Fig. 1

Histograms showing number of selected satellite data (combination of all the scalar, scalar gradient, vector and vector gradient data) distributed according to IMF \(B_z\) (top left), IMF \(B_y\) (top right) and the merging electric field at the magnetopause \(E_\text{m}\), as estimated by coupling function \(0.33 v^{4/3} B_t^{2/3} \sin ^{8/3} \left( | \Theta | / 2 \right) \) mV/m with v the solar wind speed in km/s, \(B_t=\sqrt{B_y^2 + B_z^2}\) the Interplanetary Magnetic Field magnitude in the \(y-z\) plane in GSM coordinates in nT, and \(\Theta = \arctan (B_y/B_z)\). IMF and E_m values are averages of 1-min values for 2 h prior to the time of the observation. y-axis shows the number of observations per bin