  Edge localised mode (ELM) measurements from reproducibly similar plasmas in
the Joint European Torus (JET) tokamak, which differ only in their gas puffing
rate, are analysed in terms of the pattern in the sequence of inter-ELM time
intervals. It is found that the category of ELM defined empirically as Type I -
typically more regular, less frequent, and having larger amplitude than other
ELM types - embraces substantially different ELMing processes. By quantifying
the structure in the sequence of inter-ELM time intervals using delay time
plots, we reveal transitions between distinct phase space dynamics, implying
transitions between distinct underlying physical processes. The control
parameter for these transitions between these different ELMing processes is the
gas puffing rate.
