Proposed sequence of events to explain the properties of the 11 October 2013 SEP intensities at STA and STB. The top panel represents the configuration of magnetic field lines before the event, with STA-connected field lines on the left and STB-connected field lines on the right. The red lines in the top panel represent the confined flare of ≈03:35 UT. As the pressure wave forms around the expanding CME flux rope, open and closed magnetic field lines are pushed aside and are potentially forced to undergo interchange reconnection. Initially trapped pre-energised particles are suddenly released into open fields in the vicinity of the shock for further acceleration.