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

Abstract

The local ground geomagnetic field fluctuations (ΔB) are dominated by high frequencies and 83% of the power is located at periods of 32 min or less. By forming 10min root-mean-square (RMS) of ΔB 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 ΔX and ΔY at Brorfelde (BFE: 11.67° E, 55.63° N), Denmark, and Uppsala (UPS: 17.35° E, 59.90° 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 ΔX and ΔY 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 Bz, and velocity V, and the 10-min standard deviation of the proton number density σ n, The average proton number density n has no influence. © European Geosciences Union 2005.