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

• Main Author: P. Wintoft
• Format: Article
• Language: English
• Published: Copernicus Publications 2005-07-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/23/1949/2005/angeo-23-1949-2005.pdf
• ISSN: 0992-7689; 1432-0576

The local ground geomagnetic field fluctuations (Δ <i>B</i>) 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 Δ <i>B</i> 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 Δ <i>X</i> and Δ <i>Y</i> 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 Δ <i>X</i> and Δ <i>Y</i> 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 <i>X</i>- and <i>Y</i>-directions, respectively, at UPS. The most important inputs to the models are the 10-min averages of the solar wind magnetic field component <i>B_z</i> and velocity <i>V</i>, and the 10-min standard deviation of the proton number density σ_n. The average proton number density <i>n</i> has no influence.<p> <b>Keywords.</b> Magnetospheric physics (Solar wind - magnetosphere interactions) – Geomagnetism and paleomagnetism (Rapid time variations)