Evolution of Prolate Molecular Clouds at HII Boundaries: I. Formation of
  fragment-core structures
  The evolution of a prolate cloud at an Hii boundary is investigated using
Smoothed Particle Hydrodynamics (SPH). The prolate molecular clouds in our
investigation are set with their semi-major axis perpendicular to the radiative
direction of a plane parallel ionising Extreme Ultraviolet (EUV) flux.
  Simulations on three high mass prolate clouds reveal that EUV radiation can
trigger distinctive high density core formation embedded in a final linear
structure. This contrasts with results of the previous work in which only an
isotropic Far Ultraviolet (FUV) interstellar background flux was applied.
  A systematic investigation on a group of prolate clouds of equal mass but
different initial densities and geometric shapes finds that the distribution of
the cores over the final linear structure changes with the initial conditions
of the prolate cloud and the strength of the EUV radiation flux. These highly
condensed cores may either scatter over the full length of the final linear
structure or form two groups of high density cores at two foci, depending on
the value of the ionising radiation penetration depth d_EUV, the ratio of the
physical ionising radiation penetration depth to the minor axis of the cloud.
Data anlysis on the total mass of the high density cores and the core formation
time finds that the potential for EUV radiation triggered star formation
efficiency is higher in prolate clouds with shallow ionisation penetration
depth and intermediate major to minor axial ratio, for the physical
environments investigated.
  Finally, it is suggested that the various fragment-core structures observed
at Hii boundaries may result from the interaction between ionising radiation
and pre-existing prolate clouds of different initial geometrical and physical
conditions.
