  The observations of post eruption arcades (PEAs) in X-rays and EUV reveal
strong localised brightenings at the loop top regions. The origin of these
brightenings and their dynamics is not well understood to date. Here, we study
the dynamics of PEAs using one-dimensional hydrodynamic modelling with the
focus on the the understanding of the formation of localised brightening.Our
findings suggest that these brightenings are the result of collisions between
the counter-streaming chromospheric evaporation from both the foot points. We
further perform forward modelling of the emission observed in simulated results
in various spectral lines observed by the Extreme-Ultraviolet Imaging Telescope
aboard Hinode. The forward modelled intensities in various spectral lines are
in close agreement with a flare observed in December 17, 2006 by EIS.
