Forecasting the Probability of Large Rates of Change of the Geomagnetic Field in the UK: Timescales, Horizons and Thresholds

Smith, A. W., Forsyth, C., Rae, Jonathan, Garton, T. M., Bloch, T., Jackman, C. M. and Bakrania, M. (2021) Forecasting the Probability of Large Rates of Change of the Geomagnetic Field in the UK: Timescales, Horizons and Thresholds. Space Weather, 19 (9). e2021SW002788. ISSN 1542-7390

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Abstract

Large Geomagnetically Induced Currents (GICs) pose a risk to ground based infrastructure such as power networks. Large GICs may be induced when the rate of change of the ground magnetic field is significantly elevated. We assess the ability of three different machine learning model architectures to process the time history of the incoming solar wind and provide a probabilistic forecast as to whether the rate of change of the ground magnetic field will exceed specific high thresholds at a location in the UK. The three models tested represent feed forward, convolutional and recurrent neural networks.

We find all three models are reliable and skillful, with Brier skill scores, ROC scores and PR scores of approximately 0.25, 0.95 and 0.45, respectively. When evaluated during two example magnetospheric storms we find that all scores increase significantly, indicating that the models work better during active intervals. The models perform excellently through the majority of the storms, however they do not fully capture the ground response around the initial sudden commencements. We attribute this to the use of propagated solar wind data not allowing the models notice to forecast impulsive phenomenon.

Increasing the volume of solar wind data provided to the models does not produce appreciable increases in model performance, possibly due to the fixed model structures and limited training data. However, increasing the horizon of the forecast from 30 minutes to 3 hours increases the performance of the models, presumably as the models need not be as precise about timing.

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