  Globally-propagating shocks in the solar corona have long been studied to
quantify their involvement in the acceleration of energetic particles. However,
this work has tended to focus on large events associated with strong solar
flares and fast coronal mass ejections (CMEs), where the waves are sufficiently
fast to easily accelerate particles to high energies. Here we present
observations of particle acceleration associated with a global wave event which
occurred on 1 October 2011. Using differential emission measure analysis, the
global shock wave was found to be incredibly weak, with an Alfv\'en Mach number
of ~1.008-1.013. Despite this, spatially-resolved type III radio emission was
observed by the Nan\c{c}ay RadioHeliograph at distinct locations near the shock
front, suggesting localised acceleration of energetic electrons. Further
investigation using a magnetic field extrapolation identified a fan structure
beneath a magnetic null located above the source active region, with the
erupting CME contained within this topological feature. We propose that a
reconfiguration of the coronal magnetic field driven by the erupting CME
enabled the weak shock to accelerate particles along field lines initially
contained within the fan and subsequently opened into the heliosphere,
producing the observed type III emission. These results suggest that even weak
global shocks in the solar corona can accelerate energetic particles via
reconfiguration of the surrounding magnetic field.
