Research Article

Solar wind driven empirical forecast models of the time derivative of the ground magnetic field

¹ Swedish Institute of Space Physics, Scheelevägen 17, 223 70 Lund, Sweden
² Finnish Meteorological Institute, Erik Palménin Aukio 1, 00560 Helsinki, Finland

^* Corresponding author: peter@lund.irf.se

Received: 29 October 2014
Accepted: 16 February 2015

Abstract

Empirical models are developed to provide 10–30-min forecasts of the magnitude of the time derivative of local horizontal ground geomagnetic field (|dB_h/dt|) over Europe. The models are driven by ACE solar wind data. A major part of the work has been devoted to the search and selection of datasets to support the model development. To simplify the problem, but at the same time capture sudden changes, 30-min maximum values of |dB_h/dt| are forecast with a cadence of 1 min. Models are tested both with and without the use of ACE SWEPAM plasma data. It is shown that the models generally capture sudden increases in |dB_h/dt| that are associated with sudden impulses (SI). The SI is the dominant disturbance source for geomagnetic latitudes below 50° N and with minor contribution from substorms. However, at occasions, large disturbances can be seen associated with geomagnetic pulsations. For higher latitudes longer lasting disturbances, associated with substorms, are generally also captured. It is also shown that the models using only solar wind magnetic field as input perform in most cases equally well as models with plasma data. The models have been verified using different approaches including the extremal dependence index which is suitable for rare events.