Numerical Simulations of a Shock Interacting with Multiple Magnetized
  Clouds
  We present 2D adiabatic magnetohydrodynamic (MHD) simulations of a shock
interacting with groups of two or three cylindrical clouds. We study how the
presence of a nearby cloud influences the dynamics of this interaction, and
explore the resulting differences and similarities in the evolution of each
cloud. The understanding gained from this small-scale study will help to
interpret the behaviour of systems with many 10's or 100's of clouds.
  We observe a wide variety of behaviour in the interactions studied, which is
dependent on the initial positions of the clouds and the orientation and
strength of the magnetic field. We find: i) some clouds are stretched along
their field-lines, whereas others are confined by their field-lines; ii)
upstream clouds may accelerate past downstream clouds (though magnetic tension
can prevent this); iii) clouds may also change their relative positions
transverse to the direction of shock propagation as they "slingshot" past each
other; iv) downstream clouds may be offered some protection from the oncoming
flow as a result of being in the lee of an upstream cloud; v) the cycle of
cloud compression and re-expansion is generally weaker when there are nearby
neighbouring clouds; vi) the plasma $\beta$ in cloud material can vary rapidly
as clouds collide with one another, but low values of $\beta$ are always
transitory.
  This work is relevant to studies of multi-phase regions, where fast,
low-density gas interacts with dense clouds, such as in circumstellar bubbles,
supernova remnants, superbubbles and galactic winds.
