These plots shows the relationship between the ignition amplifier edge (falling) and the firing of the coil.  You can see the ignition amplifier doing its job.  As soon as the firing period is over high current starts flowing in the primary of the coil to re-build the field.  As soon as it senses a full charge the current is reduced.  You can see this by rise in voltage on the negative terminal and the ringing caused by the inductance of the coil.  As soon as the ignition amplifier (SA) gets the falling edge the amplifier's coil driver opens and the field (energy that was stored in the primary) collapses inducing a much higher voltage into the secondary firing the spark plug.  The primary voltage is pretty gnarly during this period of time.  The duration of the spark event, or at least the period that the output driver is open, is determined by the ECU.