Hourly values of X, Y and Z geomagnetic components recorded at Coimbra Station (IAGA code: COI) and local geomagnetic K indices for 2007 to 2014

For the 2007 to 2014 period, we use a statistical approach to evaluate the performance of Tsyganenko and Sitnov [2005, doi:10.1029/2004JA010798] semi-empirical model (TS05) in estimating the magnetospheric transient signal observed at four Northern Hemisphere mid-latitude ground stations: Coimbra, Portugal; Panagyurishte, Bulgary; Novosibirsk, Russia and Boulder, USA. We find that the TS05 performance is clearly better for the X (North-South) than for the Y (East-West) field components and for more geomagnetically active days as determined by local K-indices.

For ~ 50% (X) and ~ 30% (Y) of the total number of geomagnetically active days, correlation values yield r > 0.7. During more quiet conditions, only ~30% (X) and ~15% (Y) of the number of analysed days yield r > 0.7. We compute separate contributions from different magnetospheric currents to data time variability and to signal magnitude.