AbstractArc traces and luminous phenomena at the divertor tiles of ASDEX‐Upgrade were recorded, and experimentally modelled by artificially ignited arcs. At the graphite surfaces the arcs produced relatively immobile spots that were uniformly distributed in toroidal direction. To explain the latter effect, the behavior of flux tubes emanating from the arc spots is discussed. It is concluded that arcing should not be neglected in theoretical models that describe processes in high power machines.