(a) The occurrence ratio of mesoscale FAC events in the dawnside (solid line) and duskside (dotted line) sectors against the IMF inclination angle in the X–Y plane in the GSM coordinate. An angle of zero indicates the sunward direction, and a negative angle means that the IMF has a negative B_Y component. (b) The occurrence ratio of mesoscale FAC events in the dawnside (solid line) and duskside (dotted line) sectors for the Parker Spiral configuration (red) and Ortho-Parker Spiral configuration (green) of IMF against IMF inclination angle in X–Y plane in the GSE coordinate.