Fig. 2

Histogram of the coupling function, \({\text{d}}\phi_{\text{MP}} /{\text{d}}t\), for a IMF B_y > 2 nT and b IMF B_y < − 2 nT. In each panel, the blue trace is for the Northern hemispheric events, whereas the red trace is for the Southern hemispheric events. The time-weighted coupling function, \({\text{d}}\phi^{\text{W}}_{\text{MP}} /{\text{d}}t\), for both cases is limited within 0.2 MWb/s (see text for details)