sweden, it is shown that the 10-min standard deviation GIC may be computed from a linear model using the RMS AX and Delta Y at Brorfelde (BFE: 11.67 degrees E, 55.63 degrees N), Denmark, and Uppsala (UPS: 17.35 degrees E, 59.90 degrees N), Sweden, with a correlation of 0.926 +/- 0.015. From recurrent neural network models, that are driven by solar wind data, it is shown that the log RMS Delta X and Delta Y at the two locations may be predicted up to 30 min in advance with a correlation close to 0.8: 0.78 +/- 0.02 for both directions at BFE; 0.81 +/- 0.02 and 0.80 +/- 0.02 in the X- and Y-directions, respectively, at UPS. The most important inputs to the models are the 10-min averages of the solar wind magnetic field component B, and velocity V, and the 10-min standard deviation of the proton number density a,. The average proton number density n has no influence.