  An array of excitable Josephson junctions under global mean-field interaction
and a common periodic forcing shows emergence of two important classes of
coherent dynamics, librational and rotational motion in the weaker and stronger
coupling limits, respectively, with transitions to chimeralike states and
clustered states in the intermediate coupling range. In this numerical study,
we use the Kuramoto complex order parameter and introduce two measures, a
libration index and a clustering index to characterize the dynamical regimes
and their transition and locate them in a parameter plane.
